Medical gas pipes

Abstract

A conduit for transporting medical gas includes an elongated tube, a sheath provided around the elongated tube, and a pair of connectors at opposite ends of the elongated tube. The elongated tube is formed from a breathable material to mitigate condensation within the lumen. During use, water molecules within the lumen of the elongated tube are dissipated by absorption into the breathable material, diffusion through the breathable material, and release into the surrounding air. The breathable material may tend to expand and soften upon absorbing water molecules. Expansion of the elongated tube may be selectively restricted by the sheath. The restriction by the sheath may mitigate softening of the breathable material.

Description

[Technical field]

[0001]

[0001] This application claims the benefit of priority to US Provisional Patent Application No. 63 / 329,205, entitled "Respiratory Conduit," which is incorporated herein by reference in its entirety.

[0002] background Field

[0002] The present disclosure relates to a conduit for use in the transport of medical gases. More particularly, but not exclusively, the present disclosure relates to a conduit including a breathable material that is permeable to water molecules for use in a respiratory ventilation circuit of a respiratory assistance system or in an air delivery circuit of a surgical air delivery system. [Background technology]

[0003] 2. Description of Related Art

[0003] For patients receiving respiratory assistance, it has been shown to be clinically beneficial if the temperature and humidity of the respiratory gas delivered to the patient by the respiratory assistance system are comparable to levels that occur naturally in healthy lungs (typically about 37°C and 100% relative humidity). Thus, to improve patient comfort and recovery, the respiratory gas may be heated and humidified.

[0004]

[0004] Similarly, there are clinical benefits to warming and humidifying the insufflation gas delivered by a surgical insufflation system to a patient's abdominal or peritoneal cavity, for example during laparoscopic surgery. The insufflation gas may be delivered from a cylinder stored at room temperature (e.g., about 19°C to 21°C), with a relative humidity approaching 0%. Warming and humidifying the insufflation gas can reduce cell damage and / or desiccation, limit adhesion formation, or reduce other deleterious effects.

[0005]

[0005] In a medical gas system (e.g., a respiratory assistance system or a surgical insufflation system), medical gas (respiratory gas or insufflation gas, respectively) may be transported to and from a patient by a conduit. The conduit has a tube wall defining a lumen for the passage of the medical gas. The outer surface of the tube wall is typically exposed to the ambient air surrounding the outer surface of the conduit. The ambient air is typically at a relatively lower temperature and humidity than the warmed and humidified medical gas flow in the lumen. In a hospital environment, for example, one or more of the temperature and humidity of the ambient air is typically regulated by the hospital's heating, ventilation, and air conditioning (HVAC) system for comfort and air quality. In an environment such as a patient's home, one or more of the temperature and humidity of the ambient air may be regulated or unregulated. The temperature and humidity of the ambient air may vary significantly throughout the day and seasons, especially if not regulated.

[0006]

[0006] The temperature difference between the medical gas and the surrounding air causes the heated and humidified medical gas to cool as it travels along the length of the conduit. When the temperature of the medical gas drops below its dew point, the water vapor in the medical gas stream condenses into liquid water droplets.

[0007]

[0007] Condensation may also form upstream and downstream of the conduit. For example, in a respiratory support system, condensation may form in the ventilator or anesthesia machine due to the high humidity of the breathing gas carried to the ventilator or anesthesia machine by the expiratory conduit. Condensation may accumulate in filters or flow sensors in the ventilator or anesthesia machine.

[0008] Condensation and other liquids may drain into one or more conduits from one or more of other sources, such as the nebulizer, the yoke, the catheter mount, the patient interface, the patient, etc.

[0009]

[0009] The accumulation of condensation or other liquids within the conduits or other components of a medical gas system can cause a variety of problems, including one or more of the following: - Incorrect sensor readings, Filter saturation, Alarms (e.g. audible and visual), Damage to the flow source or its components (e.g., flow sensor); The need for regular drainage, which may interrupt surgery or treatment; and -Blockage of flow path. Summary of the Invention [Means for solving the problem]

[0010] overview

[0010] In a first aspect, a medical gas conduit for use in a medical gas system includes an elongated tube defining an inner lumen for the passage of a flow of medical gas, at least a portion of the elongated tube including a breathable material configured to expand due to absorption of water molecules in use; and a sheath provided around at least a portion of the elongated tube, the sheath configured to limit expansion of at least a portion of the elongated tube in at least one of a radial and longitudinal direction due to absorption of water molecules by the breathable material in use.

[0011]

[0011] In a second aspect, a medical gas conduit for use in a medical gas system comprises: an elongated tube defining an inner lumen for the passage of a flow of medical gas, at least a portion of the elongated tube being corrugated, the elongated tube comprising a breathable material configured to expand in use due to absorption of water molecules, and a plurality of corrugations; and a sheath provided around at least a portion of the elongated tube and configured to limit expansion of the elongated tube in at least a longitudinal direction of the elongated tube, the elongated tube being configured such that the pitch of the plurality of corrugations changes in use depending on the absorption of water molecules by the breathable material and the restriction of the elongated tube by the sheath.

[0012]

[0012] In a third aspect, a medical gas conduit for use in a medical gas system includes an elongated tube defining an inner lumen for the passage of a flow of medical gas, at least a portion of the elongated tube including a breathable material configured to expand due to absorption of water molecules in use; and a sheath provided around at least a portion of the elongated tube, each end of the sheath being secured to a corresponding end of the elongated tube, the sheath being configured such that, in use, as the breathable material expands due to absorption of water molecules, the length and diameter of the sheath change inversely proportional to one another.

[0013]

[0013] In a fourth aspect, a medical gas conduit for use in a medical gas system includes an elongated tube defining an inner lumen for the passage of a flow of medical gas; a sheath provided around at least a portion of the elongated tube; and a pair of connectors for pneumatically coupling the elongated tube to other components of the respiratory system, each of the pair of connectors securing a respective end of the sheath to a corresponding end of the elongated tube, and at least a first of the pair of connectors including a plurality of apertures through which one or more of the elongated tube and the sheath are exposed.

[0014]

[0014] In a fifth aspect, a medical gas conduit for use in a medical gas system includes an elongated tube defining an inner lumen for the passage of a flow of medical gas; and a sheath provided around at least a portion of the elongated tube, the sheath configured to be at least partially spaced from a maximum outer diameter of the elongated tube when the medical gas conduit is in an equilibrium state.

[0015]

[0015] In a sixth aspect, a medical gas conduit for use in a medical gas system comprises: an elongated tube defining an inner lumen for the passage of a flow of medical gas, at least a portion of the elongated tube comprising a breathable material configured to expand upon absorption of water molecules, in use; and a sheath provided around at least a portion of the elongated tube, configured to selectively limit expansion of the elongated tube due to absorption of water molecules, in use, the elongated tube and sheath being configured such that, at least under some conditions, compliance of the medical gas conduit is dependent on physical interaction between the elongated tube and the sheath.

[0016]

[0016] In a seventh aspect, a medical gas conduit for use in a medical gas system includes an elongated tube defining an inner lumen for the passage of a flow of medical gas, at least a portion of the elongated tube including a breathable material configured to expand upon absorbing water molecules, in use; and a sheath loosely provided around at least a portion of the elongated tube, the elongated tube configured to, in use, exert a circumferential stress on the sheath, at least under some conditions.

[0017]

[0017] In an eighth aspect, a medical gas conduit for use in a medical gas system includes an elongated tube defining an inner lumen for the passage of a flow of medical gas; and a sheath provided around at least a portion of the elongated tube, the braided tubular mesh comprising a biaxial braid of a plurality of braided elements spaced apart around the circumference of the sheath and extending helically around the elongated tube, each of the plurality of braided elements including a pair of adjacent filaments.

[0018]

[0018] In a ninth aspect, a medical gas conduit for use in a medical gas system comprises an elongated tube defining an inner lumen for the passage of a flow of medical gas, at least a portion of the elongated tube comprising a breathable material, at least a portion of the elongated tube configured to absorb between about 100% and 250%, preferably between about 100% and 180%, more preferably between about 110% and 150%, even more preferably between about 120% and 140%, or between about 130% and 145%, and even more preferably between about 135% and 145%, for example about 138% or 139%, of its own dry mass in water molecules in an immersion test.

[0019]

[0019] In a tenth aspect, a medical gas conduit for use in a medical gas system comprises an elongated tube defining an inner lumen for the passage of a flow of medical gas, at least a portion of the elongated tube comprises a breathable material, at least a portion of the elongated tube is configured to absorb about 40% to 80%, preferably about 40% to 60%, more preferably about 45% to 55%, even more preferably about 48% to 51%, for example about 49%, of its own dry mass in water molecules in an immersion test, and the medical gas conduit does not include a heater wire.

[0020]

[0020] In an eleventh aspect, a medical gas conduit for use in a medical gas system includes an extruded elongated tube defining an inner lumen for the passage of a flow of medical gas, at least a portion of the elongated tube comprising a breathable material; and a pair of connectors at each end of the elongated tube for pneumatically coupling the medical gas conduit to other components of the medical gas system, at least one of the pair of connectors including a first connector component at least partially inserted within the inner lumen of the elongated tube, and a second connector component overmolded onto the first connector component and the elongated tube.

[0021]

[0021] In a twelfth aspect, a medical gas conduit for use in a medical gas system comprises an elongated tube defining an inner lumen for the passage of a flow of medical gas, at least a portion of the elongated tube comprising a breathable material, the breathable material comprising two melting points in a differential scanning calorimetry (DSC) test each of which is greater than about 197°C, preferably greater than about 202°C, more preferably greater than about 204°C, even more preferably greater than about 205°C, and most preferably greater than about 206°C, for example at or above about 207°C, and the medical gas conduit does not comprise a heater wire.

[0022]

[0022] In a thirteenth aspect, a medical gas conduit for use in a medical gas system includes an elongated tube defining an inner lumen for the passage of a flow of medical gas, at least a portion of the elongated tube includes a breathable material, the breathable material includes three melting points in differential scanning calorimetry (DSC) testing, and the medical gas conduit does not include a heater wire.

[0023]

[0023] In a fourteenth aspect, a medical gas conduit for use in a medical gas system comprises an elongated tube defining an inner lumen for the passage of a flow of medical gas, at least a portion of the elongated tube comprising a breathable material, the breathable material having a minimum melting point in a differential scanning calorimetry (DSC) test greater than about 37°C, preferably greater than about 42°C, more preferably greater than about 44°C, more preferably greater than about 45°C, and even more preferably greater than about 46°C, for example a temperature of about 47°C.

[0024]

[0024] In a fifteenth aspect, a medical gas conduit for use in a medical gas system includes an elongated tube defining an inner lumen for the passage of a flow of medical gas, at least a portion of the elongated tube includes a breathable material configured to expand due to absorption of water molecules in use, and the medical gas conduit comprises a breathable material configured to expand due to absorption of water molecules in at least one conditioned state in use, the breathable material being configured to expand by up to about 50%, preferably up to about 33%, more preferably up to about 25%, even more preferably up to about 20%, and most preferably up to about 32%, of the length of the elongated tube closest to a patient interface of the medical gas system in at least one conditioned state in use. and an outlet region comprising up to about 50%, preferably up to about 33%, more preferably up to about 25%, even more preferably up to about 20%, and most preferably up to about 10% of the length of the elongated tube nearest the gas return inlet of the gas source of the medical gas system; and an intermediate region comprising up to about 50%, preferably up to about 33%, more preferably up to about 25%, even more preferably up to about 20%, and most preferably up to about 10% of the length of the elongated tube intermediate the inlet region and the outlet region.

[0025]

[0025] The medical gas conduit of any one of the ninth to fifteenth aspects may include a sheath provided around at least a portion of the elongated tube.

[0026]

[0026] The medical gas conduit of any one of the fourth, fifth or eighth aspects may include an elongated tube comprising a breathable material.

[0027]

[0027] The following technical features may be applied to the medical gas conduit of any one of the first to fifteenth aspects.

[0028]

[0028] The medical gas conduit may be an exhalation conduit, the medical gas system may be a respiratory support system, and the medical gas flow may be a respiratory gas flow; or the medical gas conduit may be an inhalation conduit, the medical gas system may be a respiratory support system, and the medical gas flow may be a respiratory gas flow; or the medical gas conduit may be an exhaust conduit, the medical gas system may be a surgical insufflation system, and the medical gas flow may be a insufflation gas flow.

[0029]

[0029] The diameter and length of at least one, and preferably both, of the elongate tube and sheath may vary over time during use.

[0030]

[0030] The length and diameter of the sheath may be configured to change inversely proportionally during use as the elongated tube expands due to the absorption of water molecules.

[0031]

[0031] The slope of the sheath length versus diameter may be between about -100 and -20, preferably between about -50 and -20, more preferably between about -40 and -35, and most preferably about -37. Alternatively, the slope of the sheath length versus diameter may be between about -75 and -25, preferably between about -60 and -40, more preferably between about -55 and -45, and most preferably about -52.

[0032]

[0032] The sheath length versus diameter gradient may be substantially linear between about 24 mm and 32 mm sheath diameters.

[0033]

[0033] The sheath alone can be configured to fit a rod having an outer diameter in the range of between about 23 mm and 43 mm.

[0034]

[0034] The sheath may include a plurality of openings, preferably quadrilateral openings, which are configured to undergo an affine transformation as, in use, the elongated tube expands due to absorption of water molecules by the breathable material.

[0035]

[0035] The sheath may be configured to be at least partially spaced from the elongate tube when the medical gas conduit is in at least one of, and preferably both of, a dry and equilibrium state.

[0036]

[0036] The elongate tube and sheath may be configured such that, in at least one cross section through the medical gas conduit, the sheath is spaced outwardly from at least a portion of the circumference of the elongate tube in any one or more of a dry state, an equilibrium state, and at least one conditioned state, during use.

[0037]

[0037] The elongate tube and sheath may be configured such that during use, in at least one conditioned state, the elongate tube exerts a circumferential stress on the sheath.

[0038]

[0038] The elongate tube and sheath may be configured such that in at least one cross section through the medical gas conduit, during use and in at least one conditioned state, the sheath contacts the entire circumference of the elongate tube.

[0039]

[0039] The breathable material may be unfoamed, or the breathable material may be foamed.

[0040]

[0040] The breathable material may comprise a block copolymer, preferably a block copolymer comprising one or more of the following: a hard segment of polybutylene terephthalate; and a soft segment of an ether-type macroglycol.

[0041]

[0041] The block copolymer may constitute at least about 90% of the breathable material, preferably at least about 92%, more preferably at least about 95%, and even more preferably at least about 97%, for example about 97% or about 98.5%, based on one or more of mass, weight and volume.

[0042]

[0042] The breathable material may include one or more additives, such as one or more of a blowing agent, a colorant, an ultraviolet (UV) stabilizer, a UV absorber, and a processing aid. The one or more additives may comprise up to about 10%, preferably up to about 8%, more preferably up to about 5%, and most preferably up to about 3%, for example about 3% or about 2%, of the breathable material, based on one or more of mass, weight, and volume.

[0043]

[0043] At least a portion of the elongated tube may be configured to absorb more than about 33% of its own dry mass in water molecules in an immersion test, more preferably between about 33% and 200%, even more preferably between about 100% and 160%, even more preferably between about 120% and 140%, and most preferably between about 130% and 135%, for example about 133%.

[0044]

[0044] At least a portion of the elongated tube may be configured to absorb between about 45% and 250%, preferably between about 65% and 200%, more preferably between about 75% and 175%, even more preferably between about 100% and 160%, even more preferably between about 110% and 150%, even more preferably between about 120% and 140%, even more preferably between about 130% and 140%, and most preferably between about 133% and 139%, for example about 139%, of its own dry mass in water molecules in an immersion test.

[0045]

[0045] During immersion testing while separated from the sheath, at least a portion of the elongated tube may be configured to expand, during immersion testing, by between about 20% and 70%, preferably between about 25% and 50%, more preferably between about 30% and 50%, for example about 32%, in one or more, preferably each, of the radial direction, longitudinal direction, and wall thickness.

[0046]

[0046] When immersed in a state separated from the sheath, at least a portion of the elongated tube may be configured to expand by one or more, preferably all of: between about 37% and 47%, preferably about 42%, in the radial direction; between about 32% and 42%, preferably about 37%; and / or between about 29% and 39%, preferably about 34%, in the wall thickness.

[0047]

[0047] The medical gas conduit may include a pair of connectors at both ends of the medical gas conduit, the pair of connectors configured to pneumatically couple the elongated tube to other components of the medical gas system, at least one of the pair of connectors including a first connector component and a second connector component, and corresponding ends of the elongated tube and the sheath are secured between the first connector component and the second connector component.

[0048]

[0048] The first connector component may extend into the lumen of the elongate tube.

[0049]

[0049] The second connector component may be overmolded onto one or more, preferably all of the first connector component, the elongate tube and the sheath.

[0050]

[0050] The second connector component may include a plurality of apertures, preferably between 2 and 6 apertures, for example 4 apertures, through which the elongate tube and sheath are exposed.

[0051]

[0051] The end of the elongated tube may be positioned substantially concentrically around a portion of the first connector component, the end of the sheath may be positioned substantially concentrically around the end of the elongated tube, and the second connector component may be positioned substantially concentrically around the end of the sheath.

[0052]

[0052] At least one of the first connector component and the second connector component may be at least partially formed from one or more of polycarbonate, polypropylene, and polyethylene.

[0053]

[0053] At least one of the pair of connectors may be configured to prevent or inhibit expansion of an end of an elongate tube secured between the first connector component and the second connector component.

[0054]

[0054] The elongated tube and the sheath may not be fixed to one another intermediate the pair of connectors.

[0055]

[0055] The conduit may be configured such that, in use, the elongate tube tapers towards at least one, and preferably both, of the pair of connectors in at least one conditioned state.

[0056]

[0056] The conduit may be configured so that the sheath tapers towards at least one, and preferably both, of the pair of connectors in at least one, and preferably both, of the equilibrium and conditioned states.

[0057]

[0057] The medical gas conduit is configured so that, in use: when initially absorbing water molecules, the elongated tube is configured to expand relatively unrestricted by the sheath, and when further water molecules are absorbed, the elongated tube is configured to expand relatively restricted by the sheath.

[0058]

[0058] The elongate tube may be configured to expand relatively constrained by the sheath after extended use.

[0059]

[0059] The sheath may be configured to not restrict expansion of the elongated tube when the elongated tube is in an equilibrium state during use, and to restrict expansion of the elongated tube when the elongated tube is in at least one conditioned state during use.

[0060]

[0060] The medical gas conduit may be configured such that, in use: upon initial absorption of water molecules, the elongated tube expands radially relatively unrestricted by the sheath, and upon absorption of further water molecules, the elongated tube expands further radially relatively restricted by the sheath.

[0061]

[0061] The sheath may be configured not to restrict radial expansion of the elongated tube when the elongated tube is in an equilibrium state, and to restrict radial expansion of the elongated tube when the elongated tube is in at least one conditioned state during use.

[0062]

[0062] The medical gas conduit may be configured such that, in use, upon initial absorption of water molecules, the elongated tube expands longitudinally relatively unrestricted by the sheath, and upon absorption of further water molecules, the elongated tube expands longitudinally relatively restricted by the sheath.

[0063]

[0063] The medical gas conduit may be configured such that, in use, upon absorption of further water molecules, the elongated tube is configured to expand radially and the sheath is configured to at least partially contract the medical gas conduit longitudinally.

[0064]

[0064] The sheath may be configured to not restrict longitudinal expansion of the elongate tube in an equilibrium state and to restrict longitudinal expansion of the elongate tube in at least one conditioned state.

[0065]

[0065] The medical gas conduit may be configured such that, in use, upon initial absorption of water molecules, the elongated tube is free to expand radially and longitudinally, and upon further absorption of water molecules, the elongated tube is configured to engage with the sheath such that further expansion is restricted in at least one of the radial and longitudinal directions.

[0066]

[0066] The sheath may be configured to allow the elongated tube to expand freely in the radial and longitudinal directions in an equilibrium state, and may be configured to restrict expansion of the elongated tube in at least one of the radial and longitudinal directions in at least one conditioned state.

[0067]

[0067] The medical gas conduit may be configured such that, in use, upon initial absorption of water molecules, the elongated tube is free to expand radially to engage the inner surface of the sheath, and upon further absorption of water molecules, the elongated tube is configured to expand further radially, causing the sheath to expand radially and contract longitudinally.

[0068]

[0068] The elongate tube and sheath may be configured such that radial expansion of the elongate tube engages the elongate tube with the sheath, causing the sheath to expand radially and contract longitudinally.

[0069]

[0069] The elongated tube may be configured to have a first length before use, a second length upon initial absorption of water molecules, and a third length upon further absorption of water molecules, the second length being longer than the first length and the third length.

[0070]

[0070] The elongated tube may be configured to have a first length in an equilibrium state, a second length in at least one conditioned state in which radial expansion of the elongated tube is not limited by the sheath, and a third length in at least one other conditioned state in which radial expansion of the elongated tube is limited by the sheath, the second length being longer than the first length and the third length.

[0071]

[0071] The third length can be within about 90% to 110% of the first length, and preferably can be approximately equal to the first length.

[0072]

[0072] The elongated tube may include multiple corrugations.

[0073]

[0073] The medical gas conduit may be configured such that, in use, the profile of each of the multiple corrugations changes as the elongated tube expands due to the absorption of water molecules.

[0074]

[0074] Each of the multiple corrugations may be partially defined by a pair of side walls, and the elongate tube and sheath may be configured to reorient, preferably radially, during use, such that the side walls reorient as the elongate tube absorbs water molecules.

[0075]

[0075] The side walls may be configured to reorient beyond the radial direction as the elongated tube continues to absorb water molecules.

[0076]

[0076] The medical gas conduit may be configured such that the pitch of the multiple corrugations is substantially uniform along the length of the elongated tube when the elongated tube is in at least one of a dry state and an equilibrium state, and that the pitch of the multiple corrugations varies along the length of the elongated tube when the elongated tube is in at least one conditioned state.

[0077]

[0077] The elongate tube may include a cuff portion at an end of the elongate tube, where the cuff portion is not corrugated.

[0078]

[0078] The sheath may comprise a tubular mesh, preferably a braided tubular mesh.

[0079]

[0079] The sheath may include a biaxial braid of multiple braided elements each extending helically around the elongated tube.

[0080]

[0080] Each of the multiple braided elements may include two or three filaments.

[0081]

[0081] The sheath may include at least one of: between about 75 and 125 braided elements, preferably between about 90 and 100 braided elements, e.g., about 96 braided elements; and between about 150 and 250 filaments, preferably between about 180 and 200 filaments, e.g., about 192 filaments.

[0082]

[0082] The elongate tube may be configured to have a substantially uniform diameter in at least one of a dry state and an equilibrium state; and, in use, to have a substantially non-uniform diameter in at least one conditioned state.

[0083]

[0083] The medical gas conduit may be configured such that the elongated tube has localized expansion in one or more areas of elevated relative humidity or condensed water volume within the lumen during at least one conditioned condition during use.

[0084]

[0084] The medical gas conduit may be an expiratory conduit configured such that the elongated tube, in a conditioned state in use, has localized expansion in one or more of: an inlet region comprising up to about 50%, preferably up to about 33%, more preferably up to about 25%, even more preferably up to about 20%, and most preferably up to about 10% of the length of the elongated tube nearest the patient interface of the medical gas system; an outlet region comprising up to about 50%, preferably up to about 33%, more preferably up to about 25%, even more preferably up to about 20%, and most preferably up to about 10% of the length of the elongated tube nearest the gas return inlet of the gas source of the medical gas system; and an intermediate region comprising up to about 50%, preferably up to about 33%, more preferably up to about 25%, even more preferably up to about 20%, and most preferably up to about 10% of the length of the elongated tube intermediate the inlet region and the outlet region.

[0085]

[0085] In a differential scanning calorimetry (DSC) test, the breathable material may have a minimum melting point at a temperature greater than about 37°C, preferably greater than about 42°C, more preferably greater than about 44°C, more preferably greater than about 45°C, and most preferably greater than about 46°C, for example at a temperature of about 47°C.

[0086]

[0086] In the DSC test, the breathable material may have a minimum melting point at a temperature between about 37°C and 100°C, preferably between about 40°C and 60°C, more preferably between about 40°C and 50°C, for example at a temperature of about 47°C.

[0087]

[0087] In a differential scanning calorimetry (DSC) test, the breathable material may have a melting point at a temperature between about 42°C and 52°C, preferably between about 44°C and 50°C, more preferably between about 45°C and 49°C, and even more preferably between about 46°C and 47°C, for example at a temperature of about 47°C.

[0088]

[0088] In a differential scanning calorimetry (DSC) test, the breathable material may include two melting points at temperatures greater than about 197°C, preferably greater than about 202°C, more preferably greater than about 204°C, even more preferably greater than about 205°C, and most preferably greater than about 206°C, for example at or above a temperature of about 207°C.

[0089]

[0089] In a differential scanning calorimetry (DSC) test, the breathable material may include two melting points at temperatures between about 202°C and 225°C, preferably between about 204°C and 223°C, more preferably between about 205°C and 222°C, and even more preferably between about 206°C and 221°C, for example at temperatures of about 207°C and 220°C.

[0090]

[0090] In a differential scanning calorimetry (DSC) test, the breathable material may include two melting points having a temperature difference of less than about 23°C, preferably less than about 18°C, more preferably less than about 16°C, even more preferably less than about 15°C, and most preferably less than about 14°C, for example a temperature difference of about 13°C.

[0091]

[0091] In a differential scanning calorimetry (DSC) test, the breathable material may include two melting points having a temperature difference between about 150°C and 170°C, preferably between about 155°C and 165°C, more preferably between about 158°C and 162°C, and even more preferably between about 159°C and 161°C, for example a temperature difference of about 160°C.

[0092]

[0092] In differential scanning calorimetry (DSC) testing, the breathable material may include three melting points at temperatures between about 42°C and 225°C, more preferably between about 44°C and 223°C, even more preferably between about 45°C and 222°C, and most preferably between about 46°C and 221°C.

[0093]

[0093] In a differential scanning calorimetry (DSC) test, the breathable material may have a melting point at at least one, preferably all three of the following temperatures: between about 42°C and 52°C, preferably between about 44°C and 50°C, more preferably between about 45°C and 49°C, even more preferably between about 46°C and 47°C, for example at a temperature of about 47°C; between about 202°C and 212°C, preferably between about 204°C and 210°C, more preferably between about 205°C and 209°C, even more preferably between about 206°C and 208°C, for example at a temperature of about 207°C; and between about 215°C and 225°C, preferably between about 217°C and 223°C, more preferably between about 218°C and 222°C, even more preferably between about 219°C and 221°C, for example at a temperature of about 220°C.

[0094]

[0094] The medical gas conduit may be configured to have a compliance in at least one conditioned state of less than about 4 ml / cmH2O, preferably less than about 2.5 ml / cmH2O, and more preferably less than about 1.2 ml / cmH2O.

[0095]

[0095] The elongate tube separate from the sheath may be configured to have a compliance in at least one conditioned state of greater than about 4 ml / cmH2O, preferably greater than about 5 ml / cmH2O.

[0096]

[0096] The medical gas conduit may be configured to have a flow resistance of less than about 0.06 cmH2O / l / min at a flow rate of 30 l / min, less than about 0.12 cmH2O / l / min at a flow rate of 15 l / min, or less than about 0.74 cmH2O / l / min at a flow rate of 2.5 l / min, in at least one conditioned state.

[0097]

[0097] The medical gas conduit may be configured to have an increase in flow resistance due to bending in at least one conditioned state of less than 150%, less than 125%, or less than 115%, for example about 113%.

[0098]

[0098] The medical gas conduit is configured, in at least one conditioned state, to meet any one or more, preferably all, of the length, leakage, flow resistance, and compliance requirements of the International Organization for Standardization (ISO) International Standard 5367:2014(E) standard.

[0099]

[0099] The medical gas conduit may be configured to have a compliance of less than about 4 ml / cmH2O, preferably less than about 2.5 ml / cmH2O, and more preferably less than about 1.2 ml / cmH2O after extended use.

[0100]

[0100] The elongate tube separate from the sheath may be configured to have a compliance greater than about 4 ml / cmH2O, preferably greater than 5 ml / cmH2O, after extended use.

[0101]

[0101] The medical gas conduit may be configured to have a flow resistance of less than about 0.06 cmH2O / l / min at a flow rate of 30 l / min; less than about 0.12 cmH2O / l / min at a flow rate of 15 l / min; or less than about 0.74 cmH2O / l / min at a flow rate of 2.5 l / min after extended use.

[0102]

[0102] The medical gas conduit may be constructed to have an increase in flow resistance due to bending of less than 150% after extended use.

[0103]

[0103] The medical gas conduit may be configured to meet any one or more, preferably all, of the length, leakage, flow resistance, and compliance requirements of International Organization for Standardization (ISO) International Standard 5367:2014(E) after extended use.

[0104]

[0104] The elongate tube and sheath may be flexible to reduce tubing drag on one or more of the y-tube and patient interface of the medical gas system during use.

[0105]

[0105] When separated from the sheath, the elongate tube may be more flexible in the conditioned state than in the equilibrium state.

[0106]

[0106] The conduit for medical gas may include an expiratory conduit, the medical gas system may include a respiratory assistance system, the flow of medical gas may include a flow of respiratory gas, and the expiratory conduit may be configured to form more than about 80% of the total length of the expiratory branch of the respiratory assistance system when in use, preferably more than about 90%, more preferably more than about 95%.

[0107]

[0107] The medical gas conduit or elongate tube may have a length, at equilibrium, of between about 0.8m and 1.2m, such as about 1.0m; between about 1.0m and 2.5m, preferably between about 1.1m and 1.4m, more preferably between about 1.2m and 1.3m, such as about 1.25m; between about 1.4m and 1.6m, such as about 1.5m; between about 1.5m and 1.7m, such as about 1.6m; or between about 1.5m and 1.8m, such as about 1.6m or about 1.8m; or between about 2.2m and 2.6m, more preferably between about 2.3m and 2.5m, such as about 2.4m.

[0108]

[0108] The medical gas conduit may, at equilibrium, measure a length of between about 1.1m and 1.8m, preferably between about 1.2m and 1.8m, more preferably between about 1.2m and 1.3m, or between about 1.4m and 1.6m, or between about 1.5m and 1.7m, for example about 1.2m or 1.5m or 1.6m.

[0109]

[0109] The wall thickness of the elongated tube, in a dry state, may be between about 0.5 mm and 0.9 mm, preferably between about 0.6 mm and 0.8 mm, more preferably between about 0.65 mm and 0.75 mm, even more preferably between about 0.68 mm and 0.72 mm, and most preferably between about 0.69 mm and 0.71 mm, for example about 0.70 mm.

[0110]

[0110] The wall thickness of the elongate tube, in a saturated state separated from the sheath, may be between about 0.7 mm and 1.1 mm, preferably between about 0.8 mm and 1.0 mm, more preferably between about 0.85 mm and 0.95 mm, even more preferably between about 0.90 mm and 0.94 mm, and most preferably between about 0.91 mm and 0.93 mm, for example about 0.92 mm.

[0111]

[0111] The maximum outer diameter of the elongate tube, in a dry state, may be between about 20 mm and 26 mm, preferably between about 21 mm and 25 mm, more preferably between about 22 mm and 24 mm, for example about 23 mm.

[0112]

[0112] The maximum outer diameter of the elongate tube, in a saturated state separated from the sheath, may be between about 25 mm and 35 mm, preferably between about 28 mm and 32 mm, more preferably between about 29 mm and about 31 mm, for example about 30 mm.

[0113]

[0113] The elongated tube may be extruded.

[0114]

[0114] The elongated tube may be corrugated.

[0115]

[0115] The elongated tube may be corrugated and the sheath may be configured to be at least partially spaced from the peaks of the corrugations of the elongated tube when the medical gas conduit is in an equilibrium state.

[0116]

[0116] The medical gas conduit may not include any reinforcing framework or rods within the lumen.

[0117]

[0117] The breathable material may be configured to, in use, at least partially dry the flow of medical gas as it travels along the length of the lumen.

[0118]

[0118] The at least one conditioned condition may include a simulated conditioned condition.

[0119]

[0119] The medical gas system may include a Y-shaped tube and a gas source, with the medical gas conduit configured to be directly coupled to each of the outlets of the Y-shaped tube; and a gas return inlet of the gas source, or a filter directly coupled to the gas return inlet.

[0120]

[0120] Medical gas conduits may not include a water trap or provision for a water trap.

[0121]

[0121] The medical gas conduit may be configured for use as or within an expiratory leg of a medical gas system, where the expiratory leg does not include a water trap.

[0122]

[0122] The medical gas conduit may not include a heater wire.

[0123]

[0123] Other technical features will be apparent to those skilled in the art from the following drawings, descriptions, and claims.

[0124]

[0124] In a sixteenth aspect, a ventilation circuit kit for use in a respiratory assistance system comprises an inspiratory conduit; a Y-shaped tube; and an expiratory conduit, at least one of the inspiratory conduit and the expiratory conduit comprising a medical gas conduit described in any one of the first to fifteenth aspects.

[0125]

[0125] The ventilation circuit kit may include a humidification chamber.

[0126]

[0126] The ventilation circuit kit may include any one or more of: a humidifier supply conduit; a patient interface; a filter; a pressure relief valve; a pressure regulator; and a catheter mount.

[0127]

[0127] The ventilation circuit kit may not include a heater wire associated with the medical gas conduit; and / or a water trap associated with the medical gas conduit.

[0128]

[0128] In a seventeenth aspect, the air delivery circuit kit comprises an exhaust conduit comprising a medical gas conduit of any one of the first to fifteenth aspects; and an exhaust filter.

[0129]

[0129] The air supply circuit kit may include any one or more of an air supply device supply conduit; an adapter; a humidifier supply conduit; an air supply gas filter; a humidification chamber; a funnel; a delivery conduit; a surgical cannula; a diffusion device; and an additional exhaust conduit.

[0130]

[0130] In an eighteenth aspect, a respiratory assistance system for use in providing respiratory therapy to a patient comprises: a gas source configured to supply a flow of respiratory gas; a humidifier configured to heat and humidify the flow of respiratory gas; a humidifier supply conduit configured to transport the flow of respiratory gas from an outlet of the gas source to an inlet of the humidifier; an inhalation conduit configured to transport the flow of respiratory gas from the outlet of the humidifier to an inlet of a Y-shaped or patient interface for supply to a patient; and an exhalation conduit configured to transport the flow of medical gas from the outlet of the Y-shaped or patient interface to a gas return inlet of the gas source or a filter at the gas return inlet; at least one of the inhalation conduit and the exhalation conduit comprises a conduit for medical gas of any one of the first to fifteenth aspects.

[0131]

[0131] The respiratory assistance system may not include a heater wire associated with the medical gas conduit; and / or a water trap associated with the medical gas conduit.

[0132]

[0132] In a nineteenth aspect, a surgical gas delivery system configured to supply an insufflation gas to a body cavity of a patient includes an insufflation device configured to supply a flow of insufflation gas; a humidifier configured to heat and humidify the flow of insufflation gas; a humidifier supply conduit configured to transport the flow of insufflation gas from an outlet of the insufflation device to an inlet of the humidifier; a delivery conduit configured to transport the flow of insufflation gas from the outlet of the humidifier to an inlet of a surgical cannula for delivery to the patient's body cavity; and an exhaust conduit configured to carry the flow of insufflation gas and surgical smoke away from the patient's body cavity, the exhaust conduit including a medical gas conduit of any one of the first to fifteenth aspects.

[0133]

[0133] In a twentieth aspect, a method of forming a conduit for use in transporting medical gas includes providing a sheath around an elongated tube, the elongated tube defining an inner lumen for the passage of a flow of medical gas; clamping a first end of the sheath to a first end of the elongated tube; and overmolding a connector onto the first end of the sheath and the first end of the elongated tube to secure the connector, sheath, and elongated tube together.

[0134]

[0134] The step of overmolding the connector may include at least partially inserting a first connector component into a lumen of a wall of the elongated tube at the first end of the elongated tube; and overmolding a second connector component around the first connector component, the first end of the sheath, and the first end of the elongated tube.

[0135]

[0135] The method may include the step of injection molding the first connector component prior to at least partially inserting the first connector component into the first end of the elongate tube.

[0136]

[0136] The step of clamping the first end of the sheath to the first end of the elongated tube may include positioning the first end of the sheath and the first end of the elongated tube within a mold, the mold including a plurality of protrusions that engage and clamp the sheath to the elongated tube.

[0137]

[0137] The multiple protrusions may form multiple apertures in the connector when the connector is overmolded, with the sheath exposed through the multiple apertures.

[0138]

[0138] The method may include the steps of clamping the second end of the sheath to the second end of the elongated tube; and overmolding a second connector onto the second end of the sheath and the second end of the elongated tube to secure the second connector, the second end of the sheath, and the second end of the elongated tube together.

[0139]

[0139] The method may include a step of longitudinally contracting the sheath such that the second end of the sheath overlaps the second end of the elongated tube prior to clamping the second end of the sheath to the second end of the elongated tube.

[0140]

[0140] The method may include a step of extruding an elongated tube.

[0141]

[0141] The method may include the step of corrugating the elongated tube.

[0142]

[0142] The method may include cutting an elongated tube from the tubular extrusion.

[0143]

[0143] The method may include cutting the sheath from a length of sheath material to a predetermined sheath length selected such that when the sheath is provided around the elongated tube and the sheath is deformed to the length of the elongated tube, the sheath is at least partially radially spaced from the elongated tube.

[0144]

[0144] The sheath may comprise a tubular mesh, preferably a braided tubular mesh.

[0145]

[0145] The sheath may include at least one of: between about 75-125 monofilament or multifilament braided elements, preferably between about 90-100 braided elements, e.g., about 96 braided elements; and between about 150-250 filaments, preferably between about 180-200 filaments, e.g., about 192 filaments; or the sheath may include at least one of: between about 40-60 monofilament or multifilament braided elements, preferably between about 45-55 braided elements, e.g., about 48 braided elements; and between about 120-180 filaments, preferably between about 135-165 filaments, e.g., about 144 filaments.

[0146]

[0146] The elongated tube may comprise a breathable material, preferably a block copolymer, more preferably a block copolymer comprising a hard segment of polybutylene terephthalate; and a soft segment of an ether-type macroglycol.

[0147]

[0147] The method may not include the step of providing at least one, and preferably both, of a heater wire and a water trap in the conduit.

[0148]

[0148] In a 21st aspect, a conduit may be formed by the method of the 20th aspect, wherein, in use, the elongated tube may be configured to expand upon absorbing water molecules, and the sheath is configured to selectively limit the expansion of the elongated tube.

[0149]

[0149] In a twenty-second aspect, a conduit for a respiratory assistance system comprises: an elongated tube defining an inner lumen for the passage of a flow of respiratory gas, the elongated tube comprising a material that is permeable to water molecules and that expands due to absorption of water molecules; and a sheath provided around the elongated tube; the sheath configured to limit expansion of the elongated tube in at least one of a radial and longitudinal direction due to absorption of water molecules.

[0150]

[0150] In a twenty-third aspect, a conduit for a respiratory assistance system comprises: a corrugated tube defining an inner lumen for the passage of a flow of respiratory gas, the corrugated tube comprising a plurality of corrugations and a material that is permeable to water molecules and expands due to absorption of water molecules; and a sheath provided around the corrugated tube, the sheath being configured, in use, to limit expansion of the corrugated tube in at least a longitudinal direction of the corrugated tube, wherein the corrugated tube is configured such that the pitch of the plurality of corrugations varies in use depending on the absorption of water molecules by the corrugated tube and the restriction of the corrugated tube by the sheath.

[0151]

[0151] In a twenty-fourth aspect, a conduit for a respiratory assistance system includes an elongated tube defining an inner lumen for the passage of a flow of respiratory gas, the elongated tube comprising a material that is permeable to water molecules and that expands due to the absorption of water molecules; and a sheath provided around the elongated tube, each end of the sheath being fixed to a corresponding end of the elongated tube, the sheath being configured such that the length and diameter of the sheath vary inversely proportional to each other.

[0152]

[0152] In a twenty-fifth aspect, a conduit for a respiratory assistance system includes an elongated tube defining an inner lumen for the passage of a flow of respiratory gas; a sheath provided around the elongated tube; and a pair of connectors for pneumatically coupling the elongated tube to other components of the respiratory system, each of the pair of connectors securing a respective end of the sheath to a corresponding end of the elongated tube, and at least a first of the pair of connectors including a plurality of apertures through which the elongated tube and the sheath are exposed.

[0153]

[0153] In a twenty-sixth aspect, a conduit for a respiratory assistance system includes an elongated tube defining an inner lumen for the passage of a flow of respiratory gas, the elongated tube comprising a material that is permeable to water molecules, the elongated tube being capable of absorbing more than about 33% of its own mass in water molecules in an immersion test, and the conduit does not include at least one of a heater wire and a water trap.

[0154]

[0154] In a 27th aspect, a conduit for a respiratory assistance system comprises: an elongated tube defining an inner lumen for the passage of a flow of respiratory gas; and a sheath provided around the elongated tube, the sheath configured to be at least partially spaced apart from the elongated tube in a radial direction.

[0155]

[0155] In a twenty-eighth aspect, a conduit for use in a respiratory assistance system comprises: an elongated tube defining an inner lumen for the passage of a flow of respiratory gas, the elongated tube comprising a material that is permeable to water molecules and that expands upon absorbing water molecules; and a sheath provided around the elongated tube, wherein compliance of the conduit under at least some operating conditions depends on physical interaction between the elongated tube and the sheath.

[0156]

[0156] In a twenty-ninth aspect, a conduit for use in a respiratory assistance system comprises: an elongated tube defining a lumen for the passage of a flow of respiratory gas, the elongated tube comprising a material that is permeable to water molecules; and a pair of connectors at each end of the elongated tube for fluidly coupling the conduit with other components of the respiratory assistance system, at least one of the pair of connectors including a first connector component at least partially inserted within the lumen at one of the respective ends of the elongated tube, and a second connector component overmolded onto the first connector component and the elongated tube.

[0157]

[0157] In a 30th aspect, a respiratory assistance system includes a gas source configured to generate pressurized ventilation gas; a humidifier configured to heat and humidify the pressurized ventilation gas; a dry line conduit configured to transport the pressurized ventilation gas from an outlet of the gas source to an inlet of the humidifier; an inhalation conduit configured to transport the pressurized ventilation gas from the outlet of the humidifier to an inlet of a Y-shaped tube for supply to a patient; and an exhalation conduit configured to transport exhaled ventilation gas from the outlet of the Y-shaped tube to a gas return inlet of the gas source; wherein the exhalation conduit may include any one of the conduits of the 21st to 29th aspects.

[0158]

[0158] In a thirty-first aspect, a method of forming a conduit for use in a respiratory assistance system includes: providing a sheath around an elongated tube defining an inner lumen for the passage of a flow of respiratory gas; clamping a first end of the sheath to a first end of the elongated tube; and overmolding a connector onto the first end of the sheath and the first end of the elongated tube to secure the connector, sheath, and elongated tube together.

[0159]

[0159] In a thirty-second aspect, a conduit is formed by the method of the thirty-first aspect, wherein the elongated tube is configured to expand upon absorbing water molecules and the sheath is configured to selectively limit the expansion of the elongated tube.

[0160]

[0160] Other aspects and technical features will be readily apparent to one of ordinary skill in the art from the following figures, descriptions, and claims.

[0161] BRIEF DESCRIPTION OF THE DRAWINGS

[0161] To facilitate easy identification of any particular element or discussion of an action, the most significant digit or digits of a reference numeral refer to the number of the figure in which that element is first introduced. Like reference numerals are used in different figures and in different examples to denote like features.

[0162]

[0162] The examples will now be described in further detail with reference to the accompanying drawings. [Brief description of the drawings]

[0163] [Figure 1]

[0163] FIG. 1 is a schematic diagram of a respiratory assistance system that may include a conduit according to the present disclosure. [Diagram 2]

[0164] FIG. 1 is a schematic diagram of an alternative respiratory assistance system that may include a conduit according to the present disclosure. [Diagram 3]

[0165] FIG. 3 is a detailed diagram of an exemplary humidifier that may be used in the respiratory assistance system of FIG. [Figure 4]

[0166] 1 is a schematic diagram of a bubble CPAP system that may include a conduit according to the present disclosure. [Diagram 5]

[0167] 1 is a schematic diagram of an alternative bubble CPAP system that may incorporate a conduit according to the present disclosure. [Figure 6]

[0168] 1 is a schematic diagram of a surgical air insufflation system that may include a conduit according to the present disclosure. [Figure 7]

[0169] 1 is a schematic diagram of an exemplary conduit according to the present disclosure, partially cut away; [Figure 8]

[0170] FIG. 2 is a schematic isometric detail view of one end of an exemplary conduit according to the present disclosure. [Figure 9]

[0171] FIG. 2 is a schematic side detail view of one end of an exemplary conduit according to the present disclosure. [Figure 10]

[0172] FIG. 2 is a schematic exploded side detail view of one end of an exemplary conduit according to the present disclosure. [Figure 11]

[0173] 1 is a schematic cross-sectional side detailed view of one end of an exemplary conduit according to the present disclosure. [Figure 12]

[0174] 1 is a schematic exploded isometric detail view of one end of an exemplary conduit according to the present disclosure. FIG. [Figure 13]

[0175] FIG. 2 is a schematic isometric detail view of an elongated tube and sheath of an exemplary conduit according to the present disclosure. [Figure 14]

[0176] 1 is a schematic side detail view of an elongated tube and sheath of an exemplary conduit according to the present disclosure. [Figure 15]

[0177] 1 is a schematic end cross-sectional view of an exemplary conduit elongate tube and sheath according to the present disclosure. [Figure 16]

[0178] 1 is a schematic cross-sectional side detailed view of an elongate tube and sheath of an exemplary conduit according to the present disclosure. [Figure 17]

[0179] 1 is a graph of differential scanning calorimetry (DSC) test results for breathable materials for conduits according to the present disclosure. [Figure 18]

[0180] 1 is a schematic detail view of a sheath of an exemplary conduit according to the present disclosure, the conduit being in an equilibrium state; [Figure 19]

[0181] FIG. 19 is a schematic detail of the sheath of FIG. 18 with the conduit in a conditioned state; [Figure 20]

[0182] 1 is a graph of length versus diameter gradient for a selection of braided tubular mesh sheaths that may be used in conduits according to the present disclosure. [Figure 21]

[0183] The change in state of an exemplary elongated tube of a conduit according to the present disclosure due to absorption of water molecules and pressure is shown diagrammatically without (FIGS. 21(a)-(d)) and with (FIGS. 21(e)-(h)) a sheath. [Figure 22]

[0184] 1 is a schematic cross-sectional detail of an exemplary conduit corrugated profile according to the present disclosure in an equilibrium state; FIG. [Figure 23]

[0185] FIG. 23 is a schematic cross-sectional detail of the conduit of FIG. 22 in a conditioned state. [Figure 24]

[0186] 2 is a schematic cross-sectional detail view of a portion of an elongated tube of an exemplary conduit according to the present disclosure in an equilibrium state. FIG. [Diagram 25]

[0187] FIG. 25 is a schematic cross-sectional detail of the elongated tube of FIG. 24 in a conditioned state without a sheath. [Figure 26]

[0188] FIG. 26 is a schematic cross-sectional detail of the elongated tube of FIGS. 24 and 25 in a conditioned state when constrained by a sheath (not shown). [Figure 27]

[0189] 1 is a schematic diagram of a respiratory assistance system including an expiratory conduit according to the present disclosure in use; [Figure 28]

[0190] 1 is a flow chart of an exemplary method of manufacturing a conduit according to the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0164] Detailed Description System Overview

[0191] The present technology relates to medical gas conduits that have particular application in a variety of different medical gas systems, such as respiratory assistance systems and surgical ventilation systems, some examples of which are described below.

[0165] Respiratory Support Systems

[0192] 1, a first exemplary respiratory support system 100 for providing non-invasive ventilation (NIV) therapy is shown in a partially cutaway view. The respiratory support system 100 includes a gas source 102, a humidifier supply conduit 104, a humidifier 106, an inspiratory conduit 108, a y-tube 110, a patient interface 112, and an expiratory conduit 114.

[0166]

[0193] The gas source 102 in the illustrated example may be a room-in ventilator with a pressure generator 116, such as a blower. The pressure generator 116 draws ambient air into the gas source 102 via a gas inlet 118 and pressurizes it to a pressure greater than ambient pressure to generate a source of breathing gas. The ambient air may be supplemented with other gases, such as supplemental oxygen (not shown).

[0167]

[0194] The gas source 102 may have a gas source controller 120 that controls the operation of the pressure generator 116. The control may be based on inputs received from one or more of a user interface 122 and one or more sensors (not shown).

[0168]

[0195] In other examples, the gas source 102 may include a positive displacement pump, such as a bellows pump, or may receive breathing gas from a remote source (i.e., a non-intubation type ventilator). The gas source controller 120 may control the pressure of the breathing gas delivered to the patient, for example, by controlling a proportional solenoid valve.

[0169]

[0196] Mechanical ventilation can range from providing supplemental pressure and flow to assist the patient during spontaneous ventilation ("respiratory support") to providing complete control of all ventilation ("life support").

[0170]

[0197] For an adult patient, the breathing gas may be delivered to the patient and returned to the gas source, e.g., a ventilator, at a flow rate of up to 120 liters per minute (l / min), e.g., in the range of about 30-80 l / min. The breathing gas may be delivered to the patient and returned to the gas source, e.g., a ventilator, at a pressure of up to about 6 kilopascals (kPa) (about 60 cmH2O).

[0171]

[0198] For neonatal or pediatric patients, breathing gas may be delivered to the patient and returned to the gas source at a flow rate of approximately 0.5 to 60 l / min. The exact flow rate may depend on the therapy and the weight of the patient. Breathing gas may be delivered to the patient and returned to the gas source at a pressure of up to approximately 6 kPa (approximately 60 cmH2O).

[0172]

[0199] Components of the respiratory assistance system, such as the conduits, may be tested and labeled for use at higher pressures, such as 8 kPa (approximately 80 cmH2O).

[0173]

[0200] Patients receiving mechanical ventilation may be connected to a respiratory support system for 24 hours or more, and in some cases for months or even permanently, depending on the patient's condition.

[0174]

[0201] In another example, the gas source 102 may be an anesthesia machine. For anesthesia applications, the respiratory support system may deliver a mixture of breathing gas and anesthesia agent to the patient, for example to sedate the patient and render him or her unconscious for surgery. The anesthesia gas mixture may be delivered to the patient at a flow rate of up to about 20 l / min, or in certain "low flow" applications up to about 10 l / min. The anesthesia gas mixture may be delivered at a pressure of up to about 6 kPa. However, the pressure is typically lower than mechanical ventilation. The anesthesia machine may include a reventilation system that delivers gas to the patient via an inspiratory conduit and returns exhaled gases to the anesthesia machine via an expiratory conduit. The anesthesia machine and the ventilation circuit typically form a closed loop to prevent the anesthesia agent from leaking into the surrounding environment. Typically, the patient does not need to be connected to the anesthesia machine for more than 24 hours. Most patients receiving anesthesia agents may be connected to the ventilation circuit for much less than 24 hours. The patients receiving anesthesia agents may be continuously monitored by an anesthesiologist while they are under anesthesia.

[0175]

[0202] The gas source 102 supplies breathing gas to the humidifier 106 via the gas source outlet 124 and the humidifier supply conduit 104. In the illustrated example, the humidifier 106 may be an active (heated) pass-over humidifier. The humidifier chamber 126 may be mounted on or otherwise in thermal contact with a chamber heater 128. The humidifier chamber 126 may be removably engaged to the chamber heater 128. A volume of water within the humidifier chamber 126 is heated to evaporate water into a headspace of the humidifier chamber 126. At an inlet to the humidifier chamber 126, breathing gas is received from the humidifier supply conduit 104. The breathing gas may pass through the headspace of the humidifier chamber 126 to absorb water vapor and pass to an outlet of the humidifier chamber 126.

[0176]

[0203] The chamber heater 128 may be controlled by a humidifier controller 130 based on inputs from a user interface 132 and one or more sensors to achieve one or more desired levels of heating and humidification of the respiratory gas.

[0177]

[0204] In some examples, the humidification chamber 126 may have a float valve (not shown) for automatically refilling the water reservoir from a sterile water bag (not shown). The humidifier 106 may be, for example, an F&P 810™, 820™, 850™, or 950™ heated humidifier available from Fisher & Paykel Healthcare Limited, Auckland, New Zealand. The humidification chamber 126 may include a water supply tube and water spike (not shown) for fluidly connecting with the sterile water bag.

[0178]

[0205] The humidifier controller 130 of the humidifier 106 may control the temperature of the chamber heater 128. The chamber heater 128 may be controlled so that the humidified respiratory gas is received by the patient at or near a predetermined temperature and humidity. If the patient is undergoing invasive ventilation, the patient's upper airway is bypassed and respiratory gas may be delivered to the patient at a temperature of about 37° C. and a relative humidity of about 100%. If the patient is undergoing non-invasive ventilation, respiratory gas may be delivered to the patient's upper airway at a temperature of about 31° C. and a relative humidity of 70%. The respiratory gas may be further heated and humidified by the patient's upper airway and may reach the patient's lungs at a temperature of about 37° C. and a relative humidity of about 100%.

[0179]

[0206] One or more of the desired temperature and desired humidity of the respiratory gas may be adjustable using the user interface 132. Alternatively, or in addition, the humidifier 106 and the gas source 102 may be in electronic communication with each other such that settings of the humidifier 106 may be viewed and / or adjusted from the gas source 102, or vice versa. The humidifier controller 130 may receive signals from one or more sensors to provide open-loop or closed-loop control of one or more of the temperature and humidity of the respiratory gas.

[0180]

[0207] In other examples, the humidifier 106 may be a passive (non-heated) pass-over humidifier, a heat and moisture exchanger (HME), a nebulizing humidifier, or a humidifier that provides a continuous or cyclically controlled flow of humidification liquid to a heating element to produce instantaneous or near instantaneous evaporation.

[0181]

[0208] The respiratory assistance system 100 of FIG. 1 illustrates the gas source 102 and the humidifier 106 as separate devices. In other examples, the gas source 102 and the humidifier 106 may be integrated with each other. In such examples, the humidifier supply conduit 104 may be or may include an internal duct within the housing of the integrated device. The functions of the gas source controller 120 and the humidifier controller 130 may be performed by a single controller or a distributed control system. Similarly, the user interface 122 and the user interface 132 may be replaced by a single user interface that may receive inputs for control of both the pressure generator 116 and the chamber heater 128.

[0182]

[0209] Still referring to the example respiratory assistance system 100 of FIG. 1 , breathing gas is conveyed from the humidifier 106 towards the patient by a flexible inlet conduit 108. In some examples, the inlet conduit 108 may have a length of about 1.0 meter (m) to about 2.5 m. In some examples, the inlet conduit 108 may have a length of about 1.5 m to 1.8 m, such as about 1.6 m or 1.8 m. In some examples, such as for anesthesia applications, the inlet conduit 108 may have a length of about 2.2 m to 2.6 m, such as about 2.4 m.

[0183]

[0210] The inhalation conduit 108 may be corrugated. In some examples, for example, for adult patients, the corrugated inhalation conduit 108 may have a maximum outer diameter (i.e., the diameter of the inhalation conduit 108 as measured on the outer surface at the apex of the corrugations) of about 20 millimeters (mm) to 30 mm, or about 23 mm to 25 mm, such as about 24 mm. In other examples, for example, for neonatal or pediatric patients, the maximum outer diameter may be about 10 mm to 20 mm, or about 14 mm to 16 mm, such as about 15 mm. The inhalation conduit 108 may also have a corrugated inner surface. In other examples, the inhalation conduit 108 may have a substantially smooth (e.g., non-corrugated) inner surface.

[0184]

[0211] The inhalation conduit 108 may have a heater wire 134 (only a portion of which is shown for clarity). The heater wire 134 may be, for example, wrapped around the outside of the tube wall, embedded within the tube wall, or located within the lumen of the inhalation conduit 108. The heater wire 134 may be powered by the humidifier 106. The heater wire 134 may be controlled by the humidifier controller 130 to mitigate heat loss of the breathing gas as it travels along the length of the inhalation conduit 108. In some examples, the heater wire 134 may maintain or possibly increase the temperature of the breathing gas as it travels along the length of the inhalation conduit 108.

[0185]

[0212] In some examples, the inlet conduit 108 may have a composite structure composed of two or more components coiled in a lumen. The first coiled component may be an elongated hollow body and the second coiled component may be an elongated structural component. The first and second coiled components may be wound in a double helix configuration. The heating wires and / or the sensing wires may be embedded in the elongated structural component. The inlet conduit 108 may have a connector with a printed circuit board (PCB). The heating wires and / or the sensing wires may be connected to the PCB. Further design and manufacturing details of such conduits are disclosed in U.S. Patent Application Publication Nos. 2015 / 0306333, 2017 / 0100556, 2019 / 0076620, and 2022 / 0355059, all of which are assigned to Fisher & Paykel Healthcare Ltd, the contents of each of which are incorporated by reference in their entirety herein.

[0186]

[0213] A sensor probe 136 may be removably inserted into apertures at the patient and humidifier ends of the inhalation conduit 108. The sensor probe 136 may include, for example, one or more of temperature, humidity, and flow sensors. A sensor lead 138 may connect the sensor probe 136 to the humidifier 106, such that a signal from the sensor probe 136 may be used as an input to a control algorithm for one or more of the pressure generator 116, the chamber heater 128, and the heater wires 134. In other examples, sensors may be integrated into one or more of the humidifier 106 and the inhalation conduit 108. In some examples, one or more of the sensor leads 138 may be embedded in the tube wall or may be located in the lumen. In some examples, one or more sensors may be integrated into the inhalation conduit 108.

[0187]

[0214] The inlet conduit 108 may include connectors at both ends to establish and maintain pneumatic connections with the outlet of the humidification chamber 126 and the inlet of the wye 110, respectively. In some examples, for example, for an adult patient, the connectors may be adapters with 22 mm cone connectors, respectively. The connectors may have a 1:40 taper conforming to the International Organization for Standardization (ISO) 5356-1:2015 (Anesthesia and Respiratory Equipment - Cone Connectors - Part 1: Cones and Sockets) standard. In other examples, for example, for a neonatal or pediatric patient, the connectors may be any of a 15 mm tapered male cone connector, a 15 mm tapered female cone connector, a 12 mm tapered male cone connector, a 12 mm tapered female cone connector, and any combination of two thereof.

[0188]

[0215] In some examples, the connector on the humidifier side of the inhalation conduit 108 may have a socket for receiving the sensor probe 136. In some examples, the connector on the humidifier side of the inhalation conduit 108 may have a socket for establishing an electrical connection between the humidifier 106 and the heater wire 134. In other examples, the humidifier 106 and connector may have corresponding integrated electrical contacts such that physically connecting the inhalation conduit 108 to the humidifier 106 establishes both a pneumatic connection and an electrical connection in a single action.

[0189]

[0216] Respiratory gas is delivered by an inhalation conduit 108 to a yoke 110 adjacent or near the patient. The yoke 110 fluidly couples the inhalation conduit 108 (via the yoke inlet), the patient interface 112 (via the yoke patient inlet / outlet), and the exhalation conduit 114 (via the yoke outlet). The three limbs of the yoke 110 in this example (inlet, outlet, and patient inlet / outlet) form a Y-shape, although it should be understood that the term is not intended to be limited to this particular configuration.

[0190]

[0217] In some examples, an interface conduit (not shown) may be provided between the patient inlet / outlet of the yoke 110 and the patient interface 112.

[0191]

[0218] In other examples, the patient interface 112 may have an integrated yoke or separate inlets and outlets for connection of the inhalation conduit 108 and the exhalation conduit 114, respectively. In such examples, the separate yoke 110 may be omitted from the system.

[0192]

[0219] In the illustrated example, the patient interface 112 is a nasal mask suitable for non-invasive ventilation by delivering humidified breathing gas to the patient's nasal passages, although in other examples, the patient interface 112 may be any invasive or non-invasive patient interface.

[0193]

[0220] Examples of non-invasive patient interfaces include: · A total face mask that creates a seal around the patient's eyes, nose, and mouth; · A full-face mask that forms a seal around the patient's nose and mouth; · A nasal mask that forms a seal around the patient's nose; A small nasal mask that seals around the patient's nostrils and below the nose; · Nasal pillow interfaces that create a seal around each of the patient's nostrils; · Sealing nasal cannulas that create a seal inside each of the patient's nostrils; · Non-sealing nasal cannulas that extend into the patient's nostrils without blocking the nasal passages; · An oral mask that creates a seal around the patient's mouth; Miniature nasal masks, nasal pillow interfaces, or hybrid masks combining nasal cannulas and oral masks; · Combinations of the above (e.g. nasal cannulas and full face masks).

[0194]

[0221] Examples of invasive patient interfaces include: Endotracheal tubes, and Tracheostomy tubes.

[0195]

[0222] Gases exhaled by the patient and excess breathing gas from the gas source 102 that is not inhaled by the patient are received from the Y-shaped tube 110 by an expiratory conduit 114. The expiratory conduit 114 conveys the breathing gas to a gas return inlet 140 of the gas source 102.

[0196]

[0223] The expiratory conduit 114 may have connectors at both ends for establishing and maintaining a respective pneumatic connection with the outlet of the Y-tube 110 and the gas source 102 (or an optional filter intermediate the expiratory conduit 114 and the gas return inlet 140). In some examples, for example, for an adult patient, the connectors may each be an adapter with a 22 mm conical connector, for example a 22 mm tapered female connector. The connectors may have a 1:40 taper conforming to the ISO 5356-1:2015 standard. In other examples, for example, for a neonatal or pediatric patient, the connectors may be any of a 15 mm tapered male connector, a 15 mm tapered female conical connector, a 12 mm tapered male connector, a 12 mm tapered female conical connector, and any combination of two thereof.

[0197]

[0224] Because the gases inhaled and exhaled by the patient are humidified by the humidifier 106 and, in the case of non-invasive ventilation, by the patient's upper airways, the gases received by the expiratory conduit 114 may have a relative humidity as high as 100% (i.e., saturated).

[0198]

[0225] The expiratory conduit 114 does not necessarily have a heater wire. As described in more detail below, advantages may be gained by omitting the heater wire from the expiratory conduit 114. However, in some examples, the expiratory conduit 114 may be provided with a heater wire. In such examples, the heater wire may be wrapped around the outside of the tube wall, embedded in the tube wall, or disposed within the lumen of the expiratory conduit 114.

[0199]

[0226] The expiratory conduit 114 in this example also does not have a water trap or provision for a water trap.

[0200]

[0227] In some examples, the expiratory conduit 114 may have a length of about 1.0 m to about 2.5 m, or about 1.4 m to about 1.6 m, such as about 1.5 m. In some examples, the expiratory conduit 114 may have a length of about 1.5 m to about 1.7 m, such as about 1.6 m. In other examples, such as for anesthesia applications, the expiratory conduit 114 may have a length of about 2.3 m to about 2.5 m, such as about 2.4 m. In other examples, the expiratory conduit 114 may have a length of about 1.1 m to about 1.4 m, or about 1.2 m to about 1.3 m, such as about 1.25 m.

[0201]

[0228] The expiratory conduit 114 may be corrugated. In some examples, for example, with an adult patient, the corrugated expiratory conduit 114 may have a maximum outer diameter (i.e., the diameter of the expiratory conduit 114 as measured on the outer surface at the peak of the corrugation) of about 20 mm to 30 mm, or about 23 mm to 25 mm, such as about 24 mm. In other examples, for example, with a neonatal or pediatric patient, the corrugated expiratory conduit 114 may have a maximum outer diameter of about 10 mm to 20 mm, or about 14 mm to 16 mm, such as about 15 mm. The expiratory conduit 114 may have a corrugated inner surface. In other examples, the expiratory conduit 114 may have a substantially smooth (e.g., non-corrugated) inner surface.

[0202]

[0229] In another example, the exhalation conduit 114 may be spirally wound.

[0203]

[0230] In some examples, one or more of the inhalation conduit 108 and the exhalation conduit 114 may have an identification element. The identification element may be, for example, a resistor, a capacitor, or an integrated circuit (IC). The identification element may enable one or more of the humidifier 106 and the gas source 102 to identify the conduit. In some examples, the one or more of the humidifier 106 and the gas source 102 may automatically adjust one or more treatment parameters based on the identification of the conduit. In some examples, the identification element may enable identification of the type (e.g., model) of the conduit. In some examples, the identification element may communicate with the humidifier 106 or the gas source 102 via a wired connection. In other examples, the identification element may be configured to communicate wirelessly, for example using radio frequency identification (RFID).

[0204]

[0231] A filter (not shown) may be provided between the expiratory conduit 114 and the gas return inlet 140. In some examples, a filter may additionally or alternatively be provided within the gas source 102.

[0205]

[0232] The humidifier supply conduit 104, the humidification chamber 126, the inhalation conduit 108, the yoke 110, and the exhalation conduit 114 together form a ventilation circuit. More specifically, this particular configuration forms a two-limb ventilation circuit 142.

[0206]

[0233] The humidifier supply conduit 104, the humidification chamber 126, and the inlet conduit 108 form an inlet leg 144 of a ventilation circuit 142. The inlet leg 144 extends from the outlet of the gas source 102 to the wye 110.

[0207]

[0234] The expiratory conduit 114 in this example forms an expiratory leg 146 of the ventilation circuit 142. The expiratory leg 146 extends from the wye 110 (or, in some cases, directly from the patient interface 112) to the gas return inlet 140 of the gas source 102 (or, in some cases, to a filter in the gas return inlet 140).

[0208]

[0235] The wye 110 may be considered part of either the inspiratory limb 144 or the expiratory limb 146, or both.

[0209]

[0236] 1, the expiratory conduit 114 may form the entirety of the expiratory limb 146 (excluding the Y-piece 110). In other examples, the expiratory limb may also include one or more of a filter and a second expiratory conduit connected end-to-end to the expiratory conduit 114. In some examples, the expiratory conduit 114 may form a majority of the length of the expiratory limb 146, for example, greater than about 80%, greater than about 90%, or greater than about 95%.

[0210]

[0237] The expiratory conduit 114 may define the entire flow path from the wye 110 (or the patient interface 112, as the case may be) to the gas return inlet 140 of the gas source 102 (or an optional filter, as the case may be). That is, no additional conduit may be required in the expiratory leg of the ventilation circuit.

[0211]

[0238] With the possible exception of portions of the expiratory conduit 114 which are inadvertently or temporarily covered by the patient's extremities, clothing, bedding, etc. during use, the entire expiratory conduit 114 is typically exposed to the surrounding environment, e.g., the ambient air of the hospital room.

[0212]

[0239] The techniques of the present disclosure are particularly suited for use as the expiratory conduit 114 of the respiratory assistance system 100.

[0213]

[0240] In some instances, the techniques of the present disclosure may alternatively or additionally be suitable for use as the inhalation conduit 108. In anesthesia procedures, for example, mitigating condensation in the inhalation conduit 108 may take priority over maintaining 100% relative humidity in the breathing gas delivered to the patient.

[0214]

[0241] 2 illustrates a further example respiratory support system 200 for providing NIV therapy. Similar to respiratory support system 100, respiratory support system 200 includes a gas source 102, a humidifier supply conduit 104, a humidifier 106, an inhalation conduit 108, a yoke 110, a patient interface 112, and an exhalation conduit 114. Except as described below or apparent from the drawings, respiratory support system 200 is similar to respiratory support system 100 of FIG. 1, and descriptions of respiratory support system 100 are intended to apply to respiratory support system 200 as well.

[0215]

[0242] In some instances, heater wires 134, 202 may be provided in both the inhalation conduit 108 and the exhalation conduit 114. However, in some instances, the heater wire 202 in at least the exhalation conduit 114 may be omitted.

[0216]

[0243] The heater wire 202 in the expiratory conduit 114 may, for example, be wrapped around the outside of the tube wall, embedded within the tube wall, or disposed within the lumen of the expiratory conduit 114.

[0217]

[0244] The expiratory heater wire 202 may be powered by the humidifier 106. The heater wire 202 may be controlled by the humidifier controller 130 to mitigate heat loss of the respiratory gas as it travels along the length of the expiratory conduit 114. In some examples, the heater wire 202 may be controlled to increase, maintain, or even decrease the temperature of the respiratory gas as it travels along the length of the expiratory conduit 114.

[0218]

[0245] Sensors 204 (e.g., one or more of temperature, humidity, and flow sensors) may be integrated into the inhalation conduit 108, within a connector of the inhalation conduit 108. One or more of the sensors 204 may be electrically connected to the humidifier 106 by a sensor wire embedded in the tube wall or by a sensor wire provided within the lumen of the inhalation conduit 108.

[0219]

[0246] The inhalation conduit 108 may have an electro-pneumatic connector 206 with integrated electrical contacts that may be configured to establish both a pneumatic and an electrical connection with the humidifier 106 in a single action upon physically connecting the connector to the humidifier 106. This may avoid the need for a removable sensor probe 136 and sensor lead 138 of the respiratory assistance system 100 shown in FIG.

[0220]

[0247] The humidifier 106 may have a sensor probe 136 (hidden in FIG. 2) at or near the outlet of the humidification chamber 126, as described in more detail with respect to FIG.

[0221]

[0248] The gas source 102 in this example has a supplemental gas inlet 208 for the provision of supplemental gas, such as supplemental oxygen, to the patient.

[0222]

[0249] The technology of the present disclosure is particularly suitable for use as the expiratory conduit 114 of a respiratory assistance system 200. In some instances, such as in anesthesia procedures, it may alternatively or additionally be suitable for use as the inspiratory conduit 108.

[0223]

[0250] 3 shows in greater detail an example of a humidifier 106 that may be used in the respiratory assistance system 200. Also shown (in part) are the humidifier supply conduit 104 and the inlet conduit 108.

[0224]

[0251] The humidifier 106 depicted in Figure 3 is an F&P 950™ respiratory humidifier available from Fisher & Paykel Healthcare. The humidifier 106 shown has a heater base 302 and a removable and replaceable humidification chamber 126. The heater base 302 may include a chamber heater 128 (hidden in Figure 3), a user interface 132, and a controller (not shown). The humidifier 106 may also have a removable and replaceable cartridge 304.

[0225]

[0252] The user interface 132 in this example may include a touchscreen display 306 (i.e., for receiving input from and providing input to a user). The user interface 132 may also include one or more of a switch 308 and an indicator light 310. The switch 308 may be a mechanical (e.g., push button or toggle switch) or a touch-controlled electrical (e.g., capacitive) switch. The switch 308 may be a power / standby button. The indicator light 310 may be used to indicate when an error condition occurs. The indicator light 310 may be a light-emitting diode (LED). The indicator light 310 may be any suitable shape or form (e.g., bar-shaped, circular, rectangular, square, the perimeter of the touchscreen display 306, etc.). The indicator light 310 may selectively illuminate a single color (e.g., red, yellow, or green) or illuminate two or more different colors (e.g., yellow and red) to indicate error conditions of different priority.

[0226]

[0253] The humidification chamber 126 may be removably received by the heater base 302 in thermal contact with a chamber heater 128 (hidden beneath the humidification chamber 126 in FIG. 3).

[0227]

[0254] The cartridge 304 may house electronics. The electronics may include one or more sensors. The sensors in the cartridge 304 may sense one or more properties of the respiratory gas flowing through the humidification chamber 126 during use. The sensors may be provided on one or more sensor probes 136 (hidden) that protrude from the cartridge. The sensor probes 136 may protrude from one or more apertures at the inlet and outlet of the humidification chamber during use. The apertures may be closed by elastomeric seals. The elastomeric seals may be elastically deformed by the sensor probes 136 when the humidification chamber 126 is received by the heater base 302.

[0228]

[0255] The cartridge 304 may include an electrical connector that electrically connects with the heater base 302 for communication (e.g., serial communication) with the controller. The cartridge 304 may include a microcontroller communicatively coupled to the sensor and the controller.

[0229]

[0256] In use, the outlet end of the humidifier supply conduit 104 is pneumatically coupled to the inlet of the humidification chamber 126. The electro-pneumatic connector 206 of the inlet conduit 108 is electrically coupled to the cartridge 304 and pneumatically coupled to the outlet of the humidification chamber 126 to convey a flow of humidified gas towards the patient. The electro-pneumatic connector 206 may establish a removable, lockable connection with one or more of the humidification chamber 126 and the cartridge 304. The electro-pneumatic connector 206 may have a release button 312. The release button 312 may be actuated to facilitate disconnection of the electro-pneumatic connector 206 from the humidifier 106.

[0230]

[0257] The electro-pneumatic connector 206 may be configured to be physically and pneumatically coupled to the humidification chamber 126 before the humidification chamber 126 is placed on the heater base 302. The electro-pneumatic connector 206 may also be configured to be electrically connected to the humidifier 106 when the humidification chamber 126 is placed on the heater base 302 in a sliding motion (e.g., horizontally).

[0231]

[0258] Alternatively, or in addition, the electro-pneumatic connector 206 may be configured such that it can be physically and pneumatically coupled to the humidification chamber 126 when the humidification chamber 126 is already installed in the heater base 302, and can be physically and electrically connected to the humidifier 106 substantially simultaneously, e.g., in a single operation.

[0232]

[0259] The inlet conduit 108 in one example may have a substantially smooth inner surface. The inlet conduit 108 may have a lower resistance to flow than a comparable corrugated tube and accordingly may have a relatively small inner diameter (when compared to the minimum inner diameter of the corrugated tube). For example, the inlet conduit 108 in this example may have a substantially uniform inner diameter of about 15 mm to 19 mm, e.g., about 17 mm, for an adult patient, and about 10 mm to 14 mm, e.g., about 12 mm, for a neonatal or pediatric patient. In some examples, the inlet conduit 108 may be spirally wound.

[0233]

[0260] The electro-pneumatic connector 206 may have electrical terminals respectively coupled to at least one of the pair of sensor wires and the pair of heater wires 134 (hidden in FIG. 3). One or more of the sensor wires and heater wires 134 may be embedded within the tube wall of the air inlet conduit 108. The sensor wires and heater wires 134 may form respective sensing and heating circuits.

[0234]

[0261] The electro-pneumatic connector 206 may have electrical terminals electrically coupled to an identification element, e.g., a resistor, embedded within the electro-pneumatic connector 206. The controller of the humidifier 106 may be configured to identify the type of inhalation conduit 108 coupled to the humidifier 106, e.g., by applying a voltage across the respective electrical terminals and measuring the current through the resistor. A resistance of, e.g., about 100 ohms (Ω) may indicate to the controller that a first type of inhalation conduit 108, e.g., an adult conduit, is connected to the humidifier 106, and a resistance of, e.g., about 200 Ω may indicate to the controller that a second type of inhalation conduit 108, e.g., a neonatal conduit, is connected to the humidifier 106.

[0235]

[0262] In other examples, the electro-pneumatic connector 206 may have an identification element that includes an IC having a non-transitory memory configured to store identification data, as described above.

[0236]

[0263] The electrical terminals of the electro-pneumatic connector 206 may be configured to establish electrical connections with corresponding terminals on the cartridge 304. Thus, an existing heater base 302 may be retrofitted with a replacement cartridge 304 that may include one or more of the additional electronics and electrical terminals to provide new functionality to the humidifier 106. Similarly, if desired, the humidifier 106 may be retrofitted with a replacement cartridge 304 for compatibility with an alternative inlet conduit. Alternatively, the electrical terminals of the electro-pneumatic connector 206 and cartridge 304 may be arranged such that selected "core" terminals establish electrical connections with corresponding terminals of two or more different cartridges, while "optional" terminals or pads establish electrical connections only with specific terminals or pads of selected cartridges that are configured to utilize those connections.

[0237]

[0264] At the distal end of the inhalation conduit 108 (i.e., the patient end, not shown in FIG. 3), a sensor, such as a temperature sensor, may be electrically coupled to a pair of sensing wires to form a sensing circuit. The heating wires may be electrically coupled to each other to form a heating circuit. Additional wires or conductors may be similarly electrically coupled at the distal end of the tube, if desired.

[0238]

[0265] The humidifier 106, e.g., the cartridge 304, may have a socket or an integrated cable configured for connection to the expiratory conduit 114, e.g., to provide power to the optional expiratory heater wire 202 (not shown in FIG. 3).

[0239]

[0266] Referring to FIG. 4, a further exemplary respiratory assistance system 400 is shown, this time in the form of a bubble CPAP system for providing bubble continuous positive airway pressure (CPAP) therapy.

[0240]

[0267] Except as described below and shown in the drawings, the respiratory assistance system 400 of FIG. 4 may be similar to the respiratory assistance systems 100, 200 of FIGS. 1 and 2, respectively.

[0241]

[0268] The gas delivered to the patient may be ambient air, oxygen, a mixture of the two, or a mixture of ambient air and other supplemental gases. The gas may include a drug. The drug may be added via a nebulizer. In this example, the gas source 102 may be, or may include, a wall source, for example, of a hospital. The flow of gas delivered to the patient in the respiratory assistance system 400 may be delivered at a substantially constant flow rate.

[0242]

[0269] For neonatal or pediatric patients, the breathing gas in a bubble CPAP system may be delivered to the patient at a flow rate of about 2 liters per kilogram per minute (L / kg / min). In some examples, the flow rate may be between about 1 L / min and 15 L / min, between about 4 L / min and 15 L / min, or between about 6 L / min and 8 L / min. The breathing gas may be delivered to the patient at a pressure of about 3 cmH2O to 10 cmH2O.

[0243]

[0270] The respiratory assistance system 400 may include a pressure regulator 402. In the illustrated example, the pressure regulator 402 is in the form of a bubbler.

[0244]

[0271] The bubbler may be configured to contain a liquid 404, for example water. The bubbler may have an adjustable inlet probe 406 configured to extend into the bubbler for immersion in the liquid 404. The inlet probe 406 may be configured to pneumatically couple to the expiratory conduit 114. The bubbler may act as a pressure regulator by venting gas from the respiratory assistance system 400 if the pressure exceeds a desired level. This may maintain an average or mean pressure at a target level. The target pressure level may be adjusted by immersing the inlet probe 406 to a desired depth in the liquid 404.

[0245]

[0272] A potential problem with condensation in the ventilation circuit of a bubble CPAP system is that at least some of the condensation may be discharged into the bubbler, which may increase the volume of liquid in the bubbler and increase the depth of the inlet probe 406. This may cause the positive end expiratory pressure (PEEP) to increase above the target level when in use.

[0246]

[0273] During use, gas escapes from the end of the inlet probe 406 as bubbles to the surface of the liquid 404. This bubbling can cause small fluctuations in the pressure of the gas. These fluctuations can have therapeutic benefits for the patient.

[0247]

[0274] The respiratory assistance system 400 may have a pressure relief valve 408 to vent excess gas if the pressure exceeds a selected level.

[0248]

[0275] The respiratory assistance system 400 of this example provides another example of a dual limb ventilation circuit 142. The term "circuit" does not imply that the ventilation circuit must necessarily form a closed loop, although in at least some examples it may. The inspiratory leg 144 may also include an optional pressure relief valve 408. The expiratory leg 146 may also include a pressure regulator 402.

[0249]

[0276] 5, a further example of a respiratory assistance system 500 is shown, again in the form of a bubble CPAP system. Except as described below, the respiratory assistance system 500 of FIG. 5 may be similar to the respiratory assistance system 400 of FIG. 4.

[0250]

[0277] In this example, the gas source 102 includes a flow generator, e.g., a blower 502. The blower 502 may include an electric motor that drives an impeller that pressurizes ambient air to create a supply of respiratory gas. By using the flow generator to generate the flow of gas, the respiratory assistance system 500 can provide bubble CPAP therapy without the need for a wall source. The gas source 102 may include a battery power source for the blower 502. This battery power source allows the respiratory assistance system 500 to provide therapy, at least temporarily, without the gas source 102 being plugged into a power outlet with a power cable, for example while the patient is being moved between wards.

[0251]

[0278] The flow generator may draw in ambient air for delivery to the patient. The respiratory assistance system 500 may be simpler and less expensive to use as it does not require a gas reservoir or a gas source, e.g., a wall source. Using the flow generator to pressurize the abundant ambient air may eliminate the risk of the gas supply being depleted, which may result in an interruption in patient treatment.

[0252]

[0279] The gas source 102 and humidifier 106 may be integrated as a single respiratory therapy device 504. In some examples, the gas source 102 and humidifier 106 may share a single housing 506. The humidification chamber 126 may be removable from the housing 506 for replacement or refilling. In other examples, the housing 506 may be formed by a separate flow generator housing and a humidifier housing that can be attached together to form the integrated respiratory therapy device 504.

[0253]

[0280] The humidifier supply conduit 104 may be or may include a duct within the housing 506 .

[0254]

[0281] The respiratory therapy device 504 may include a gas inlet 118. The gas inlet 118 may receive ambient air from the environment surrounding the respiratory therapy device 504. The gas inlet 118 may include a filter for filtering the ambient air.

[0255]

[0282] The respiratory therapy device 504 may have a supplemental gas inlet (not shown) for receiving a supplemental gas, e.g., oxygen, or gas to be delivered to the patient. The respiratory therapy device 504 may have a gas mixer for mixing the supplemental gas with ambient air. The controller may be configured to control the concentration of the supplemental gas delivered to the patient, e.g., using a proportional valve (not shown).

[0256]

[0283] The gas source 102 and the humidifier 106 may share a single controller (not shown) that controls the operation of any one or more of the chamber heater 128, the heater wires 134, the blower 502, and the proportional valve.

[0257]

[0284] In some examples, the expiratory conduit 114 does not have a heater wire. In other examples, the expiratory conduit 114 may have a heater wire. In some examples, the expiratory conduit 114 does not have a water trap. In some examples, the expiratory conduit 114 has neither a heater wire nor a water trap.

[0258]

[0285] The techniques of the present disclosure are particularly suited for use in the expiratory conduit 114 of a respiratory assistance system 400.

[0259]

[0286] One or more of the inspiratory conduits 108 and expiratory conduits 114 of each of the exemplary respiratory assistance systems 100, 200, 400, 500 (and others) may be sold separately or packaged and sold as part of a ventilation circuit kit. A ventilation circuit kit may include a combination of any two or more of the following: ·Humidifier supply conduit 104; · Humidification chamber 126; · Intake duct 108; ·Y-tube 110; · Patient interface 112; Catheter mounts; · Exhalation conduit 114; ·filter; · Pressure relief valve 408; pressure regulator 402; and · Pressure lines and other accessories such as one or more connector adapters.

[0260]

[0287] In some examples, the ventilation circuit kit may include the inhalation conduit 108, the Y-shaped conduit 110, and the exhalation conduit 114. The ventilation circuit kit may optionally include one or more of the other components listed above, such as the humidification chamber 126.

[0261]

[0288] In some examples, the ventilation circuit kit may include a humidifier supply conduit 104, an inhalation conduit 108, a yoke 110, an exhalation conduit 114, and a filter. The ventilation circuit kit may also include a humidification chamber 126. The ventilation circuit kit may optionally include one or more of the other components listed above.

[0262]

[0289] In other examples, the ventilation circuit kit may include a humidifier supply conduit 104, an inhalation conduit 108, an exhalation conduit 114, and a pressure regulator 402. The pressure regulator 402 may be a bubbler. The ventilation circuit kit may also optionally include one or more of a humidification chamber 126 and a pressure relief valve 408. The ventilation circuit kit may optionally include one or more of the other components listed above.

[0263]

[0290] In some instances, the ventilation circuit kit may be partially or entirely pre-assembled. Pre-assembly of the ventilation circuit may facilitate quicker set-up of the ventilation circuit. Pre-assembly may reduce the risk of misconnection, for example, transposition of the inspiratory conduit 108 and expiratory conduit 114.

[0264]

[0291] In some instances, the ventilation circuit kits may be packaged together, for example in a sealed plastic bag. Multiple ventilation circuit kits, for example 10 ventilation circuit kits, may be packaged together, for example in a cardboard box.

[0265] Surgical Air Delivery System

[0292] 6, there is shown a surgical insufflation system 600. The surgical insufflation system 600 may be configured to deliver insufflation gas to a body cavity of a patient, for example, for a laparoscopic procedure.

[0266]

[0293] In some instances, the insufflation gas may be carbon dioxide. In some instances, a drug may be added to the insufflation gas.

[0267]

[0294] The insufflation gas is pressurized to a pressure above atmospheric pressure and may create a working space within the patient's body, for example, within the abdominal or peritoneal cavity, for a surgeon or surgical team to perform a surgical procedure, which may include cauterization, which generates surgical smoke within the working space.

[0268]

[0295] The surgical insufflation system 600 may include one or more of the gas source 102, an insufflation device supply conduit 602, an insufflation device 604, an insufflation gas filter (not shown), a humidifier supply conduit 104, a humidifier 106, a delivery conduit 606, a surgical cannula 608, and a smoke evacuation system 610. In other examples, the surgical insufflation system may include a recirculation system (not shown), for example in place of the smoke evacuation system 610.

[0269]

[0296] The gas source 102 may be, for example, a wall source 612 or a compressed gas cylinder 614. In other examples, the insufflation device may be configured to pressurize ambient air.

[0270]

[0297] One or more insufflation gas filters may be provided between the insufflation device 604 and the surgical cannula 608. An insufflation gas filter may be provided between the insufflation device 604 and the humidifier 106, for example between the outlet of the insufflation device 604 and the inlet end of the humidifier supply conduit. An insufflation gas filter may alternatively or additionally be provided between the humidifier 106 and the surgical cannula 608, for example between the outlet of the humidifier 106 and the inlet end of the delivery conduit 606.

[0271]

[0298] An adapter (not shown) may be provided at the outlet of the insufflation device 604 , for example between the insufflation device 604 and the insufflation gas filter or humidifier supply conduit 104 .

[0272]

[0299] In other examples, such as in a surgical insufflation system configured for open surgery, the insufflation gas filter or humidifier supply conduit 104 may be connected directly to the gas outlet port of a CO2 gas supply stand.

[0273]

[0300] The humidifier 106 may include one or more of the humidification chamber, chamber heater, humidifier controller, and user interface described above with respect to the exemplary respiratory assistance systems 100, 200, 400, 500. The humidifier 106 in this example may be an F&P HumiGard™ SH870 Surgical Humidifier, also available from Fisher & Paykel Healthcare. In other exemplary surgical air delivery systems, the humidifier 106 may be omitted or may be rendered inoperative during the entire procedure or portions of the procedure.

[0274]

[0301] A funnel may be provided to aid in filling the humidification chamber 126 with liquid, for example sterile water, via the inlet or outlet of the humidification chamber 126 .

[0275]

[0302] The connector on one end of the delivery conduit 606 can be a luer lock connector. The luer lock connector may be configured to connect directly to a surgical cannula 608. In other examples, such as in a surgical insufflation system configured for open surgery, the delivery conduit 606 may instead be configured to connect to a diffusion device.

[0276]

[0303] The delivery conduit 606 may otherwise be similar to the inhalation conduit 108 of the respiratory assistance systems 100, 200, 400, 500. For example, the delivery conduit 606 may include a heater, such as the heater wire 134. In some examples, the delivery conduit 606 may be corrugated. In other examples, the delivery conduit may be coiled.

[0277]

[0304] The smoke exhaust system 610 may include an exhaust conduit 616 and an exhaust filter 618 .

[0278]

[0305] In some examples, the exhaust conduit 616 may be between about 0.8 m and 1.2 m in length, for example about 1.0 m.

[0279]

[0306] The smoke exhaust system 610 may be configured to couple to a vacuum source 620, for example a wall source. In some examples, the smoke exhaust system 610 may include an additional exhaust conduit 622. The additional exhaust conduit 622 may be configured to be coupled between the exhaust filter 618 and the vacuum source 620. In some examples, the additional exhaust conduit 622 may have generally the same structure as the exhaust conduit 616. In some examples, the additional exhaust conduit 622 may have the same length as the exhaust conduit 616. In other examples, the additional exhaust conduit 622 may have a different structure than the exhaust conduit 616. In some examples, the additional exhaust conduit 622 may differ from the exhaust conduit 616 in one or more of length, diameter, material.

[0280]

[0307] A recirculation system (not shown) may include an exhaust conduit 616, an exhaust filter 618, and a further exhaust conduit coupled to a further surgical cannula, which may allow the exhausted insufflation gas to be filtered and recirculated back to the patient's body cavity.

[0281]

[0308] In the illustrated exemplary surgical air delivery system 600, the humidifier supply conduit 104, the humidification chamber 126, the delivery conduit 606, the exhaust conduit 616, the exhaust filter 618, and the further exhaust conduit 622 form an air delivery circuit. More specifically, this particular configuration forms a dual limb air delivery circuit 624. The humidifier supply conduit 104, the humidification chamber 126, and the delivery conduit 606 may be said to form an inlet branch of the dual limb air delivery circuit 624. The smoke exhaust system 610 (e.g., the exhaust conduit 616, the exhaust filter 618, and the further exhaust conduit 622) may be said to form an outlet branch of the dual limb air delivery circuit 624.

[0282]

[0309] Also shown in FIG. 6 is a scope 626 and a laparoscopic monitor 628 .

[0283]

[0310] In use, insufflation gas is supplied from the gas source 102 through the insufflation device supply conduit 602 to the insufflation device 604. The insufflation device 604 may control the pressure of the insufflation gas. The insufflation device 604 supplies the insufflation gas to the inlet of the humidifier 106 via the humidifier supply conduit 104. The insufflation gas is heated and humidified by the humidifier 106. The heated and humidified insufflation gas is then supplied via the delivery conduit 606 to the surgical cannula 608 and thereafter to the patient's body cavity.

[0284]

[0311] In some instances, the pressure of the insufflation device 604 can be set between about 5 mm / Hg and 20 mm / Hg depending on the size of the patient and the amount of inflation required. The flow rate of the insufflation device 604 can be set between about 1 L / min and 12 L / min depending on the requirements of a particular operation.

[0285]

[0312] Insufflation gases and surgical smoke (if any) may flow from the patient's body cavity into the surgical cannula 608 and through the exhaust conduit 616 to the exhaust filter 618. In some instances, insufflation gases and surgical smoke (if any) may flow from the patient's body cavity into a dedicated exhaust cannula (not shown) and through the exhaust conduit 616 to the exhaust filter 618. That is, the surgical cannula 608 is not necessarily connected to the exhaust conduit 616.

[0286]

[0313] The exhaust filter 618 may include a filter media. The filter media may capture contaminants in the insufflation gas or surgical smoke. The contaminants may include one or more of particulate matter, odors, and gaseous hydrocarbons. In some examples, the filtered gas downstream of the exhaust filter 618 may be nearly 100% carbon dioxide. In some examples, the exhaust filter removes 99.999% of all particles, cells, and viruses. In some examples, the exhaust filter may have a retention capacity of up to 0.02 microns. The filtered gas may be exhausted to the ambient air. It may be exhausted away from the patient and the surgical team.

[0287]

[0314] In some examples, the humidifier 106 may be configured to humidify the insufflated gas to or near saturation, i.e., 100% relative humidity. Because the patient's body cavity is already moist and humid, the insufflated gas may not lose significant amounts (if any) of water within the body and may become fully saturated if the saturation point has not been reached.

[0288]

[0315] In other examples, the surgical insufflation system may omit the humidifier 106 and provide the patient with a relatively dry insufflation gas, e.g., less than about 90%, less than about 80%, or less than about 70% relative humidity. This relatively dry insufflation gas may be humidified as it passes through the patient's body cavity, absorbing moisture from the relatively warmer, more humid environment within the body cavity above the internal organs.

[0289]

[0316] As the insufflation gas leaves the patient's body cavity, it travels along the tube walls of the exhaust conduit 616, which may be cooler than the insufflation gas because they are exposed to the ambient air. Water vapor in the insufflation gas may condense from the gas onto the tube walls of the exhaust conduit 616. Water vapor may similarly condense on or within one or more other components of the delivery circuit, such as the exhaust filter 618 and the further exhaust conduit 622.

[0290]

[0317] One or more of the water vapor condensing in the exhaust filter 618 and the effluent water vapor from the exhaust conduit 616 may saturate the exhaust filter 618. The exhaust filter 618 may become at least partially clogged. The blockage of the exhaust filter 618 may increase back pressure. The blockage of the exhaust filter 618 may prevent dissipation of surgical smoke within the patient's body cavity. Surgical smoke lodged in the patient's body cavity or within the exhaust conduit 616 may be dangerous to the patient. The lodged surgical smoke may obscure or impede the surgeon's vision. The obstructed filtration may allow contaminants that may be harmful to the operating room to escape.

[0291]

[0318] The techniques of the present disclosure are particularly suitable for use in the smoke exhaust system 610 of the surgical air delivery system 600, for example as one or more of the exhaust conduit 616 and the further exhaust conduit 622. In some examples, the smoke exhaust system 610 does not have one or more of a heater wire and a water trap. However, in some examples, one or more of the exhaust conduit 616 and the further exhaust conduit 622 may have a heater wire.

[0292]

[0319] The smoke evacuation system 610 of the exemplary surgical insufflation system 600 may be sold separately or as part of an insufflation circuit kit. The insufflation circuit kit may include an evacuation conduit 616 and one or more of the following: · insufflation system supply conduit 602; ·adapter; · Air delivery gas filters; ·Humidifier supply conduit 104; · Humidification chamber 126; ·funnel; ·Delivery conduit 606; Surgical cannulas 608; · Diffusers; · exhaust filters 618; · Further exhaust conduit 622 .

[0293]

[0320] In one example, the air delivery circuit kit may include an exhaust conduit 616 and an exhaust filter 618 .

[0294]

[0321] In another example, the air delivery circuit kit may include an adapter, an air delivery gas filter, a humidifier supply conduit 104, a humidification chamber 126, a funnel, a delivery conduit 606, an exhaust conduit 616, and an exhaust filter 618.

[0295]

[0322] In another example, the air delivery circuit kit may include an air delivery gas filter, a humidifier supply conduit 104, a humidification chamber 126, a delivery conduit 606, an exhaust conduit 616, and an exhaust filter 618.

[0296]

[0323] In some examples, the air delivery circuit kit, or one or more components of the kit, may be packaged, for example, in a sealed plastic bag. Multiple air delivery circuit kits, for example, 10 air delivery circuit kits, may be packaged together, for example, in a cardboard box.

[0297]

[0324] In some instances, the air delivery circuit kit may be partially or entirely pre-assembled. Pre-assembly may facilitate faster set-up of the air delivery circuit. Pre-assembly may reduce the risk of misconnections.

[0298]

[0325] In one example, the insufflation gas filter, the humidifier supply conduit 104, and the humidification chamber 126 may be pre-assembled with each other. The delivery conduit 606 in this example is not pre-assembled with any other components of the delivery circuit. The insufflation gas filter, the humidifier supply conduit 104, and the humidification chamber 126 may be non-sterile. The delivery conduit 606 may be sterile. The delivery conduit 606 may be individually packaged, for example, in a sealed plastic bag. The individually packaged delivery conduit 606 may be packaged with the insufflation gas filter, the humidifier supply conduit 104, and the humidification chamber 126, for example, in another plastic bag.

[0299] conduit structure

[0326] An exemplary conduit according to the present disclosure is described below with reference to a conduit 700 suitable for use as an expiratory conduit 114 in an exemplary respiratory assistance system 100, 200, 400, 500. However, the present technology may be suitable for use as any one of the other conduits in the respiratory assistance systems 100, 200, 400, 500, alternative respiratory assistance systems, or other medical systems. For example, a conduit according to the present disclosure may be used as an inhalation conduit 108 in a ventilation circuit configured for use with an anesthesia machine, or as an exhaust conduit 616 in, for example, a surgical ventilation system 600.

[0300]

[0327] Condensate build-up in the inspiratory conduit of a respiratory support system may be reduced by reducing the level of active humidification, thereby reducing the relative humidity of the gas delivered to the patient. However, this is not optimal for patient comfort or recovery. Also, this does not necessarily address condensation in the expiratory conduit due to additional humidification of the gas in the patient's upper airway during NIV therapy. Also, this does not necessarily address condensation that flows from intervening patient interface components, such as a catheter mount, into one or more of the inspiratory and expiratory limbs.

[0301]

[0328] Other options for mitigating condensation in the inhalation and exhalation conduits include the use of one or more of insulation, water traps, and heaters.

[0302]

[0329] Insulating the conduit reduces the rate of heat loss of the breathing gas as it travels along the length of the conduit. The conduit may, for example, include an outer jacket of insulating material or an air gap in the tube wall. However, such insulation may increase one or more of the diameter, weight, and cost of the conduit, reduce the flexibility of the conduit, or may have only limited effectiveness. Additionally, insulation does not address condensation that may flow into the conduit from other sources, such as any one or more of the gas source, filter, y-tube, catheter mount, and patient interface.

[0303]

[0330] The water trap is intended to collect and dispose of accumulated condensate. The inspiratory and expiratory conduits are often dangling between the patient and the ventilator, respectively, and condensate may accumulate at the lowest point of the tube. The water trap is usually located at or near the middle of the expiratory limb, so as to be close to the lowest expected position of the expiratory limb when in use. However, the location of the water trap is fixed and may not necessarily coincide with the lowest position. The healthcare professional may need to periodically manipulate the conduit by lifting a portion of the conduit so that the accumulated condensate drains towards the water trap. If not done carefully, this may simultaneously drain some of the condensate towards, for example, the patient or the ventilator. Condensate may also become trapped in the corrugated parts of the conduit. Furthermore, the increased weight of the water trap and the collected condensate may increase the drag on the tube. The water trap also needs to be emptied periodically, which may interrupt the patient's treatment. Emptying the water trap also carries the risk of infection. Water traps do play a role in dealing with condensation problems once they occur, and they may play a role in dealing with condensation from other sources as well, but they don't address the source of the problem and have their own drawbacks.

[0304]

[0331] In some instances, a conduit according to the present disclosure may omit a water trap.

[0305]

[0332] The heater is intended to maintain or raise the temperature of the breathing gas above the dew point, which may mitigate the formation of condensation within the conduit. The heater may comprise a resistive heater wire disposed within the lumen of the conduit or embedded within the tube wall of the conduit. Potential disadvantages of heater wire may include one or more of the following: · the need to establish an electrical connection between the conduit and a power source (such as a humidifier in a respiratory support system); - Complex heating and humidification algorithms; - the temperature and absolute / relative humidity of the gas received by the ventilator are relatively high; · The need for compliance with additional standards specific to heated wire vent tubes (e.g., International Electrotechnical Commission (IEC) 60601-1 (IEC:2005+A1:2012(E)) Clause 11.2); Reduced shelf life; and · The power consumption during use of a heating conduit contributes to the overall carbon dioxide emissions of the heating conduit over its lifetime, e.g. about 50% of the carbon dioxide emissions.

[0306]

[0333] An alternative form of heater is a "water jacket" heater, whereby heated water (or other liquid) is circulated around the outside of the lumen to heat the flow of breathing gas within the lumen, which has the further disadvantages of increasing the bulk, weight and cost of the conduit, adding the need to heat and pump the water, and risking water leaking into the lumen of the conduit.

[0307]

[0334] In some examples, a conduit according to the present disclosure may omit both the heater, e.g., the heater wire, and the water jacket. In other examples, the conduit may include the heater wire. However, omission of the heater wire may have one or more of the following advantages: · Simplification of manufacturing; · Reducing manufacturing and material costs; · Improved usability by avoiding the need to establish an electrical connection between the conduit and a power source such as the humidifier 106 or gas source 102; Avoidance of the need for heater wire control algorithms; · Improved safety; Reduced surface temperature; -Improved aerodynamic performance; · Reducing regulatory burden (e.g., International Electrotechnical Commission (IEC) 60601-1 (IEC:2005+A1:2012(E)) Clause 11.2); · A reduction in the temperature of the gas received at the gas return inlet 140; · Improved reliability; · Longer shelf life (e.g. where electrical insulation is a limiting factor); Extended period of use (e.g. where electrical insulation is a limiting factor); and · Reduction in pipeline electricity consumption and therefore carbon dioxide emissions.

[0308]

[0335] Another method of mitigating condensation in conduits, particularly expiratory conduits, is to form the tube walls from a breathable material (defined in the glossary below). Breathable materials are permeable to water molecules but relatively impermeable to liquid water and respiratory gases. Water molecules within the lumen of such conduits can be absorbed by the breathable material of the tube walls, diffuse through the breathable material, and released into the surrounding air down a gradient from the more humid side to the less humid side. This is known as the solution-diffusion mechanism. In contrast, porous membranes such as expanded PTFE (ePTFE) fabrics (e.g., Gore-Tex® fabrics available from WL Gore & Associates) are permeable to water molecules (and potentially pathogens) by a pore-flow mechanism, in which water passes through pores (i.e., holes) that extend from one side of the membrane to the other.

[0309]

[0336] When viewed under a scanning electron microscope (SEM) at 150x or 2500x magnification, an unfoamed breathable material may be completely devoid of channels and pores. A foamed breathable material may have numerous closed cell voids, but no open channels or pores extending from one major surface to the other. A porous membrane has open channels or pores extending from one major surface to the other.

[0310]

[0337] The use of breathable materials can reduce the absolute humidity of the respiratory gas flow within the lumen as the respiratory gas travels along the length of the conduit, resulting in a reduction in the dew point of the respiratory gas. Examples of such conduits are the expiratory conduits of various ventilation circuits using EVAQUA™ technology available from Fisher & Paykel Healthcare, such as the RT280™ and RT340™ adult ventilation circuits using EVAQUA™ technology. These expiratory conduits omit the water trap but include heater wires. These have been shown to be effective in reducing the formation of condensation within the conduit. However, it has been found that, at least under some conditions, condensation from other sources (such as catheter mounts, patient-derived, nebulizers, etc.) can accumulate within the conduit during extended use.

[0311]

[0338] Details of such breathable conduits are disclosed in US Pat. Nos. 6,769,431 and 10,532,177, both assigned to Fisher & Paykel Healthcare Limited.

[0312]

[0339] It has been found that breathable materials that are relatively more permeable to water molecules can be more effective at mitigating condensation, however, such breathable materials can absorb relatively large amounts of water molecules during use, which has been found to significantly alter the mechanical properties of the conduit.

[0313]

[0340] This poses challenges in meeting certain standards or other design requirements. Respiratory ventilation circuit conduits may be required to meet certain minimum requirements as defined by formal standards such as ISO 5367:2014(E) (Anesthetic and respiratory equipment - Ventilation sets and connectors). This standard specifies basic requirements such as: i. Materials, ii. Length; iii. Connection; iv. Leaks, v. Resistance to flow, and vi. Compliance.

[0314]

[0341] FIG. 7 illustrates an isometric schematic view of an exemplary conduit 700 according to the present disclosure.

[0315]

[0342] The conduit 700 can be used in respiratory assistance systems such as respiratory assistance systems 100, 200, 400, 500 shown by way of example in Figures 1, 2, 4, and 5, respectively. In particular, the conduit 700 can be used as the expiratory conduit 114 in the respiratory assistance system 100 and will be described in this context hereinafter.

[0316]

[0343] As shown, the conduit 700 includes an elongated tube 702 , a sheath 704 provided around the elongated tube 702 , and a pair of connectors 706 at each end of the elongated tube 702 .

[0317]

[0344] 7-16, the structure of the conduit 700, and in particular the structure of the sheath 704, are in schematic form for clarity. The structure of one example of the sheath 704 is described in further detail below with respect to Figures 18 and 19. Additionally, it should be understood that in other examples, the sheath 704 may be omitted.

[0318]

[0345] In another example, the conduit may have two (or more) elongated tubes. The two elongated tubes may have different properties. The different properties may include, for example, one or more of different materials, corrugations, structures, breathability, diameters, insulation, or heating. The two elongated tubes may be disposed end-to-end. They may be secured together or fluidly coupled by an intermediate connector. For example, the intermediate connector may be provided at approximately the midpoint of the conduit or at a point about one-third of the length of the conduit.

[0319]

[0346] Both the elongate tube 702 and the sheath 704, and thus the conduit 700, may be flexible. This may reduce tube drag. As described in more detail below, the flexibility of the elongate tube 702 may change during use. However, the sheath 704 may mitigate this effect.

[0320]

[0347] The conduit 700 may be relatively lightweight, which may reduce tube drag. The omission of a water trap provides flexibility that may allow the conduit 700 to be relatively lightweight. In use, accumulation of condensate in the water trap may cause the conduit to be relatively heavy. In some examples, the conduit 700 may have a mass of between about 130 gm and 170 gm, between about 140 gm and 160 gm, or between about 145 gm and 155 gm, such as about 150 grams (gm), in an equilibrium state. In some examples, the conduit 700 may have a mass of between about 260 gm and 300 gm, between about 270 gm and 290 gm, or between about 275 gm and 285 gm, such as about 280 gm, in a conditioned state.

[0321]

[0348] The elongated tube 702 is defined by a tube wall that defines an interior lumen for the passage of breathing gas from one end of the conduit 700 to the other. In the illustrated example, the conduit 700 has a single elongated tube 702 and a single lumen, whereas two or more parallel tubes define two or more parallel lumens. Multiple smaller diameter tubes may be prone to one or more of kinking and obstructions and may be less flexible than a comparable single tube / lumen.

[0322]

[0349] The tube wall may have a wavy profile including a plurality of parallel annular corrugations, as described in further detail below. The corrugations may have one or more of the following advantages: improving the flexibility of the elongate tube 702, facilitating controlled deformation, and reducing kinking.

[0323]

[0350] The corrugations may extend along the length of the elongated tube 702 between the connectors 706. More than 80% or more than 90% of the length of the elongated tube 702 may be corrugated. As described in more detail below, the end portions of the elongated tube 702 engaged by the connectors 706 may not be corrugated. The lack of corrugations in the end portions may improve the seal between the elongated tube 702 and the connectors 706. In other examples, the tube walls may have a helical (e.g., single helix or double helix) profile. In some examples, one or more portions of the elongated tube 702 between the connectors may not have a corrugated / helical profile.

[0324]

[0351] The tube walls of the elongated tube 702 may be formed from a breathable material (described in further detail below) that is permeable to water molecules. The breathable material may be highly permeable to water molecules. The breathable material allows water molecules to pass through the tube walls to the surrounding air. The breathable material of the tube walls may reduce the absolute humidity of the breathing gas in the lumen as it travels along the length of the conduit 700 during use. The breathable material of the tube walls may dissipate condensed water or other liquids, e.g., from the patient, that may be present in the lumen. The breathable material may substantially prevent the passage of breathing gases (e.g., nitrogen, oxygen, carbon dioxide, and helium) through the tube walls. The breathable material may prevent the passage of liquid water droplets through the tube walls. The breathable material may prevent the passage of pathogens through the tube walls.

[0325]

[0352] The breathable material in this example forms the entirety of both the length and circumference of the elongated tube 702, at least between the connectors 706. In other examples, the breathable material may define only a portion or portions of one or more of the length and circumference of the elongated tube 702. For example, the breathable material may be co-extruded with another dissimilar (e.g., non-breathable) material. The dissimilar material may provide structural support to the elongated tube 702.

[0326]

[0353] Forming the entire elongated tube 702 from an air permeable material advantageously provides a relatively larger surface area of ​​air permeable material, thereby increasing the overall permeability and condensation mitigation effectiveness of the elongated tube 702. It may also simplify the manufacture of the elongated tube 702. As described in more detail below, a continuous length of tubing can be extruded and cut to length to form the elongated tube 702.

[0327]

[0354] All other things being equal, the more permeable the breathable material is to water molecules, the more effective the elongated tube 702 may be in dissipating one or more of water vapor and condensed water (if any) from the lumen of the elongated tube 702. However, breathable materials have been found to absorb increasingly larger masses of water molecules relative to the dry mass of the breathable material, for example, absorbing more than about 100% of their own dry mass in water molecules in immersion tests. The mechanical properties of the elongated tube 702 may change significantly during use. For example, an elongated tube configured to absorb about 100% of its own dry mass in water molecules may be made of as much as 50% water during use and may be significantly more flexible than before use.

[0328]

[0355] Because the condition of the conduit 700 may change during use, the terms "dry," "equilibrium," "conditioned," and "saturated" are used throughout this detailed description and claims to refer to one or more of various different conditions, or ranges of conditions, of the elongated tube 702, the sheath 704, and the conduit 700. Each of these conditions is defined in the glossary below.

[0329]

[0356] In one example, it was found that an elongated tube 702 by itself (i.e., without a sheath 704 or other similar structure) made from a breathable material such that the elongated tube 702 is configured to absorb more than about 120%, such as about 133%, of its own mass in water molecules in an immersion test, was sufficiently stiff to meet the compliance requirements of the ISO 5367:2014(E) standard when in an equilibrium state or when conditioned as defined in the standard. However, it was found that when the same elongated tube 702 was used to deliver humidified respiratory gas over an extended period of time, the breathable material softened to such an extent that the elongated tube 702 in a conditioned state as defined herein may no longer meet the same compliance requirements.

[0330]

[0357] It has also been found that absorption of such relatively large amounts of water molecules by the elongated tube 702, e.g., greater than 100% of its own dry mass in an immersion test, causes significant expansion of the elongated tube 702. That is, as the water molecules are absorbed, the breathable material of the elongated tube 702 increases in volume. In at least some instances, this expansion may be readily visible to the naked eye during use. During use, one or more dimensions of the elongated tube and sheath may change over time (i.e., absorbing and releasing water molecules over time).

[0331]

[0358] In some examples, when in a conditioned state, one or more of the outer diameter, inner diameter, wall thickness, and corrugation pitch (number of corrugations per unit length) of the elongated tube 702 may vary along the length of the elongated tube 702. Meanwhile, in one or more of a dry, equilibrium, and saturated state, one or more, and possibly all, of the outer diameter, inner diameter, wall thickness, and corrugation pitch of the elongated tube 702 may be substantially uniform along at least a central portion of the elongated tube 702. This central portion may exclude the end portions of the elongated tube 702. The end portions may consist of respective cuff portions and respective tapered portions (if present) of the elongated tube 702, which may taper toward the connectors 706 (see the central portion 2102, end portion 2104, cuff portion 1002, and tapered portion 2106 shown in FIG. 21(h)). Expansion of the end portions may be limited by the respective connectors 706.

[0332]

[0359] Although the expansion of the elongate tube 702 may be non-uniform during use (e.g., in a conditioned state), the following description of Figures 7-26 assumes that the dimensional changes of the elongate tube 702 and sheath 704 occur generally uniformly for ease of representation and explanation. Non-uniform absorption and expansion of the conduit 700 is described in further detail with respect to Figure 27.

[0333]

[0360] The diameter, length, wall thickness, and other dimensions of the test specimen can be measured using non-contact methods using computed tomography (CT) scans or optical measurement systems. In some instances, contact-based measurement methods may be used, for example using a coordinate measuring machine (CMM).

[0334]

[0361] In an immersion test (described below in the glossary), a sample specimen of the elongated tube 702 separated from the sheath (i.e., free of the sheath 704 and other such constraints) may expand between about 20%-70% in one or more of the radial direction (e.g., the maximum outer diameter, the minimum inner diameter, or the average outer or inner diameter of the corrugated elongated tube 702), the longitudinal direction (i.e., the length), and the wall thickness of the tube wall from a dry state to a saturated state. In some examples, the sample specimen of the elongated tube 702 may expand between about 20%-70%, about 25%-50%, or about 30%-50% in one or more of the radial direction, the longitudinal direction, and the wall thickness. In one example, a sample specimen of the elongated tube 702 of the exemplary conduit 700 was found to expand about 42% in the radial direction, about 37% in the longitudinal direction, and about 34% in the wall thickness. In another example, a sample specimen of elongated tube 702 was found to expand radially, longitudinally, and in wall thickness by approximately 32% each.

[0335]

[0362] In some instances, the wall thickness of the elongate tube in a dry state can be between about 0.5 mm and 0.9 mm, between about 0.6 mm and 0.8 mm, between about 0.65 mm and 0.75 mm, between about 0.68 mm and 0.72 mm, or between about 0.69 mm and 0.71 mm, e.g., about 0.70 mm. In a saturated state separated from the sheath, the same tube wall can be between about 0.7 mm and 1.1 mm, between about 0.8 mm and 1.0 mm, between about 0.85 mm and 0.95 mm, between about 0.90 mm and 0.94 mm, or between about 0.91 mm and 0.93 mm, e.g., about 0.92 mm.

[0336]

[0363] In some instances, the maximum outer diameter of the elongate tube in a dry state can be between about 20 mm and 26 mm, between about 21 mm and 25 mm, or between about 22 mm and 24 mm, e.g., about 23 mm. In a saturated state separated from the sheath, the same elongate tube can have a maximum outer diameter of between about 25 mm and 35 mm, between about 28 mm and 32 mm, or between about 29 mm and 31 mm, e.g., about 30 mm.

[0337]

[0364] Referring to FIG. 7, a sheath 704 is provided around an elongated tube 702. The sheath 704 is shown in cutaway view for illustrative purposes, but in this example extends continuously between connectors 706 at both ends of the conduit 700. Although the sheath 704 is shown as being generally tubular (i.e., circular in cross section), it need not necessarily have a perfectly circular cross section. In particular, it will be appreciated that the sheath 704 may be cut to length and formed from a continuous length of flexible sheath material, which may be stored in the form of a roll of flattened sheath. For example, the sheath 704, when provided around the elongated tube 702, may tend to adopt a rather elliptical or pointed oval cross section. Furthermore, the sheath 704 need not necessarily have a uniform cross-sectional shape along its length, as shown in the drawings.

[0338]

[0365] In the illustrated example, the end of the sheath 704 is secured to the end of the elongated tube 702 by a connector 706, as described in more detail below. In this example, the elongated tube 702 and the sheath 704 are not secured to one another intermediate the connector 706. In other examples, the elongated tube 702 and the sheath 704 may be further secured to one another at one or more discrete points along the length of the conduit intermediate the connector 706, such as at approximately the midpoint or approximately one-third of the length of the elongated tube 702. In yet other examples, the sheath 704 may only extend partially along the length of the elongated tube 702. In one example, both ends of the sheath 704 may be secured to the elongated tube 702 by one of the connectors 706 and an additional intermediate connector.

[0339]

[0366] In yet another example, the conduit may have two or more sheaths along its length. The two or more sheaths may be separate from one another. The two or more sheaths may have different properties. The different properties may include one or more of different materials, braid patterns, number of braid elements, and length / diameter gradients. The two or more sheaths may be disposed substantially end-to-end with one another. The two or more sheaths may be secured to the elongated tube 702 by an intermediate connector. The intermediate connector may be provided at approximately the midpoint of the conduit or elsewhere, such as closer to the patient end. The intermediate connector may secure and fluidly couple two separately formed elongated tubes together. One or both of the separately formed elongated tubes may be at least partially formed from a breathable material. The sheath 704 may extend along the entire length of the conduit 700 between the end connectors 706. Alternatively, the sheath 704 may be provided only around the breathable elongated tube 702.

[0340]

[0367] The sheath 704 has a plurality of braided elements woven into an open mesh tubular configuration that defines a plurality of openings, as described in more detail below with reference to FIGS. 18 and 19. The sheath 704 may be highly porous and vapor permeable, and therefore does not inhibit the movement of water molecules through the breathable material from within the lumen of the elongated tube 702 toward the surrounding air. That is, water vapor and other gases may pass freely through the sheath 704. The sheath 704 may have little or no effect on the temperature and humidity of the surrounding gas adjacent the outside of the tube wall, and therefore does not affect the vapor pressure gradient across the tube wall. The open mesh structure of the sheath 704 may also allow for visual inspection of the elongated tube 702.

[0341]

[0368] When the exemplary conduit 700 is in one or more of a dry and equilibrium state, the sheath 704 may be loosely positioned about the elongated tube 702. That is, an inner diameter of the sheath 704 may exceed a corresponding outer diameter of the elongated tube 702, such that the sheath 704 is at least partially spaced from the elongated tube 702. The elongated tube 702 may be movable relative to the sheath 704 (or vice versa).

[0342]

[0369] By "at least partially spaced apart" it is intended to allow for some contact between the sheath 704 and the elongated tube 702 around or along one or more of the circumference of the conduit 700 and the length of the conduit 700. That is, the sheath 704 need not be completely spaced apart from the elongated tube 702 (although it could be completely spaced apart). In the case of a corrugated tube, "at least partially spaced apart" refers to being spaced apart from the peaks of the waves, rather than simply being spaced apart from the valley between two peaks.

[0343]

[0370] Although the sheath 704 may be described or illustrated as being concentric or coaxial with respect to the elongated tube 702, for example as shown in FIG. 15, it will be understood that in practice there may be relative movement between the elongated tube 702 and the sheath 704 during one or more of the dry and conditioned conditions. The elongated tube 702 and the sheath 704 do not necessarily share the same center in cross section. For example, the elongated tube 702 may be positioned such that it rests against the bottom of the sheath 704, and conversely, the sheath 704 may be positioned such that it rests against the top of the elongated tube 702. Thus, it will be understood that the spacing between the elongated tube 702 and the sheath 704 is not necessarily uniform either circumferentially or longitudinally of the conduit 700. Additionally, while the sheath 704 may be considered to be generally partially spaced apart, it may be in contact with the elongated tube 702 in places.

[0344]

[0371] The elongated tube 702 and the sheath 704 are shown as having a relatively uniform diameter along their length. However, in use, particularly in a conditioned state (as discussed above), one or more of the elongated tube 702 and the sheath 704 may change diameter or shape along their length, as described in more detail below with respect to FIG. 27. In one example, in a conditioned state, the sheath 704 may engage the entire circumference of the elongated tube 702 in a first portion of the conduit 700, but may be spaced from all or at least a portion of the circumference of the elongated tube 702 in a second portion of the conduit 700. In that example, the sheath 704 may be said to be at least partially spaced from the elongated tube 702 in the second portion. Alternatively, the sheath 704 may be said to be at least partially spaced from the elongated tube 702 as a whole. However, the sheath 704 is not considered to be at least partially spaced from the elongated tube 702, particularly in the first portion of the conduit 700.

[0345]

[0372] The sheath 704 may interact with the elongated tube 702 as it expands in one or more of the radial direction, longitudinal direction, and wall thickness due to absorption of water molecules during use, as described in more detail below. In particular, the sheath 704 may limit the expansion of at least a portion of the elongated tube 702 in at least one of the longitudinal and radial directions of the conduit 700 when the conduit 700 is in a constrained conditioned state. That is, the sheath 704 limits the expansion of the elongated tube 702 by applying a countervailing force under at least some conditions.

[0346]

[0373] The sheath 704 may also provide some physical protection to the elongated tube 702, such as providing one or more of strain relief, wear resistance, and distribution of point or localized loads across the multiple corrugations of the elongated tube 702.

[0347]

[0374] The connector 706 of the conduit 700 may provide a convenient and reliable pneumatic coupling of the elongated tube 702 to other components of a respiratory assistance system for transporting respiratory gases between those components. In particular, when the conduit 700 is intended to be used as the expiratory conduit 114 in the respiratory assistance system 100, the connector 706 is configured to directly pneumatically connect with the outlet of the Y-tube 110 and the gas return inlet 140 of the gas source 102, respectively. In some examples, a filter may be provided between the conduit 700 and the gas return inlet 140.

[0348]

[0375] In the illustrated example, the connector includes a standard medical taper to allow interoperability with a variety of respiratory assistance systems and components thereof.

[0349]

[0376] In some instances, particularly if the conduits include heater wires, at least one of the connectors may include a socket for establishing an electrical connection with the humidifier 106, the gas source 102, or another power source.

[0350]

[0377] Connectors 706 each define a bore that is fluidly coupled to the lumen of elongate tube 702 .

[0351]

[0378] 8 provides a detailed isometric view of one end of a conduit 700 in accordance with the present disclosure, including a connector 706, an end portion of a sheath 704, and an end portion of an elongated tube 702 (partially hidden by the sheath 704 and connector 706). Also shown is a bore 802 of the connector 706 that is fluidly coupled to the lumen of the elongated tube 702.

[0352]

[0379] 9 provides a detailed side view of an end of a conduit 700 according to the present disclosure. Also shown is what is referred to as the longitudinal direction of the conduit 700, represented by an arrow 902. It will be understood that the conduit 700 in use will not necessarily adopt a strictly linear configuration as shown in the drawings, and references to "longitudinal," "axial," etc. should not be construed as limiting to such a linear configuration.

[0353]

[0380] The sheath 704 may be a braided tubular sheath, as described in more detail below with respect to FIGS.

[0354]

[0381] 10 provides an exploded detailed view of an end of a conduit 700 in accordance with the present disclosure, including one of the connectors 706 and a portion of the elongate tube 702 and sheath 704. As shown, this exemplary connector 706 has a first connector component 1004 and a second connector component 1006.

[0355]

[0382] The first connector component 1004 may have a chamfered edge 1008. The chamfered edge 1008 may aid in the insertion of the first connector component 1004 into the lumen 1202 of the elongate tube 702.

[0356]

[0383] The first connector component 1004 may have at least one flange 1010. In some examples, the first connector component 1004 may have three flanges 1010. The flanges 1010 may extend circumferentially around the first connector component 1004. The flanges 1010 may resist inadvertent disconnection of the first connector component 1004 from the elongate tube 702, the sheath 704, and the second connector component 1006 (or vice versa). The flanges 1010 may extend radially outward from at least a portion of the first connector component 1004, and may partially define an annular channel 1012. The second connector component 1006 may be partially received within the annular channel 1012. The flange 1010 may prevent one or more of the elongate tube 702, the sheath 704, and the second connector component 1006 from sliding longitudinally out of the first connector component.

[0357]

[0384] The second connector component 1006 may have one or more apertures 1014. The apertures 1014 may be disposed in pairs on opposite sides of the second connector component 1006. The apertures 1014 may be through holes. That is, the apertures may each extend through a cylindrical wall that defines a portion of the second connector component 1006.

[0358]

[0385] As described in more detail below, the aperture 1014 may aid in the manufacture of the conduit 700. The aperture 1014 may provide a user with a firmer grip when connecting or disconnecting the conduit 700 to / from other components of a respiratory assistance system.

[0359]

[0386] Although the apertures 1014 of the exemplary conduit 700 are arranged as pairs of parallel elongated slots, there may alternatively be any number of apertures in any suitable shape or arrangement. For example, the apertures may alternatively form a chevron pattern or logo. In some examples, the chevron pattern or other identifier (such as text or symbol) may indicate a preferred flow direction or the particular component of the respiratory support system to which the respective connector 706 is intended to be coupled. This may reduce the risk of misconnection. The exemplary conduit 700 may be symmetrical and configured to be coupled in either direction between the gas source 102 (or filter) and the yoke 110. In other examples, the conduit may be directional.

[0360]

[0387] At least one of the first connector component 1004 and the second connector component 1006 may be formed from a polymeric material. The polymeric material may include any one or more of polycarbonate (PC), polypropylene (PP), and polyethylene (PE). In some examples, the first connector component 1004 and the second connector component 1006 may be formed from the same material. In other examples, the first connector component 1004 and the second connector component 1006 may be formed from different materials.

[0361]

[0388] The first connector component 1004 may be injection molded. The second connector component 1006 may be overmolded onto one or more of the elongated tube 702, the sheath 704, and the first connector component 1004. In some examples, the second connector component 1006 may be overmolded onto all three of the elongated tube 702, the sheath 704, and the first connector component 1004.

[0362]

[0389] In other examples, the sheath 704 may alternatively or additionally be secured to one or more of the connector 706 and the elongate tube 702 by ultrasonic welding, radio frequency (RF) welding, adhesives, hose clamps, clips (e.g., circlips or snap-fit ​​clips), etc.

[0363]

[0390] 10 also shows a cuff portion 1002 and a corrugated portion 1016 of the elongate tube 702. The cuff portion 1002 in this example is intended to be received between a first connector component 1004 and a second connector component 1006 of the connector 706, but is not corrugated. The absence of corrugations in the cuff portion 1002 may provide one or more of the following advantages: aiding in the insertion of the chamfered edge 1008 into the cuff portion 1002, promoting a more secure engagement between the elongate tube 702 and the connector 706, and reducing the possibility of air leakage between the elongate tube 702 and the connector 706.

[0364]

[0391] 11 is a cross-sectional view of an end of a conduit 700 according to the present disclosure. The sheath 704 is represented diagrammatically for clarity. It should be understood that the sheath 704 may taper to the diameter, e.g., inner diameter, of the connector 706, as shown, for example, in FIG. 21(e). Due to the nature of the braided tubular mesh sheath, this can be accomplished by extending the length of the sheath in the section requiring the smaller diameter.

[0365]

[0392] The first connector component 1004 defines the bore 802 of the connector 706. The first connector component 1004 may include a male or female tapered conical end 1102 configured to connect to other components of the respiratory assistance system, such as the gas return inlet 140. An opposite end of the first connector component 1004 may be partially received within the lumen 1202 of the elongated tube 702, such as at the cuff portion 1002. One or more of the elongated tube 702 and the sheath 704 may be exposed, e.g., visible, through an aperture 1014 of the second connector component 1006 of the connector 706.

[0366]

[0393] As shown, one or more ends of the elongated tube 702, e.g., the cuff portion 1002, and a corresponding end of the sheath 704 may be secured to one another by one or more of the first connector component 1004 and the second connector component 1006. The ends of the elongated tube 702 and the sheath 704 may coincide within the connector 706. In some examples, one or more of the elongated tube 702 and the sheath 704 may be secured (e.g., "sandwiched") between the first connector component 1004 and the second connector component 1006. In some examples, the sheath 704 may be positioned directly adjacent to the elongated tube 702 within the connector 706. In other examples, the sheath 704 may be spaced apart from the elongated tube 702 within the connector 706, as shown.

[0367]

[0394] 12 provides an isometric exploded detail view of an end of a conduit 700 according to the present disclosure, including an elongated tube 702, a sheath 704, and first and second connector components 1004, 1006 of a connector 706. Also shown are the cuff portion 1002 and the corrugated portion 1016 of the elongated tube 702, as well as a portion of a lumen 1202 for passing breathing gas from one end of the conduit 700 to the other.

[0368]

[0395] 13 is a detailed, partially exploded, isometric view of an elongated tube 702 and a portion of a sheath 704 of a conduit 700 in accordance with the present disclosure. Also shown is a (partial) lumen 1202 defined by the elongated tube 702.

[0369]

[0396] FIG. 14 is a side view, partially disassembled, of an elongate tube 702 and a portion of a sheath 704 of a conduit 700 in accordance with the present disclosure.

[0370]

[0397] The sheath 704 is shown in schematic form for clarity, illustrating a plurality of clockwise braided elements 904 and counterclockwise braided elements 906 of the sheath 704. The clockwise braided elements 904 and counterclockwise braided elements 906 may be interwoven, as described in more detail below and shown in Figures 18 and 19.

[0371]

[0398] 15 shows a cross section of an elongate tube 702 and sheath 704 of a conduit 700 according to the present disclosure. Connector 706 has been omitted for clarity.

[0372]

[0399] As shown, it can be observed that when the exemplary conduit 700 is in an equilibrium state, a gap 1502 may exist between the outer surface of the elongate tube 702 and the inner surface of the sheath 704. This allows at least a portion of the elongate tube 702 to expand to some extent in at least one of the radial direction 1504 and the longitudinal direction 902. However, under certain conditions, as described in more detail below, further expansion of the elongate tube 702 in the radial direction 1504 may be limited by the sheath 704. That is, in this example, the sheath 704 may selectively limit the expansion of the elongate tube 702.

[0373]

[0400] As explained above, spacing 1502 does not necessarily need to be uniform or continuous around the entire circumference of conduit 700 or along the length of conduit 700 (in longitudinal direction 902). Additionally, sheath 704 does not necessarily need to have a perfectly circular cross-section or be concentric with elongated tube 702.

[0374]

[0401] FIG. 15 also shows an example of a lumen 1202 defined by the tube wall and a direction that may be referred to as the radial direction of the conduit 700, where the radial direction 1504 is represented by the arrows.

[0375]

[0402] 16 is a detailed cross-sectional side view of a portion of a conduit 700 according to the present disclosure. Shown are the sheath 704 and the corrugated portion 1016 of the elongated tube 702. The drawing depicts only the upper portion of the length of the conduit 700 in a horizontal orientation, with the lumen 1202 toward the lower portion of the drawing and the ambient air at the top of the drawing.

[0376]

[0403] A gap 1502 can be observed between the outer surface of the elongate tube 702 at the corrugation peaks 1602 and the inner surface of the sheath 704. It can also be observed that the valleys 1604 of the corrugations 1016 in this example are flattened, i.e., the valleys are substantially cylindrical, whereas the peaks 1602, as shown, may be continuously curved.

[0377] Breathable material

[0404] The breathable material may be or may include a block copolymer, such as a thermoplastic elastomer (TPE), having both "hard segments" and "soft segments." In some examples, the hard segments may be hard, rigid, semi-crystalline polymers (e.g., polyesters such as polybutylene terephthalate (PBT) and the like) that may be hydrophobic. In some examples, the soft segments may be soft, flexible, amorphous hydrophilic polymers (e.g., ether-type macroglycols). The breathable material may combine the hydrophilic properties of the soft segments with the mechanical properties of the hard segments.

[0378]

[0405] In some examples, the block copolymer may be at least about 90%, at least about 92%, at least about 95%, or at least about 97%, e.g., about 97% or about 98.5%, of the breathable material of the elongated tube based on one or more of mass, weight, and volume.

[0379]

[0406] FIG. 17 is a graph illustrating the results of differential scanning calorimetry (DSC) testing (defined in the glossary below) on a sample specimen from an exemplary elongated tube 702 formed from a breathable material in accordance with the present disclosure.

[0380]

[0407] Line 1702 in FIG. 17 shows the differential heating value (measured in milliwatts per milligram, mW / mg) of the exemplary breathable material when heated a second time during a DSC test.

[0381]

[0408] The peak of line 1702 represents the melting point 1704 of the breathable material. As used herein, the term "melting point" refers to the temperature that corresponds to the peak in the DSC graph. It will be understood that melting may begin prior to the peak.

[0382]

[0409] In some examples, the breathable material may have two, three, or more melting points 1704. The minimum melting point 1704 of the breathable material may be a temperature greater than about 37° C., greater than about 42° C., greater than about 44° C., greater than about 45° C., or greater than about 46° C., such as a temperature of about 47° C. The minimum melting point 1704 of the breathable material may be a temperature less than about 108° C., less than about 100° C., less than about 80° C., less than about 60° C., or less than about 50° C. In some examples, the minimum melting point 1704 may be a temperature between about 37° C. and 100° C., between about 40° C. and 60° C., or between about 40° C. and 50° C.

[0383]

[0410] In some examples, the breathable material may have a melting point 1704 at a temperature between about 42°C and 52°C, between about 44°C and 50°C, between about 45°C and 49°C, or between about 46°C and 47°C, for example, at a temperature of about 47°C.

[0384]

[0411] In some examples, the breathable material may have a melting point 1704 at a temperature between about 202°C and 212°C, between about 204°C and 210°C, between about 205°C and 209°C, or between about 206°C and 208°C, for example at a temperature of about 207°C.

[0385]

[0412] In some examples, the breathable material may have a melting point 1704 at a temperature between about 215°C and 225°C, between about 217°C and 223°C, between about 218°C and 222°C, or between about 219°C and 221°C, for example at a temperature of about 220°C.

[0386]

[0413] In some examples, the breathable material may have two melting points 1704, greater than about 197°C, greater than about 202°C, greater than about 204°C, greater than about 205°C, or greater than about 206°C, for example, greater than about 207°C.

[0387]

[0414] In some examples, the breathable material may have two melting points 1704 at temperatures between about 202°C and 225°C, between about 204°C and 223°C, between about 205°C and 222°C, or between about 206°C and 221°C, such as between about 207°C and 220°C.

[0388]

[0415] In some examples, the breathable material may have two melting points 1704 with a temperature difference of less than about 23°C, less than about 18°C, less than about 16°C, less than about 15°C, or less than about 14°C, for example, a temperature difference of about 13°C.

[0389]

[0416] In some examples, the breathable material may have two melting points 1704 with a temperature difference between about 150°C and 170°C, between about 155°C and 165°C, between about 158°C and 162°C, or between about 159°C and 161°C, for example, a temperature difference of about 160°C.

[0390]

[0417] The breathable material can have three melting points 1704. The three melting points can be temperatures between about 42°C and 225°C, between about 44°C and 223°C, between about 45°C and 222°C, or between about 46°C and 221°C.

[0391]

[0418] In one particular example, the three melting points 1704 may be temperatures of about 47° C., 207° C., and 220° C. (all within ±5° C., ±3° C., ±2° C., or ±1° C.).

[0392]

[0419] In some examples, the breathable material may have a minimum melting point above 37° C. (or 42° C., 44° C., 45° C., 46° C.). As noted above, 37° C. may correspond to one or more of the temperature of the respiratory gas delivered to the patient by the respiratory assistance system and the temperature of the respiratory gas exhaled by the patient.

[0393]

[0420] The minimum melting point of the breathable material may correspond to the melting point of the soft segment of the breathable material. It has been found that by selecting a breathable material with all melting points above this temperature, melting of the soft segment of the breathable material may be mitigated when the conduit conveys heated and humidified breathing gas during use. At temperatures above the melting point of the soft segment, the soft segment may remain bonded to the hard segment. The fact that the elongated tube is "melting" is not noticeable to the user. However, it has been found that below the minimum melting point, the majority of the soft segment may remain solid during use and contribute to the structural integrity of the elongated tube. This may allow for a higher ratio of soft segments to hard segments in the breathable material, which in turn may increase the permeability of the breathable material to water molecules.

[0394]

[0421] In some examples, the temperature of the respiratory gas within the lumen of the inhalation conduit 108 may be greater than 37° C. to allow for a drop in temperature before the respiratory gas is delivered to the patient via the patient interface. In some examples, the temperature of the respiratory gas within the lumen of the inhalation conduit 108 may be as high as, for example, 50° C. or 60° C. Thus, in some examples, the minimum melting point of the breathable material may be greater than 50° C. or greater than 60° C.

[0395]

[0422] It has been found that such breathable materials are particularly suitable for use in conduits that omit a heater, e.g., a heater wire. The heater wire may be heated to a temperature well above the temperature of the breathing gas in the lumen 1202. It has been found that this heating may melt at least a portion of the soft segments of the breathable material during use, even if the temperature of the breathing gas does not exceed its minimum melting point. This occurs particularly when the heater wire is embedded in or pressed against the tube wall. By omitting the heater wire and selecting a breathable material that has a melting point above the expected or actual maximum temperature of the breathing gas, at least a majority of the soft segments remain solid during use of the conduit, thus contributing to the mechanical strength of the conduit during use. In some instances, a sheath may not be necessary.

[0396]

[0423] In other examples, the conduit may contain a heater wire and the breathable material may be selected to have a minimum melting point that is above the expected or actual maximum temperature of the heater wire in use. In other examples, the conduit may be manipulated, for example by controlling the duty cycle of the heater wire, such that the temperature of the heater wire does not exceed the minimum melting point of the breathable material. In other examples, the elongated tube 702 may be formed from breathable and non-breathable materials and the heater wire may be embedded in or pressed into the non-breathable material.

[0397]

[0424] At least a portion of the elongate tube 702 may be configured to absorb more than about 45%, more than about 65%, more than about 75%, more than about 100%, more than about 120%, or more than about 130% of its mass in water in an immersion test (described in the glossary below).

[0398]

[0425] In some examples, at least a portion of the sample of elongate tube 702 can be configured to absorb between about 45%-250%, between about 65%-200%, between about 75%-175%, between about 100%-160%, between about 110%-150%, between about 120%-140%, between about 130%-140%, or between about 133%-139%, for example about 139%, of its dry mass in water molecules in an immersion test.

[0399]

[0426] In some examples, at least a portion of the sample of elongate tube 702 may be configured to absorb between about 40% and 80%, between about 40% and 60%, between about 45% and 55%, or between about 48% and 51%, for example about 49%, of its dry mass in water molecules in an immersion test.

[0400]

[0427] In some examples, at least a portion of the sample of elongate tube 702 can be configured to absorb between about 100% and 250%, between about 100% and 180%, between about 110% and 150%, between about 120% and 140%, between about 130% and 145%, or between about 135% and 145%, such as about 138% or 139%, of its dry mass in water molecules in an immersion test.

[0401]

[0428] In some examples, at least a portion of the sample of the elongate tube may be configured to absorb more than about 33%, between about 33% and 200%, between about 100% and 160%, between about 120% and 140%, or between about 130% and 135%, for example about 133%, of its mass in water molecules in an immersion test.

[0402]

[0429] The permeability to water molecules of the breathable materials described herein has been found to mitigate condensation within the lumen to such an extent that at least one of the heater wires and the water traps can be omitted, and in some instances, both the heater wires and the water traps can be omitted.

[0403]

[0430] It has been found that in some instances, such elongated tubes 702 may be sufficiently permeable to water molecules to passively (i.e., without heating, emptying a water trap, or draining the conduit) mitigate condensation within the lumen after extended use of the conduit 700, e.g., about 24 hours of continuous use. In some instances, there may be no net accumulation of condensed water within the lumen, including condensed water from other sources such as catheter mounts, after extended use. In some instances, conduits according to the present disclosure may be sufficiently breathable such that medical personnel do not need to drain condensed water from the conduit after extended use, at least when the conduit is used in a conditioned environment, e.g., ambient air within the range of about 20° C.-24° C. and about 40%-60% relative humidity.

[0404]

[0431] In one example, a conduit having an elongated tube 702 configured to absorb between about 45%-55%, between about 46%-52%, between about 47%-51%, or between about 48%-50%, such as about 49% or about 50%, of its own mass in water molecules in an immersion test was found to be suitable for use as an expiratory conduit 114 without the need for a heater wire or water trap in at least some ambient conditions. It also did not require a sheath 704 or other such means to compensate for the softening of the elongated tube 702 as it absorbs water molecules during use. That is, the elongated tube alone, without the sheath 704, was found to meet one or more of the flow resistance and compliance requirements of ISO 5367:2014(E) in a conditioned state.

[0405]

[0432] In another example, a conduit 700 having an elongated tube 702 configured to absorb approximately 130%-140% of its mass in water molecules in immersion tests was found to be suitable for use as an exhalation conduit 114, also without a heater wire or water trap. This example was found to better mitigate condensation over a wider range of ambient conditions compared to the previous example (configured to absorb between approximately 45%-55%). The conduit 700 was provided with a sheath 704. Despite absorbing a much larger percentage of water molecules, the conduit 700 was found to meet one or more of the flow resistance and compliance requirements of ISO 5367:2014(E) in a conditioned state.

[0406]

[0433] In one example, after extended use, e.g., about 24 hours, no condensation was found to accumulate in the gas source or within the lumen of the conduit 700 when used as the expiratory conduit 114. After five days of continuous use, condensation was found to accumulate in the gas source at a rate of less than about 1 milliliter per hour (ml / hr) and within the lumen of the conduit 700 at a rate of less than about 2 ml / hr without a heater wire or water trap. However, in some examples, the conduit may optionally include at least one of a heater wire and a water trap.

[0407]

[0434] In some examples, the compliance of the conduit 700 may depend on the physical interaction between the elongate tube 702 and the sheath 704. The compliance of the conduit 700 may differ by more than 10%, more than 20%, or more than 30% with a sheath versus without a sheath when conditioned over an extended period of time.

[0408]

[0435] The breathable material may further include one or more additives. The additives may include, for example, one or more of a blowing agent, a colorant, an ultraviolet (UV) stabilizer, a UV absorber, or a processing aid. In some examples, the additives may form up to about 10%, up to about 8%, up to about 5%, or up to about 3%, for example, about 3% or 1.5%, of the breathable material of the elongated tube based on one or more of mass, weight, and volume. It will be understood that the additives themselves may not necessarily be breathable, but the breathable material as a whole will remain breathable with the additives.

[0409]

[0436] In some instances, the breathable material may be unfoamed. In other instances, the breathable material may be foamed. The breathable material may include a foaming agent additive. The foaming agent may be selected and dosed such that the breathable material is a closed cell foam. It has been found that voids formed within a foamed breathable material may increase the mass of water that may be absorbed by the breathable material. In one example, a sample of a foamed breathable material was found to absorb approximately twice the mass of water in an immersion test when compared to an unfoamed sample of comparable dry mass and configuration (e.g., corrugated profile). The voids may also improve the insulation that the tube wall provides.

[0410] sheath

[0437] 18 provides a detailed view of the sheath 704 of a conduit 700 in accordance with the present disclosure, the conduit 700 being in an equilibrium state. The sheath 704 is shown as if the conduit were lying horizontally.

[0411]

[0438] The sheath 704 may be less elastic than the elongated tube 702 such that if the elongated tube 702 is crushed, the recovery of the elongated tube 702 is not limited by the sheath 704 .

[0412]

[0439] The sheath 704 can be a mesh. The sheath 704 can have multiple braided elements woven together to form a braided tubular mesh.

[0413]

[0440] In some examples, the sheath may have a biaxial configuration. The braided elements may each be helically disposed around the elongate tube 702 in one of a clockwise or counterclockwise direction.

[0414]

[0441] Each of the clockwise braided elements 904 may be interwoven with each of the counterclockwise braided elements 906, or vice versa. In some examples, the braided elements may be interwoven in a regular braid pattern, where a clockwise braided element 904 passes under two counterclockwise braided elements 906 and then over two counterclockwise braided elements 906, as shown. In other examples, the braided elements may be interwoven in a diamond braid pattern, where a clockwise braided element 904 passes under one counterclockwise braided element 906 and then over one counterclockwise braided element 906.

[0415]

[0442] Each braided element of the braided tubular mesh sheath 704 may be oriented at a braid angle α relative to the longitudinal direction of the conduit 700 (horizontal as shown). In some examples, the braid angle α may be the same for the clockwise braided element 904 and the counterclockwise braided element 906. In some examples, the braid angle α at equilibrium may be between about 35° and 55°, or between about 40° and 50°. In one example, the braid angle may be about 45°. In some examples, the angle at the intersection between the clockwise braided element 904 and the counterclockwise braided element 906 may be between about 70° and 110°, or between about 80° and 100°. In one example, the angle at the intersection may be about 90°.

[0416]

[0443] In other examples, braided elements extending longitudinally parallel to the elongate tube 702 may be advantageous in applications where expansion of the conduit in the longitudinal direction is undesirable, and braided elements extending circumferentially may be advantageous in applications where expansion of the conduit in the radial direction is undesirable.

[0417]

[0444] In some instances, the sheath may have a triaxial or other configuration.

[0418]

[0445] In some examples, the respective braided elements 904, 906 are not bonded or otherwise permanently joined to one another where they intersect (except where the sheath 704 is fixed to the elongate tube 702, e.g., at connector 706), i.e., the braided elements 904, 906 may move relative to one another to some extent (subject to frictional forces).

[0419]

[0446] The sheath 704 may have an open braid. The clockwise braided elements 904 may be spaced apart from one another around the circumference of the sheath 704. The clockwise braided elements 904 may be substantially equally spaced apart, for example adjacent the connector 706. The counterclockwise braided elements 906 may be similarly spaced apart from one another.

[0420]

[0447] The spacing of the braided elements in the braided sheath forms a plurality of openings 908 between the braided elements. Each of the openings may be substantially rectangular in shape, for example, having a parallelogram shape or a diamond shape. The shape of the openings may change during use, undergoing an affine transformation as the dimensions of the sheath 704 change during use, as described in more detail below.

[0421]

[0448] In this equilibrium state, the opening 908 may be relatively elongated in the longitudinal direction (horizontal as shown) compared to the tangential direction (vertical as shown).

[0422]

[0449] If the braided elements 904, 906 are not bonded or otherwise permanently joined where they intersect, there may be relative movement between them as the elongated tube 702 expands and / or contracts during use. It will be appreciated that the spacing between adjacent braided elements may not necessarily be uniform along the length of the conduit. Also, not all of the openings 908 necessarily form perfect parallelograms.

[0423]

[0450] In some instances, a useful property of the sheath 704 is that the overall length (longitudinal) and diameter (radial) of the sheath 704 may vary in an inverse relationship. That is, as the sheath 704 stretches in the longitudinal direction, it tends to contract radially. Conversely, as the sheath 704 expands in the radial direction, it tends to contract longitudinally. As described in more detail below, it has been found that this property can be utilized to at least partially counteract the change in mechanical properties of the elongated tube 702 as it expands during use due to absorbing water molecules.

[0424]

[0451] In practice, the sheath may have limitations on one or more of the minimum and maximum diameters to which it can deform. In some examples, for example, for adult conduits, the sheath 704 may have an inner diameter that varies between at least about 23 mm and 43 mm (± 2 mm). That is, the sheath 704 may be configured to fit a rod having an outer diameter in the range of about 23 mm to 43 mm. It will be appreciated that the length of the sheath 704 may also vary in this range. In some examples, the sheath 704 may have an inner diameter that may vary by at least about 20 mm.

[0425]

[0452] In other instances, such as for neonatal or pediatric conduits, the sheath can have an inner diameter that can vary between at least about 12 mm and 22 mm (± 2 mm). In some instances, the sheath can have an inner diameter that can vary by at least about 10 mm.

[0426]

[0453] In some examples, the number of clockwise braided elements 904 can be equal to the number of counterclockwise braided elements 906. In some examples, the sheath 704 can have about 75-125 braided elements, or about 90-100 braided elements. The sheath 704 of the exemplary conduit 700 has a total of about 96 braided elements, consisting of 48 clockwise braided elements 904 and 48 counterclockwise braided elements 906. The sheath 704 can be suitable for a conduit 700 intended for use by an adult patient, for example.

[0427]

[0454] In other examples, the sheath may have about 40-60 braided elements, or about 45-55 braided elements, such as 24 clockwise braided elements 904 and 24 counterclockwise braided elements 906 for a total of about 48 braided elements. Such a sheath may be suitable, for example, for a conduit intended for use with a neonatal or pediatric patient.

[0428]

[0455] In some examples, one or more of the braided elements 904, 906 can have more than one filament (i.e., the braided elements can be multifilament). In other examples, one or more of the braided elements 904, 906 can be a single filament (monofilament). In some examples, all of the braided elements 904, 906 can be multifilament. In the example shown, each of the braided elements 904, 906 has two adjacent filaments. In another example, for example, in a sheath suitable for a conduit intended for use by a neonatal or pediatric patient, each of the braided elements can include three adjacent filaments.

[0429]

[0456] In some examples, the filaments 1802 may be woven in a regular braid pattern where a pair of adjacent filaments 1802 passes under two pairs of adjacent filaments 1802 and then over two pairs of adjacent filaments 1802, as shown in FIG. 18 . In other examples, the filaments 1802 may be woven in a regular braid pattern where a single filament 1802 passes under two single filaments 1802 and then over two single filaments 1802. In other examples, the filaments 1802 may be woven in a diamond braid pattern where a pair of adjacent filaments 1802 passes under a pair of adjacent filaments 1802 and then over a pair of adjacent filaments 1802. In other examples, the filaments 1802 may be woven in a diamond braid pattern where a single filament 1802 passes under and then over a single filament 1802.

[0430]

[0457] In some instances, the filaments of each braided element are untwisted, while in other instances, the filaments of each braided element may be twisted or interwoven with one another.

[0431]

[0458] The filament 1802 in the illustrated example may have a substantially circular cross-section. In other examples, the filament may have a polygonal cross-section, e.g., triangular, square, pentagonal, hexagonal, octagonal, etc. In other examples, the filament may have a rounded cross-section, e.g., elliptical, oval, rounded polygon, etc.

[0432]

[0459] The filaments 1802 of the exemplary sheath 704 may be formed from polyethylene terephthalate (PET). In other examples, the filaments 1802 may be formed from any one or more of a metal, a polymer, a ceramic, and a fibrous material.

[0433]

[0460] One or more of the filament 1802 and braided elements 904, 906, individually or collectively, can be substantially inextensible under the loads experienced during normal use.

[0434]

[0461] In some examples, the number of filaments in the clockwise braided element 904 can be equal to the number of filaments in the counterclockwise braided element 906. In some examples, the sheath can have between about 150-250 filaments, or between about 180-200 filaments. The sheath 704 of the exemplary conduit 700 can have a total of about 192 filaments.

[0435]

[0462] In other examples, for example, in a sheath suitable for a conduit intended for use by a neonatal or pediatric patient, the sheath may have between about 120-180 filaments, or between about 135-165 filaments, for example, a total of about 144 filaments.

[0436]

[0463] In some instances, the filaments may all have the same diameter. In other instances, the filaments may have two or more different diameters.

[0437]

[0464] In some examples, the filament may have a diameter between about 0.1 mm and 0.4 mm, or between about 0.2 mm and 0.3 mm. The sheath 704 of the exemplary conduit 700 may have a filament with a diameter of about 0.25 mm.

[0438]

[0465] FIG. 19 shows the sheath 704 in a conditioned state.

[0439]

[0466] As the sheath 704 expands and contracts longitudinally and radially, the opening 908 may undergo an affine transformation, i.e., the shape of the opening 908 changes. The pitch of the braided elements 904, 906 (i.e., the angle of the braided element, and therefore the number of helical turns around the elongated tube 702 per unit length) may change.

[0440]

[0467] In this equilibrium state, the opening 908 may be relatively elongated in the tangential direction compared to the longitudinal direction.

[0441]

[0468] In comparison to the equilibrium state shown in Figure 18, the opening 908 in Figure 19 can be observed to be relatively shorter in the longitudinal direction, and relatively longer in the tangential direction.

[0442]

[0469] The length and diameter of the sheath 704 may be inversely proportional. Different braided tubular meshes may be characterized by a gradient in their length to diameter (L / D) relationship.

[0443]

[0470] FIG. 20 shows a graph of length versus diameter gradient for a number of different exemplary braided tubular meshes.

[0444]

[0471] The characterization process was carried out by cutting a sample specimen of the braided tubular mesh sheath to a predetermined length (e.g., 2000 mm) while flat (as typically stored) and then measuring the length of the sample specimen while it is fitted over a number of steel rods of suitable known diameter (e.g., diameters between about 22 mm and 32 mm for adult conduits, or between about 23 mm and 32 mm). In some instances, the length vs. diameter gradient may be substantially linear within this range. Different initial lengths and diameters may result in similar characteristic responses depending on the configuration of the braided elements. The length vs. diameter gradient may be determined by plotting these measurements and the associated linear trend line on a graph. FIG. 20 shows sheaths with length vs. diameter gradients of about -23, -34, -37, -43, and -79.

[0445]

[0472] A braided tubular mesh with a relatively large absolute length vs. diameter gradient will result in a relatively large decrease in the length of the elongated tube as the diameter increases (and vice versa), whereas a smaller absolute length vs. diameter gradient will result in a relatively small change in axial length for the same increase in diameter.

[0446]

[0473] In some instances, for example, for an adult conduit, the length vs. diameter gradient of the sheath 704 of the conduit 700 may be between about -100 and -20, between about -50 and -20, or between about -40 and -35. In one example, the length vs. diameter gradient may be about -37.

[0447]

[0474] In other examples, such as for neonatal or pediatric conduits, the sheath length vs. diameter gradient can be between about -75 and -25, between about -60 and -40, or between about -55 and -45. In one example, the length vs. diameter gradient can be about -52.

[0448]

[0475] The spacing 1502 between the elongated tube 702 and the sheath 704 can be formed by cutting the selected braided tubular mesh for the sheath 704 to a length that exceeds the length of the elongated tube 702 by a predetermined distance when the sheath 704 fits outside the elongated tube 702 (i.e., the maximum outer diameter of the elongated tube 702 at the peak of the corrugation). The predetermined distance may be selected such that the final length of the conduit in the conditioned state is similar to the length of the tube in the equilibrium state, as described above. The sheath 704 is axially compressed before being secured to the elongated tube 702 such that the respective ends of the elongated tube 702 and the sheath 704 are matched, increasing the average diameter of the sheath 704 to form the spacing 1502. A relatively smaller characteristic length vs. diameter gradient may provide one or more of the following advantages: minimizing the spacing 1502, which may improve appearance, and minimizing the flat length of the braided tubular mesh, which may reduce manufacturing costs.

[0449]

[0476] In some examples, the sheath 704 may also dampen vibration or oscillation of the conduit during use. The breathable material used in the elongated tube 702 has certain properties that result in dimensional and mechanical changes as water molecules are absorbed into and diffuse throughout the breathable material at a rate that depends on the temperature and humidity boundary conditions on either side of the breathable material. Specifically, the breathable material softens and swells as it picks up water molecules. When a breathable material is formed in the elongated tube carrying a moist gas with a higher humidity level than outside the tube wall, the humidity of the breathing gas entering the elongated tube may decrease axially as the breathing gas travels through the elongated tube to the outlet as a result of natural diffusion through the breathable material and the resulting temperature drop as a result of the heat transfer rate that depends on the boundary conditions across the breathable material and as a result of the diffusion of water molecules into the breathable material while the vapor pressure gradient remains positive across the tube wall. This may result in axial variations in the dimensions and mechanical properties of the conduit. The breathable material thus has properties of a functionally graded material (FGM) as water molecules are absorbed into and diffuse through the breathable material. The diameter and length of the sheath may be selected to selectively control radial and longitudinal expansion. Water molecule uptake may be greatest at the inlet of the conduit where humidified breathing gas may enter, compared to axial locations distal to the inlet. In some instances, the parameters of the sheath may be selected to moderate or minimize longitudinal expansion of the elongated tube (relative to equilibrium) in favor of radial expansion in the hydraulic diameter of the elongated tube. The uptake of water molecules, in combination with the corrugated profile of the elongated tube due to the sheath and the resulting longitudinal contraction, may result in a thicker tube wall section relative to equilibrium. Thus, the wall thickness of the tube may change axially, and this change may be more pronounced once the sheath is engaged after a sufficient dimensional change. The breathable material may soften as a result of the uptake of water molecules, but the axial growth restriction due to the sheath may reduce the separation distance between the corrugation peaks.This reduction in separation distance may have two effects: increased wall thickness and increased circumferential strength. The stiffness of the pipe may depend on the wall thickness, inner surface finish, hydraulic diameter, and material properties. When the gas velocity exceeds a certain critical value (critical velocity) that depends on the hydraulic diameter and inner surface roughness relative to the length, bending modes of the pipe are excited. Thus, by controlling the longitudinal and radial expansion of the elongated tube, the sheath may indirectly affect the critical velocity relative to a pipe with a uniform hydraulic diameter and uniform wall thickness. Specifically, the critical velocity of the breathing gas may be increased by up to several times relative to a comparable pipe with a uniform wall thickness and hydraulic diameter. Thus, for the operating length of the elongated tube when passing moist breathing gas at typical maximum velocities appropriate for treatment, the sheath may reduce the likelihood of vibration modes along the elongated tube.

[0450] Expansion of long thin tubes during use

[0477] The use and behavior of the exemplary conduit 700 is described below, by way of example, with reference to Figures 21-26. It should be understood that this description is of a particular example only, and that the structure and arrangement of the conduit in other examples may be selected to behave differently. In other examples, the conduit may alternatively be constructed and arranged to expand primarily longitudinally, or expansion may be limited to only one of the longitudinal or radial directions by selecting a sheath having appropriate characteristics, e.g., braid pattern, length vs. diameter gradient, etc.

[0451]

[0478] It should be understood that Figure 21 is not drawn to scale and that the dimensional and proportional changes between different states may be exaggerated for illustrative purposes. Also, Figure 21 illustrates a substantially uniform expansion of elongated tube 702, except for the tapered portion toward connector 706. As described elsewhere, the expansion may not necessarily be uniform during use.

[0452]

[0479] 21(a)-(d) (left side of FIG. 21) show schematic diagrams of an elongated tube 702 without a sheath 704 and a pair of connectors 706 (referred to as unsheathed conduits 2108) in a variety of different configurations.

[0453]

[0480] 21(e)-(h) (right side of FIG. 21) show schematic diagrams of the exemplary conduit 700 described above, including a sheath 704, in a variety of different configurations.

[0454]

[0481] 21(a) and (e) show unsheathed conduit 2108 and conduit 700, respectively, in an unpressurized, equilibrium state.

[0455]

[0482] 21(b) and (f) show the unsheathed conduit 2108 and conduit 700, respectively, in an unpressurized, partially conditioned state. It can be seen that both the unsheathed conduit 2108 and conduit 700 expand both radially and longitudinally, but to a lesser extent in the conduit 700 than in the unsheathed conduit 2108.

[0456]

[0483] 21(c) and (g) show unsheathed conduit 2108 and conduit 700, respectively, in an unpressurized, conditioned state after extended use. It can be seen that unsheathed conduit 2108 has expanded further in both the radial and longitudinal directions, while conduit 700 has expanded further in the radial direction but contracted in the longitudinal direction. Conduit 700 may return to or approach its original length.

[0457]

[0484] 21(d) and (h) respectively show unsheathed conduit 2108 and conduit 700 in the same conditioned state after extended use, but now in a pressurized state. Unsheathed conduit 2108 can be seen to have expanded further in both the radial and longitudinal directions, while conduit 700 remains unchanged.

[0458]

[0485] 21(a) and (e), when initiating respiratory treatment of a patient, a new ventilation circuit 142 can be set up with a gas source 102. The conduit 700 may be removed from a package in which the gas in its lumen 1202 has approximately the same temperature and humidity as the gas outside the tube wall of the elongated tube 702 in the package. That is, there is no vapor pressure difference driving the transfer of water molecules through the tube wall of the elongated tube 702. The gas in the package may have a similar temperature and relative humidity to the ambient air, and thus the conduit 700 may be at or near equilibrium when removed from the package. In some cases, after being removed from the package, the conduit 700 may be left alone (e.g., stored in a ready-to-use state) until it is to be used, during which time ambient air fills the lumen of the elongated tube 702. If the humidity of the ambient air is different from the humidity in the package, the elongated tube 702 may absorb or release water molecules while equilibrating with the ambient air. The unsheathed conduit 2108 and the conduit 700 are shown in this equilibrium state in Figures 21(a) and 21(e), respectively, in which there is a gap 1502 between the elongated tube 702 and the sheath 704 of the conduit 700, as described above.

[0459]

[0486] The sheath 704 may be configured to be at least partially spaced from the elongate tube 702 in this equilibrium state. This spacing may mitigate further stiffening of the conduit 700 in the equilibrium state. An overly stiff conduit 700 may be problematic for ease of use. For example, tube drag at the yoke 110 or patient interface 112 may increase. In some instances, the sheath 704 in this equilibrium state may not contribute at all or may only contribute negligibly to the stiffness of the conduit 700.

[0460]

[0487] As shown in FIG. 21(e), the sheath 704 at each end may taper towards the respective connector 706, at least in an equilibrium state.

[0461]

[0488] It has been found that the breathable material of the elongate tube 702 may be sufficiently rigid to meet at least one or more of the compliance and flow resistance requirements of the ISO 5367:2014(E) standard when the conduit 700 is in an equilibrium state or when conditioned as specified in the standard, however, the conduit 700 may not necessarily meet one or more of these requirements in the conditioned state as defined herein.

[0462]

[0489] When the conduit 700 is connected to a respiratory assistance system and treatment is initiated, the lumen of the elongated tube 702 is exposed to a flow of respiratory gas whose relative humidity may be greater than 90% at the patient end and often about 100%. Ambient air may have a relative humidity between about 10%-90%, and often within the range of about 40%-60% or 45%-55% recommended for everyday health and comfort. There is a difference in partial pressure of water vapor between the respiratory gas in the lumen 1202 and the ambient air outside the elongated tube 702. By a solution-diffusion mechanism, the breathable material of the elongated tube 702 continuously absorbs water molecules from the respiratory gas and condensed water (if any) or other liquids (if any) in the lumen and releases the water molecules to the ambient atmosphere outside the elongated tube 702 according to a driving gradient.

[0463]

[0490] 27, the expansion of the elongate tube 702 in a conditioned state during use may not necessarily be uniform along the length of the elongate tube 702. However, for purposes of explanation, the following description will assume that the dimensional changes of the elongate tube 702 and sheath 704 are generally uniform.

[0464]

[0491] Due to the initial absorption of water molecules from within the lumen, the unsheathed conduit 2108 and the elongated tube 702 of the conduit 700 tend to expand in both the longitudinal direction 902 and the radial direction 1504 (as well as in wall thickness).

[0465]

[0492] In the case of an unsheathed conduit 2108, this expansion is unrestricted as shown in FIG. 21(b).

[0466]

[0493] In the case of the conduit 700, the spacing 1502 between the elongate tube 702 and the sheath 704 means that the elongate tube 702 can expand somewhat in both the longitudinal and radial directions. The longitudinal expansion of the elongate tube 702 causes a corresponding elongation of the sheath 704. The elongation of the elongate tube 702 and the sheath 704 can then cause the sheath 704 to contract in the radial direction.

[0467]

[0494] 21(c) and (g), with extended use of the conduit 700 and exposure to humidity differentials (i.e., further absorption of water molecules), the elongated tube 702 may engage the inner surface of the sheath 704. The spacing 1502 between the elongated tube 702 and the sheath 704 may disappear along at least a portion of the length of the elongated tube 702. Further expansion of the elongated tube 702 in at least one of the radial and longitudinal directions may be limited by the sheath 704. That is, each of the braided elements of the sheath 704 is under tension and the sheath 704 has a circumferential stress due to the expansion and engagement of the elongated tube 702.

[0468]

[0495] As the elongated tube 702 continues to absorb water molecules from the lumen, further radial expansion of the elongated tube 702 may occur, which may cause longitudinal contraction of the sheath 704. The conduit 700 may return to or near its original length (e.g., between about 90%-110%) (at equilibrium).

[0469]

[0496] Pressurization of the unsheathed conduit 2108 may result in further expansion in both the radial and longitudinal directions, as shown in Figure 21(d). This may be due in part to softening of the breathable material due to absorption of a relatively large amount of water molecules. However, the sheath 704 limits further expansion of the conduit 700, as shown in Figure 21(h).

[0470]

[0497] As discussed above, as the length of the elongate tube 702 changes during use, the pitch of the corrugations (i.e., the distance between adjacent peaks of the corrugations of the elongate tube 702) may also change. However, in the conduit 700, this variation is limited by the sheath 704, as is evident, for example, from a comparison of Figure 21(b) (without sheath) with Figure 21(f) (with sheath). It will be appreciated that in instances where the elongate tube 702 first expands longitudinally due to the interaction of the elongate tube 702 with the sheath 704 and then contracts back to its original length or a length close to it, the pitch of the corrugations of the elongate tube 702 will similarly increase and then decrease back to the original corrugation pitch or a distance close to it.

[0471]

[0498] As described elsewhere, the elongated tube 702 may not necessarily absorb water molecules uniformly along the length of the corrugations 1016. In particular, it will be appreciated that the breathing gas in the lumen may have a higher absolute humidity at the patient end of the conduit due to the dehumidifying effect of the breathable material on the breathing gas as it travels along the length of the elongated tube 702 toward the gas return inlet 140. Furthermore, due to gravity, condensed water formed in the lumen may flow toward and accumulate at one or more lowest portions of the annular corrugations 2202 and the elongated tube 702 (as a whole). This may cause the breathable material of the elongated tube 702 to absorb a higher concentration of water molecules in a first region of the elongated tube 702 compared to a second region of the elongated tube 702. This may cause localized expansion of the breathable material in one or more of the radial and longitudinal directions in the first region. And, the pitch (number of corrugations per unit length) of the corrugations 2202 may vary along the length of the elongated tube 702.

[0472]

[0499] The sheath 704 may allow for greater expansion of the elongated tube 702 in the first region than if the absorption and expansion were uniform along the length of the elongated tube 702. The diameter of the elongated tube 702 in the first region may exceed the average diameter of the elongated tube 702 as a whole. The expansion of the elongated tube 702 in the first region may take up slack in the sheath 704 due to the spacing 1502 in the second region of the elongated tube 702. This localized expansion may increase the surface area and permeability of the breathable material in the first region of the elongated tube 702 compared to the second region where increased permeability is most desired (i.e., in the region of the highest concentration of water molecules within the lumen where condensation is most likely to exist or form).

[0473]

[0500] The behavior of a conduit according to the present disclosure can be modified or tailored by varying a number of factors to meet specific design requirements. Many factors known to affect the behavior of a conduit according to the present disclosure include at least the following: i. Sheath length / diameter (L / D) characteristics; ii. The profile and pitch of the corrugations of the elongated tube; and iii.The spacing between the elongated tube and the sheath.

[0474]

[0501] 22 illustrates in cross section an example profile of the corrugations 2202 of the elongated tube 702 in an equilibrium state. The sheath 704 has been omitted from this drawing. The drawing shows only the upper portion of the length of the elongated tube 702 in a horizontal orientation, with the lumen 1202 toward the lower portion of the drawing and the ambient air at the top of the drawing.

[0475]

[0502] Each of the corrugations 2202 has a sidewall 2204 that converges toward a peak 1602 of the corrugation 2202 (ie, defines the maximum outer diameter of the corrugation 2202 and the elongate tube 702) when the elongate tube 702 is in an equilibrium state.

[0476]

[0503] The peaks 1602 may be substantially rounded. Each valley 1604 of the corrugations 2202 may be substantially flattened, i.e., each valley region may be substantially cylindrical (at least when the elongated tube 702 is arranged in a straight configuration).

[0477]

[0504] FIG. 23 illustrates, in cross-section, the profile of the waveform 2202 of FIG. 22 when the elongate tube 702 is in a conditioned state, more specifically, in a conditioned state in which the expansion of the elongate tube 702 is limited by the sheath 704.

[0478]

[0505] As the material of the elongated tube 702 expands due to the absorption of water molecules, the sheath 704 limits the longitudinal expansion of the elongated tube 702, as described above. As the elongated tube 702 expands against the constraints of the sheath 704, the corrugations 2202 may compress longitudinally closer together. This may cause the profile of the corrugations 2202 to change from the cross-section shown in FIG. 22 to the cross-section shown in FIG. 23. That is, as the elongated tube 702 expands against the constraints of the sheath 704, the sidewalls may reorient toward and possibly beyond the radial direction (i.e., vertically as shown). The sidewalls may reorient from an acute angle with the longitudinal direction to a radial direction (90° relative to the longitudinal direction) or possibly beyond the radial direction to an obtuse angle with the longitudinal direction.

[0479]

[0506] In the particular conditioned state shown in FIG. 23, each of the sidewalls 2204 has a generally radial orientation (extending vertically in this cross-sectional view, at 90° to the longitudinal direction), such that the sidewalls 2204 are substantially planar and adjacent sidewalls 2204 are generally parallel to one another (at least when the elongated tubes 702 are arranged in a straight configuration).

[0480]

[0507] The peaks 1602 of the corrugations 2202 joining adjacent sidewalls 2204 may also be relatively flat when compared to the initial profile of Figure 22. That is, the peaks of the corrugations 2202 may be substantially cylindrical, as shown in Figure 23. Alternatively, at equilibrium, the peaks may be continuously curved between the sidewalls 2204, as shown in Figure 22.

[0481]

[0508] The radial orientation of the sidewall 2204 in FIG. 23 represents the radial force component F R 22 , which means that a force vector 2206 equivalent to a radial force component F opposes a radially inward collapsing force. The collapsing force may be due to, for example, the weight of a patient's arm lying on the conduit. On the other hand, an unsheathed conduit 2108 may tend to maintain a wave profile generally similar to that of FIG. 22 as it expands. The force vector 2206 of FIG. 22 corresponds to a radial force component F R and the longitudinal axial force component F A The radial force component F R can be relatively smaller than that in FIG.

[0482]

[0509] As the material expands, the corrugations may tend to compress closer together due to the axial constraint of the sheath 704 relative to the elongated tube 702. This axial "spring compression force" may follow Hooke's Law, stiffening the elongated tube 702 and acting against atmospheric pressure, compressing the elongated tube 702 axially as the internal pressure decreases.

[0483]

[0510] The longitudinal restriction imposed by the sheath 704 may cause the corrugations to grow toward the gaps between the corrugations 2202 (i.e., thicker corrugations) due to absorption of water molecules. The radial restriction may cause the corrugations to grow radially inward (i.e., toward the center of the elongated tube 702). In some instances, the gaps between the corrugations 2202 may close partially or completely, resulting in effectively a single thick wall section without any rotation axis or moment effects due to the radius of the corrugations.

[0484]

[0511] One or more of these effects caused by the interaction of the elongated tube 702 and the sheath 704 as the elongated tube 702 expands due to the absorption of water molecules may mitigate the softening of the breathable material. This may enable the conduit 700 to comply with one or more of relevant standards and other voluntary design requirements across a range of different operating conditions. For example, certain exemplary unsheathed conduits 2108 have been found to have a compliance (as defined below in the glossary) of greater than 4 milliliters per centimeter of water (ml / cmH2O) or 5 ml / cmH2O when tested in conditioned conditions. In some examples, the conduit 700 of the present disclosure with a sheath 704 may have a compliance of less than about 4 ml / cmH2O, less than about 2.5 ml / cmH2O, or less than about 1.2 ml / cmH2O when tested according to the ISO 5367:2014(E) standard in conditioned conditions as defined herein.

[0485]

[0512] In other examples, compliance standards can be met over the entire range or subrange of expected operating conditions (conditioned states) by selecting a breathable material or configuring the elongated tube to absorb a relatively low percentage of water molecules, for example, between about 40%-60% of its dry mass.

[0486]

[0513] FIG. 23 also shows an alternative sheath 704 in which each braided element has three filaments 1802 arranged in parallel.

[0487]

[0514] FIG. 24 shows a cross section of a portion of an elongated tube 702 of a conduit 700 in an equilibrium state, where the elongated tube 702 is not constrained by a sheath 704 (not shown in this view).

[0488]

[0515] The sidewalls 2204 of each corrugation 2202 generally converge toward the peak 1602 of the corrugation 2202. In some examples, the sidewalls 2204 may be configured to extend from the adjacent valley at an angle θ of between about 65° and 85°, or between about 70° and 80°, relative to the longitudinal direction (horizontal in this drawing) in this equilibrium state. In the example elongate tube 702 depicted in FIG. 24, the sidewalls 2204 may extend at an angle θ of about 75° in the equilibrium state.

[0489]

[0516] 24, it can be observed that the valleys are relatively flat. As shown, in a cross section of the elongated tube 702 disposed substantially linearly between adjacent sidewalls 2204, the outer surface of the valleys may be substantially linear. The outer surface of the elongated tube 702 at the valleys may be substantially cylindrical. In contrast, the peaks 1602 may be substantially continuously curved between adjacent sidewalls 2204.

[0490]

[0517] 25 is a cross-section of elongated tube 702 in a conditioned state without sheath 704 limiting the expansion of elongated tube 702. FIG. 25 is drawn to approximately the same scale as FIG.

[0491]

[0518] Upon absorbing water molecules, it can be observed that due to unrestrained expansion of the elongated tube 702 in the longitudinal direction (horizontal in this figure), there are fewer corrugations 2202 for a given length of the elongated tube 702 (about three corrugations 2202 in FIG. 25 compared to about four corrugations 2202 in FIG. 24). The sidewalls 2204 of each corrugation 2202 generally converge toward the peak of the corrugation at about the same angle θ as in the equilibrium state of FIG. 24. That is, it was found that the sidewalls 2204 of the exemplary elongated tube 702 of FIG. 25 extend at an angle θ of about 75° in the conditioned state without a sheath.

[0492]

[0519] It can also be observed that the corrugation depth 2402, measured from the peak 1602 to the adjacent valley 1604 of the corrugations 2202 on the outer surface of the elongated tube 702, is approximately 33% greater in the conditioned state depicted in FIG. 25 due to the unrestrained expansion of the elongated tube 702.

[0493]

[0520] Figure 26 is a cross-section of elongated tube 702 in a conditioned state, this time constrained by a sheath 704 (not shown). Figure 26 is drawn to approximately the same scale as Figures 24 and 25.

[0494]

[0521] It can be observed that the pitch of the corrugations is approximately the same as in the balanced case of Figure 24. That is, the elongate tube 702 has approximately four corrugations 2202 in the illustrated length of the elongate tube 702.

[0495]

[0522] In this limited conditioned state, the sidewalls 2204 of the corrugations 2202 do not continuously converge from the valley to the peak of the corrugations 2202. In some examples, the sidewalls 2204 may form an angle θ of greater than 85°, about 90°, or greater than 90° (obtuse angle). That is, from an adjacent valley 1604 toward an intermediate peak 1602, the sidewalls 2204 of the corrugations first diverge and then converge toward the peak 1602.

[0496]

[0523] As the elongated tube 702 absorbs an increasing mass of water molecules, the side walls 2204 may reorient from the initial angle (75° in this example) to a radial direction (90°), and in some cases even beyond a radial direction (forming the obtuse angle θ shown in FIG. 26).

[0497]

[0524] 26, the side walls 2204 were found to extend at an angle θ of about 95°. Each of the side walls 2204 may have inflection points, and the peaks and valleys of each corrugation 2202 may also have inflection points.

[0498]

[0525] The profile of each of the corrugations 2202 in Figure 26 is substantially Ω (omega) shaped, whereas in Figures 21 and 22 the corrugations 2202 are generally more sinusoidal in cross-section (albeit with flattened valleys in this example). That is, in Figure 26 the corrugations fold back on themselves, whereas in Figures 21 and 22 they do not. This can form an inner narrowed waist region 2602 and an outer narrowed waist region 2604 between opposing sidewalls 2204 of adjacent corrugations 2202, midway between their respective peaks and valleys.

[0499] Uneven expansion

[0526] 27 illustrates a conduit 700 according to the present disclosure after extended use as an expiratory conduit 114 of an exemplary respiratory assistance system 2700. This drawing is not necessarily to scale. In particular, the expansion of the elongated tube 702 or sheath 704 may be exaggerated for illustrative purposes. Additionally, the inspiratory conduit 108 and expiratory conduit 114 are not shown to scale.

[0500]

[0527] Except as apparent from the drawings and the description below, respiratory assistance system 2700 may be similar to respiratory assistance system 100.

[0501]

[0528] 27 shows a filter 2702 at the gas return inlet 140 of the gas source 102. The filter 2702 may be connected directly between the expiratory conduit 114 and the gas return inlet of the gas source 102.

[0502]

[0529] The humidifier 106 in this example may be an F&P 820™ heated humidifier available from Fisher & Paykel Healthcare Limited.

[0503]

[0530] The respiratory assistance system 2700 in this example is shown in use after an extended period of delivery of humidified respiratory gas to a patient (not shown), it being understood that this represents only one of many different possible conditioned states depending on many variables including, for example, but not limited to, time of use, temperature of the respiratory gas, humidity of the respiratory gas, temperature of the ambient air, humidity of the ambient air, conduit path, type and model of gas source, patient condition and humidity contribution, atomized material, and wind impinging on the conduit.

[0504]

[0531] In this example, the expiratory limb 146, and specifically the expiratory conduit 114, omits both the heater wire and the water trap.

[0505]

[0532] As shown, the expiratory conduit 114, and more particularly the elongate tube 702 and sheath 704, are flexible at least in this conditioned state. The expiratory conduit 114 may also be flexible (possibly to different degrees) in any one or more of a dry state, an equilibrium state, and a saturated state. Because of its flexibility, the expiratory conduit 114 may assume a curved shape in use, as shown.

[0506]

[0533] It has been found that during use, the elongated tube 702 may not necessarily expand uniformly along its length between the connectors 706. That is, in a conditioned state, the diameter of the elongated tube 702 may not necessarily be uniform along its length. This may be because the concentration of water molecules within the lumen may vary along the length of the elongated tube 702. This variation may be due to one or more variations in humidity of the breathing gas (i.e., water vapor) and accumulation of condensed water (i.e., liquid water) along the length of the elongated tube 702. Meanwhile, the partial pressure of water vapor in the ambient air outside the elongated tube 702 is relatively constant along the length of the elongated tube 702.

[0507]

[0534] In this exemplary conditioned state, localized expansion of the elongate tube 702 can be observed in three distinct regions of the expiratory conduit 114: the inlet region 2704, the outlet region 2706, and the intermediate region 2708. In other examples, there may be more than one intermediate region 2708. In still other examples, the elongate tube 702 may have localized expansion in any one or more of the inlet region 2704, the outlet region 2706, and one or more intermediate regions 2708. In still other examples, there may not be any clear localized expansion.

[0508]

[0535] A region of localized expansion may be a portion of the length of the elongated tube 702 that has a larger diameter compared to an adjacent region (or regions) of the elongated tube 702. In these regions, the elongated tube 702 may have a bulging appearance. The bulging may be tapered. In some instances, the localized expansion may be readily apparent to the naked eye. In some instances, the region of localized expansion may have a maximum diameter that is at least about 5%, at least about 10%, at least about 20%, or at least about 30% larger than an adjacent region (or regions) of the elongated tube 702 (e.g., with respect to the exit region 2706, the region intermediate the exit region 2706 and the intermediate region 2708).

[0509]

[0536] It should be understood that the term "localized expansion" does not imply that the expansion is limited to these regions. The term is used in a relative sense, i.e., expansion may be more pronounced in the regions of localized expansion than in adjacent regions.

[0510]

[0537] Below, when describing the inlet region 2704, the outlet region 2706, and the intermediate region 2708, references to percentages of the length of the elongate tube 702 refer to the length of the elongate tube 702 between the connectors 706, e.g., the length excluding the cuff portion 1002 within the connector 706. It will be understood that the sum of these lengths does not exceed 100% of the length of the elongate tube 702 between the connectors 706. In some examples, the sum of the lengths of the inlet region 2704, the outlet region 2706, and the intermediate region 2708 may be less than about 75%, less than about 50%, or less than about 33% of the total length of the elongate tube 702 between the connectors 706.

[0511]

[0538] The inlet region 2704 may be within or correspond to a portion of the length of the elongated tube 702 closest to one or more of the yoke 110, the patient interface (not shown), and the patient (not shown). In some examples, the inlet region 2704 may be up to about 50%, up to about 33%, up to about 25%, up to about 20%, or up to about 10% of the length of the elongated tube.

[0512]

[0539] It has been found that at least one of the relative humidity of the breathing gas and the volume of condensed water within the lumen of the elongated tube 702 may be increased in the inlet region 2704 as compared to one or more other regions of the elongated tube 702, such as compared to a region intermediate the inlet region 2704 and the intermediate region 2708, or compared to a region intermediate the intermediate region 2708 and the outlet region 2706. The increase in relative humidity may be due, for example, to the dehumidifying effect of the breathable material as the breathing gas travels along the length of the lumen. The increase in the volume of condensed water may be due, for example, to condensed water being drained into the inlet region 2704 from the wye 110 or further upstream from the wye, such as the catheter mount, the patient interface, and the patient (none of which are shown in FIG. 27). At least some of this condensed water may accumulate within the corrugations of the elongated tube 702 at the inlet region 2704.

[0513]

[0540] The outlet area 2706 may be within or correspond to a portion of the length of the elongated tube 702 closest to one or more of the filter 2702, the gas return inlet 140, and the gas source 102. In some examples, the outlet area 2706 may be up to about 50%, up to about 33%, up to about 25%, up to about 20%, or up to about 10% of the length of the elongated tube.

[0514]

[0541] It has been found that at least one of the relative humidity of the breathing gas and the volume of condensed water within the lumen of the elongate tube 702 may be increased in the outlet region 2706 as compared to one or more other regions of the elongate tube 702, such as compared to a region intermediate the inlet region 2704 and the intermediate region 2708, or compared to a region intermediate the intermediate region 2708 and the outlet region 2706. The increased relative humidity or increased volume of condensed water may be due, for example, to condensed water being drained from the filter 2702 or the gas source 102 to the outlet region 2706.

[0515]

[0542] The intermediate region 2708 can be within a portion of the length of the elongate tube 702 that is intermediate the inlet region 2704 and the outlet region 2706. The intermediate region 2708 can be up to about 50%, up to about 33%, up to about 25%, up to about 20%, or up to about 10% of the length of the elongate tube.

[0516]

[0543] It has been found that at least one of the relative humidity of the breathing gas and the volume of condensed water within the lumen of the elongate tube 702 may be elevated in the intermediate region 2708 as compared to one or more other regions of the elongate tube 702, such as as compared to a region intermediate the inlet region 2704 and the intermediate region 2708, or as compared to a region intermediate the intermediate region 2708 and the outlet region 2706.

[0517]

[0544] The flexibility of the expiratory conduit 114 means that it may tend to sag between the yoke 110 and the gas source 102. This sagging may result in at least one low point 2710 between the yoke 110 and the gas source 102. This low point 2710 may be at a lower elevation than both ends of the expiratory conduit 114 (e.g., lower than the yoke 110 and the gas return 140). Condensed water within the lumen 1202 may tend to flow by gravity towards and accumulate at the low point 2710. This condensed water may have formed within the elongated tube 702 or may have entered the conduit from other components of the respiratory assistance system 2700 (such as the catheter mount, the yoke, the connector, or the patient). The increase in relative humidity or volume of condensed water in the intermediate region 2708 may be due to condensed water accumulating at the low point 2710.

[0518]

[0545] In some instances, during use, the conduit 700 has been found to first exhibit localized expansion at the inlet region 2704, which may then be followed by localized expansion at one or more of the outlet region 2706 and intermediate region 2708, for example, as condensation begins to form at the filter 2702 or gas source 102 and flows into the conduit 700. In some applications, periodic replacement of the filter 2702 may alleviate condensation within the filter and localized expansion at one or more of the outlet region 2706 and intermediate region 2708.

[0519]

[0546] Similarly, the expansion of the elongated tube 702 may not necessarily be uniform across one or more of the circumference and wall thickness of the tube wall, e.g., in a cross-section perpendicular to the longitudinal direction. For example, condensed water within the elongated tube 702 may accumulate in the lower region of the annular corrugations (i.e., peak 1602 when viewed from the outside of the elongated tube 702) due to gravity. In this case, the elongated tube 702 may expand more in this lower region compared to the upper region of the corrugations. It should be understood that the lowest point of the corrugations in real space is actually the "peak" of the corrugations when viewed in cross-section or when viewed from the outside of the elongated tube.

[0520]

[0547] It has been found that expansion of breathable materials can increase their permeability to water molecules when compared to restricted breathable materials under the same conditions, which may be due to the relatively larger surface area of ​​the expanded breathable material.

[0521]

[0548] The non-uniform expansion of the elongated tube 702 may advantageously increase the permeability of the elongated tube to water molecules where it is needed most, such as one or more of the inlet region 2704, the outlet region 2706, and the mid-region 2708. The elongated tube 702 may automatically adapt to different or changing operating conditions during use. In contrast, a water trap is provided at a fixed location along the length of the conduit, such as at a mid-point. As shown in FIG. 27, the mid-point or other fixed location does not necessarily coincide with a low point 2710 of the conduit, greatly limiting its effectiveness.

[0522] manufacturing

[0549] FIG. 28 is a flow chart illustrating an exemplary method 2800 of manufacturing a conduit 700 according to the present disclosure.

[0523]

[0550] In step 2802, a continuous length of tubing suitable for use as elongated tube 702 may be produced by extruding a breathable material.

[0524]

[0551] In step 2804, the extruded tube may be at least partially corrugated by passing the semi-molten extruded tube through a corrugation forming block. In some instances, some portions of the extruded tube may be left uncorrugated. These portions may become the uncorrugated cuff portions 1002. Alternatively, the entire extruded tube may be corrugated.

[0525]

[0552] In step 2806, the elongated tube 702 can be formed by cutting a length from the extruded and corrugated tube. In some examples, the extruded and corrugated tube can be cut at the non-corrugated portion. The cut can be made substantially in the center of the non-corrugated portion.

[0526]

[0553] In step 2808, a sheath 704 may be provided around the elongated tube 702. The elongated tube 702 may be inserted into the sheath 704. In some examples, the sheath 704 may be pre-cut to a predetermined length in step 2818. The sheath 704 may be cut from a roll of flattened braided tubular mesh sheath. The sheath 704 may be cut to a length longer than the elongated tube 702 when it is deformed to fit over the outside of the elongated tube 702, as described above.

[0527]

[0554] At step 2810, the first connector component 1004 may be inserted into a first end of the elongate tube 702. In some examples, at step 2820, the first connector component 1004 may be pre-injection molded.

[0528]

[0555] At step 2812, the first connector component 1004, the first end of the elongate tube 702, and the corresponding first end of the sheath 704 may be clamped together in a mold. The mold may include protrusions to hold the first end of the sheath 704 overlapping with the first end of the elongate tube 702. In some examples, the mold may include an opposing pair of protrusions.

[0529]

[0556] In step 2814, molten plastic material may be injected into the mold to form the second connector component 1006. That is, the second connector component 1006 may be overmolded onto the first connector component 1004, the first end of the elongated tube 702, and the first end of the sheath 704 to permanently secure those components. The aperture 1014 is formed by the molten plastic material flowing around the protrusions that clamp the elongated tube 702 and the sheath 704 in place. Once the molten plastic material cools and solidifies, the connector 706 is complete and may be removed from the mold.

[0530]

[0557] Steps 2810-2814 may be repeated or the same steps may be performed simultaneously and overlapping to form a second connector 706 at the opposite second end of the conduit 700. The sheath 704 may first be longitudinally contracted in step 2816 such that its end coincides with and overlaps the corresponding end of the elongate tube 702 to form the gap 1502. In some examples, the connectors 706 of the conduit 700 may be identical. In other examples, the connectors at both ends of the conduit may differ from one another. In some examples, only one of the first connector component 1004 and the second connector component 1006 may differ between the two connectors 706. In other examples, both may differ.

[0531]

[0558] In other examples, the second connector component 1006 may be separately injection molded. The second connector component 1006 may be attached to the first connector component 1004 by, for example, welding, adhesive, or an interference fit (e.g., a snap fit).

[0532] Glossary

[0559] "Breathable material" refers to a non-porous, permeable material that allows water molecules to pass through the monolithic wall of the breathable material via a solution diffusion mechanism, but does not allow bulk passage of liquid water or bulk flow of respiratory gas through the wall. Those skilled in the art will understand that the water molecules in the wall are molecularly dispersed in a medium and therefore exist in no state (solid, liquid, gas), although they are sometimes referred to in the art as vapor (e.g., the rate of movement is often referred to as moisture vapor transmission rate (MVTR) or the like). It should further be understood that a monolithic wall does not contain open channels or pores from one major surface to the other such that pathogens may be transported through such channels by capillary action along with air and liquid water droplets. However, this definition is not intended to exclude tubes formed from breathable materials that may have one or more holes through the material, such as those that may be caused by manufacturing defects, that may cause negligible microscopic pore flow that does not substantially affect the overall performance of the tube and does not affect compliance with the leakage requirements of ISO 5367:2014. Additionally, it should be understood that, as with all polymers, small molecule transport of respiratory gases (such as oxygen, carbon dioxide, nitrogen, or helium) may occur in trace or insignificant amounts (i.e., not "bulk" flow), which for breathable materials as defined herein is typically at least an order of magnitude lower than the amount of water molecules. Moreover, of particular relevance to respiratory gases delivered to or exhausted from a patient, such small molecule transport of respiratory gases may be in amounts less than that which would qualify for compliance with relevant standards, for example, in the leak test in Section 5.4 of ISO 5367:2014 (herein incorporated by reference in its entirety) as tested by the method set forth in Annex E.

[0533]

[0560] "Compliance" is defined in section 3.1.5 by ISO standard 4135:2001 (incorporated herein in its entirety by reference) as "the volume added per unit pressure increase when a gas is added to an enclosed space, expressed at atmospheric pressure, temperature and humidity of that enclosed space" (Copyright ISO 2001). The method for testing compliance of a conduit according to the present disclosure is based on the method set out in Annex E of ISO 5367:2014 (incorporated herein in its entirety by reference). First, leaks in the conduit equivalent to or exceeding 1 ml / min are sealed (as described in Annex E). Second, the conduit is conditioned at 42±3°C and at least 80% relative humidity for at least 1 hour. Third, one end of the conduit is occluded and the conduit is placed on a flat surface. Fourth, a pressure measuring device is connected to the opposite end of the conduit. Fifth, the conduit is inflated to a stable gauge pressure of 60±3 cmH2O for a period of no more than 5 seconds and the volume of air required is recorded. It will be understood that the conditioning defined by the standard may not reflect conditions of use and that the standard was not written with breathable materials in mind. To better reflect conditions of use, the compliance of a conduit formed at least in part from a breathable material can additionally or alternatively be further tested by conditioning the conduit to simulated conditioned conditions described below.

[0534]

[0561] "Conditioned" refers to one of a set of conditions in which the elongated tube is exposed to a water vapor pressure gradient and the water vapor partial pressure within the lumen is relatively high (i.e., higher than that of the ambient air) over an extended period of time. That is, the walls of the elongated tube have absorbed water molecules from within the lumen and may continue to absorb water molecules from within the lumen. In particular, a conduit that has been used to carry a flow of humidified breathing gas for a period of time and continues to be used may be said to be in a conditioned state. Thus, the walls of an elongated tube in a conditioned state will generally contain a higher concentration of water molecules than in a dry or equilibrium state, but less than in a saturated state. Reference herein to a particular characteristic of a conduit in a "a" (singular) conditioned state is not necessarily intended to apply to all conditioned states, unless otherwise clear from the context. Depending in particular on the design requirements and configuration of the conduit parameters, the relative humidity and temperature of the respiratory gas and ambient air, and the concentration of water molecules within the breathable material of the elongated tube, the expansion of the elongated tube may or may not be limited by the sheath in a particular conditioned state. That is, within the set of conditioned states, there may be a subset of unrestricted and restricted conditioned states. The conditioned states can be simulated by conditioning the conduit according to the following method: First, an ambient temperature of 22±2° C. is reached and maintained throughout the conditioning method. Second, the conduit is placed in a V-tray at equilibrium. Third, the lumen of the conduit is supplied with a gas flow at a flow rate of 10 standard liters per minute (SLPM) (reference 20° C., 101.325 kPa) and humidified for 24 hours by a humidifier set to a humidity level of 100% relative humidity (RH) and 37° C. dew point.

[0535]

[0562] "Restriction" refers to a non-negligible force exerted by the sheath on the elongate tube acting to restrain expansion of at least a portion of the elongate tube in at least one of the longitudinal and radial directions. The effect of the restriction may be localized to a portion of the tube as the tube transitions from an equilibrium state to a conditioned state, or from an unrestricted conditioned state to a restricted conditioned state. Further expansion of the elongate tube restricted by the sheath may be possible, but such expansion requires an expansion force that exceeds the restrictive force exerted by the sheath. That is, "restriction" does not necessarily mean that further expansion is completely prevented. Related terms "restricted," "restriction," "restricting," and the like should be interpreted similarly. In contrast, "unrestricted" refers to the absence of, or the presence of a negligible force exerted by the sheath on the elongate tube to resist expansion of the elongate tube. For example, the force required to deform a sheath that is not subject to hoop stress (e.g., when the conduit is in equilibrium and there is a gap between the elongated tube and the sheath, the sheath is not subject to hoop stress) may be considered a "negligible force." Expansion of the elongated tube in the presence of such a negligible force may be considered to be "unconstrained" by the sheath. Alternatively, one may say that the elongated tube is "free" to expand.

[0536]

[0563] "Differential Scanning Calorimetry (DSC)" refers to a DSC test for melting point temperature performed on an elongated tube test sample based on the method set forth in ISO standard 11357-3:2018(E) (© ISO, 2018), the entire contents of which are incorporated herein by reference. In a first step, the test sample is prepared according to ISO 11357-1:2023, the entire contents of which are incorporated herein by reference. Next, the test sample is dried according to the drying method of ISO 62:2008(E), which is briefly described with respect to the second step of the immersion test method defined below. Third, the apparatus is set up, the test sample is loaded into the crucible, and the crucible is inserted according to ISO 11357-1:2023. Fourth, the test sample is heated from a temperature of about -20°C to a temperature of about 250°C at a rate of about 10°C per minute (°C / min). Fifth, the temperature is maintained for 5 minutes. Sixth, the test sample is cooled from about 250° C. to a temperature of about −20° C. at a rate of about −10° C. / min. Seventh, the temperature is maintained for 5 minutes. Eighth, the test sample is again heated from a temperature of about −20° C. to a temperature of about 250° C. at a rate of about 10° C. / min, while recording the differential calorific value (measured in milliwatts per milligram, mW / mg) of the sample specimen. The differential calorific value can be plotted versus temperature, and the temperature corresponding to the peak of the plot identifies the melting point of the test sample.

[0537]

[0564] "Dry" refers to the state of elongated tubing or samples thereof that have been dried according to the drying method of ISO 62:2008(E), briefly described with respect to the second step of the immersion test method defined below. This is an "artificial" state, which elongated tubing will not typically be in during normal use (e.g. in assisted breathing systems). The tube walls of elongated tubing in the dry state typically have a lower concentration of water molecules than in the equilibrium, conditioned and saturated states.

[0538]

[0565] "Equilibrium" generally refers to a condition in which an elongated tube, generally free of condensed or other liquid water, is exposed to ambient air in a controlled environment, e.g., 40% to 60% relative humidity, both within the lumen of the elongated tube and on the outside of the tube wall, for a period of time sufficient for the elongated tube to reach a steady state. That is, the concentration of water molecules within the breathable material is in equilibrium with the ambient air. The tube wall of an elongated tube in equilibrium contains a concentration of water molecules that is generally higher than in a dry state, but generally lower than in a conditioned or saturated state. Depending on the configuration of the conduit parameters of the conduit, the ambient conditions (including the temperature and relative humidity of the ambient air), and the concentration of water molecules within the breathable material of the elongated tube, the expansion of the elongated tube may or may not be restricted by the sheath. However, in at least some instances, the conduit may be designed to have a spacing between the sheath and the elongated tube in equilibrium to allow at least a portion of the elongated tube to expand before being restricted by the sheath.

[0539]

[0566] "Immersion test" refers to a test to measure water absorption based on the ISO 62:2008(E) standard (© ISO, 2008), which is incorporated herein by reference in its entirety. First, at least three tubular test specimens are cut from the elongated tube to lengths of 25±1 mm. The cuts are made perpendicular to the longitudinal direction of the elongated tube. The cut edges should be smooth and crack-free. The specimens contain only the active plastic responsible for the water absorption properties. The heater wire, sleeve, and mechanical support materials are removed non-destructively, if possible. Second, the specimens are dried. The specimens may be dried for at least 24 hours in a convection or vacuum oven maintained at 50±2°C, or dried in a vacuum oven at 60°C, -40°C dew point, and 14 cubic meters per hour (m3) of air. 3Optionally, the specimen may be dried in an industrial dryer with a drying time of 1000 s (m) / h and a drying time of 600 min (m). The specimen is periodically weighed to the nearest 1 mg and returned to the oven / dryer until the mass is constant within ±1 mg. Third, the specimen is cooled to room temperature in the desiccator. Fourth, the specimen is weighed (m1) and its dimensions are measured. Fifth, the specimen is immersed in distilled water for 24 hours. There must be at least 8 ml of distilled water per square centimeter of the total surface area of ​​the specimen, and a minimum of 300 ml of distilled water per specimen. If necessary, the specimen may be placed in a stainless steel wire basket connected to an anchor weight by a stainless steel wire. Sixth, the specimen is removed from the water and the surface water is wiped off with a lint-free cloth. Seventh, within 1 minute of removing the specimen from the water, the specimen is weighed to the nearest 1 mg. Eighth, steps 6 (immersion) and 7 (weighing) are repeated until the mass of the specimen is constant within ±1 mg (m2). Ninth, if the sample is known or suspected to contain significant amounts of water-soluble components, the second step (drying) is repeated and the sample is weighed to correct for the water-soluble material lost during the immersion test. If the mass after reconditioning is less than the mass after conditioning, the difference represents the water-soluble material lost during the immersion test. The water absorption of each sample is calculated as the percent change in mass, c, relative to the initial mass, using the following formula:

number

number

[0540]

[0567] "ISO" refers to the International Organization for Standardization and, more specifically, to the international standards established by that organization. These standards are subject to copyright and may be purchased directly from the International Organization for Standardization (http: / / www.ISO.org).

[0541]

[0568] "Leak", "Leakage" and "Leakage Test" refer to the method described in Section 5.4 and Annex E of the ISO 5367:2014 standard (© ISO 2014), which is incorporated herein by reference in its entirety. This standard defines the following limits for a complete ventilation set or conduit supplied ready for use in a Ventilator Ventilation System (VBS) or anesthesia ventilation system: 70 ml / min for adult patients (intended delivery volume ≧300 ml), 40 ml / min for pediatric patients (50<300 ml), or 30 ml / min for neonatal patients (≦50 ml) at a pressure of 60±3 cmH2O. For a single ventilation tube not intended for use in a VBS or anesthesia ventilation system, the leakage limit is 25 ml / min at 60±3 cmH2O. Briefly, leakage is tested according to the standard by first conditioning the conduit at a temperature of 23±3° C. for at least 1 hour. One end of the conduit is then closed. Third, apply and maintain an internal gas pressure of 60±3 cmH2O. Fourth, record the air flow rate required to maintain that pressure. It will be understood that the conditioning defined in this standard may not reflect conditions of use, and that this standard has not been drafted with breathable materials in mind. To better reflect conditions of use, conduits made at least in part from breathable materials may additionally or alternatively be tested for leakage by conditioning the conduit to the simulated conditioned conditions described above.

[0542]

[0569] "Extended use," "extended use period," and "extended period," etc., refer to use of a conduit in a respiratory assistance system (or surgical ventilation system) carrying heated and humidified breathing gas (or insufflation gas) for a continuous period of at least 24 hours. Extended use periods may be simulated by the simulated conditioned conditions described above.

[0543]

[0570] "Flow resistance" and "Flow resistance test" refer to the method described in the ISO 5367:2014 standard (© ISO 2014), the entire contents of which are incorporated herein by reference in their entirety, in section 5.5 and annex F. This standard defines the flow resistance limits of the conduit as supplied ready for use as follows: for adult patients (intended delivery volume ≧300 ml), 0.06 cmH2O / l / min at a flow rate of 30 l / min, for pediatric patients (50<300 ml), 0.12 cmH2O / l / min at a flow rate of 15 l / min and 0.74 cmH2O / l / min at a flow rate of 2.5 l / min. Briefly, flow resistance is tested by first conditioning the conduit at a temperature of 23±3° C. for at least 1 hour. The flow rate of the flow control device is then adjusted and maintained for 30 seconds and the pressure is recorded. Third, the conduit is attached to the outlet of the buffer reservoir and the free end of the conduit is clamped so that the conduit is held straight. Fourth, the air flow is adjusted again and maintained for 30 seconds and the pressure is recorded. Fifth, the pressure rise through the conduit is calculated from the difference in the recorded pressures. The increase in flow resistance due to bending is tested by first conditioning the conduit at a temperature of 42 ± 3 °C and a relative humidity of at least 80% for at least 1 hour. The conduit is then suspended over a cylinder of 25 mm diameter and a tensile force is applied to maintain contact with half the circumference of the cylinder. Third, an air flow is applied and the pressure is recorded after 5 minutes. Fourth, the pressure rise through the conduit is calculated from the pressure difference between the bent conduit and the straight conduit. It will be understood that the conditioning defined in the standard may not reflect the conditions of use and that the standard was not written with breathable materials in mind. To better reflect conditions of use, the flow resistance of a conduit formed at least in part from a breathable material may additionally or alternatively be further tested by conditioning the conduit to the simulated conditioned conditions described above.

[0544]

[0571] "Saturated" refers to the condition where the elongated tube or a sample thereof is subjected to a period of immersion testing (i.e., immersed in liquid water) until the permeable material no longer absorbs or nearly absorbs any more water molecules, i.e., until the combined mass of the permeable material and absorbed water molecules is at or near maximum. This is an "artificial" condition, and elongated tubes are not typically in this condition during normal use (i.e., in use in assisted ventilation systems). The tube walls of an elongated tube in a saturated condition generally contain a higher concentration of water molecules than in any of the dry, equilibrium, and conditioned conditions. [Explanation of symbols]

[0545] List of drawing elements 100 Respiratory Support System 102 Gas Source 104 Humidifier supply conduit 106 Humidifier 108 Intake duct 110 Y-tube 112 Patient Interface 114 Exhalation tube 116 Pressure Generator 118 Gas inlet 120 Gas Source Controller 122 User Interface 124 Gas source outlet 126 Humidification Chamber 128 Chamber heater 130 Humidifier Controller 132 User Interface 134 Heater Wire 136 Sensor Probe 138 Sensor lead wire 140 Gas return inlet 142 Ventilation circuit 144 Intake branch 146 Expiratory branch 200 Respiratory Support System 202 Heater wire 204 Sensors 206 Electro-pneumatic connector 208 Supplementary gas inlet 302 Heater Base 304 Cartridge 306 Touch Screen Display 308 Switch 310 Indicator Light 312 Release button 400 Respiratory Support System 402 Pressure Regulator 404 Liquid 406 Inlet Probe 408 Pressure Relief Valve 500 Respiratory Support System 502 Blower 504 Respiratory therapy equipment 506 Housing 600 Surgical Air Supply System 602 Air supply pipe 604 Air supply device 606 Delivery Conduit 608 Surgical Cannula 610 Smoke Exhaust System 612 Wall Source 614 Compressed Gas Cylinders 616 Discharge conduit 618 Exhaust Filter 620 Vacuum source 622 Further Emission Pipes 624 Air supply circuit 626 Scope 628 Laparoscopic Monitor 700 Conduit 702 Long thin tube 704 Sheath 706 Connector 802 Boa 902 Longitudinal 904 Clockwise Braided Element 906 Counterclockwise Braided Element 908 Opening 1002 Cuff part 1004 first connector component 1006 Second connector component 1008 Chamfered Edges 1010 flange 1012 Circular Channel 1014 Aperture 1016 Waveform part 1102 Tapered cone end 1202 Lumen 1502 Interval 1504 Radial 1602 Peak 1604 Valley 1702 line 1704 Melting point 1802 Filament 2102 Central part 2104 End section 2106 Tapered section 2108 Unsheathed conduit 2202 Waveform 2204 Side wall 2206 Force Vector 2402 Depth 2602 Narrowed inner waist area 2604 External narrowed waist area 2700 Respiratory Support System 2702 Filter 2704 Entrance area 2706 Exit area 2708 Intermediate area 2710 low point 2800 Conduit formation method 2802 Extrusion molding step 2804 Waveform Step 2806 Tube Cutting Step 2808 Thread cutting step 2810 Connector Insertion Step 2812 Clamp Step 2814 Connector Overmolding Step 2816 Sheath shrink step 2818 Sheath cutting step 2820 Connector molding step

Claims

1. A conduit for medical gases used in medical gas systems, An elongated tube defining a lumen for the passage of a flow of medical gas, wherein at least a portion of the elongated tube contains a breathable material configured to expand upon the absorption of water molecules during use; A sheath provided around at least a portion of the elongated tube, wherein the sheath is configured to restrict the expansion of at least a portion of the elongated tube in at least one of the radial and longitudinal directions due to the absorption of water molecules by the breathable material during use. Medical gas conduits, including those for medical gases.

2. The medical gas conduit according to claim 1, wherein the diameter and length of at least one, preferably both, of the elongated tube and the sheath are configured to change over time during use.

3. The medical gas conduit according to claim 1, wherein the length and diameter of the sheath are configured to change inversely as the elongated tube expands during use due to the absorption of water molecules.

4. The medical gas conduit according to claim 1, wherein the gradient between the length and diameter of the sheath is between approximately -100 and -20.

5. The medical gas conduit according to claim 1, wherein the gradient between the length and diameter of the sheath is substantially linear between sheath diameters of approximately 24 mm and 32 mm.

6. The medical gas conduit according to claim 1, wherein the elongated tube and the sheath are configured such that, in at least one cross-section passing through the medical gas conduit, the sheath is spaced outward from at least a portion of the circumference of the elongated tube in use, in one or more of the following states: dry, equilibrium, and at least one conditioned state.

7. The medical gas conduit according to claim 1, wherein the elongated tube and the sheath are configured such that, in at least one cross-section passing through the medical gas conduit, the sheath contacts the entire circumference of the elongated tube during use and in at least one conditioned state.

8. The medical gas conduit according to claim 1, wherein at least a portion of the elongated tube is configured to absorb more than about 33% of its own dry mass in water molecules during an immersion test.

9. The medical gas conduit according to claim 1, wherein at least a portion of the elongated tube is configured to absorb between approximately 45% and 250% of its dry mass in water molecules during an immersion test.

10. The medical gas conduit according to claim 1, wherein, in an immersion test while separated from the sheath, at least a portion of the elongated tube is configured to expand by about 20% to 70% in one or more directions, preferably in the radial direction, longitudinal direction, and wall thickness.

11. The aforementioned medical gas conduit, when in use: Upon initial absorption of water molecules, the elongated tube is configured to expand without being relatively restricted by the sheath. The configuration is such that when water molecules are absorbed further, the elongated tube expands, being relatively restricted by the sheath. A medical gas conduit according to claim 1, configured as described above.

12. The aforementioned sheath, When the elongated tube is in equilibrium during use, the expansion of the elongated tube is not restricted. The expansion of the elongated tube is restricted when the elongated tube is in at least one conditioned state during use. A medical gas conduit according to claim 1, configured as described above.

13. The aforementioned medical gas conduit, when in use: Upon initial absorption of water molecules, the elongated tube is configured to expand radially without being relatively restricted by the sheath. Upon further absorption of water molecules, the elongated tube is configured to expand further radially, relatively restricted by the sheath. A medical gas conduit according to claim 1, configured as described above.

14. The medical gas conduit according to claim 1, wherein the sheath is configured not to restrict the longitudinal expansion of the elongated tube in an equilibrium state, but to restrict the longitudinal expansion of the elongated tube in at least one conditioned state.

15. When the aforementioned medical gas conduit is in use, The elongated tube is configured to expand freely in the radial and longitudinal directions upon initial absorption of water molecules. Upon further absorption of water molecules, the elongated tube is configured to engage with the sheath, thereby restricting further expansion in at least one of the radial and longitudinal directions. A medical gas conduit according to claim 1, configured as described above.

16. The medical gas conduit according to claim 1, wherein the elongated tube and the sheath are configured such that the elongated tube engages with the sheath due to the radial expansion of the elongated tube, causing the sheath to expand radially and contract longitudinally.

17. The medical gas conduit according to claim 1, wherein the elongated tube is configured to have a first length before use, a second length after initially absorbing water molecules, and a third length after further absorbing water molecules, wherein the second length is longer than the first length and the third length.

18. The medical gas conduit according to claim 1, wherein the elongated tube is configured to have a first length in equilibrium, a second length in at least one conditioned state in which the radial expansion of the elongated tube is not restricted by the sheath, and a third length in at least one other conditioned state in which the radial expansion of the elongated tube is restricted by the sheath, wherein the second length is longer than the first length and the third length.

19. A ventilation circuit kit for use in respiratory support systems, Intake conduit; Y-shaped pipe; and Including an exhalation conduit, at least one of the inhalation conduit and the exhalation conduit includes a medical gas conduit as described in any one of claims 18. Ventilation circuit kit.

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