Medical tubing for breathing circuits

Abstract

A breathing circuit for use in respiratory therapy includes an inspiratory tube and an expiratory tube. The inspiratory tube of the breathing circuit has a smooth bore. The expiratory tube of the breathing circuit is corrugated. Preferably, the expiratory tube is vapor permeable. Using a combination of a smooth bore inspiratory tube and a corrugated expiratory tube has the unexpected result of improving the performance of the breathing circuit and its components.

Description

[Technical field]

[0001] Incorporation by Reference This application claims priority from U.S. Provisional Patent Application No. 62 / 621,463, filed January 24, 2018, the entire contents of which are incorporated herein by reference in their entireties. This application is related to International Application No. PCT / NZ Patent Application Publication No. 2017 / 050099, filed July 21, 2017, and U.S. Provisional Patent Application No. 62 / 365,285, filed July 21, 2016, the entire contents of each of which are incorporated herein by reference in their entireties. Additionally, the following disclosure makes reference to various features of U.S. Patent Application Publication No. 13 / 517,925, published as U.S. Patent Application Publication No. 2013 / 0098360A1, U.S. Patent Application Publication No. 14 / 123,485, published as U.S. Patent Application Publication No. 2014 / 0202462A1, and U.S. Patent Application Publication No. 14 / 649,801, published as U.S. Patent Application Publication No. 2015 / 0306333A1, the entire disclosures of which are hereby incorporated by reference for all purposes whatsoever which they contain as if fully set forth herein.

[0002] The present disclosure relates generally to tubing suitable for medical applications, and in particular to medical tubing for use in a breathing circuit suitable for providing humidified gas to a patient and / or removing gas from a patient, such as in a respiratory humidification system. [Background technology]

[0003] In a breathing circuit, various components carry heated and / or humidified gases to and from a patient. Respiratory humidification helps reduce the likelihood of infection and / or tissue damage. Summary of the Invention

[0004] Certain features, aspects and advantages of the present disclosure recognize the need for an improvement that can increase the removal of vapor from the exhaled gas in the expiratory tube while increasing the amount of vapor in the humidified gas delivered to the patient through the inhalation tube without increasing the overall flow resistance in the tube. Certain features, aspects and advantages of the present disclosure recognize the need for an improvement that reduces the compression volume of the breathing circuit, or at least reduces the compression volume of the rim of the breathing circuit. As described herein, there may be a trade-off in both compression volume and flow resistance between the inhalation and expiratory tubes. There may be a reduction in compression volume and / or flow resistance in the inhalation tube and an increase in compression volume and / or flow resistance in the expiratory tube. The reduction in compression volume in the inhalation tube may be due at least in part to a reduction in the inhalation tube diameter. The reduction in tube diameter may be made possible by a reduction in flow resistance that may be due at least in part to having a smooth bore. The increase in compression volume in the expiratory tube may be due at least in part to an increase in the wall surface area, tube diameter, tube cross-sectional area or wall length of the expiratory tube. The increase in flow resistance in the expiratory tube may be due at least in part to a corrugated structure. Increasing the compression volume and flow resistance in the expiratory tract can improve its permeability due to various factors as described herein. This tradeoff between the inspiratory and expiratory tracts can maintain the same overall compression volume and / or flow resistance in the breathing circuit as a whole.

[0005] The lower the compressible capacity of the breathing circuit, the lower the air compliance of the breathing circuit for a given compliance, and the lower the air compliance of the breathing circuit relative to the patient's lung compliance, the less likely there is an error in the delivered tidal volume.

[0006] A circuit kit for use in respiratory therapy of a patient may include a breathing circuit. The breathing circuit may include an inspiratory tube configured to receive an inspiratory gas flow from a gas source. The inspiratory tube may include an inspiratory inlet, an inspiratory outlet, and an inner wall surrounding an inspiratory central bore. The inner wall of the inspiratory tube may be smooth. The breathing circuit may include an expiratory tube configured to receive an expiratory gas flow from a patient. The expiratory tube may include an expiratory inlet, an expiratory outlet, and an inner wall surrounding an expiratory central bore. The inner wall of the expiratory tube may be corrugated. The inspiratory tube may have an inner diameter of 5 to 14.5 mm. The expiratory tube may have a nominal inner diameter of 15 to 22 mm. The inspiratory tube may have an inner diameter of 4 to 17 mm. The expiratory tube may have a nominal inner diameter of 10.5 to 20.5 mm.

[0007] The circuit kit may include a y-piece configured to couple the inhalation tube and the expiratory tube. The circuit kit may include a chamber for holding a volume of water and placing on the humidifier. The circuit kit may include a dry line for conveying flow from a ventilator or other gas source to the humidifier inlet. The inhalation tube may have an inner diameter of 6mm to 14mm. The inhalation tube may have an inner diameter of 6mm to 13mm. The inhalation tube may have an inner diameter of 6mm to 12mm. The inhalation tube may have an inner diameter of 6mm to 11mm. The inhalation tube may have an inner diameter of 7mm to 10mm. The inhalation tube may have an inner diameter of 8mm to 9mm. The expiratory tube may have a nominal inner diameter of 15.5mm to 21mm. The expiratory tube may have a nominal inner diameter of 16mm to 20mm. The expiratory tube may have a nominal inner diameter of 16mm to 19mm. The expiratory tube may have a nominal inner diameter of 18mm to 20mm. The expiratory tube may have a nominal inner diameter of 19mm to 20mm. The inhalation tube may have an inner diameter of 6mm to 10mm. The inhalation tube may have an inner diameter of 11mm to 15mm. The inhalation tube may have an inner diameter of 9mm to 13mm. The inhalation tube may have an inner diameter of 10mm to 14mm. The inhalation tube may have an inner diameter of 7mm to 13mm. The inhalation tube may have an inner diameter of 8mm to 14mm. The expiratory tube may have a nominal inner diameter of 11mm to 15mm. The expiratory tube may have a nominal inner diameter of 12mm to 16mm. The expiratory tube may have a nominal inner diameter of 14mm to 18mm. The expiratory tube may have a nominal inner diameter of 16 mm to 20 mm. The expiratory tube may have a nominal inner diameter of 13 mm to 19 mm. The expiratory tube may have a nominal inner diameter of 14 mm to 20 mm. The inhalation or expiratory tube may have a length of 1.5 m to 2.5 m. The inhalation or expiratory tube may have a length of 1.6 m to 2.5 m. The inhalation tube may enclose a heating element in the inhalation central bore or in the wall of the tube. The expiratory tube may include a heating element. The expiratory tube may be breathable. The inner wall of the expiratory tube may be permeable to water vapour and substantially impermeable to the bulk flow of liquid and expiratory gases flowing through the expiratory tube. The inhalation tube may include a plurality of bubbles, each having a flat surface that forms at least a part of the wall of the inhalation central bore, in longitudinal cross section. The circuit kit may be suitable for treating patients with tidal volumes in the range of 50ml to 300ml.The circuit kit may be suitable for treating pediatric and adolescent patients. The difference between the inner diameter of the inhalation tube and the nominal diameter of the expiratory tube may be between 1 mm and 14 mm. The inner diameter of the inhalation tube may be smaller than the nominal diameter of the expiratory tube by a value between 1 mm and 14 mm. The inhalation tube and / or the expiratory tube may include multiple sections for accommodating other equipment such as a water trap, and / or an intermediate connector with one or more sensors, and / or a PCB, and / or a controller. The system may include a circuit kit and a humidifier.

[0008] A circuit kit for use in respiratory therapy of a patient may include a breathing circuit. The breathing circuit may include an inspiratory tube configured to receive an inspiratory gas flow from a gas source. The inspiratory tube may include an inspiratory inlet, an inspiratory outlet, and an inner wall surrounding an inspiratory central bore. The inner wall of the inspiratory tube may be smooth. The breathing circuit may include an expiratory tube configured to receive an expiratory gas flow from a patient. The expiratory tube may include an expiratory inlet, an expiratory outlet, and an inner wall surrounding an expiratory central bore. The inner wall of the expiratory tube may be corrugated. The inspiratory tube may have an inner diameter of 10-21 mm. The expiratory tube may have a nominal inner diameter of 22-30 mm. The inspiratory tube may have an inner diameter of 9.5-24 mm. The expiratory tube may have a nominal inner diameter of 19-31.5 mm.

[0009] The circuit kit may include a y-piece configured to couple the inhalation tube and the exhalation tube. The circuit kit may include a chamber for holding a volume of water and placing on the humidifier. The circuit kit may include a dry line for conveying flow from a ventilator or other gas source to the humidifier outlet. The inhalation tube may have an inner diameter of 10mm to 20mm. The inhalation tube may have an inner diameter of 11mm to 20mm. The inhalation tube may have an inner diameter of 11mm to 19mm. The inhalation tube may have an inner diameter of 11mm to 18mm. The inhalation tube may have an inner diameter of 11mm to 17mm. The inhalation tube may have an inner diameter of 11mm to 16mm. The inhalation tube may have an inner diameter of 11mm to 15mm. The inhalation tube may have an inner diameter of 12mm to 15mm. The inhalation tube may have an inner diameter of 13mm to 14mm. The expiratory tube may have a nominal inner diameter of 22mm to 29mm. The expiratory tube may have a nominal inner diameter of 23mm to 30mm. The expiratory tube may have a nominal inner diameter of 24mm to 30mm. The expiratory tube may have a nominal inner diameter of 24mm to 29mm. The expiratory tube may have a nominal inner diameter of 25mm to 28mm. The expiratory tube may have a nominal inner diameter of 25.5mm to 27mm. The inhalation tube may have an inner diameter of 11mm to 15mm. The inhalation tube may have an inner diameter of 12mm to 16mm. The inhalation tube may have an inner diameter of 18mm to 22mm. The inhalation tube may have an inner diameter of 19mm to 23mm. The inhalation tube may have an inner diameter of 10mm to 16mm. The inhalation tube may have an inner diameter of 17mm to 23mm. The expiratory tube may have a nominal inner diameter of 25mm to 29mm. The expiratory tube may have a nominal inner diameter of 26mm to 30mm. The expiratory tube may have a nominal inner diameter of 20mm to 24mm. The expiratory tube may have a nominal inner diameter of 21mm to 25mm. The expiratory tube may have a nominal inner diameter of 24mm to 30mm. The expiratory tube may have a nominal inner diameter of 20mm to 26mm. The inhalation or expiratory tube may have a length of 1.5m to 2.5m. The inhalation or expiratory tube may have a length of 1.6m to 2.5m. The inhalation tube may surround a heating element in the inhalation central bore or in the wall of the tube. The expiratory tube may include a heating element. The expiratory tube may be breathable. The inner wall of the expiratory tube may be permeable to water vapor and substantially impermeable to the bulk flow of liquid and expiratory gases passing through the expiratory tube.The inhalation tube may include a plurality of bubbles, each having a flat surface in longitudinal cross section forming at least a part of the wall of the inhalation central bore. The circuit kit may be suitable for treating patients with a tidal volume of more than 300 ml. The circuit kit may be suitable for treating adult patients. The difference between the inner diameter of the inhalation tube and the nominal diameter of the expiratory tube may be between 1 mm and 20 mm. The inner diameter of the inhalation tube may be smaller than the nominal diameter of the expiratory tube by a value between 1 mm and 20 mm. The inhalation tube and / or the expiratory tube may include a water trap, and / or an intermediate connector with one or more sensors, and / or a PCB, and / or multiple sections for accommodating other equipment such as a controller. The system may include a circuit kit and a humidifier.

[0010] A circuit kit for use in respiratory therapy of a patient may include a breathing circuit. The breathing circuit may include an inspiratory tube configured to receive an inspiratory gas flow from a gas source. The inspiratory tube may include an inspiratory inlet, an inspiratory outlet, and an inner wall surrounding an inspiratory central bore. The inner wall of the inspiratory tube may be smooth. The breathing circuit may include an expiratory tube configured to receive an expiratory gas flow from a patient. The expiratory tube may include an expiratory inlet, an expiratory outlet, and an inner wall surrounding an expiratory central bore. The inner wall of the expiratory tube may be corrugated. The inspiratory tube may have an inner diameter of 4-12 mm. The expiratory tube may have a nominal inner diameter of 13-18 mm. The inspiratory tube may have an inner diameter of 3-13 mm. The expiratory tube may have a nominal inner diameter of 9.5-19 mm.

[0011] The circuit kit may include a y-piece configured to couple the inhalation tube and the expiratory tube. The circuit kit may include a chamber for holding a volume of water and placing on the humidifier. The circuit kit may include a dry line for conveying flow from the ventilator to the other gas source to the humidifier inlet. The inhalation tube may have an inner diameter of 5mm to 11mm. The inhalation tube may have an inner diameter of 6mm to 10mm. The inhalation tube may have an inner diameter of 6mm to 8mm. The inhalation tube may have an inner diameter of 9mm to 10mm. The expiratory tube may have a nominal inner diameter of 13mm to 17mm. The expiratory tube may have a nominal inner diameter of 14mm to 17mm. The expiratory tube may have a nominal inner diameter of 15mm to 16.5mm. The expiratory tube may have a nominal inner diameter of 14mm to 15mm. The inhalation or exhalation tube may have a length of 1.5m to 2.5m. The inhalation or exhalation tube may have a length of 1.6m to 2.5m. The inhalation tube may have an inner diameter of 5mm to 9mm. The inhalation tube may have an inner diameter of 6mm to 10mm. The inhalation tube may have an inner diameter of 7mm to 11mm. The inhalation tube may have an inner diameter of 8mm to 12mm. The inhalation tube may have an inner diameter of 4mm to 11mm. The inhalation tube may have an inner diameter of 6mm to 12mm. The exhalation tube may have a nominal inner diameter of 13mm to 17mm. The exhalation tube may have a nominal inner diameter of 12mm to 16mm. The exhalation tube may have a nominal inner diameter of 11mm to 15mm. The exhalation tube may have a nominal inner diameter of 14mm to 18mm. The expiratory tube may have a nominal inner diameter of 12 mm to 18 mm. The expiratory tube may have a nominal inner diameter of 10 mm to 16 mm. The inhalation tube may enclose a heating element in the inhalation central bore or in the wall of the tube. The expiratory tube may include a heating element. The expiratory tube may be breathable. The inner wall of the expiratory tube may be permeable to water vapor and substantially impermeable to the bulk flow of liquid and expiratory gases flowing through the expiratory tube. The inhalation tube may include a plurality of bubbles, each having a flat surface in longitudinal cross section that forms at least a portion of the wall of the inhalation central bore. The circuit kit may be suitable for treating patients with a tidal volume of 50 ml or less. The circuit kit may be suitable for treating neonatal patients. The difference between the inner diameter of the inhalation tube and the nominal diameter of the expiratory tube may be between 1 mm and 14 mm. The inner diameter of the inhalation tube can be smaller than the nominal diameter of the expiratory tube by a value between 1 mm and 14 mm.The inhalation and / or exhalation tubes may include multiple sections to accommodate other equipment such as a water trap, and / or an intermediate connector with one or more sensors, and / or a PCB, and / or a controller. The system may include a circuit kit and a humidifier.

[0012] A circuit kit for use in respiratory therapy of a patient may be provided. The breathing circuit may include an inspiratory tube configured to receive an inspiratory gas flow from a gas source. The inspiratory tube may include an inspiratory inlet, an inspiratory outlet, and an inner wall surrounding an inspiratory central bore. The inner wall of the inspiratory tube may be smooth. The breathing circuit may include an expiratory tube configured to receive an expiratory gas flow from a patient. The expiratory tube may include an expiratory inlet, an expiratory outlet, and an inner wall surrounding an expiratory central bore. The inner wall of the expiratory tube may be corrugated.

[0013] In some embodiments, the inhalation tube may have an inner diameter of 3mm to 11mm and the exhalation tube may have a nominal inner diameter of 8mm to 16mm. The inhalation tube may have an inner diameter of 4mm to 8mm. The exhalation tube may have a nominal inner diameter of 11mm to 15mm. The inhalation tube may have an inner diameter of 6mm to 10mm. The exhalation tube may have a nominal inner diameter of 10mm to 14mm. The inhalation tube or the exhalation tube may have a length of 1.5m to 2.5m. In some embodiments, the inhalation tube may have an inner diameter of 5mm to 13mm and the exhalation tube may have a nominal inner diameter of 15mm to 23mm. The inhalation tube may have an inner diameter of 5mm to 9mm. The exhalation tube may have a nominal inner diameter of 18mm to 22mm. The inhalation tube may have an inner diameter of 8mm to 12mm. The expiratory tube may have a nominal inner diameter of 16mm to 20mm. The expiratory tube or inhalation tube may have a length of 1.5m to 2.5m. In some embodiments, the expiratory tube may have an inner diameter of 10mm to 18mm and the exhalation tube may have a nominal inner diameter of 24mm to 32mm. The expiratory tube may have an inner diameter of 9mm to 13mm. The exhalation tube may have a nominal inner diameter of 27mm to 31mm. The expiratory tube may have an inner diameter of 15mm to 19mm. The exhalation tube may have a nominal inner diameter of 24mm to 28mm. The expiratory tube or inhalation tube may have a length of 1.5m to 2.5m. The expiratory tube may have an inner diameter and a length. The exhalation tube may have a nominal inner diameter and a length. In some embodiments, the circuit kit is suitable for treating adult patients. In some embodiments, the circuit kit is suitable for treating pediatric and adolescent patients. In some embodiments, the circuit kit is suitable for treating pediatric and neonatal patients.

[0014] The breathing circuit may include an inspiratory rim for conveying inhaled gas to the patient. The inspiratory rim may include a first elongate member including a hollow body, the hollow body being helically wound to at least partially define a first elongate tube having a longitudinal axis, a first lumen extending along the longitudinal axis, and a hollow wall surrounding the lumen. The inspiratory rim may include a second elongate member helically wound and joined between adjacent turns of the first elongate member, the second elongate member forming at least a portion of the lumen of the first elongate tube. The breathing circuit may include an expiratory rim for conveying expiratory gas from the patient. The expiratory rim may include an inlet and an outlet. The expiratory rim may include a third elongate member including a second tube surrounding the second lumen. The second lumen can be configured to accommodate a bulk flow of exhaled gas, the second tube being permeable to water vapor and substantially impermeable to liquid water and the bulk flow of exhaled gas.

[0015] The wall of the expiratory tube may comprise a foamed or non-foamed polymer that is permeable to water vapor and substantially impermeable to the bulk flow of liquid water and expiratory gas. The foamed polymer may comprise a solid thermoplastic elastomer material having air bubbles distributed throughout. The non-foamed polymer may comprise an extruded solid thermoplastic elastomer material that is permeable to water vapor and substantially impermeable to the bulk flow of liquid water and expiratory gas. The first lumen of the inhalation rim may have a smooth bore. The second elongated member of the inhalation rim may surround at least one heating element. The first elongated member of the inhalation rim may form a plurality of bubbles with flat surfaces in the lumen in longitudinal cross section. The second elongated member of the inhalation rim may surround at least one heating element, the at least one inhalation heating element being between a bubble of the plurality of bubbles and the inhalation central bore. The third elongated member of the expiratory rim may be corrugated. The first elongate tube can surround a heating element within its lumen. The third elongate member of the expiratory rim can surround a heating element within the second lumen. The third elongate member of the expiratory rim can include a heating element attached to an inner wall of the second tube. The third elongate member of the expiratory rim can include a heating element embedded in a wall of the second tube. The second tube can have an interior surface adjacent the second lumen, and the expiratory rim further includes a plurality of reinforcing ribs circumferentially disposed on the interior surface and generally longitudinally aligned between the inlet and the outlet.

[0016] The device may include a breathing circuit. The breathing circuit may include an inhalation tube configured to receive an inhalation gas flow from a gas source, the inhalation tube including an inhalation inlet, an inhalation outlet, and a wall surrounding an inhalation central bore. An inner wall of the inhalation tube may be smooth. The breathing circuit may include an expiratory tube configured to receive an expiratory gas flow from a patient. The expiratory tube may include an expiratory inlet, an expiratory outlet, and a wall surrounding an expiratory central bore. An inner wall of the expiratory tube may be corrugated. A wall of the expiratory tube may be permeable to water vapor and substantially impermeable to the bulk flow of liquid and expiratory gas flowing through the expiratory tube.

[0017] The wall of the expiratory tube may include a foamed or non-foamed polymer that is permeable to water vapor and substantially impermeable to the bulk flow of liquid water and expiratory gas. The inhalation tube may surround a heating element in its central bore. The inhalation tube may include a heating element attached to its wall. The inhalation tube may include a heating element embedded in its wall. The expiratory tube may include a heating element in its central bore. The expiratory tube may include a heating element attached to its inner wall. The expiratory tube may include a heating embedded in its inner wall. The inhalation tube may include a plurality of bubbles having a flat surface in the lumen in a longitudinal cross section. The inhalation tube may include at least one heating element, and the at least one inhalation heating element is between a bubble of the plurality of bubbles and the inhalation central bore. The expiratory tube may include a plurality of reinforcing ribs arranged circumferentially on the inner surface and generally aligned longitudinally between the inlet and the outlet. The breathing circuit may include a humidifier configured to humidify an inhaled gas flow to the patient. The humidifier may include a humidification chamber configured to store a quantity of liquid and configured to be in fluid communication with the inhaled gas flow. The humidifier may include a heater configured to heat a quantity of liquid in the humidification chamber to generate steam such that the inhaled gas flow is humidified with the steam.

[0018] The respiratory apparatus may include a humidifier configured to humidify an inhaled gas flow to a patient. The respiratory apparatus may include an inhalation tube configured to receive the inhaled gas flow from the humidifier. The inhalation tube may include an inhalation inlet, an inhalation outlet, and a wall surrounding an inhalation central bore. An inner wall of the inhalation tube may be smooth. The respiratory apparatus may include an exhalation tube configured to receive an exhalation gas flow from a patient. The exhalation tube may include an exhalation inlet, an exhalation outlet, and a wall surrounding an exhalation central bore. The exhalation central bore may be corrugated. The wall of the exhalation tube may be permeable to water vapor and substantially impermeable to the bulk flow of liquid and exhaled gas flowing through the exhalation tube.

[0019] The inhalation tube may include at least one heating element in its central bore. The inhalation tube may include at least one heating element attached to its inner wall. The inhalation tube may include at least one heating element surrounded in its wall. The exhalation tube may include at least one heating element in the exhalation central bore. The exhalation tube may include at least one heating element attached to its inner wall. The exhalation tube may include at least one heating element embedded in its inner wall. The inhalation tube may include a spirally wound member forming, in longitudinal cross section, a plurality of bubbles having flat surfaces at the inhalation central bore. The inhalation tube may surround the at least one heating element, and the at least one inhalation heating element may be between a bubble of the plurality of bubbles and the inhalation central bore. The wall of the exhalation tube may include a foamed polymer.

[0020] The respiratory device may include a humidifier configured to humidify an inhaled gas flow to a patient. The humidifier may include a humidification chamber configured to store a quantity of liquid and configured to be in fluid communication with the inhaled gas flow. The humidifier may include a heater configured to heat a quantity of liquid in the humidification chamber to generate steam such that the inhaled gas flow is humidified with the steam. The respiratory device may include an inhalation tube configured to receive the humidified inhaled gas flow from the humidifier. The inhalation tube may include a wall surrounding an inhalation central bore. The inhalation central bore of the inhalation tube may be smooth. The inhalation tube may include a first helically wound elongate member that, in a longitudinal cross section, forms a plurality of bubbles having flat surfaces at the inhalation central bore. The bubbles may be configured to insulate the inhalation central bore. The inhalation tube may include a helically wound second elongate member joined between adjacent turns of the first elongate member, the second elongate member forming at least a portion of the lumen of the first elongate tube and including at least one inhalation heating element embedded within the second elongate member. The respiratory device may include an exhalation tube configured to receive an exhalation gas flow from the patient. The exhalation tube may include a conduit surrounding an exhalation central bore. The exhalation central bore may be corrugated. The conduit may be permeable to water vapor and may be substantially impermeable to liquid flow through the conduit. The exhalation tube may include at least one exhalation heating element within the exhalation central bore. The respiratory device may include a control system configured to deliver power to the heater of the humidifier, the at least one inhalation heating element, and the at least one exhalation heating element.

[0021] The wall of the expiratory tube may include a foamed or non-foamed polymer that is permeable to water vapor and substantially impermeable to the bulk flow of liquid water and expiratory gas. The foamed polymer may include a solid thermoplastic elastomer material having air bubbles distributed throughout. The non-foamed polymer may include an extruded solid thermoplastic elastomer material that is permeable to water vapor and substantially impermeable to the bulk flow of liquid water and expiratory gas. At least one inspiratory heating element may be between a bubble of the plurality of bubbles and the inspiratory central bore. The respiratory device may include a patient interface assembly between the inspiratory tube and the expiratory tube. The power delivered by the control system may be calculated to provide increased humidification by the humidifier and controlled condensate management by the at least one expiratory heating element and the at least one inspiratory heating element. The respiratory device may include a ventilator configured to supply an inspiratory gas flow and to receive an expiratory gas flow. The ventilator may be configured to supply a pulsed inspiratory gas flow to the humidifier. The ventilator may be configured to provide a constant flow of inspired gas to the humidifier. The ventilator may be configured to provide a bias flow of gas.

[0022] The respiratory apparatus may include a humidifier configured to humidify an inhaled gas flow to a patient. The respiratory apparatus may include an inhalation tube configured to receive an inhaled gas flow from a gas source. The inhalation tube may include an inhalation inlet, an inhalation outlet, and a wall surrounding an inhalation central bore. The inner wall of the inhalation tube may be smooth. The respiratory apparatus may include an exhalation tube configured to receive an exhalation gas flow from a patient. The exhalation tube may include an exhalation inlet, an exhalation outlet, and a wall surrounding an exhalation central bore. The inner wall of the exhalation tube may be corrugated. The wall of the exhalation tube may be permeable to water vapor and substantially impermeable to the bulk flow of liquid and exhaled gas flowing through the exhalation tube.

[0023] The wall of the expiratory tube may comprise a foamed or non-foamed polymer that is permeable to water vapor and substantially impermeable to the bulk flow of liquid water and expiratory gases. The inhalation tube may comprise at least one heating element in its central bore. The inhalation tube may comprise at least one heating element attached to its inner wall. The inhalation tube may comprise at least one heating element surrounded in its wall. The first elongated member of the inhalation rim may form a plurality of bubbles having flat surfaces in the lumen in a longitudinal cross section. The inhalation tube may surround the at least one heating element, and the at least one inhalation heating element may be between a bubble of the plurality of bubbles and the inhalation central bore. The expiratory tube may comprise at least one heating element in the expiratory central bore. The expiratory tube may comprise at least one heating element attached to its inner wall. The expiratory tube may comprise at least one heating element embedded in its inner wall. The expiratory tube may include a plurality of reinforcing ribs disposed circumferentially on an interior surface and generally longitudinally aligned between the inlet and the outlet. The respiratory device may include a heater of the humidifier and a control system configured to deliver power to the at least one heating element.

[0024] The breathing circuit may include a combination of a smooth-bore inhalation tube and a corrugated vapor-permeable expiratory tube to increase the vapor in the humidified gas delivered to the patient through the inhalation limb of the circuit and to increase the removal of vapor from the expiratory gas in the expiratory limb of the circuit without increasing the overall flow resistance of the tube, thus avoiding increased pressure loss in the breathing circuit. A smooth-bore inhalation tube may provide a trade-off opportunity. A smooth bore may reduce flow resistance, thereby allowing a reduction in the diameter or cross-sectional area of ​​the inhalation tube while maintaining an acceptable flow resistance. This reduction in the diameter or cross-sectional area of ​​the inhalation tube reduces the compression capacity of the inhalation tube. A smaller diameter inhalation tube may reduce the compression capacity of at least a portion of the breathing circuit, thereby reducing the possibility of error in the delivered tidal volume. A ventilator is typically meant to deliver a set amount of gas to the patient with each breath (the "tidal volume"). Reducing the error in the delivered tidal volume may ensure that the patient receives an accurate amount of gas.

[0025] The use of a combination of a smooth bore inhalation tube and a corrugated expiratory tube has an unexpected synergistic effect that improves the performance of the breathing circuit and its components beyond expectations. Using a smooth bore inhalation tube with a smaller inner diameter than a comparable corrugated tube can reduce the compression volume of the tube. This reduction in compression volume can ensure that an adequate amount of gas is delivered to the patient. As described herein, an inhalation tube with a smaller inner diameter can reduce the overall compression volume and air compliance of the breathing circuit. As described herein, an inhalation tube with a smaller inner diameter can have a reduced compression volume, which can be a tradeoff for an increased compression volume of the expiratory tube.

[0026] For practical reasons, the compression capacity, and therefore the compliance, of the breathing circuit tube is usually much greater than the patient's lungs. Factors that influence the compression capacity of the breathing circuit tube include minimizing the resistance to gas flow in the tube and being able to make the tube long enough to manage the patient within the bed space. This is exacerbated by some pulmonary disease states where the patient has very stiff, low-compliance lungs. In addition, low compression capacity due to reduced length (e.g. shortened tube) is in direct conflict with both maneuverability and breathability of the expiratory limb. In practice, longer tubes are generally better, such as to allow freedom of movement and positioning of the patient. In practice, a larger surface area in the expiratory limb is generally better, to increase the breathability of the expiratory limb.

[0027] In order to maintain a sufficiently low compression capacity, there are potential trade-offs between the components of the breathing circuit. The diameter or cross-sectional area of ​​the inhalation tube can be reduced. However, reducing the inner diameter of the inhalation tube also increases the resistance to flow (RTF) in the inhalation tube. It has been found that smoothing the inner bore of the inhalation tube can compensate for this increase in RTF, since a smooth bore reduces the RTF compared to a tube with a corrugated bore or another type of non-smooth bore. The use of a smooth bore also has the added benefit of reducing vapor and condensate entrapment. It has also been found that if the reduction in RTF caused by the use of a smooth bore exceeds the increase in RTF caused by reducing the inner diameter of the tube, there is a net reduction in RTF in the breathing circuit, or at least a net reduction in RTF in the inhalation tube. A smooth bore in the inhalation tube can reduce the RTF, thereby allowing for a reduction in the diameter of the inhalation tube that would normally increase the RTF, to balance the smoothness of the bore with the reduction in diameter. As described herein, a reduction in diameter or cross-sectional area can reduce the compression capacity. This reduction in the compressive capacity of the inspiratory tube can offset an increase in the compressive capacity of the expiratory tube, such as by increasing the diameter or cross-sectional area of ​​the expiratory tube, which creates a larger surface area for the expiratory tube and increases the vapor permeability of the expiratory tube.

[0028] Particular features, aspects and advantages of embodiments of the invention related to the compression capacity of breathing circuit components feature one or more combinations of the following: reduced inner diameter of the inhalation tube, smooth bore of the inhalation tube, reduced compression capacity of the inhalation tube, increased compression capacity of the expiratory tube, increased diameter of the expiratory tube, increased surface area of ​​the expiratory tube and / or increased vapor permeability of the expiratory tube. Particular features, aspects and advantages of the present disclosure reflect embodiments of the invention in which this net reduction in RTF with a smooth bore inhalation tube allows other components of the circuit to be modified without changing the overall compression capacity, overall RTF and / or overall pressure loss of the circuit as a whole. The use of a smooth bore inhalation tube allows for the use of a longer corrugated expiratory tube that would otherwise increase the RTF in the circuit. Increasing the length of the expiratory tube improves the ability of the tube to remove vapors from the expiratory gases, at least in part due to increased residence time. Increasing the diameter of the expiratory tube improves the ability of the tube to remove vapors from the expiratory gases, due to increased surface area of ​​the wall that is permeable to vapor. When the use of a smooth bore intake tube reduces the overall circuit RTF, the increase in RTF resulting from an increase in the length of the expiratory tube may not result in a net increase in RTF in the overall circuit, a net increase in compression volume, and / or a corresponding loss in pressure. For example, based on the design, an increase in the length of the expiratory tube and a decrease in the diameter of the smooth bore intake tube may be net neutral with respect to RTF.

[0029] The use of a smooth-bore inspiratory tube in the breathing circuit instead of a corrugated or similarly non-smooth walled tube may be combined with the use of a wider (larger cross-sectional area or diameter) expiratory tube in the breathing circuit, which reduces the RTF. The trade-off may not be in the RTF being reduced in both tubes in this case. A smooth bore reduces the RTF compared to a tube with a corrugated bore or another type of non-smooth bore. However, the reduction in RTF in the inspiratory tube may be offset by a reduction in diameter or cross-sectional area, which increases the RTF. A larger cross-sectional area or diameter expiratory tube also reduces the RTF. Instead, there may be a trade-off in compression capacity due to the change in diameter or cross-sectional area of ​​the inspiratory and expiratory tubes, which decreases in the inspiratory tube but increases in the expiratory tube. A smaller diameter inspiratory tube has a smaller compression capacity. A larger diameter expiratory tube has a larger compression capacity.

[0030] The breathing circuit may include an inhalation rim for conveying inhalation gas to the patient. The inhalation rim includes a first elongate member including a hollow body, the hollow body being helically wound to at least partially define a first elongate tube having a longitudinal axis, a first lumen extending along the longitudinal axis, and a hollow wall surrounding the lumen. The inhalation rim further includes a second elongate member helically wound and joined between adjacent turns of the first elongate member, the second elongate member forming at least a portion of the inner wall of the lumen of the first elongate tube. The breathing circuit further includes an expiratory rim for conveying expiratory gas from the patient. The expiratory rim includes a third elongate member including an inlet, an outlet, and a second tube including a second lumen. The second lumen is configured to accommodate a bulk flow of exhaled gas, the second tube being permeable to water vapor and substantially impermeable to liquid water and the bulk flow of exhaled gas.

[0031] The breathing circuit described above may also have one, some or all of the following characteristics and any of the characteristics described in this disclosure. The wall of the expiratory tube may include a foamed or non-foamed polymer that is permeable to water vapor and substantially impermeable to the bulk flow of liquid water and expiratory gas. For the purposes of this disclosure, any material described as "permeable to water vapor and substantially impermeable to the bulk flow of liquid water and gas" (or substantially similar phrases) is defined herein as a material that allows water vapor molecules to pass through it by diffusion, facilitated diffusion, passive transport, active transport or another similar mechanism for selectively transporting water vapor molecules, but does not have a leak path from one outer major surface of the material to another outer major surface of the material that allows the passage of liquid water or bulk flow of gas through the leak path.

[0032] The expanded polymer may include a solid thermoplastic elastomer material having air bubbles disposed therethrough. The non-expanded polymer may include a solid thermoplastic elastomer material that is permeable to water vapor and substantially impermeable to the bulk flow of liquid water and expiratory gases. The first lumen of the inhalation rim may have a smooth bore. The second elongate member of the inhalation rim may surround at least one heating element. The first elongate member of the inhalation rim may form a plurality of bubbles having flat surfaces in the lumen in a longitudinal cross section. The second elongate member of the inhalation rim may further include at least one heating element, and the at least one inhalation heating element may be disposed between a bubble of the plurality of bubbles and the inhalation central bore. The third elongate member of the expiratory rim may be corrugated. The first elongate tube may surround a heating element in its lumen. The third elongate member of the expiratory rim may surround a heating element in the second lumen. The third elongate member of the expiratory rim may include a heating element attached to the inner wall of the second tube. The third elongate member of the expiratory rim may include a heating element embedded in the wall of the second tube. The second tube may have an interior surface adjacent to the second lumen, and the expiratory rim may further include a plurality of reinforcing ribs circumferentially disposed on the interior surface and generally aligned longitudinally between the inlet and the outlet. The foamed polymer is desirably selected or manufactured such that the solid thermoplastic elastomer material selectively transports water vapor molecules, but the pores distributed throughout do not form leak paths that allow the passage of bulk flow of liquid water or gas through the leak paths.

[0033] The device may include a breathing circuit. The breathing circuit further includes an inhalation tube configured to receive an inhalation gas flow from a gas source. The inhalation tube includes an inhalation inlet, an inhalation outlet, and a wall surrounding an inhalation central bore, and an inner wall of the inhalation tube is smooth. The breathing circuit further includes an expiratory tube configured to receive an expiratory gas flow from a patient. The expiratory tube includes an expiratory inlet, an expiratory outlet, and a wall surrounding an expiratory central bore. The inner wall of the expiratory tube is corrugated, and the wall of the expiratory tube is permeable to water vapor and substantially impermeable to liquids and gases flowing through the expiratory tube.

[0034] The aforementioned device may also have one, some or all of the following characteristics and any of the characteristics described in this disclosure: The wall of the expiratory tube may include a foamed polymer that is permeable to water vapor and substantially impermeable to the bulk flow of liquid water and expiratory gases. The inhalation tube may enclose a heating element in its central bore or in the wall of the tube. The inhalation tube may include a heating element attached to its wall. The inhalation tube may include a heating element embedded in its wall. The expiratory tube may include a heating element in its central bore. The expiratory tube may include a heating element attached to its inner wall. The expiratory tube may include a heating element embedded in its inner wall. The inhalation tube may include a plurality of bubbles having a flat surface in the lumen in a longitudinal cross section. The inhalation tube may include at least one heating element, and the at least one inhalation heating element may be disposed between a bubble of the plurality of bubbles and the inhalation central bore.

[0035] Additionally, the expiratory tube may include a plurality of reinforcing ribs circumferentially disposed on an interior surface and generally longitudinally aligned between the inlet and the outlet. The breathing circuit may further include a humidifier configured to humidify the inhaled gas flow delivered to the patient. The humidifier may include a humidification chamber configured to store a quantity of liquid and configured to be in fluid communication with the inhaled gas flow, and a heater configured to heat a quantity of liquid in the humidification chamber to generate steam such that the inhaled gas flow is humidified with the steam.

[0036] The respiratory apparatus may include a humidifier, an inhalation tube, and an exhalation tube. The humidifier is configured to humidify an inhalation gas flow to a patient. The inhalation tube is configured to receive the inhalation gas flow from the humidifier. The inhalation tube includes an inhalation inlet, an inhalation outlet, and a wall surrounding an inhalation central bore, the inner wall of the inhalation tube being smooth. The exhalation tube is configured to receive the exhalation gas flow from the patient. The exhalation tube includes an exhalation inlet, an exhalation outlet, and a wall surrounding an exhalation central bore, the exhalation central bore being corrugated, and the wall of the exhalation tube is permeable to water vapor and substantially impermeable to the bulk flow of liquid and exhalation gas flowing through the exhalation tube.

[0037] The aforementioned breathing device may also have one, some or all of the following characteristics and any of the characteristics described in this disclosure: The inhalation tube may include at least one heating element in its central bore. The inhalation tube may include at least one heating element attached to its inner wall. The inhalation tube may include at least one heating element surrounded or embedded in its wall. The expiratory tube may include at least one heating element in the expiratory central bore. The expiratory tube may include at least one heating element attached to its inner wall. The expiratory tube may include at least one heating element embedded in its inner wall. The inhalation tube may include a spirally wound member forming, in longitudinal cross section, a plurality of bubbles having flat surfaces at the inhalation central bore. The inhalation tube may surround at least one heating element, and at least one inhalation heating element may be disposed between a bubble of the plurality of bubbles and the inhalation central bore. The wall of the expiratory tube may include a foamed or non-foamed polymer.

[0038] The respiratory device may include a humidifier, an inhalation tube, an exhalation tube, and a control system. The humidifier is configured to humidify an inhalation gas flow delivered to a patient. The humidifier includes a humidification chamber and a heater. The humidification chamber is configured to store a quantity of liquid and is configured to be in fluid communication with the inhalation gas flow. The heater is configured to heat the quantity of liquid in the humidification chamber to generate steam such that the inhalation gas flow is humidified with the steam. The inhalation tube is configured to receive the humidified inhalation gas flow from the humidifier. The inhalation tube includes a wall surrounding an inhalation central bore, the central bore of the inhalation tube being smooth. The inhalation tube further includes a first elongated member wound in a spiral shape forming, in a longitudinal cross section, a plurality of bubbles having flat surfaces at the inhalation central bore. The bubbles are configured to insulate the inhalation central bore. The inhalation tube further includes a helically wound second elongate member joined between adjacent turns of the first elongate member. The second elongate member forms at least a portion of the lumen of the first elongate tube and includes at least one inhalation heating element embedded within the second elongate member. The exhalation tube is configured to receive an exhalation gas flow from the patient. The exhalation tube includes a conduit surrounding an exhalation central bore, the exhalation central bore being corrugated, and the conduit being permeable to water vapor and substantially impermeable to liquid flow through the conduit. The exhalation tube further includes at least one exhalation heating element within the exhalation central bore. The control system may be configured to deliver power to a heater of the humidifier. The control system may be configured to deliver power to the at least one inhalation heating element. The control system may be configured to deliver power to the at least one exhalation heating element. The control system may be configured to deliver power to the heater of the humidifier and the at least one inspiratory heating element. The control system may be configured to deliver power to the heater of the humidifier and the at least one expiratory heating element. The control system may be configured to deliver power to the at least one inspiratory heating element and the at least one expiratory heating element. The control system is configured to deliver power to two or more of the following: the heater of the humidifier, the at least one inspiratory heating element, and the at least one expiratory heating element.The control system is configured to deliver power to a heater of the humidifier, at least one inspiratory heating element, and at least one expiratory heating element.

[0039] The aforementioned respiratory device may also have one, some or all of the following characteristics and any of the characteristics described in this disclosure: The wall of the expiratory tube may include a foamed or non-foamed polymer that is permeable to water vapor and substantially impermeable to the bulk flow of liquid water and expiratory gases. The foamed polymer may include a solid thermoplastic elastomer material having bubble pores distributed throughout. The non-foamed polymer may include a solid thermoplastic elastomer material that is permeable to water vapor and substantially impermeable to the bulk flow of liquid water and expiratory gases. At least one inspiratory heating element may be between a bubble of the plurality of bubbles and the inspiratory central bore. The respiratory device may further include a patient interface assembly between the inspiratory tube and the expiratory tube. The power delivered by the control system may be calculated to provide increased humidification by the humidifier. The power delivered by the control system may be calculated to provide controlled condensate management by the at least one expiratory heating element. The power delivered by the control system may be calculated to provide controlled condensate management by the at least one inspiratory heating element. Power delivered by the control system may be calculated to provide increased humidification by the humidifier and controlled condensate management by the at least one expiratory heating element and the at least one inspiratory heating element. The respiratory apparatus may further include a ventilator configured to supply an inspiratory gas flow and to receive an expiratory gas flow. The ventilator may be configured to supply a pulsed inspiratory gas flow to the humidifier. The ventilator may be configured to supply a constant inspiratory gas flow to the humidifier. The ventilator may be configured to supply a bias flow of gas.

[0040] The respiratory device may include a humidifier, an inhalation tube, and an exhalation tube. The humidifier is configured to humidify an inhalation gas flow to a patient. The inhalation tube is configured to receive an inhalation gas flow from a gas source. The inhalation tube includes an inhalation inlet, an inhalation outlet, and a wall surrounding an inhalation central bore, and an inner wall of the inhalation tube is smooth. The exhalation tube is configured to receive an exhalation gas flow from the patient. The exhalation tube includes an exhalation inlet, an exhalation outlet, and a wall surrounding an exhalation central bore. The inner wall of the exhalation tube is corrugated, and the wall of the exhalation tube is permeable to water vapor and substantially impermeable to liquids and gases flowing through the exhalation tube. The wall of the exhalation tube may include a foamed polymer that is permeable to water vapor and substantially impermeable to the bulk flow of liquid water and exhalation gas. The inhalation tube may include at least one heating element within its central bore. The breathing apparatus may also have one, some or all of the following characteristics and any of the characteristics described in this disclosure: The inhalation tube may include at least one heating element attached to its inner wall. The inhalation tube may include at least one heating element surrounded in its wall. The first elongate member of the inhalation rim may form a plurality of bubbles having flat surfaces in the lumen in a longitudinal cross section. The inhalation tube may surround at least one heating element, and the at least one inhalation heating element may be between a bubble of the plurality of bubbles and the inhalation central bore. The exhalation tube may include at least one heating element in the exhalation central bore. The exhalation tube may include at least one heating element attached to its inner wall. The exhalation tube may include at least one heating element embedded in its inner wall. The exhalation tube may include a plurality of reinforcing ribs arranged circumferentially on the inner surface and generally aligned longitudinally between the inlet and the outlet. The respiratory apparatus may further include a control system configured to deliver power to the heater and the at least one heating element of the humidifier.

[0041] Certain features, aspects, and advantages of the present disclosure will now be described with reference to the drawings. The drawings and corresponding description are provided to illustrate certain features, aspects, and advantages of the present disclosure and are not intended to limit the scope of the disclosure. [Brief description of the drawings]

[0042] [Figure 1] FIG. 1 is a schematic diagram of a breathing circuit incorporating one or more medical tubing. [Figure 1A] FIG. 1 is a schematic diagram of a breathing circuit incorporating one or more medical tubing. [Figure 1B] 1 shows three graphs illustrating the effect of breathing circuit compliance on tidal volume error. [Figure 2A] FIG. 2 is a side view of a portion of a composite pipe. [Figure 2B] FIG. 2B is a longitudinal cross-sectional view of the composite tube of FIG. 2A. [Figure 3A] FIG. 2 is a side plan view of a portion of a tube incorporating a vapor permeable foamed polymeric material. [Figure 3B] FIG. 3B is a cross-sectional view of the tube of FIG. 3A. [Figure 4A] FIG. 13 is a front perspective view of a section of a tube incorporating integral reinforcing ribs, where the tube is partially corrugated. [Figure 4B] FIG. 4B is a front perspective view of the portion of the tube of FIG. 4A, where the tube is generally corrugated. [Figure 5A] FIG. 1 is a front perspective view of a section of a tube incorporating ribs; [Figure 5B] FIG. 5B is a front perspective view of the tube of FIG. 5A. [Figure 6] FIG. 2 is a schematic diagram of a portion of an expiratory tube. [Figure 7] FIG. 2 is a schematic diagram of a portion of an expiratory tube. [Figure 8] FIG. 1 is a schematic diagram of a breathing circuit including a humidifier, an inspiratory tube, and an expiratory tube. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0043] A breathing circuit that includes one or more medical tubes To understand the present disclosure in more detail, reference is first made to Fig. 1, which shows a breathing circuit 100. Such a breathing circuit 100 may be a respiratory humidification circuit. The breathing circuit 100 includes one or more medical tubes. The breathing circuit 100 may include an inspiratory tube 103 and an expiratory tube 117.

[0044] As used herein, medical tubing is a broad term that should be given its ordinary and accustomed meaning to those skilled in the art (i.e., not limited to any special or specialized meaning) and includes, but is not limited to, cylindrical and non-cylindrical elongated shapes that define a lumen or contain a passageway, such as a hollow elongated body that is configured for use in a medical procedure and that otherwise meets applicable standards for such use. An inhalation tube is a medical tubing that is configured to deliver respiratory gases to a patient. An exhalation tube is a medical tubing that is configured to direct exhalation gases away from a patient.

[0045] Gas may be transported within circuit 100 of Figure 1. Ambient gas flows from gas source 105 to humidifier 107. Humidifier 107 may humidify the gas. Gas source 105 may be a ventilator, blower or fan, a tank containing compressed gas, a wall supply within a healthcare facility, or any other suitable source of breathing gas.

[0046] The humidifier 107 is connected to the inlet 109 (end for receiving humidified gas) of the inhalation tube 103 via a port 111, thereby supplying humidified gas to the inhalation tube 103. The gas flows through the inhalation tube 103 to the outlet 113 (end for discharging humidified gas) of the inhalation tube 103 and then flows to the patient 101 via a patient interface 115 connected to the outlet 113. The exhalation tube 117 is connected to the patient interface 115. The exhalation tube 117 returns the humidified gas exhaled from the patient interface 115 to the gas source 105 or to the surrounding atmosphere. As used herein, a patient interface has a broad meaning and should be given its ordinary and accustomed meaning to those skilled in the art, and includes, but is not limited to, any one or more of a full face mask, a nasal mask, an oral mask, an oral-nasal mask, a nasal pillow mask, a nasal cannula, a nasal prong, a laryngeal mask, or any other suitable coupling between the medical circuit and the patient's airway.

[0047] Gas may enter the gas source 105 through a vent 119. A blower or fan 121 may force gas into the gas source 105 by drawing air or other gas through the vent 119. The blower or fan 121 may be a variable speed blower or fan. An electronic controller 123 may control the speed of the blower or fan. In particular, the function of the electronic controller 123 may be controlled by an electronic master controller 125. This function may be controlled in response to inputs from the master controller 125 and a user-set predetermined desired value (preset value) of pressure or blower or fan speed via a dial or other suitable input device 127.

[0048] The humidifier 107 includes a humidification chamber 129. The humidification chamber 129 may be configured to contain a quantity of water 130 or other suitable humidification liquid. The humidification chamber 129 may be removable from the humidifier 107. Being removable allows the humidification chamber 129 to be more easily sterilized or disposed of after use. The humidification chamber 129 portion of the humidifier 107 may be of unitary construction or may be formed of multiple components joined together to define the humidification chamber 129. The body of the humidification chamber 129 may be formed from a non-conductive glass or plastic material. The humidification chamber 129 may also include conductive components. For example, the humidification chamber 129 may include a highly thermally conductive base (aluminum base) configured to contact or correspond with a heater plate 131 on the humidifier 107 when the humidification chamber 129 is mounted on the humidifier 107.

[0049] The humidifier 107 may include electronic controls. The humidifier 107 may include an electronic, analog, or digital master controller 125. The master controller 125 may be a microprocessor-based controller that executes computer software commands stored in associated memory. In response to user-set humidity or temperature values ​​entered via a user input device 133 and other inputs, the master controller 125 determines when (or to what level) to energize the heater plate 131 to heat a volume of water 130 in a humidification chamber 129.

[0050] The temperature probe 135 may be connected to the inlet conduit 103 near the patient interface 115 or the temperature probe 135 may be connected to the patient interface 115. The temperature probe 135 may be incorporated into the inlet conduit 103. The temperature probe 135 detects the temperature near or at the patient interface 115. A signal reflective of the temperature may be provided by the temperature probe 135 to an electronic, analog or digital master controller 125. A heating element (not shown) may be used to regulate the temperature of the patient interface 115 and / or inlet conduit 103 to raise the temperature of the inlet conduit 103 and / or patient interface 115 above a saturation temperature, thereby reducing the opportunity for unwanted condensation.

[0051] 1, exhaled humidified gas is returned from the patient interface 115 through an expiratory tube 117 to the gas source 105. The expiratory tube 117 may include a vapor permeable material, as described in more detail below. The vapor permeable expiratory tube may be corrugated.

[0052] The expiratory tube 117 may have a temperature probe and / or a heating element, as described above with respect to the inhalation tube 103, to reduce the chance of condensation reaching the gas source 105. The expiratory tube 117 does not need to return the exhaled gases to the gas source 105. The exhaled humidified gases may flow directly to the surrounding environment or to other auxiliary equipment such as an air scrubber / filter (not shown).

[0053] In FIG. 1, the intake pipe 103 encompasses or includes a conduit having a smooth bore. The term smooth bore should be given its normal accustomed meaning in the art, including but not limited to non-corrugated bores, lumens or passages. The term "smooth bore" may be used to describe a pipe having an interior surface that does not include significant internal corrugations, annular ribs, bumps or cavities that significantly affect the flow of gas within the pipe. The term "smooth bore" may also be used to describe a pipe that does not have repetitive interior surface features that disrupt the generally laminar flow through the passage or lumen defined by the smooth bore. The term corrugated should be given its normal accustomed meaning in the art, including but not limited to having a raised or grooved surface. Advantageously, a smooth bore will result in a conduit having a lower RTF than a comparably sized conduit having a corrugated bore. A smooth bore reduces flow resistance, allowing the bore (i.e., diameter or cross-sectional area) to be reduced, resulting in a lower compression capacity when compared to a corrugated pipe with similar flow resistance. The air inlet conduit may be a composite conduit. A composite conduit may be generally defined as a conduit that includes two or more distinct portions or, more specifically, two or more components that are joined to define the conduit. The composite conduit may be helically wound. The composite conduit may be helically wound in such a manner that two or more components are helically intertwined or joined side-by-side in a helical configuration.

[0054] The expiratory tube 117 includes or includes a conduit having at least a vapor permeable portion. The vapor permeability enhances the removal of humidity. At least the vapor permeable portion of the expiratory tube 117 can be corrugated. The corrugated structure can be on the inside of the tube. The corrugated structure increases the internal surface area of ​​the tube. The amount of vapor that can be diffused through a vapor permeable material is correlated to the surface area of ​​the material that is in direct contact with the vapor. The corrugated structure also increases the turbulence of the gas in the expiratory tube. More turbulence means better mixing of the gas, thereby moving water vapor to the outer wall of the expiratory tube 117. More turbulence can increase local residence time within the corrugated structure of the expiratory tube, which, when combined with the vapor permeable properties, further enhances the removal of humidity. The increased local residence time also reduces the temperature of the gas swirling within each corrugated "pocket" relative to that of a comparably sized smooth bore tube, and increases the relative humidity of these gases relative to that of a comparably sized smooth bore tube. The increase in relative humidity increases the vapor pressure gradient across the walls of the expiratory tube 117 relative to that of a comparably sized smooth bore tube and also increases the vapor diffusion through the walls of the corrugated expiratory tube relative to that of a comparably sized smooth bore tube.

[0055] The vapor-permeable corrugated conduit may be formed at least in part from a foamed or non-foamed polymer that is permeable to water vapor and substantially impermeable to the bulk flow of liquid water and gas. The expiratory tube 117 may include a wall that defines a space within the expiratory tube 117. At least a portion of the wall may be formed from a foamed material configured to be permeable to water vapor and substantially impermeable to the bulk flow of liquid water and gas. At least a portion of the wall may be formed from a non-foamed extruded solid material that is permeable to water vapor and substantially impermeable to the bulk flow of liquid water and gas.

[0056] The vapor-permeable expiratory tube 117 may be formed from a non-foam-based material. The non-foam-based material may include a spirally wrapped vapor-permeable tape, or the non-foam-based material may be extruded into a continuous tube. The corrugated structure of the expiratory tube 117 may be achieved with a non-foam-based material. The non-foam-based material may include beads of various diameters arranged in an alternating pattern to form a corrugated interior surface. Alternatively, the corrugated structure may be created in the tube by methods known in the art, such as molding or stamping.

[0057] The intake tube 103 includes a smooth bore conduit. The smooth bore conduit may be heated and insulated to minimize condensation formation and maximize humidity delivery. The reduction in condensation formation in the intake tube allows more vapor in the humidified gas to be delivered to the patient. Several factors affect condensation formation in the intake tube 103, including the internal bore diameter, the smoothness of the internal bore, the level of insulation of the tube, the presence of a heating element (such as a wire or element) associated with the tube 103, and the location of the heating element within the tube 103 (whether the heating element is located within the internal bore of the tube 103 or within the wall of the tube 103). Specifically, decreasing the internal bore diameter of the intake tube 103 increases the velocity of the gas as it travels within the intake tube 103. Increasing the smoothness of the bore reduces turbulence and creates a more parabolic wavefront across the inner wall of the lumen. Thus, by reducing the internal bore diameter and making the internal bore smooth, the high velocity gas located near the center of the tube will transfer less heat to the low velocity gas located near the tube wall. Smooth bore tubes also do not provide pockets where vapor can be trapped or condensation can accumulate, as does a corrugated tube. Thus, vapors carried by the gas are encouraged to exit the tube and thus be delivered to the patient.

[0058] Increasing the degree of tubing insulation maximizes humidity delivery by reducing heat loss at the walls of the inspiratory tubing 103 and minimizing condensation formation. Adding more insulation to the inspiratory tubing 103 also makes the breathing circuit 100 more efficient by reducing the extent to which the heating element must work to maintain the target temperature and humidity, because the insulated tubing better maintains the temperature and absolute humidity of the gases as they travel through the tubing.

[0059] Adding a heating element to the inspiratory tube 103 also maximizes humidification delivery and reduces condensation. Placing one or more heating elements within the wall of the inspiratory tube 103 maximizes humidification and minimizes condensation formation, contributing to the efficiency of the inspiratory tube 103, breathing circuit 100, or humidification system. When a heating element is located within the wall of the inspiratory tube 103, it heats the wall but does not directly heat the gas. Heating the wall reduces the relative humidity of the gas near the wall (heating the gas increases the temperature and reduces the relative humidity). Placing a heating element on the lumen side of the inner wall of the insulating "bubble" (defined below) of the inspiratory tube 103 (described in more detail below) can further reduce heat loss to the outside through the wall of the inspiratory tube 103, further maximizing humidification and minimizing condensation formation. As used herein, the term "bubble" refers to the cross-sectional shape of a hollow body formed from an elongated wind or turn of a first elongated member 203, for example, as shown in FIG. 2B, taken at a cross-section of the wind or turn. As used herein, any reference to a "bubble" refers to an elongated hollow body having a shape in cross-section defined by a wall having a hollow space therein. With reference to FIG. 2B, such shapes may include an oval or a "D" shape. Such shapes may include, but are not limited to, an "O" shape and other regular and irregular shapes, both symmetrical and asymmetrical.

[0060] The expiratory tube 117 may include a corrugated conduit to maximize vapor removal while minimizing condensate formation and increasing local residence time within the corrugated structure. The expiratory tube 117 may include a vapor permeable conduit to maximize vapor removal. The expiratory tube 117 may include a heated conduit to maximize vapor removal while minimizing condensate formation. The expiratory tube 117 may include a corrugated, vapor permeable and / or heated conduit to maximize vapor removal while minimizing condensate formation and increasing local residence time within the corrugated structure. Reducing condensate formation within the expiratory tube 117 allows more vapor to diffuse across the walls of the expiratory tube 117. The presence of a heating element may maintain the relative humidity of the gas below 100% (i.e., maintain the temperature of the gas above the dew point saturation temperature). Placing a heating element near or within the walls of the expiratory tube 117 causes heating of the gas near the walls of the expiratory tube 117. Condensation formation is avoided or limited by maintaining the temperature of the gas near the walls of the expiratory tube 117 above the dew point. The inlet tube 103 and the expiratory tube 117 are described in more detail elsewhere herein.

[0061] Referring again to FIG. 1, the gas source 105 is typically to deliver a set amount of gas to the patient 101 for each breath. This set amount may be referred to as the tidal volume or the delivered volume. It is desirable for the patient 101 to receive a precise amount of gas to reduce the potential risk of lung damage and increase the likelihood of adequate ventilation. When a gas source 105, such as a ventilator, generates a patient's breath, the gas source 105 must fill both the patient's lungs and the breathing circuit 100, which may include filters, a supply tube from the ventilator to a humidifier, a humidifier chamber, an inhalation tube, an exhalation tube, and any other components shown or described with respect to FIG. 1. Thus, the gas source 105 must estimate or otherwise take into account and compensate for the gas used to fill the breathing circuit 100 to increase the likelihood of accurate delivery of the amount of gas to the patient.

[0062] The gas source 105 can perform a test on the air compliance of the breathing circuit 100. In this test, the gas source 105 attempts to determine the volume required to generate a certain pressure. The air compliance depends at least on the compression volume. The lower the compression volume of the breathing circuit 100, the lower the air compliance of the breathing circuit 100 for a given distensibility. The lower the air compliance of the breathing circuit relative to the patient's lung compliance, the less likely there is an error in the delivered tidal volume. If the measurement of the air compliance of the breathing circuit is in error by a small amount and the air compliance of the breathing circuit is large compared to the patient's lung compliance, the percentage error in the tidal volume delivered to the patient will be very large. For example, if the measurement of the air compliance of the breathing circuit is in error by 5% and the air compliance of the breathing circuit is large compared to the patient's lung compliance, the percentage error in the tidal volume delivered to the patient will be potentially much larger than 5%.

[0063] FIG. 1B shows three graphs. The graph in FIG. 1B shows the error in delivered tidal volume with a theoretical 10% error introduced into the gas source measurement of the air compliance of the breathing circuit. The three graphs are for three different circuit compliance specifications (e.g., neonatal, adult, and pediatric). For the neonatal circuit, the breathing circuit compliance (C bs ) is 0.9ml.cmH20 -1 In an adult circuit, the breathing circuit compliance (C bs ) is 2.1ml.cmH20 -1 In pediatric circuits, the breathing circuit compliance (C bs ) is 1.3ml.cmH20 -1 Each graph shows the error in delivered tidal volume in a patient with poor respiratory system compliance.

[0064] It has been found that the error increases significantly as the patient's weight decreases. The patient's weight correlates with the intended tidal volume. As the patient's weight decreases, the intended tidal volume decreases. Comparison of the graphs in FIG. 1B shows that for a given tidal volume, the error increases as the breathing circuit compliance increases. It has been found that it is desirable to keep the overall compression volume and breathing circuit compliance as low as possible relative to the lung characteristics of the patient to be treated.

[0065] For practical reasons such as minimizing the resistance of the tube to gas flow and being able to make the tube long enough to manage the patient in the bed space, the compression capacity, and therefore compliance, of the breathing circuit tube is usually much greater than the patient's lungs. This difference is magnified by some pulmonary disease states where the patient has very stiff, low-compliance lungs. The low compression capacity that can result from a short tube can be a disadvantage in terms of maneuverability. Longer tubes, which benefit from a larger surface area, and a ventilated expiratory rim, can be a disadvantage in terms of compression capacity.

[0066] The relevance of the compression volume is that there may be a trade-off between the components of the breathing circuit in maintaining a sufficiently low compression volume. A smooth bore in the inspiratory tube 103 reduces flow resistance, allowing the diameter of the inspiratory tube 103 to be reduced, and therefore the compression volume to be reduced. This reduction in the compression volume of the inspiratory tube 103 allows the compression volume of the expiratory tube 117 to be increased by increasing its diameter. Increasing the diameter of the expiratory tube 117 increases the surface area of ​​the expiratory tube 117, improving the vapor permeability of the tube 117.

[0067] It has been recognized that incorporating an inhalation tube 103 having a smaller diameter smooth bore conduit in conjunction with an exhalation tube 117 having a corrugated conduit allows the exhalation tube 117 to be larger in diameter and / or longer than would otherwise be possible while maintaining the compression capacity of the overall system. Additionally or alternatively, combining a small diameter smooth bore inhalation tube 103 with a large diameter corrugated exhalation tube 117 can maintain the overall pressure drop. Additionally or alternatively, combining a small diameter smooth bore inhalation tube 103 with a large diameter corrugated exhalation tube 117 can maintain the resistance to flow (RTF) of the breathing circuit 100 at a desirable level. Increasing the length of the conduit typically unnecessarily increases the compression capacity of the conduit and therefore the compression capacity of the overall breathing circuit. Increasing the length of the conduit typically unnecessarily increases the RTF of the conduit and therefore the RTF of the overall breathing circuit. On the other hand, if the conduit is vapor permeable, increasing the length advantageously improves the ability of the conduit to remove vapors from the exhaled gases. It has been found that combining an inhalation tube 103 having a small diameter smooth bore with an exhalation tube 117 having a large diameter corrugated vapor permeable conduit improves the ability of the exhalation tube 117 to remove water vapor from the breathing circuit without increasing the compression capacity, pressure drop and / or RTF of the overall system.

[0068] It was further recognized that the incorporation of an inlet tube 103 having a smooth bore conduit in conjunction with an outlet tube 117 having a corrugated conduit allows the humidifier 107 to improve humidity performance, providing therapeutic benefit to the patient while operating near fully saturated gas, without the added risk of liquid damaging the gas source 105 or condensation being discharged back to the patient.

[0069] An intake tube 103 having a smooth-bore, spirally wound conduit can be paired with an expiratory tube 117 having a corrugated vapor permeable conduit. As mentioned above, the smooth bore of the intake tube 103 has a lower RTF than a similarly sized corrugated bore. The smooth bore of the intake tube 103 can also have a smaller inner diameter than the corrugated conduit. Typically, reducing the inner diameter reduces the compression capacity and unnecessarily increases the RTF of the intake tube. Nevertheless, the smooth bore characteristics can be selected such that the reduction in RTF associated with the smooth bore of the intake tube 103 outweighs the increase in RTF resulting from the smaller inner diameter of the intake tube 103. This selection of a smaller diameter intake tube 103 also reduces the compression capacity of the intake tube 103. This selection therefore allows the corrugated expiratory tube 117 paired with the smooth bore intake tube 103 to be longer and / or have a larger diameter or cross-sectional area without increasing the overall system pressure loss or compression capacity. Increasing the length and / or diameter of the expiratory tube 117 usually unnecessarily increases the tube's RTF and compression capacity. However, increasing the length and / or diameter also improves the vapor-permeable tube's ability to remove vapor from the exhaled gas. In this configuration, pairing a smooth-bore inhalation tube 103 with a corrugated expiratory tube 117 improves the performance of the expiratory tube 117. The system pressure loss of the breathing circuit that may exist from the ventilator outlet to the ventilator inlet can be affected by the pressure characteristics (RTF) of each element in the circuit. Referring again to FIG. 1, assuming constant pressure characteristics of the supply tube from the ventilator to the humidifier, humidifier chamber, interface tube and interface body, the main factors that contribute to the system pressure loss are the flow resistance and dimensions (length and diameter) of the inhalation tube 103 and expiratory tube 117. Any change to one of these factors should be advantageously balanced with the other factors to avoid increasing the system's pressure loss, RTF and / or compression capacity. As described herein, the primary factors contributing to the compression volume are the tube profile, compliance and dimensions (length and diameter or cross-sectional area) of the inspiratory tube 103 and expiratory tube 117. There may be a trade-off between decreasing the compression volume of the inspiratory tube 103 while maintaining the compression volume of the breathing circuit, and increasing the compression volume of the expiratory tube 117.As described herein, increasing the compressible capacity of the expiratory tube 117 is beneficial in terms of the vapor permeability of the expiratory rim.

[0070] The smooth bore of the inlet tube 103 reduces flow resistance (compared to a corrugated inlet tube) and can reduce overall system pressure loss. This allows any or all of the other three factors (flow resistance of the corrugated expiratory tube 117 or the dimensions of either tube) to be altered to increase system pressure loss. The inside diameter of the inlet tube 103 can desirably be smaller than a comparable corrugated inlet tube, thereby increasing the velocity of gas flowing through the inlet tube 103. However, the smaller diameter again adds some flow resistance. The length of the corrugated expiratory tube 117 can be increased without increasing system pressure loss, so long as the increase in RTF due to the smaller diameter is sufficiently smaller than the decrease in RTF due to the use of a smooth bore. Increasing the length of the expiratory tube 117 increases the surface area of ​​the tube wall of the expiratory tube 117. The amount of vapor that can diffuse through a vapor permeable material is related to the surface area of ​​the material. Increasing the length and / or diameter of the expiratory tube 117 increases the surface area of ​​the walls of the expiratory tube 117 and also increases the residence time of the gas within the expiratory tube 117. The amount of vapor that can diffuse through a permeable material also correlates to the length of time the vapor-carrying gas is in contact with the material.

[0071] The compression capacity (cumulative volume of the entire gas flow path) of the breathing circuit can be balanced as well. For example, a change in the dimensions (cross-sectional area or diameter, length) of the inhalation tube 103 can offset a change in the dimensions (cross-sectional area or diameter, length) of the corrugated expiratory tube 117. As described herein, a decrease in the diameter of the inhalation tube 103 can reduce the compression capacity. This decrease in compression capacity can improve the accuracy of the delivered tidal volume. As described herein, a decrease in the diameter of the inhalation tube 103 can offset an increase in the diameter and / or the length of the expiratory tube 117. As described herein, a change in the dimensions of the expiratory tube 117 can facilitate the function of the expiratory tube 117, such as by increasing the vapor permeability of the expiratory tube 117. Since a change in the tube dimensions affects both the pressure loss of the system and the compression capacity of the system, when making a change, both equations should advantageously be balanced or selected simultaneously. A decrease in the diameter of the inhalation tube 103 can increase the average gas velocity in the tube, while increasing the flow resistance and decreasing the compression capacity. Adding a length of corrugated expiratory tube 117 increases the flow resistance as well as the compression volume. Table 1 summarizes the effect of various features on the metrics of these two systems.

[0072] [Table 1]

[0073] Pairing a corrugated expiratory tube 117 with a smooth-bore inhalation tube 103 can make the inhalation tube 103 perform better. Pairing a large-diameter expiratory tube 117 with a small-bore inhalation tube 103 can be net neutral in terms of compression capacity, but can increase the functionality of the breathing circuit (e.g., increase vapor diffusion in the expiratory tube 117). In this configuration, the smooth-bore inhalation tube 103 minimizes condensate formation and therefore maximizes humidity delivery. The overall compression capacity can be reduced by changes in dimensions such as the diameter and length of the inhalation tube 103 and expiratory tube 117. In some configurations, the inhalation tube 103 is insulated, which helps make heating elements such as the humidifier 107 and / or heater plate 131 more efficient in generating the humidity delivered to the patient 101. The heater plate 131 does not have to work as hard because it does not need to generate such a high target temperature at the humidification chamber port 111. This is because the heated and insulated intake tube 103 better maintains the absolute humidity of the gas flowing from the humidifier chamber port 111 through the intake tube 103 .

[0074] Locating the heater wire within the wall of the intake tube 103 also increases the efficiency with which the intake tube 103 maintains the relative humidity of the gas. The heater wire can heat the wall of the intake tube 103 rather than the gas flowing within the lumen of the intake tube 103, thereby reducing the relative humidity of the gas near the wall of the intake tube 103. If the intake tube 103 comprises a composite conduit having a spirally wound hollow body or "bubble" tube (described in more detail below), the heater wire is below the insulating bubble (on the lumen side of the inner wall), thereby reducing heat loss to the outside through the wall of the intake tube 103.

[0075] The smooth bore intake tube 103 promotes laminar gas flow, creating a more parabolic wavefront across the lumen of the intake tube 103 with gas near the center of the lumen having a higher velocity than gas near the wall of the intake tube 103. In this configuration, the high velocity gas has less time to transfer heat to adjacent lower velocity gas during its passage from the inlet 109 to the outlet 113. In conjunction with the inward direction of the heat generated by the heater wire, this configuration helps to further increase the heat retained by the gas flow.

[0076] The smooth bore intake tube 103 also does not provide pockets where vapor can become trapped or condensation can accumulate, as does a corrugated tube, and thus vapor carried by the gas is encouraged to remain in the vapor phase and exit the intake tube 103 and thus be delivered to the patient 101.

[0077] The corrugated expiratory tube 117 maximizes vapor removal and minimizes condensate formation. The expiratory tube 117 can be vapor permeable to facilitate diffusion of vapor through the walls of the expiratory tube 117 to the outside atmosphere. In some configurations, the expiratory tube 117 is vapor permeable and heated, and controlled heating along the tube facilitates diffusion of vapor through the walls of the expiratory tube 117 to the outside atmosphere. Vapor transferred to the outside atmosphere is not delivered to the gas source 105. The corrugated expiratory tube 117 creates turbulence in the portion of the gas flow adjacent the walls of the expiratory tube 117, increasing the residence time of the gas adjacent the walls within the corrugations. The increased residence time increases the opportunity for vapor diffusion through the walls of the expiratory tube 117. The increased residence time also reduces the temperature of the gas swirling within the "pockets" of each corrugation, increasing the relative humidity of these gases. The increased relative humidity increases the vapor pressure gradient across the walls of the expiratory tube 117, further increasing vapor diffusion through the walls.

[0078] As described below, the expiratory tube 117 may include a heater wire wrapped around the center of the lumen of the expiratory tube 117. A heater wire positioned in this manner adds turbulence to the gas flow while minimizing condensation formation. More turbulence means better mixing of the gas, thereby moving water vapor to the outer wall of the expiratory tube 117. The corrugated expiratory tube 117 also provides "pockets" of the corrugation, which has the advantage of collecting any liquid that condenses from the vapor. Liquid trapped within the corrugation is liquid that is not delivered to the gas source 105. In some configurations, the heater wire may be positioned within the wall of the expiratory tube 117. The presence of the heater wire within the expiratory tube 117 also minimizes condensation formation within the expiratory tube.

[0079] The combination of a smooth bore inspiratory tube 103 and a corrugated expiratory tube 117 allows the humidifier 107 to improve humidity performance. In both invasive and non-invasive ventilation, there is a contribution from the patient and a bias flow. In both, the expiratory tube 117 may function to reduce the amount of humidity returned to the gas source 105. The function of the expiratory tube 117 may be such that it sufficiently reduces the amount of humidity returned to the gas source 105.

[0080] The function of the expiratory tube can enable the humidifier 107 and inhalation tube 103 to deliver higher levels of humidity to the patient 101. If the expiratory tube 117 cannot sufficiently reduce the amount of humidity returned to the gas source 105, then the ability of the humidifier 107 and inhalation tube 103 to deliver higher levels of humidity to the patient 101 would need to be reduced or inhibited, since some of that excess humidity would be carried through the expiratory tube 117 to the gas source 105.

[0081] Applicant has made a surprising discovery related to the breathing circuit that there may be a trade-off between the components of the breathing circuit 100, specifically the inspiratory tube 103 and the expiratory tube 117, with respect to compression capacity within the overall system. It was recognized that there may be a reduction in the diameter of the inspiratory tube 103 by switching from a corrugated tube to a smooth bore tube while maintaining the same resistance to flow (RTF). Applicant has surprisingly found that the diameter of the expiratory tube 117 may be increased up to its theoretical maximum nominal diameter while maintaining the overall compression capacity of the breathing circuit. For a corrugated tube, the nominal diameter is equal to the average of the maximum and minimum diameters of the corrugated tube.

[0082] Typical industry standard corrugated tubing diameters for breathing circuits include 10 mm, 15 mm, and 22 mm. Sometimes in the industry, these tubing sizes are merely names or refer simply to the size of the connectors at the ends of the tubing, rather than referring to the actual inner, outer, and / or nominal diameter of the tubing. Although not limiting in nature, smaller diameter tubing, such as 10 mm tubing or 12 mm tubing, may be useful for neonatal patients, 15 mm tubing may be useful for pediatric patients, and 22 mm tubing may be useful for adult patients. Other inner or nominal diameters of the tube are contemplated, such as 1 mm, 2 mm, 3 mm, 4 mm, 5 mm, 6 mm, 7 mm, 8 mm, 9 mm, 10 mm, 11 mm, 12 mm, 13 mm, 14 mm, 15 mm, 16 mm, 17 mm, 18 mm, 19 mm, 20 mm, 21 mm, 22 mm, 23 mm, 24 mm, 25 mm, 26 mm, 27 mm, 28 mm, 29 mm, 30 mm, and ranges including two or more diameters disclosed herein. Assuming the RTF of the intake rim is constant, it has been found that the diameter of the intake tube 103 can be reduced if the bore is smooth instead of corrugated.

[0083] Given three standard corrugated pipe diameters, 10 mm, 15 mm and 22 mm, it has surprisingly been found that flow resistance can be matched between smooth bore pipes of various internal diameters and corrugated pipes of various nominal diameters. Each corrugated pipe has an RTF that can be measured by a test device. Each corrugated pipe has an RTF that can be theoretically calculated using the dimensions of the tube. Similarly, each smooth bore pipe has an RTF that can be measured by a test device. In addition to or instead of testing, the RTF can be theoretically calculated. It has been found that for each corrugated pipe having a nominal diameter, the RTF can be matched to a corresponding smooth bore pipe of a smaller diameter. As one non-limiting example found by the applicant, a corrugated pipe having a 10 mm nominal diameter can be substantially equivalent to a 6.9 mm smooth bore pipe based on the two pipes having the same RTF. As another example found by the applicant, a corrugated pipe having a 15 mm nominal diameter can be substantially equivalent to a 8 mm smooth bore pipe based on substantially similar RTFs. As yet another example, it has been discovered by the applicant that a corrugated tube having a nominal diameter of 22 mm can be substantially equivalent to a smooth bore tube of 13.5 mm based on substantially similar RTF. Thus, the smooth bore inspiratory tube 103 can be reduced in diameter compared to a corrugated inspiratory tube without increasing the RTF of the inspiratory rim of the breathing circuit.

[0084] The overall compression capacity of the breathing circuit is taken to be the sum of the compression capacity of the inspiratory limb and the compression capacity of the expiratory limb. Given three industry standard corrugated tube diameters, 10 mm, 15 mm and 22 mm, the compression capacity of the breathing circuit can be determined. Each corrugated tube has a compression capacity that can be measured by a test device. Each corrugated tube has a compression capacity that can be theoretically calculated based on the dimensions of the corrugated tube. For corrugated tubes, the compression capacity can be calculated based on the assumption that the nominal diameter of the corrugated tube is equal to the average of the maximum and minimum diameters of the corrugated tube. It has been found that the overall compression capacity of a breathing circuit with corrugated inspiratory and expiratory tubes can be maintained in a breathing circuit 100 in which the inspiratory tube 103 has a smooth bore and the expiratory tube is corrugated.

[0085] It was found that the change in compression volume of the inspiratory limb can be traded off with a change in compression volume of the expiratory limb of the breathing circuit while maintaining the overall compression volume of the breathing circuit produced by a standard corrugated tube. It was found that the smooth bore inspiratory tube 103 can have a reduced diameter while maintaining the RTF of the inspiratory limb. By reducing the diameter of the inspiratory tube of the inspiratory limb (achievable by changing from a corrugated tube to a smooth bore tube), there was a reduction in the compression volume of the inspiratory limb of the breathing circuit. It was found that this reduction in compression volume with the smooth bore inspiratory tube 103 can be traded off with an increase in the compression volume of the corrugated expiratory tube 117 while maintaining the overall compression volume of the breathing circuit. The reduction in compression volume of the smooth bore inspiratory tube 103 can be determined and added to the compression volume allowance of the expiratory tube 117.

[0086] It has been found that the expiratory tube 117 may have a theoretical maximum nominal diameter based on the reduction in the compression capacity of the inhalation tube 103. As one non-limiting example found by the applicant, a 6.9 mm smooth bore inhalation tube 103 can offset a 14.7 mm corrugated expiratory tube 117 without a change in the overall compression capacity of the breathing circuit. As another example found by the applicant, a 8 mm smooth bore inhalation tube 103 can offset a 19.3 mm corrugated expiratory tube 117 without a change in the overall compression capacity of the breathing circuit. As yet another example found by the applicant, a 13.5 mm smooth bore inhalation tube 103 can offset a 27.4 mm corrugated expiratory tube 117 without a change in the overall compression capacity of the breathing circuit. The theoretical maximum nominal diameter of the corrugated expiratory tube 117 maintains the total breathing circuit compression capacity. This compression capacity remains unchanged. This is because the reduction in compression volume due to the change in the design of the inhalation tube 103 allows for an increase in compression volume in the design of the exhalation tube 117 .

[0087] It has been found that the heater wire in the inhalation tube 103 has a detrimental effect on the RTF (i.e., the heater wire in the inhalation tube 103 increases the RTF when all other factors are held constant) and therefore the presence of the heater wire may limit the reduction in diameter of the smooth bore inhalation tube 103. As one non-limiting example found by the applicant, based on the RTF excluding the RTF of the heater wire, a corrugated tube having a nominal diameter of 10 mm may be substantially equivalent to a 9.3 mm smooth bore tube. Compared to a nominal 10 mm corrugated inhalation and expiratory circuit, it has been found that a 9.3 mm smooth bore inhalation tube 103 may offset a 13.4 mm corrugated expiratory tube 117 without a change in the overall compression capacity of the breathing circuit. As another example found by the applicant, based on the RTF excluding the RTF of the heater wire, a corrugated tube having a nominal diameter of 15 mm may be substantially equivalent to a 12.7 mm smooth bore tube. It has been found that, compared to a nominal 15 mm corrugated inhalation and exhalation circuit, a 12.7 mm smooth bore inhalation tube 103 can offset a 16.6 mm corrugated exhalation tube 117 without a change in the overall compression capacity of the breathing circuit. As yet another example found by the applicant, a corrugated tube having a nominal diameter of 22 mm can be substantially equivalent to a 20.3 mm smooth bore tube, based on the RTF excluding the heater wire RTF. It has been found that, compared to a nominal 22 mm corrugated inhalation and exhalation circuit, a 20.3 mm smooth bore inhalation tube 103 can offset a 22.9 mm corrugated exhalation tube 117 without a change in the overall compression capacity of the breathing circuit.

[0088] As another non-limiting example discovered by the applicant, based on the RTF taking into account the RTF of the heater wire, a corrugated tube having a nominal diameter of 10 mm can be substantially equivalent to a smooth bore tube of 5.9 mm. In comparison to nominal 10 mm corrugated inhalation and exhalation circuits, it has been discovered that a 5.9 mm smooth bore inhalation tube 103 can offset a 12.8 mm corrugated exhalation tube 117 without a change in the overall compression capacity of the breathing circuit. A corrugated tube having a nominal diameter of 10 mm can be substantially equivalent to a 5.9 mm smooth bore tube of 12.8 mm without a change in the overall compression capacity of the breathing circuit. 3The RTF of a corrugated tube having a nominal diameter of 10 mm can be calculated using the trend line. Using the trend line, the smooth bore intake pipe 103 can have a nominal diameter of 5.9 mm, which is the inside diameter of an equivalent smooth bore at the same pressure. For the standard tube and the smooth bore intake pipe 103, the RTF can be the same or nearly the same, e.g., 75.93 cmH2O / l / min. The smooth bore intake pipe can have a nominal diameter of 27,631.9 mm, for example. 3 / m. In such a case, the compression capacity difference may be, for example, 50,907.9 mm 3 The corrugated expiratory tube 117 may have a compression volume difference of, for example, 129,447.7 mm / m compared to the compression volume of a corrugated tube having a nominal diameter of 10 mm. 3 / m. Thus, the corrugated expiratory tube 117 may have a maximum nominal diameter of 12.8 mm to maintain the overall compression capacity of the circuit (inspiratory and expiratory limbs). Additionally or alternatively, the corrugated expiratory limb may have a nominal diameter smaller than the maximum and the inspiratory and / or expiratory limbs may be extended beyond the prior art length. For example, the inspiratory and expiratory limbs may be provided in lengths such as 1.75 m or other lengths disclosed herein. Those skilled in the art will appreciate that this option, i.e., increasing the length of the inspiratory and / or expiratory limbs rather than using the maximum expiratory diameter possible, or increasing the length (of the inspiratory and / or expiratory limbs) and increasing the diameter to a smaller diameter than the maximum possible diameter, is available for each embodiment disclosed herein and may be utilized to achieve the beneficial technical effects described herein.

[0089] As another example, it has been discovered by the applicant that a corrugated tube having a nominal diameter of 15 mm can be substantially equivalent to a 6.7 mm smooth bore tube based on the RTF determined using trend lines and taking into account the RTF of the heater wire. In comparison to nominal 15 mm corrugated inhalation and exhalation circuits, it has been discovered that a 6.7 mm smooth bore inhalation tube 103 can offset a 20.1 mm corrugated exhalation tube 117 without a change in the overall compression capacity of the breathing circuit. Using trend lines, the compression capacity of the 15 mm corrugated tube, for example, is 176,714.6 mm. 3 Similarly, the smooth bore intake pipe 103 may have a length of 34,820.4 mm 3 / m. The compression capacity difference between the standard tube and the new smooth bore intake pipe 103 is 141,894.2 mm 3 The corrugated expiratory tube 117 may have a compression volume of 15 mm nominal diameter corrugated tube and a compression volume difference of, for example, 318,608.8 mm 3 / m. Furthermore, because these are values ​​per meter, as described further herein, one skilled in the art should understand that the length of the inspiratory and / or expiratory limbs may be further increased as compared to the length of the prior art limbs without increasing the overall compression capacity of the circuit.

[0090] As yet another example discovered by the applicant, based on the RTF determined by using trend lines and taking into account the RTF of the heater wire, a corrugated tube having a nominal diameter of 22 mm can be substantially equivalent to a 10.9 mm smooth bore tube. In comparison to the nominal 22 mm corrugated inhalation and exhalation circuits, it has been discovered that a 10.9 mm smooth bore inhalation tube 103 can offset a 29.1 mm corrugated exhalation tube 117 without a change in the overall compression capacity of the breathing circuit. Using trend lines, the compression capacity of the 22 mm corrugated tube is 380,132.7 mm. 3 / m. The smooth bore intake pipe 103 has a length of 93,664.1 mm 3 / m. The compression capacity difference between the standard tube and the new smooth bore intake pipe 103 is 286,468.6 mm 3 The corrugated expiratory tube 117 may have a compression volume difference of, for example, 666,601.3 mm compared to the compression volume of a corrugated tube having a nominal diameter of 22 mm. 3 / m. Furthermore, because these are values ​​per meter, as described further herein, one skilled in the art should understand that the length of the inspiratory and / or expiratory limbs may be further increased as compared to the length of the prior art limbs without increasing the overall compression capacity of the circuit.

[0091] As yet another non-limiting example discovered by the applicant, a corrugated tube having a nominal diameter of 10 mm can be substantially equivalent to a 7.8 mm smooth bore tube based on the RTF, excluding the RTF of the heater wire, determined using trend lines. In comparison to nominal 10 mm corrugated inhalation and exhalation circuits, it has been discovered that a 7.8 mm smooth bore inhalation tube 103 can offset an 11.8 mm corrugated exhalation tube 117 without a change in the overall compression capacity of the breathing circuit. Using trend lines, the compression capacity of the 10 mm corrugated tube is 78,539.8 mm. 3 / m. The smooth bore intake pipe 103 has a length of 47,523.4 mm 3 / m. The compression capacity difference between the standard tube and the new smooth bore intake pipe 103 is 31,016.5 mm 3 The corrugated expiratory tube 117 may have a compression volume difference of, for example, 109,556.3 mm / m compared to the compression volume of a corrugated tube having a nominal diameter of 10 mm. 3 / m. Furthermore, because these are values ​​per meter, as described further herein, one skilled in the art should understand that the length of the inspiratory and / or expiratory limbs may be further increased as compared to the length of the prior art limbs without increasing the overall compression capacity of the circuit.

[0092] As another example, it has been discovered by the applicant that a corrugated tube having a nominal diameter of 15 mm can be substantially equivalent to a 10.5 mm smooth bore tube, based on the RTF excluding the RTF of the heater wire. In comparison to nominal 15 mm corrugated inhalation and exhalation circuits, it has been discovered that a 10.5 mm smooth bore inhalation tube 103 can offset an 18.5 mm corrugated exhalation tube 117 without a change in the overall compression capacity of the breathing circuit. Using trend lines, the compression capacity of the 15 mm corrugated tube is 176,714.6 mm. 3 The smooth bore intake pipe 103 can be 85,910.6 mm 3 The compression capacity difference between the standard tube and the new smooth bore intake pipe 103 is 90,804.0 mm. 3 The corrugated expiratory tube 117 may have a compression volume difference of, for example, 267,518.6 mm compared to the compression volume of a corrugated tube having a nominal diameter of 15 mm. 3 Furthermore, since these are values ​​per meter, as described further herein, one skilled in the art should understand that the length of the inhalation and / or exhalation limbs may be further increased compared to the length of the prior art limbs without increasing the overall compression capacity of the circuit.

[0093] As yet another example, it has been discovered by the applicant that a corrugated tube having a nominal diameter of 22 mm can be substantially equivalent to a 16.9 mm smooth bore tube, based on the RTF excluding the RTF of the heater wire. In comparison to nominal 22 mm corrugated inhalation and exhalation circuits, it has been discovered that a 16.9 mm smooth bore inhalation tube 103 can offset a 26.1 mm corrugated exhalation tube 117 without a change in the overall compression capacity of the breathing circuit. Using trend lines, the compression capacity of the 22 mm corrugated tube is 380, 132.7 mm. 3 / m. The smooth bore intake pipe 103 can be 224, 424.7 mm 3 / m. The compression capacity difference between the standard tube and the new smooth bore intake pipe 103 is 155,708.0 mm 3The corrugated expiratory tube 117 may have a compression volume difference of, for example, 535,840.7 mm / m compared to the compression volume of a corrugated tube having a nominal diameter of 22 mm. 3 / m. Furthermore, because these are values ​​per meter, as described further herein, one skilled in the art should understand that the length of the inspiratory and / or expiratory limbs may be further increased as compared to the length of the prior art limbs without increasing the overall compression capacity of the circuit.

[0094] Another example discovered by the applicant is that based on the RTF taking into account the RTF of the heater wire, a corrugated tube having a nominal diameter of 15 mm can be substantially equivalent to a smooth bore tube of 6.7 mm. It has been found that a 6.7 mm smooth bore inhalation tube 103 can offset a 20.1 mm corrugated expiratory tube 117 without a change in the overall compression capacity of the breathing circuit, as compared to a nominal 15 mm corrugated inhalation and expiratory circuit. Another example discovered by the applicant is that based on the RTF taking into account the RTF of the heater wire, a corrugated tube having a nominal diameter of 15 mm can be substantially equivalent to a smooth bore tube of 10.0 mm. It has been found that a 10.0 mm smooth bore inhalation tube 103 can offset a 18.7 mm corrugated expiratory tube 117 without a change in the overall compression capacity of the breathing circuit, as compared to a nominal 15 mm corrugated inhalation and expiratory circuit. In another example, the applicant has found that, based on the RTF taking into account the RTF of the heater wire, a corrugated tube having a nominal diameter of 15 mm can be substantially equivalent to a smooth bore tube of 11.7 mm. Compared to the nominal 15 mm corrugated inhalation and exhalation circuits, it has been found that the smooth bore inhalation tube 103 of 11.7 mm can offset the corrugated exhalation tube 117 of 17.7 mm without a change in the overall compression capacity of the breathing circuit. In another example, the applicant has found that, based on the RTF taking into account the RTF of the heater wire, a corrugated tube having a nominal diameter of 15 mm can be substantially equivalent to a smooth bore tube of 13.5 mm. Compared to the nominal 15 mm corrugated inhalation and exhalation circuits, it has been found that the smooth bore inhalation tube 103 of 13.5 mm can offset the corrugated exhalation tube 117 of 16.4 mm without a change in the overall compression capacity of the breathing circuit. Furthermore, because these are values ​​per meter, as described further herein, one skilled in the art should understand that the length of the inhalation and / or exhalation limbs may be further increased compared to the limb lengths of the prior art without increasing the overall compression capacity of the circuit.

[0095] The compression capacity of the 15mm corrugated tube using trend lines is 176,714.6mm 3 / m. The smooth bore intake pipe 103 is 34,820 mm for a 6.7 mm intake pipe. 3 / m, 78,539.8mm with 10.0mm intake pipe 3 , 107,513.2mm with 11.7mm intake pipe 3 / m and 13.5mm intake pipe for 143,138.8mm 3 / m. The compression capacity difference between the standard tube and the new smooth bore intake pipe 103 is 141,894.2 mm for a 6.7 mm intake pipe. 3 / m, 98,174.8mm with 10.0mm intake pipe 3 / m, 69,201.4mm with 11.7mm intake pipe 3 / m and 13.5mm intake pipe for a total of 33,575mm 3 The corrugated expiratory tube 117 may have a compression volume of 15 mm nominal diameter corrugated tube and a compression volume difference of 318,608.8 mm for a 6.7 mm inspiratory tube. 3 / m, 274,889.4mm with 10.0mm intake pipe 3 / m, 245,916.0mm with 11.7mm intake pipe 3 / m and 13.5mm intake pipe for 210, 290.4mm 3 / m. Furthermore, because these are values ​​per meter, as described further herein, one skilled in the art should understand that the length of the inspiratory and / or expiratory limbs may be further increased as compared to the length of the prior art limbs without increasing the overall compression capacity of the circuit.

[0096] As another example, it has been discovered by the applicant that a corrugated tube having a nominal diameter of 15 mm can be substantially equivalent to a 10.5 mm smooth bore tube based on the RTF excluding the RTF of the heater wire. It has been discovered that a 10.5 mm smooth bore inhalation tube 103 can offset an 18.5 mm corrugated expiratory tube 117 without a change in the overall compression capacity of the breathing circuit, compared to a nominal 15 mm corrugated inhalation and expiratory circuit. Furthermore, since these are values ​​per meter, as described further herein, it should be understood by one skilled in the art that the length of the inhalation limb and / or expiratory limb can be further increased compared to the length of the limbs of the prior art without increasing the overall compression capacity of the circuit.

[0097] The compression capacity of the 15mm corrugated tube using trend lines is 176,714.6mm 3 / m. The smooth bore intake pipe 103 is 85,910.6 mm for a 10.5 mm intake pipe. 3 The compression capacity difference between the standard tube and the new smooth bore intake pipe 103 is 90,804.0 mm for a 10.5 mm intake pipe. 3 The corrugated expiratory tube 117 may have a compression volume of 267,518.6 mm for a 10.5 mm inspiratory tube compared to a compression volume of 15 mm nominal diameter corrugated tube. 3 / m. Furthermore, because these are values ​​per meter, as described further herein, one skilled in the art should understand that the length of the inspiratory and / or expiratory limbs may be further increased as compared to the length of the prior art limbs without increasing the overall compression capacity of the circuit.

[0098] As an example discovered by the applicant, there may be a trend line of RTF pressure vs. inner diameter for a corrugated tube at 5 L / min. Taking into account the heater wire, one possible equation for this trend line calculated by the applicant is approximately y=2149322.2385x -4.4519 , R 2= 0.9727. One possible equation for this trend line calculated by the applicant, excluding the heater wire, is approximately y = 603928.0681x -4.4380 , R 2 = 0.9964. An example found by the applicant could be the nominal diameter of the corrugated tube vs. RTF pressure at 5 L / min. Taking into account the heater wire, one possible equation for this trend line calculated by the applicant is approximately y = 26.0327x -0.2185 , R 2 = 0.9727. One possible equation for this trend line calculated by the applicant, excluding the heater wire, is approximately y = 20.0518x -0.2245 , R 2 = 0.9964. The RTF limit according to ISO standards at this flow rate is 0.9 cmH2O (88.25 Pa) with two thresholds of 9.78 mm with heater wire and 7.33 mm without heater wire. As an example discovered by applicant, there may be a trend line of RTF pressure vs. inner diameter for a smooth bore tube at 5 L / min. One possible equation for this trend line calculated by applicant is approximately y = 15.3164x -0.2191 , R 2 =0.9933.

[0099] Another example discovered by the applicant can be the trend line of RTF pressure vs. inner diameter for a corrugated tube at 15 L / min. Taking into account the heater wire, one possible equation for this trend line calculated by the applicant is approximately y=22141877.6970x -4.5927 , R 2 = 0.9780. One possible equation for this trend line calculated by the applicant, excluding the heater wire, is approximately y = 64442935.7622x -5.5152 , R 2= 0.9907. An example found by the applicant can be the nominal diameter of the corrugated tube vs. RTF pressure at 15 L / min. Taking into account the heater wire, one possible equation for this trend line calculated by the applicant is approximately y = 38.8945x -0.2129 , R 2 = 0.9780. One possible equation for this trend line calculated by the applicant, excluding the heater wire, is approximately y = 25.9216x -0.1796 , R 2 =0.9907. The limit of RTF according to ISO standard is 0.9 cmH2O (88.25 Pa) and the two thresholds are 14.98 mm with heater wire and 11.59 mm without heater wire. As an example discovered by the applicant, there may be a trend line of RTF pressure vs. inner diameter for a smooth bore tube at 15 L / min. One possible equation for this trend line calculated by the applicant is approximately y=27.3664x -0.3158 , R 2 =0.9421.

[0100] As yet another example identified by the applicant, there may be a trendline of RTF pressure vs. internal diameter for a corrugated tube at 30 L / min. Taking into account the heater wire, one possible equation for this trendline calculated by the applicant is approximately y=79343411.8635x -4.5906 , R 2 = 0.9657. One possible equation for this trend line calculated by the applicant, excluding the heater wire, is approximately y = 528987202.1853x -5.8298 , R 2 = 0.9828. An example found by the applicant could be the nominal diameter of the corrugated tube vs. RTF pressure at 30 L / min. Taking into account the heater wire, one possible equation for this trend line calculated by the applicant is approximately y = 50.3401x -0.2104 , R 2= 0.9657. One possible equation for this trend line calculated by the applicant, excluding the heater wire, is approximately y = 30.9550x -0.1686 , R 2 = 0.9828. The limit of RTF according to the ISO standard is 0.9 cmH2O (88.25 Pa) and the two thresholds are 19.61 mm with heater wire and 14.54 mm without heater wire. As an example discovered by the applicant, there may be a trend line of RTF pressure vs. inner diameter for a smooth bore tube at 30 L / min. One possible equation for this trend line calculated by the applicant is approximately y = 26.9650X -0.2260 , R 2 =0.8419.

[0101] It has been discovered that there are many advantages to the breathing circuit 100. As described herein, a larger nominal diameter corrugated expiratory tube 117 increases surface area and residence time, both of which increase vapor diffusion when the expiratory tube is made of a material that allows the movement of water molecules through the walls of the expiratory tube. When used with a smooth walled inspiratory tube, the theoretical maximum nominal diameter of the corrugated expiratory tube 117 has the advantage of increasing vapor diffusion during the residence time of the gas in the expiratory tube, while maintaining the overall compression capacity of the entire breathing circuit.

[0102] The breathing circuit is designed to match the RTF of the inhalation tube 103 from a corrugated tube of a first nominal diameter to a smooth bore tube of a second diameter, the second diameter being smaller than the first diameter. The smooth bore tube of the second diameter has a smaller compression volume than the corrugated tube of the first diameter, thereby creating a compression volume allowance for the breathing circuit including the smaller smooth bore tube of the second diameter as the inhalation rim. This compression volume allowance can be offset by a corrugated tube of a third nominal diameter as the expiratory rim, the third nominal diameter being larger than the first nominal diameter. Compared to a breathing circuit having an inspiratory rim with a corrugated tube of a first nominal diameter and an expiratory rim with a corrugated tube of the first nominal diameter, a modified breathing circuit has an inspiratory rim with a smooth bore tube of a second diameter and an expiratory rim with a corrugated tube of a third nominal diameter, the overall compression volume between the breathing circuits is the same or less, and the RTF of the inspiratory rim is the same or less. In some embodiments discovered by the applicant, these advantages are achievable by an expiratory rim with a corrugated tube of a third nominal diameter, the third nominal diameter being larger than the first nominal diameter.

[0103] In another example, surprisingly discovered by the applicant, a nominal 13 mm corrugated inhalation tube and a nominal 13 mm corrugated exhalation tube have a compression capacity when used together to form a breathing circuit. Taking an inhalation rim as an example, the corrugated inhalation tube has an RTF that can be measured to obtain an actual RTF or calculated to obtain a theoretical RTF. The RTF of the 13 mm corrugated inhalation tube can be substantially equal to a smooth bore inhalation tube 103. The smooth bore inhalation tube 103 has a smaller diameter than the corresponding 13 mm corrugated inhalation tube. This reduction in diameter between the corrugated inhalation tube and the smooth bore inhalation tube 103 corresponds to a reduction in the compression capacity of the inhalation rim.

[0104] The inspiratory limb and the expiratory limb together form a breathing circuit. The nominal 13 mm corrugated inspiratory tube and the nominal 13 mm corrugated expiratory tube define a first total compression volume of the breathing circuit. This first total compression volume can be maintained or reduced in a modified breathing circuit with a smooth bore inspiratory tube 103. In a modified breathing circuit with a smooth bore inspiratory tube 103, the inspiratory limb has a reduced compression volume due to the reduced diameter of the tube. In a modified breathing circuit with a smooth bore inspiratory tube 103, the expiratory limb can be designed with a larger nominal diameter. The larger nominal diameter expiratory limb has a larger compression volume that offsets the reduced compression volume of the inspiratory limb in considering the total compression volume of the breathing circuit. Thus, the reduced compression volume resulting from the use of a smooth bore inspiratory tube 103 can absorb the increased compression volume due to the corrugated expiratory tube 117. A breathing circuit having a nominal 13 mm corrugated inhalation tube and a nominal 13 mm corrugated expiratory tube has an overall compression capacity that is the same as or less than a smooth bore inhalation tube 103 and a corrugated expiratory tube 117. However, the inhalation tube 103 has a smaller diameter than the corresponding inhalation limb of a breathing circuit having a nominal 13 mm corrugated inhalation tube, and the corrugated expiratory tube 117 has a larger nominal diameter than the corresponding expiratory limb of a breathing circuit having a nominal 13 mm corrugated expiratory tube.

[0105] Different diameter tubes may be used with different patient populations. Additionally, the intended delivery or tidal volume may vary between tubes of the same or different diameters as well as within the same or different breathing circuits. In some embodiments, smaller diameter tubes may be used with neonatal and pediatric patients while larger diameter tubes may be used with adult patients. The modified breathing circuit may be suitable for treating patients with tidal volumes in the range of 50ml to 300ml. The modified breathing circuit may be suitable for treating patients with tidal volumes of 300ml or more. The modified breathing circuit may be suitable for treating patients with tidal volumes of 50ml or less. The modified breathing circuit may be suitable for treating pediatric or adolescent patients. The modified breathing circuit may be suitable for treating adult patients. The modified breathing circuit may be suitable for treating neonatal patients.

[0106] The modified breathing circuit may be tested according to standard ISO 5367:2014(E), which is incorporated by reference in its entirety. In the adult patient category, the intended delivery volume is 300 ml or more. In the pediatric category, the intended delivery volume is 50 ml to 300 ml. In the neonatal category, the intended delivery volume is 50 ml or less. In the adult patient category, the flow resistance limit is 0.03 hPa / l / min / m (cmH20 / l / min / m). In the pediatric patient category, the flow resistance limit is 0.06 hPa / l / min / m (cmH20 / l / min / m). In the neonatal patient category, the flow resistance limit is 0.37 hPa / l / min / m (cmH20 / l / min / m). In the adult patient category, the flow time is 30 L / min. In the pediatric patient category, the flow time is 15 L / min. In the neonatal patient category, the flow time is 2.5 L / min. Table 1 is reproduced below: The following table may set out the flow resistance limits per meter per patient category for breathing tubes supplied cut to length.

[0107] [Table 2]

[0108] In some advantageous configurations of the modified breathing circuit, the inhalation tube 103 may have an inner diameter of 5 mm to 14.5 mm, while the expiratory tube 117 may have a nominal inner diameter of 15 mm to 22 mm. In some advantageous configurations of the modified breathing circuit, the inhalation tube 103 may have an inner diameter of 10 mm to 21 mm, while the expiratory tube 117 may have a nominal inner diameter of 22 mm to 30 mm. In some advantageous configurations, the inhalation tube 103 may have an inner diameter of 4 mm to 12 mm, while the expiratory tube 117 may have a nominal inner diameter of 13 mm to 18 mm. In some advantageous configurations of the modified breathing circuit, the inhalation tube 103 may have an inner diameter of 4 mm to 17 mm, while the expiratory tube 117 may have a nominal inner diameter of 10.5 mm to 20.5 mm. In some advantageous configurations of the modified breathing circuit, the inhalation tube 103 may have an inner diameter of 9.5 mm to 24 mm, while the expiratory tube 117 may have a nominal inner diameter of 19 mm to 31.5 mm. In some advantageous configurations of the modified breathing circuit, the inhalation tube 103 may have an inner diameter of 3 mm to 13 mm, while the expiratory tube 117 may have a nominal inner diameter of 9.5 mm to 19 mm.

[0109] In some advantageous configurations of the modified breathing circuit, the inhalation tube 103 may have an inner diameter of 4 mm to 8 mm, while the expiratory tube 117 may have a nominal inner diameter of 11 mm to 15 mm. In some advantageous configurations of the modified breathing circuit, the inhalation tube 103 may have an inner diameter of 5 mm to 9 mm, while the expiratory tube 117 may have a nominal inner diameter of 18 mm to 22 mm. In some advantageous configurations, the inhalation tube 103 may have an inner diameter of 9 mm to 13 mm, while the expiratory tube 117 may have a nominal inner diameter of 27 mm to 31 mm. In some advantageous configurations of the modified breathing circuit, the inhalation tube 103 may have an inner diameter of 6 mm to 10 mm, while the expiratory tube 117 may have a nominal inner diameter of 10 mm to 14 mm. In some advantageous configurations of the modified breathing circuit, the inhalation tube 103 may have an inner diameter of 8.5 mm to 12.5 mm, while the expiratory tube 117 may have a nominal inner diameter of 16.5 mm to 20.5 mm. In some advantageous configurations of the modified breathing circuit, the inhalation tube 103 may have an inner diameter of 15 mm to 19 mm, while the expiratory tube 117 may have a nominal inner diameter of 24 mm to 28 mm.

[0110] The intake pipe 103 may have a diameter between 1mm and 30mm, e.g. 1mm, 2mm, 3mm, 4mm, 5mm, 6mm, 7mm, 8mm, 9mm, 10mm, 11mm, 12mm, 13mm, 14mm, 15mm, 16mm, 17mm, 18mm, 19mm, 20mm, 21mm, 22mm, 23mm, 24mm, 25mm, 26mm, 27mm, 28mm, 29mm, 30mm or a range incorporating any of the aforementioned values, e.g. 6mm The inner diameter of the intake pipe 103 may be 1 mm to 14 mm, 6 mm to 13 mm, 6 mm to 12 mm, 6 mm to 11 mm, 7 mm to 10 mm, 8 mm to 9 mm, 10 mm to 20 mm, 11 mm to 20 mm, 11 mm to 19 mm, 11 mm to 18 mm, 11 mm to 17 mm, 11 mm to 16 mm, 11 mm to 15 mm, 12 mm to 15 mm, 13 mm to 14 mm, 5 mm to 11 mm, 6 mm to 10 mm, 6 mm to 8 mm, 9 mm to 10 mm, etc. The intake pipe 103 may have an inner diameter of any value between any of these values.

[0111] The intake pipe 103 may have an inner diameter within a range of 0mm to 2mm, 1mm to 3mm, 2mm to 4mm, 3mm to 5mm, 4mm to 6mm, 5mm to 7mm, 6mm to 8mm, 7mm to 9mm, 8mm to 10mm, 9mm to 11mm, 10mm to 12mm, 11mm to 13mm, 12mm to 14mm, 13mm to 15mm, 14mm to 16mm, 15mm to 17mm, 16mm to 18mm, 17mm to 19mm, 18mm to 20mm, 19mm to 21mm, 20mm to 22mm, 21mm to 23mm, 22mm to 24mm, 23mm to 25mm, 24mm to 26mm, 25mm to 27mm, 26mm to 28mm, 27mm to 29mm, 28mm to 30mm, etc. The intake pipe 103 may have an inner diameter within a range of 0mm to 4mm, 1mm to 5mm, 2mm to 6mm, 3mm to 7mm, 4mm to 8mm, 5mm to 9mm, 6mm to 10mm, 7mm to 11mm, 8mm to 12mm, 9mm to 13mm, 10mm to 14mm, 11mm to 15mm, 12mm to 16mm, 13mm to 17mm, 14mm to 18mm, 15mm to 19mm, 16mm to 20mm, 17mm to 21mm, 18mm to 22mm, 19mm to 23mm, 20mm to 24mm, 21mm to 25mm, 22mm to 26mm, 23mm to 27mm, 24mm to 28mm, 25mm to 29mm, 26mm to 30mm, etc. The intake pipe 103 may have an inner diameter within a range of 0mm to 6mm, 1mm to 7mm, 2mm to 8mm, 3mm to 9mm, 4mm to 10mm, 5mm to 11mm, 6mm to 12mm, 7mm to 13mm, 8mm to 14mm, 9mm to 15mm, 10mm to 16mm, 11mm to 17mm, 12mm to 18mm, 13mm to 19mm, 14mm to 20mm, 15mm to 21mm, 16mm to 22mm, 17mm to 23mm, 18mm to 24mm, 19mm to 25mm, 20mm to 26mm, 21mm to 27mm, 22mm to 28mm, 23mm to 29mm, 24mm to 30mm, etc.The intake pipe 103 may have an inner diameter within the range of 0 mm to 8 mm, 1 mm to 9 mm, 2 mm to 10 mm, 3 mm to 11 mm, 4 mm to 12 mm, 5 mm to 13 mm, 6 mm to 14 mm, 7 mm to 15 mm, 8 mm to 16 mm, 9 mm to 17 mm, 10 mm to 18 mm, 11 mm to 19 mm, 12 mm to 20 mm, 13 mm to 21 mm, 14 mm to 22 mm, 15 mm to 23 mm, 16 mm to 24 mm, 17 mm to 25 mm, 18 mm to 26 mm, 19 mm to 27 mm, 20 mm to 28 mm, 21 mm to 29 mm, 22 mm to 30 mm, etc. The intake pipe 103 may also have an inner diameter of any value between any of these values.

[0112] The expiratory tube 117 may have a length of 1 mm to 40 mm, for example, 1 mm, 2 mm, 3 mm, 4 mm, 5 mm, 6 mm, 7 mm, 8 mm, 9 mm, 10 mm, 11 mm, 12 mm, 13 mm, 14 mm, 15 mm, 16 mm, 17 mm, 18 mm, 19 mm, 20 mm, 21 mm, 22 mm, 23 mm, 24 mm, 25 mm, 26 mm, 27 mm, 28 mm, 29 mm, 30 mm, 31 mm, 32 mm, 33 mm, 34 mm, 35 mm, 36 mm, 37 mm, 38 mm, The expiratory tube 117 may have a nominal inner diameter of 15.5 mm to 21 mm, 16 mm to 20 mm, 16 mm to 19 mm, 18 mm to 20 mm, 19 mm to 20 mm, 22 mm to 29 mm, 23 mm to 30 mm, 24 mm to 30 mm, 24 mm to 29 mm, 25 mm to 28 mm, 25.5 mm to 27 mm, 13 mm to 17 mm, 14 mm to 17 mm, 15 mm to 16.5 mm, 14 mm to 15 mm, etc. It is also possible for the expiratory tube 117 to have an inner diameter of any value between any of these values.

[0113] Exhalation pipe 117 is 0mm~2mm, 1mm~3mm, 2mm~4mm, 3mm~5mm, 4mm~6mm, 5mm~7mm, 6mm~8mm, 7mm~9mm, 8mm~10mm, 9mm~11mm, 10mm~12mm , 11mm~13mm, 12mm~14mm, 13mm~15mm, 14mm~16mm, 15mm~17mm, 16mm~18mm, 17mm~19mm, 18mm~20mm, 19mm~21mm, 20mm~22m m, 21 mm to 23 mm, 22 mm to 24 mm, 23 mm to 25 mm, 24 mm to 26 mm, 25 mm to 27 mm, 26 mm to 28 mm, 27 mm to 29 mm, 28 mm to 30 mm, 29 mm to 31 mm, 30 mm to 32 mm, 31 mm to 33 mm, 32 mm to 34 mm, 33 mm to 35 mm, 34 mm to 36 mm, 35 mm to 37 mm, 36 mm to 38 mm, 37 mm to 39 mm, 38 mm to 40 mm, etc. Exhalation pipe 117 is 0mm~4mm, 1mm~5mm, 2mm~6mm, 3mm~7mm, 4mm~8mm, 5mm~9mm, 6mm~10mm, 7mm~11mm, 8mm~12mm, 9mm~13mm, 10 mm~14mm, 11mm~15mm, 12mm~16mm, 13mm~17mm, 14mm~18mm, 15mm~19mm, 16mm~20mm, 17mm~21mm, 18mm~22mm, 19mm~23 mm, 20mm to 24mm, 21mm to 25mm, 22mm to 26mm, 23mm to 27mm, 24mm to 28mm, 25mm to 29mm, 26mm to 30mm, 27mm to 31mm, 28mm to 32mm, 29mm to 33mm, 30mm to 34mm, 31mm to 35mm, 32mm to 36mm, 33mm to 37mm, 34mm to 38mm, 35mm to 39mm, 36mm to 40mm, etc.The expiratory tube 117 can be 0mm to 6mm, 1mm to 7mm, 2mm to 8mm, 3mm to 9mm, 4mm to 10mm, 5mm to 11mm, 6mm to 12mm, 7mm to 13mm, 8mm to 14mm, 9mm to 15mm, 10mm to 16mm, 11mm to 17mm, 12mm to 18mm, 13mm to 19mm, 14mm to 20mm, 15mm to 21mm, 16mm to 22mm, 17mm to 23mm, 18mm to 24mm, 19mm to 25mm, 20mm to 26mm, 21mm to 28mm, 22mm to 29mm, 23mm to 30mm, 24mm to 31mm, 25mm to 32mm, 26mm to 33mm, 27mm to 34mm, 28mm to 35mm, 29mm to 40mm, 30mm to 41mm, 31mm to 42mm, 32mm to 43mm, 33mm to 44mm, 34mm to 45mm, 35mm to 46mm, 36mm to 47mm, 37mm to 48mm, 38mm to 49mm, 40mm to 41mm, 42mm to 45mm, 43mm to 46mm, 44mm to 47mm, 45mm to 48mm, 46mm to 49mm, 47mm to 48mm, 48mm to 50mm, 49mm to 51mm, 52mm to 53mm, 53mm to 54mm, 54mm to 55mm, 55mm It may have an inner nominal diameter within the range of 4mm, 19mm to 25mm, 20mm to 26mm, 21mm to 27mm, 22mm to 28mm, 23mm to 29mm, 24mm to 30mm, 25mm to 31mm, 26mm to 32mm, 27mm to 33mm, 28mm to 34mm, 29mm to 35mm, 30mm to 36mm, 31mm to 37mm, 32mm to 38mm, 33mm to 39mm, 34mm to 40mm, etc. The expiratory tube 117 can be 0mm to 8mm, 1mm to 9mm, 2mm to 10mm, 3mm to 11mm, 4mm to 12mm, 5mm to 13mm, 6mm to 14mm, 7mm to 15mm, 8mm to 16mm, 9mm to 17mm, 10mm to 18mm, 11mm to 19mm, 12mm to 20mm, 13mm to 21mm, 14mm to 22mm, 15mm to 23mm, 16mm to 24mm, 17mm to The exhalation tube 117 may have an inner nominal diameter within the range of 25 mm, 18 mm to 26 mm, 19 mm to 27 mm, 20 mm to 28 mm, 21 mm to 29 mm, 22 mm to 30 mm, 23 mm to 31 mm, 24 mm to 32 mm, 25 mm to 33 mm, 26 mm to 34 mm, 27 mm to 35 mm, 28 mm to 36 mm, 29 mm to 37 mm, 30 mm to 38 mm, 31 mm to 39 mm, 32 mm to 40 mm, etc. It is also possible for the exhalation tube 117 to have an inner nominal diameter of any value between any of these values.

[0114] The difference between the diameter of the inhalation tube 103 and the diameter of the exhalation tube 117 may be between 0mm and 20mm, e.g. 0.5mm, 1mm, 1.5mm, 2mm, 2.5mm, 3mm, 3.5mm, 4mm, 4.5mm, 5mm, 5.5mm, 6mm, 6.5mm, 7mm, 7.5mm, 8mm, 8.5mm, 9mm, 9.5mm, 10mm, 11mm, 12mm, 13mm, 14mm, 15mm, 16mm, 17mm, 18mm, 19mm, 20mm or any of the aforementioned values. Incorporating ranges, e.g. 0mm~2mm, 1mm~3mm, 2mm~4mm, 3mm~5mm, 4mm~6mm, 5mm~7mm, 6mm~8mm, 7mm~9mm, 8mm~10mm, 9mm~11mm, 10mm~12mm, 11mm~13mm, 12mm~14mm, 13mm~15mm, 14mm~16mm, 15mm~17mm, 16mm~18mm, 17mm~19mm, 18mm~20mm, 0mm~4mm, 1mm~5mm, 2mm~6mm, 3mm~7mm, 4mm~8mm, 5mm~9mm, 6mm~10mm, 7mm~11mm, 8mm~12mm, 9mm~13mm, 10mm~14mm, 11mm~15mm, 12mm~16mm, 1 3mm~17mm, 14mm~18mm, 15mm~19mm, 16mm~20mm, 0mm~6mm, 1mm~7mm, 2mm~8mm, 3mm~9mm, 4mm~10mm, 5mm~11mm, 6mm~12mm, 7m The inner diameter of the inhalation tube 103 may be less than the nominal inner diameter of the exhalation tube 117. The difference may be any value between any of these values.

[0115] As another non-limiting but preferred example discovered by the applicant, based on the RTF, a corrugated tube having a nominal diameter of 15 mm can be substantially equivalent to a smooth bore tube of 11.7 mm. It has been discovered that an 11.7 mm smooth bore inhalation tube 103 can offset an expiratory limb of up to 18.5 mm or 20.1 mm (with or without a heater wire, respectively). However, the applicant has surprisingly discovered that a diameter of 14.5 mm, less than the maximum diameter used in the corrugated expiratory tube 117, still allows the desired technical effect without increasing the overall compression volume of the breathing circuit compared to a nominal 15 mm corrugated inhalation and exhalation circuit.

[0116] Moreover, in this preferred example, as further described herein, the length of the inhalation and / or exhalation limbs can be further increased as compared to prior art or typical limb lengths without increasing the overall compression capacity of the circuit. Such increased length provides a further technical benefit in that such limbs have improved maneuverability and improved patient mobility, particularly for neonatal and pediatric patients who require kangaroo care or other care in which the patient is held. In some embodiments, the inhalation or exhalation conduits can be approximately 1.75 m, as described below. A smooth bore inhalation tube 103 according to an embodiment of the present invention can have a tube diameter of approximately 11.7 mm. A smooth bore inhalation tube 103 can have a tube length of approximately 1.75 m. A smooth bore inhalation tube 103 according to an embodiment of the present invention can have a tube diameter of approximately 188, 148 mm. 3 / m rim compression capacity. The corrugated expiratory tube 117 may have a tube diameter of 14.5 mm. The corrugated expiratory tube 117 may have a tube length of about 1.75 m. The corrugated expiratory tube 117 may have a tube length of about 288,977 mm. 3 The total compression volume of the smooth bore intake tube 103 and the corrugated expiratory tube 117 is approximately 477,125 mm 3 / m. An equivalent standard tube has a diameter of 15 mm and a length of 1.5 m. The standard tube is a dual waveform circuit typically designed for pediatric patients. In a standard tube, the intake tube may have a tube diameter of 15 mm and a tube length of 1.5 m. The standard intake tube has a length of 265,072 mm. 3With a standard tube, the expiratory tube may have a tube diameter of 15 mm and a tube length of 1.5 m. 3 The total compression capacity of the inlet and outlet tracts of a standard circuit is 530,144 mm. 3 / m. As will be appreciated by those skilled in the art, compared to a standard circuit, the improved circuit of this embodiment (i.e., 11.7 mm smooth bore inhalation and 14.5 waveform exhalation) allows for a larger flow before reaching the ISO standard resistance limit of the 15 mm waveform inhalation rim (increasing the upper size of patients that can be treated), and the overall circuit compression volume is smaller than the 15 mm waveform pair (allowing for treating patients with smaller tidal volumes). Additionally, the increased length over the 1.5 m rim increases maneuverability and improves mobility for the patient and caregiver. The larger diameter of the exhalation rim, especially of the ventilated rim disclosed herein, increases the residence time and therefore allows for more moisture to be wicked to the ambient air (and away from sensitive ventilator components that may be damaged by moisture).

[0117] In some embodiments, the smooth bore inlet tube 103 allows for a larger flow before reaching a resistance limit. In some embodiments, this can result in an increase in the upper size limit of patients that can be treated. In some embodiments, the smooth bore inlet tube 103 allows for a larger flow compared to a 15 mm corrugated standard tube. In some embodiments, the overall circuit compression capacity is less than a standard corrugated tube pair. In some embodiments, this can result in a smooth bore inlet tube 103 and a corrugated expiratory tube 117 allowing patients with low tidal volumes to be treated. In some embodiments, the smooth bore inlet tube 103 and a corrugated expiratory tube 117 can advantageously allow for a larger flow before reaching a resistance limit compared to a corresponding standard circuit. In some embodiments, the smooth bore inlet tube 103 and a corrugated expiratory tube 117 can advantageously treat a wider range of patients by increasing the upper size limit of patients that can be treated compared to a corresponding standard circuit. In some embodiments, a smooth bore inlet tube 103 and a corrugated expiratory tube 117 may advantageously have a lower overall circuit compression capacity compared to a corresponding standard circuit. In some embodiments, a smooth bore inlet tube 103 and a corrugated expiratory tube 117 may advantageously treat patients with lower tidal volumes compared to a corresponding standard circuit.

[0118] The intake pipe 103 has a length of 1 m to 4 m, for example, 1.0 m, 1.05 m, 1.1 m, 1.15 m, 1.2 m, 1.25 m, 1.3 m, 1.35 m, 1.4 m, 1.45 m, 1.5 m, 1.55 m, 1.6 m, 1.65 m. m, 1.7m, 1.75m, 1.8m, 1.85m, 1.9m, 1.95m, 2.0m, 2.05m, 2.1m, 2.15m, 2.2m, 2.25m, 2.3m, 2.35m, 2.4m, 2.45m, 2.5 The length may be 2.5, 2.6, 2.65, 2.7, 2.75, 2.8, 2.85, 2.9, 2.95, 3.0, 3.1, 3.15, 3.2, 3.25, 3.3, 3.35, 3.4, 3.45, 3.5, 3.55, 3.6, 3.65, 3.7, 3.75, 3.8, 3.85, 3.9, 3.95, 4.0 m or a range incorporating any of the foregoing values. The exhalation pipe 117 is 1m to 4m, for example 1.0m, 1.05m, 1.1m, 1.15m, 1.2m, 1.25m, 1.3m, 1.35m, 1.4m, 1.45m, 1.5m, 1.55m, 1.6m, 1.65m , 1.7m, 1.75m, 1.8m, 1.85m, 1.9m, 1.95m, 2.0m, 2.05m, 2.1m, 2.15m, 2.2m, 2.25m, 2.3m, 2.35m, 2.4m, 2.45m, 2.5m , 2.55m, 2.6m, 2.65m, 2.7m, 2.75m, 2.8m, 2.85m, 2.9m, 2.95m, 3.0m, 3.1m, 3.15m, 3.2m, 3.25m, 3.3m, 3.35m, 3.4m, 3.45m, 3.5m, 3.55m, 3.6m, 3.65m, 3.7m, 3.75m, 3.8m, 3.85m, 3.9m, 3.95m, 4.0m or a range incorporating any of the aforementioned values. One skilled in the art will recognize that the total length of the inhalation or exhalation conduit can be broken down into multiple sections to accommodate other equipment such as a water trap, and / or an intermediate connector with one or more sensors, and / or a PCB, and / or a controller. The length can also be any value between any of these values.

[0119] In some embodiments, lower compliance can allow for a wider range of patient sizes, hi some embodiments, lower compliance can allow for longer circuits while still being within the range of acceptable patient sizes. In some embodiments, instead of a length of 1.1 to 1.5m, the inhalation and / or exhalation conduits may be longer, for example, to 1.55m, 1.6m, 1.65m, 1.7m, 1.75m, 1.8m, 1.85m, 1.9m, 1.95m, 2.0m, 2.05m, 2.1m, 2.15m, 2.2m, 2.25m, 2.3m, 2.35m, 2.4m, 2.45m, 2.5m, 2.55m, 2.6m, 2.65m, 2.7m, 2.75m, 2.8m, 2.85m, 2.9m, 2.95m, 3.0m, 1.6m or more, 1.5 to 2.0mm, preferably 1.75m, preferably 2.0m, or a range incorporating any of the aforementioned values. In some embodiments, longer inspiratory and / or expiratory conduits can be of great advantage in patient mobility, especially for neonatal and pediatric patients who require kangaroo care or other care in which the child is held. In some embodiments, the inspiratory or expiratory conduits can be less than 4m.

[0120] As described herein, tests have examined the difference in pneumatic properties of corrugated and smooth bore tubing used in breathing circuits for transporting humidified gas to and from a patient. Tests have examined the pneumatic advantage of a combination of a smooth bore inspiratory limb and a corrugated expiratory limb over a conventional corrugated inspiratory limb and a corrugated expiratory limb for three standard tubing sizes: 10 mm, 15 mm, and 22 mm. In some embodiments, the breathing set is a water trap-free corrugated dual limb breathing set intended to deliver humidified gas that may be heated.

[0121] Flow resistance test results showed that for a given nominal diameter corrugated tube (10mm, 15mm and 22mm), a smooth bore inspiratory tube of a smaller nominal diameter can be used to maintain the same resistance to flow (RTF) value. In some embodiments, heater wire is used in the breathing circuit to maintain the temperature of the humidified gas to and from the patient, and the corrugated inspiratory limb typically uses a spirally wound heater wire design. The heater wire in the air path increases the RTF of the circuit. In some embodiments, the smooth bore inspiratory tube can have the heater wire built into the wall of the tube outside of the air path so that the heater wire does not affect the RTF. By taking this into account in the RTF measurement, the size of the equivalent smooth bore tube is further reduced.

[0122] As described herein, a smaller nominal diameter smooth bore inhalation tube is directly related to a reduction in the compression volume (compliance) of the inhalation rim. This reduction in compression volume can allow for the use of a larger nominal diameter corrugated expiratory tube while maintaining a comparable overall breathing set compliance value. In some embodiments, the advantage of a larger expiratory rim surface area is that there is more area where vapor transfer (breathability) can occur. For a given standard breathing tube size of 10mm, 15mm and 22mm with corrugated inhalation and investigation tubes, a comparable smooth bore inhalation and investigation tube combination is described herein. Tests were conducted on three common standard sizes of breathing circuits, e.g., breathing sets of 10mm, 15mm and 22mm.

[0123] There are several important pneumatic properties of the breathing set as described herein to deliver effective respiratory assistance to the patient. The pneumatic compliance of the breathing set includes the sum of the pneumatic compliances of all components in the kit. The pneumatic compliance can be thought of as a measure of the volume required to raise the pressure in the breathing set to a desired level. A breathing set with low pneumatic compliance may require less additional volume for a given pressure change than a breathing set with high pneumatic compliance. The pneumatic compliance may directly affect the ventilator's waveform delivery to the patient. In some applications, maintaining or reducing the pneumatic compliance may be important when treating a given patient population. The pneumatic compliance of the breathing tube can be separated into two main components: compression capacity and tube stiffness. The larger the internal volume of the circuit, the greater the compression capacity. The greater the internal volume, the greater the amount of air that needs to be compressed to raise the pressure. For example, two steel tubes of the same length, one with an internal diameter of 10 mm and the other with an internal diameter of 20 mm, will have a larger compression capacity for the 20 mm tube than the 10 mm tube due to the larger internal volume. The stiffer the tube wall, the lower the compliance. A stiffer tube will stretch less and therefore require less air to reach a given pressure. For example, in two tubes of the same length and inner diameter, one steel and one rubber, with the same wall thickness, the compression capacity of both tubes will be the same. However, the rubber tube can expand and increase its volume when pressure increases, leading to a larger change in volume and higher compliance.

[0124] Resistance to flow (RTF) can be thought of as a measurement of how much pressure is required to pass a given flow rate of air through the tubing. Flow resistance is usually expressed as cmH2O / l / min. The main properties of the tubing that affect RTF include tubing diameter and surface roughness. In some embodiments, larger, smoother tubing is advantageous to reduce RTF. Flow resistance can be an important pneumatic property for a breathing circuit, as it limits the size of the waveform / breath that can be delivered to the patient within a specified inspiration time.

[0125] Nominal diameter can be considered a property of the pipe. It is a way of incorporating the difference in the inside diameter of the corrugated pipe. It can be calculated as follows:

number

[0126] One objective of the test was to examine the effect of smooth bore tubing on the pneumatic characteristics of the breathing circuit in terms of corrugated tubing in the range of tubing sizes typically utilized in respiratory support therapy. Applicant discovered that compliance and flow resistance are important characteristics to consider. RTF data was collected for various corrugated and smooth bore tubing. This flow resistance test resulted in various trendlines as described herein. A trendline created by plotting pressure against diameter (or nominal diameter) at a given flow rate for the corrugated tubing was used to identify an equivalent smooth bore tubing that would give the same RTF value. This flow resistance evaluation was to give an equivalent RTF between a corrugated standard tubing and a smooth bore inhalation tubing. Compliance was calculated for the equivalent corrugated and smooth bore tubing. The difference between the compliances was calculated. This compliance comparison test allowed the increase in compliance with the smooth bore tubing to be examined. The new expiratory limb compliance was the original corrugated compliance value plus the compliance difference found from the above calculation. A new maximum expiratory tubing diameter can then be calculated from this new value. The compliance of the expiratory rim and the sizing of the tube allows the difference in compliance from using a smooth bore inhalation tube to be added to the compliance of the corrugated expiratory tube, thereby increasing the maximum size of the expiratory corrugated tube compared to a standard corrugated tube. Furthermore, since all tests were performed on one tube cut to a length of 1 m, one skilled in the art will understand that larger expiratory diameters up to the maximum calculated herein can be used (which are larger than prior art expiratory diameters for this type of breathing circuit) and / or the inhalation and / or expiratory tubes can be longer than prior art breathing circuit lengths.

[0127] During flow resistance testing, flow sweeps were performed on each tube to determine the flow resistance at flow rates from 1.2 to 70 l / min. The tests provided an understanding of the differences in RTF in several different commercially available, typical individual tubes, both smooth bore and corrugated internal profiles, with various diameters (or nominal diameters). In some cases, tests were performed with a heater wire present in the bore, and in other cases, tests were performed without the presence of a heater wire in the bore. The tubes were cut to a nominal length of 1 m. Thus, the RTF values ​​expressed herein are in mm 3 The units are RTF / m. The results show that the flow resistance curves of both the corrugated and smooth bore tube samples are similar. However, when comparing similar sized nominal diameter corrugated and smooth bore tubes, it is seen that the smooth bore tube has a lower RTF value for a given flow rate.

[0128] The relationship between flow resistance of corrugated and smooth bore tubes was analyzed to determine which nominal diameter smooth bore tube would produce an equivalent RTF value to the corrugated tube at a given flow rate. In the tests, the flow rate was 5 l / min for 10 mm tube. The flow rate was 15 l / min for 15 mm tube. The flow rate was 30 l / min for 22 mm tube.

[0129] To understand the pneumatic benefits of changing to a smooth bore tube, the compliance values ​​of comparable corrugated and smooth bore tubes can be compared. The compliance of the breathing limb is composed of the compression volume and the stiffness of the material. Many different materials can be taken into account. The compression volume aspect of compliance was compared in tests as described herein. The compression volume can be determined in part by the internal area of ​​the tube. For corrugated tubes, the nominal diameter can be used. The compression volume can be calculated for a corrugated standard tube and a smooth bore intake tube. The difference between these values ​​can also be calculated.

[0130] For a given breathing circuit kit containing an inspiratory limb and an expiratory limb, the advantage of a lower elasticity smooth bore inspiratory limb means that a higher percentage of the total compliance of the kit can be used by the expiratory limb. The new maximum compliance of the expiratory limb can be the sum of the compression volume difference and the compliance of the expiratory limb with a standard waveform. From this calculation, a new maximum nominal diameter of the expiratory limb can be determined.

[0131] The purpose of a heated humidified breathing circuit is to maintain humidity in the gas from the chamber to the patient. A heater wire can be installed in the breathing tube to maintain temperature and reduce condensation of humidity along the tube. In some embodiments, the heater wire is a helically wound filament that spans the length of the limb. The heater wire can affect RTF because it restricts flow. In some embodiments, a smooth bore tube can have an internal heater wire in the wall. The internal heater wire can be removed from the gas path and therefore does not interfere with RTF.

[0132] For a given nominal diameter corrugated tube, a smaller nominal diameter intake smooth bore tube can be used to maintain the same flow resistance value. Furthermore, if the helical heater wire is taken into account in the flow resistance measurement of the corrugated tube, the nominal diameter of the equivalent smooth bore intake tube can be made even smaller to maintain the same flow resistance value. As a direct result of having a smaller nominal diameter, the smooth bore intake tube has a lower compression capacity compared to the corresponding standard corrugated tube. A smooth bore intake tube can allow a higher percentage of the total compliance of the breathing set to be allocated to the expiratory limb, thereby allowing a larger surface area.

[0133] A circuit kit for use in respiratory therapy of a patient may include various features. The circuit kit includes a breathing circuit. The breathing circuit includes an inspiratory tube for receiving an inspiratory gas flow from a gas source. The inspiratory tube includes an inspiratory inlet, an inspiratory outlet, and an inner wall surrounding an inspiratory central bore. The inner wall of the inspiratory tube is smooth. The breathing circuit includes an expiratory tube for receiving an expiratory gas flow from a patient. The expiratory tube includes an expiratory inlet, an expiratory outlet, and an inner wall surrounding an expiratory central bore. The inner wall of the expiratory tube is corrugated. The circuit kit may include a y-piece for connecting the inspiratory tube and the expiratory tube. The circuit kit may include a chamber for holding a volume of water and for placement on the humidifier. The circuit kit may include a dry line for conveying flow from a ventilator to another gas source to the humidifier inlet. The circuit kit may be used in a respiratory device system including a gas source, such as a respiratory ventilator, and / or a humidifier. The system may include a circuit kit and a humidifier.

[0134] The circuit kit may have dimensions based in part on a patient population. The inhalation tube may have an inner diameter of 5-14.5mm and the exhalation tube may have a nominal inner diameter of 15-22mm. The circuit kit may have dimensions based in part on a patient population. The inhalation tube may have an inner diameter of 4-17mm and the exhalation tube may have a nominal inner diameter of 10.5-20.5mm. The inhalation tube may have an inner diameter of 6mm-14mm. The inhalation tube may have an inner diameter of 6mm-13mm. The inhalation tube may have an inner diameter of 6mm-12mm. The inhalation tube may have an inner diameter of 6mm-11mm. The inhalation tube may have an inner diameter of 7mm-10mm. The inhalation tube may have an inner diameter of 8mm-9mm. The exhalation tube may have a nominal inner diameter of 15.5mm-21mm. The expiratory tube may have a nominal inner diameter of 16mm to 20mm. The expiratory tube may have a nominal inner diameter of 16mm to 19mm. The expiratory tube may have a nominal inner diameter of 18mm to 20mm. The expiratory tube may have a nominal inner diameter of 19mm to 20mm. The inhalation tube may have an inner diameter of 6mm to 10mm. The inhalation tube may have an inner diameter of 11mm to 15mm. The inhalation tube may have an inner diameter of 9mm to 13mm. The inhalation tube may have an inner diameter of 10mm to 14mm. The inhalation tube may have an inner diameter of 7mm to 13mm. The inhalation tube may have an inner diameter of 8mm to 14mm. The expiratory tube may have a nominal inner diameter of 11mm to 15mm. The expiratory tube may have a nominal inner diameter of 12mm to 16mm. The expiratory tube may have a nominal inner diameter of 14mm to 18mm. The expiratory tube may have a nominal inner diameter of 16mm to 20mm. The expiratory tube may have a nominal inner diameter of 13mm to 19mm. The expiratory tube may have a nominal inner diameter of 14mm to 20mm.

[0135] The difference between the inner diameter of the inhalation tube and the nominal diameter of the expiratory tube may be between 1 mm and 14 mm. The inner diameter of the inhalation tube may be smaller than the nominal diameter of the expiratory tube by a value between 1 mm and 14 mm. The circuit kit may be suitable for treating patients with tidal volumes in the range of 50 ml to 300 ml. The circuit kit may be suitable for treating pediatric and adolescent patients.

[0136] The circuit kit may have dimensions based in part on the patient population. The inhalation tube may have an internal diameter of 10-21 mm. The exhalation tube may have a nominal internal diameter of 22-30 mm. The inhalation tube may have an internal diameter of 9.5-24 mm. The exhalation tube may have a nominal internal diameter of 19-31.5 mm. The inhalation tube may have an internal diameter of 10 mm-20 mm. The inhalation tube may have an internal diameter of 11 mm-20 mm. The inhalation tube may have an internal diameter of 11 mm-19 mm. The inhalation tube may have an internal diameter of 11 mm-18 mm. The inhalation tube may have an internal diameter of 11 mm-17 mm. The inhalation tube may have an internal diameter of 11 mm-16 mm. The inhalation tube may have an internal diameter of 11 mm-15 mm. The inhalation tube may have an inner diameter of 12mm to 15mm. The inhalation tube may have an inner diameter of 13mm to 14mm. The exhalation tube may have a nominal inner diameter of 22mm to 29mm. The exhalation tube may have a nominal inner diameter of 23mm to 30mm. The exhalation tube may have a nominal inner diameter of 24mm to 30mm. The exhalation tube may have a nominal inner diameter of 24mm to 29mm. The exhalation tube may have a nominal inner diameter of 25mm to 28mm. The exhalation tube may have a nominal inner diameter of 25.5mm to 27mm. The inhalation tube may have an inner diameter of 11mm to 15mm. The inhalation tube may have an inner diameter of 12mm to 16mm. The inhalation tube may have an inner diameter of 18mm to 22mm. The inhalation tube may have an inner diameter of 19mm to 23mm. The inhalation tube may have an internal diameter of 10 mm to 16 mm. The inhalation tube may have an internal diameter of 17 mm to 23 mm. The exhalation tube may have a nominal internal diameter of 25 mm to 29 mm. The exhalation tube may have a nominal internal diameter of 26 mm to 30 mm. The exhalation tube may have a nominal internal diameter of 20 mm to 24 mm. The exhalation tube may have a nominal internal diameter of 21 mm to 25 mm. The exhalation tube may have a nominal internal diameter of 24 mm to 30 mm. The exhalation tube may have a nominal internal diameter of 20 mm to 26 mm. The difference between the internal diameter of the inhalation tube and the nominal diameter of the expiratory tube may be 1 mm to 20 mm. The internal diameter of the inhalation tube may be smaller than the nominal diameter of the expiratory tube by a value of 1 mm to 20 mm. The circuit kit may be suitable for treating patients with a tidal volume of more than 300 ml. The circuit kit may be suitable for treating adult patients.

[0137] The circuit kit may have dimensions based in part on the patient population. The inhalation tube may have an inner diameter of 4-12 mm. The exhalation tube may have a nominal inner diameter of 13-18 mm. The inhalation tube may have an inner diameter of 3-13 mm and the exhalation tube may have a nominal inner diameter of 9.5-19 mm. The inhalation tube may have an inner diameter of 5 mm-11 mm. The inhalation tube may have an inner diameter of 6 mm-10 mm. The inhalation tube may have an inner diameter of 6 mm-8 mm. The inhalation tube may have an inner diameter of 9 mm-10 mm. The exhalation tube may have a nominal inner diameter of 13 mm-17 mm. The exhalation tube may have a nominal inner diameter of 14 mm-17 mm. The exhalation tube may have a nominal inner diameter of 15 mm-16.5 mm. The expiratory tube may have a nominal inner diameter of 14mm to 15mm. The inhalation tube may have an inner diameter of 5mm to 9mm. The inhalation tube may have an inner diameter of 6mm to 10mm. The inhalation tube may have an inner diameter of 7mm to 11mm. The inhalation tube may have an inner diameter of 8mm to 12mm. The inhalation tube may have an inner diameter of 4mm to 11mm. The inhalation tube may have an inner diameter of 6mm to 12mm. The expiratory tube may have a nominal inner diameter of 13mm to 17mm. The expiratory tube may have a nominal inner diameter of 12mm to 16mm. The expiratory tube may have a nominal inner diameter of 11mm to 15mm. The expiratory tube may have a nominal inner diameter of 14mm to 18mm. The expiratory tube may have a nominal inner diameter of 12mm to 18mm. The expiratory tube may have a nominal internal diameter of 10 mm to 16 mm. The difference between the internal diameter of the inspiratory tube and the nominal diameter of the expiratory tube may be between 1 mm and 14 mm. The internal diameter of the inspiratory tube may be smaller than the nominal diameter of the expiratory tube by a value between 1 mm and 14 mm. The circuit kit may be suitable for treating patients with a tidal volume of 50 ml or less. The circuit kit may be suitable for treating neonatal patients.

[0138] The inhalation or exhalation tube may have further features. The inhalation or exhalation tube may have a length of 1.5m to 2.5m. The inhalation or exhalation tube may have a length of 1.6m to 2.5m. The length of the inhalation or exhalation tube may be broken down into sections to accommodate other equipment such as a water trap, and / or an intermediate connector with one or more sensors, and / or a PCB, and / or a controller. The inhalation tube may enclose a heating element in the inhalation central bore or may be enclosed within the inner wall. The exhalation tube may include a heating element. The exhalation tube may be breathable. The inner wall of the exhalation tube may be permeable to water vapor and substantially impermeable to the bulk flow of liquid and exhaled gas flowing in the exhalation tube. The inhalation tube may include a plurality of bubbles, each having a flat surface forming at least a part of the wall of the inhalation central bore, in a longitudinal cross section. The system may include a circuit kit and a humidifier.

[0139] FIG 1A shows a breathing circuit 100 that may be similar to FIG 1 described herein. Such a breathing circuit 100 may be a respiratory humidification circuit. The breathing circuit 100 includes one or more medical tubes. The breathing circuit 100 may include an inspiratory tube 103 and an expiratory tube 117.

[0140] Gas may be transported within circuit 100 of Figure 1A. Ambient gas flows from gas source 105 to humidifier 107. Humidifier 107 may humidify the gas. Gas source 105 may be a ventilator, blower or fan, a tank containing compressed gas, a wall supply within a medical facility, or any other suitable source of breathing gas.

[0141] The humidifier 107 is connected to the inlet 109 (end for receiving humidified gas) of the inhalation tube 103 via a port 111, thereby supplying humidified gas to the inhalation tube 103. Gas flows through the inhalation tube 103 to the outlet 113 (end for discharging humidified gas) of the inhalation tube 103 and then flows to the patient 101 via a patient interface 115 connected to the outlet 113. An exhalation tube 117 is connected to the patient interface 115. The exhalation tube 117 returns the humidified gas exhaled from the patient interface 115 to the gas source 105 or to the ambient atmosphere.

[0142] Gas may enter the gas source 105 through a vent 119. A blower of a fan 121 may force gas into the gas source 105 by drawing air or other gas through the vent 119. The blower or fan 121 may be a variable speed blower or fan. An electronic controller 123 may control the speed of the blower or fan. In particular, the function of the electronic controller 123 may be controlled by an electronic master controller 125. The function may be controlled in response to inputs from the master controller 125 and a user-set predetermined desired value (preset value) of pressure or blower or fan speed via a dial or other suitable input device 127.

[0143] The humidifier 107 includes a humidification chamber 129. The humidification chamber 129 may be configured to contain a quantity of water 130 or other suitable humidification liquid. The humidification chamber 129 may be removable from the humidifier 107. Being removable allows the humidification chamber 129 to be more easily sterilized or disposed of after use. The humidification chamber 129 portion of the humidifier 107 may be of unitary construction or may be formed of multiple components joined together to define the humidification chamber. The body of the humidification chamber 129 may be formed from a non-conductive glass or plastic material. The humidification chamber 129 may also include conductive components. For example, the humidification chamber 129 may include a highly thermally conductive base (aluminum base) configured to contact or correspond with a heater plate 131 on the humidifier 107 when the humidification chamber 129 is mounted on the humidifier 107.

[0144] The humidifier 107 may include electronic controls. The humidifier 107 may include an electronic, analog, or digital master controller 125. The master controller 125 may be a microprocessor-based controller that executes computer software commands stored in associated memory. In response to user-set humidity or temperature values ​​entered via a user input device 133 and other inputs, the master controller 125 determines when (or to what level) to energize the heater plate 131 to heat a volume of water 130 in a humidification chamber 129.

[0145] As mentioned above, any suitable patient interface may be used for the patient interface 115. The temperature probe 135 may be connected to the inlet conduit 103 near the patient interface 115 or the temperature probe 135 may be connected to the patient interface 115. The temperature probe 135 may be incorporated into the inlet conduit 103. The temperature probe 135 detects the temperature near or at the patient interface 115. A signal reflective of the temperature may be provided by the temperature probe 135 to an electronic, analog or digital master controller 125. A heating element (not shown) may be used to regulate the temperature of the patient interface 115 to raise the temperature of the patient interface 115 above a saturation temperature, thereby reducing the chance of unwanted condensation. A heating element 145 may also be used to regulate the temperature of the inlet conduit 103 to raise the temperature of the inlet conduit 103 above a saturation temperature, thereby reducing the chance of unwanted condensation.

[0146] 1A, exhaled humidified gas is returned from the patient interface 115 through an expiratory tube 117 to the gas source 105. The expiratory tube 117 may include a vapor permeable material, as described in more detail below. The vapor permeable expiratory tube may be corrugated.

[0147] The expiratory tube 117 may have a temperature probe and / or a heating element, as described above with respect to the inhalation tube 103, to reduce the chance of condensation reaching the gas source 105. The expiratory tube 117 does not need to return the exhaled gases to the gas source 105. The exhaled humidified gases may flow directly to the surrounding environment or to other auxiliary equipment such as an air scrubber / filter (not shown).

[0148] In FIG. 1A, the intake pipe 103 includes or comprises a conduit having a smooth bore. The smooth bore causes the intake pipe 103 to have a lower RTF than a conduit of comparable dimensions having a corrugated bore. The smooth bore reduces flow resistance, allowing the bore (i.e., diameter or cross-sectional area) to be reduced, resulting in a lower compression capacity when compared to a corrugated pipe with similar flow resistance. The intake conduit may be a composite conduit. A composite conduit may be generally defined as a conduit that includes two or more distinct portions or, more specifically, two or more components that are joined to define the conduit. The composite conduit may be spirally wound. The composite conduit may be spirally wound in such a manner that two or more components are helically intertwined or joined side-by-side in a helical configuration.

[0149] The expiratory tube 117 includes or includes a conduit having at least a vapor permeable portion. The vapor permeability enhances the removal of humidity. At least the vapor permeable portion of the expiratory tube 117 can be corrugated. The corrugated structure can be on the inside of the tube. The corrugated structure increases the internal surface area of ​​the tube. The amount of vapor that can be diffused through a vapor permeable material is correlated to the surface area of ​​the material that is in direct contact with the vapor. The corrugated structure also increases the turbulence of the gas in the expiratory tube. More turbulence means better mixing of the gas, thereby moving water vapor to the outer wall of the expiratory tube 117. More turbulence can increase the local residence time within the corrugated structure of the expiratory tube, which, when combined with the vapor permeable properties, further enhances the removal of humidity. The increased residence time within the corrugated structure also reduces the temperature of the gas swirling within each corrugated "pocket" relative to that of a comparably sized smooth bore tube, and increases the relative humidity of these gases relative to that of a comparably sized smooth bore tube. The increase in relative humidity increases the vapor pressure gradient across the walls of the expiratory tube 117 relative to that of a comparably sized smooth bore tube and also increases the vapor diffusion through the walls of the corrugated expiratory tube relative to that of a comparably sized smooth bore tube.

[0150] The vapor-permeable corrugated conduit may be formed at least in part from a foamed or non-foamed polymer that is permeable to water vapor and substantially impermeable to the bulk flow of liquid water and gas. The expiratory tube 117 may include a wall that defines a space within the expiratory tube 117. At least a portion of the wall may be formed from a vapor-permeable foamed material configured to allow the transmission of water vapor but substantially prevent the transmission of the bulk flow of liquid water and gas. At least a portion of the wall may be formed from a non-foamed extruded solid material that is permeable to water vapor and substantially impermeable to the bulk flow of liquid water and gas.

[0151] The vapor-permeable expiratory tube 117 may be formed from a non-foam-based material. The non-foam-based material may include a spirally wrapped vapor-permeable tape, or the non-foam-based material may be extruded into a continuous tube. The corrugated structure of the expiratory tube 117 may be achieved with a non-foam-based material. The non-foam-based material may include beads of various diameters arranged in an alternating pattern to form a corrugated interior surface. Alternatively, the corrugated structure may be created in the tube by methods known in the art, such as molding or stamping.

[0152] The intake tube 103 includes a smooth bore conduit. The smooth bore conduit may be heated and insulated to minimize condensation formation and maximize humidity delivery. The reduction in condensation formation in the intake tube allows more vapor in the humidified gas to be delivered to the patient. Several factors affect condensation formation in the intake tube 103, including the internal bore diameter, the smoothness of the internal bore, the level of insulation of the tube, the presence of a heating element 145 (such as a wire or element) associated with the tube 103, and the location of the heating element within the tube 103 (whether the heating element is located within the internal bore of the tube 103 or within the wall of the tube 103). Specifically, decreasing the internal bore diameter of the intake tube 103 increases the velocity of the gas as it travels within the intake tube 103. Increasing the smoothness of the bore reduces turbulence and creates a more parabolic wavefront across the lumen. Thus, by reducing the internal bore diameter and making the internal bore smooth, the high velocity gas located near the center of the tube will transfer less heat to the low velocity gas located near the tube wall. Smooth bore tubes also do not provide pockets where vapor can be trapped or condensation can accumulate, as does a corrugated tube. Thus, vapors carried by the gas are encouraged to exit the tube and thus be delivered to the patient.

[0153] Increasing the degree of tubing insulation reduces heat loss at the walls of the inspiratory tubing 103, maximizing humidity delivery and minimizing condensation formation. Adding more insulation to the inspiratory tubing 103 also makes the breathing circuit 100 more efficient by reducing the extent to which the heating element must work to maintain the target temperature and humidity, because the insulated tubing better maintains the temperature and absolute humidity of the gases as they travel through the tubing.

[0154] Adding a heating element to the inhalation tube 103 also maximizes humidification and reduces condensation. Placing one or more heating elements within the wall of the inhalation tube 103 maximizes humidification and minimizes condensation formation, contributing to the efficiency of the inhalation tube 103, breathing circuit 100, or humidification system. When a heating element is located within the wall of the inhalation tube 103, it heats the wall but does not directly heat the gas. Heating the wall reduces the relative humidity of the gas near the wall (heating the gas increases the temperature and reduces the relative humidity). Placing a heating element 145 on the lumen side of the inner wall of the insulating "bubble" (defined elsewhere) of the inhalation tube 103 (described in more detail below) can further reduce heat loss to the outside through the wall of the inhalation tube 103, further maximizing humidification and minimizing condensation formation.

[0155] The expiratory tube 117 may include a corrugated conduit to maximize vapor removal while minimizing condensate formation and increasing local residence time within the corrugated structure. The expiratory tube 117 may include a vapor permeable conduit to maximize vapor removal while minimizing condensate formation. The expiratory tube 117 may include a corrugated, vapor permeable and / or heated conduit to maximize vapor removal while minimizing condensate formation and increasing local residence time within the corrugated structure. Reducing condensate formation within the expiratory tube 117 allows more vapor to diffuse across the walls of the expiratory tube 117. The presence of the heating element 155 allows the relative humidity of the gas to be maintained below 100% (i.e., the temperature of the gas is maintained above the dew point saturation temperature). Placing the heating element 155 near or within the wall of the expiratory tube 117 causes the heating element 155 to primarily heat the gas near the wall of the expiratory tube 117. Condensation formation is avoided or limited by maintaining the temperature of the gas near the walls of the expiratory tube 117 above the dew point. The inlet tube 103 and the expiratory tube 117 are described in more detail elsewhere herein.

[0156] It has been recognized that incorporating an inhalation tube 103 having a smaller diameter smooth bore conduit in conjunction with an exhalation tube 117 having a corrugated conduit allows the exhalation tube 117 to be larger in diameter and / or longer than would otherwise be possible while maintaining the compression capacity of the overall system. Additionally or alternatively, combining a small diameter smooth bore inhalation tube 103 with a large diameter corrugated exhalation tube 117 can maintain the overall pressure drop. Additionally or alternatively, combining a small diameter smooth bore inhalation tube 103 with a large diameter corrugated exhalation tube 117 can maintain the resistance to flow (RTF) of the breathing circuit 100 at a desirable level. Increasing the length of the conduit typically unnecessarily increases the compression capacity of the conduit and therefore the compression capacity of the overall breathing circuit. Increasing the length of the conduit typically unnecessarily increases the RTF of the conduit and therefore the RTF of the overall breathing circuit. On the other hand, if the conduit is vapor permeable, increasing the length advantageously improves the ability of the conduit to remove vapors from the exhaled gases. It has been found that combining an inhalation tube 103 having a small diameter smooth bore with an exhalation tube 117 having a corrugated, vapor permeable, large bore conduit improves the ability of the exhalation tube 117 to remove water vapor from the breathing circuit without increasing the compression capacity, pressure drop and / or RTF of the overall system.

[0157] It was further recognized that the incorporation of an inlet tube 103 having a smooth bore conduit in conjunction with an outlet tube 117 having a corrugated conduit allows the humidifier 107 to improve humidity performance, providing therapeutic benefit to the patient while operating near fully saturated gas, without the added risk of liquid damaging the gas source 105 or condensation being discharged back to the patient.

[0158] An intake tube 103 having a smooth bore, spirally wound conduit can be paired with an expiratory tube 117 having a corrugated vapor permeable conduit. As discussed above, the smooth bore of the intake tube 103 has a lower RTF than a similarly sized corrugated bore. The smooth bore of the intake tube 103 can also have a smaller inner diameter than the corrugated conduit. Typically, reducing the inner diameter reduces the compression capacity and unnecessarily increases the RTF of the intake tube. Nevertheless, the smooth bore characteristics can be selected such that the reduction in RTF associated with the smooth bore of the intake tube 103 outweighs the increase in RTF resulting from the smaller inner diameter of the intake tube 103. The selection of this smaller diameter intake tube 103 also reduces the compression capacity of the intake tube 103. This selection therefore allows for a longer corrugated expiratory tube 117 paired with a smooth bore intake tube 103 without increasing the overall system pressure loss and / or compression capacity. Increasing the length of the expiratory tube 117 usually unnecessarily increases the tube's RTF and compression capacity. However, increasing the length also improves the vapor-permeable tube's ability to remove vapor from the exhaled gas. In this configuration, pairing a smooth-bore inspiratory tube 103 with a corrugated expiratory tube 117 improves the performance of the expiratory tube 117. The system pressure loss of the breathing circuit that may exist from the ventilator outlet to the ventilator inlet can be affected by the pressure characteristics (RTF) of each element in the circuit. Referring again to FIG. 1A, assuming that the pressure characteristics of the supply tube from the ventilator to the humidifier, humidifier chamber, interface tube and interface body are constant, the main factors that contribute to the system pressure loss are the flow resistance and dimensions (length and diameter) of the inspiratory tube 103 and expiratory tube 117. Any change to one of these factors should be advantageously balanced with the other factors to avoid increasing the system's pressure loss, RTF and / or compression capacity. As described herein, the primary factors contributing to the compression volume are the tube profile, compliance and dimensions (length and diameter or cross-sectional area) of the inspiratory tube 103 and expiratory tube 117. There may be a trade-off between decreasing the compression volume of the inspiratory tube 103 while maintaining the compression volume of the breathing circuit, and increasing the compression volume of the expiratory tube 117.As described herein, increasing the compressible capacity of the expiratory tube 117 is beneficial in terms of the vapor permeability of the expiratory rim.

[0159] The smooth bore of the inlet tube 103 reduces flow resistance (compared to a corrugated inlet tube) and can reduce overall system pressure loss. This allows any or all of the other three factors (flow resistance of the corrugated expiratory tube 117 or the dimensions of either tube) to be altered to increase system pressure loss. The inside diameter of the inlet tube 103 can desirably be smaller than a comparable corrugated inlet tube, thereby increasing the velocity of gas flowing through the inlet tube 103. However, the smaller diameter again adds some flow resistance. The length of the corrugated expiratory tube 117 can be increased without increasing system pressure loss, so long as the increase in RTF due to the smaller diameter is sufficiently smaller than the decrease in RTF due to the use of a smooth bore. Increasing the length of the expiratory tube 117 increases the surface area of ​​the tube wall of the expiratory tube 117. The amount of vapor that can diffuse through a vapor permeable material is related to the surface area of ​​the material. Increasing the length of the expiratory tube 117 increases the surface area of ​​the walls of the expiratory tube 117 and also increases the residence time of the gas within the expiratory tube 117. The amount of vapor that can diffuse through a permeable material also correlates to the length of time the vapor-carrying gas is in contact with the material.

[0160] The compression capacity (cumulative volume of the entire gas flow path) of the breathing circuit can be balanced as well. For example, a change in the dimensions (cross-sectional area or diameter, length) of the inhalation tube 103 can offset a change in the dimensions (cross-sectional area or diameter, length) of the corrugated expiratory tube 117. As described herein, a decrease in the diameter of the inhalation tube 103 can reduce the compression capacity. This decrease in compression capacity can improve the accuracy of the delivered tidal volume. As described herein, a decrease in the diameter of the inhalation tube 103 can offset an increase in the diameter and / or the length of the expiratory tube 117. As described herein, a change in the dimensions of the expiratory tube 117 can facilitate the function of the expiratory tube 117, such as by increasing the vapor permeability of the expiratory tube 117. Since a change in the tube dimensions affects both the pressure loss of the system and the compression capacity of the system, when making a change, both equations should advantageously be balanced or selected simultaneously. A decrease in the diameter of the inhalation tube 103 can increase the average gas velocity in the tube, while increasing the flow resistance and decreasing the compression capacity. Adding length of the corrugated expiratory tube 117 increases the flow resistance as well as the compression volume. Table 1 (above) summarizes the effect of various features on the metrics of these two systems.

[0161] Pairing a corrugated expiratory tube 117 with a smooth-bore inhalation tube 103 can make the inhalation tube 103 perform better. Pairing a large-diameter expiratory tube 117 with a small-bore inhalation tube 103 can be net neutral in terms of compression capacity, but can increase the functionality of the breathing circuit (e.g., increase vapor diffusion in the expiratory tube 117). In this configuration, the smooth-bore inhalation tube 103 minimizes condensate formation and therefore maximizes humidity delivery. The overall compression capacity can be reduced by changes in dimensions such as the diameter and length of the inhalation tube 103 and expiratory tube 117. In some configurations, the inhalation tube 103 is insulated, which helps make heating elements such as the humidifier 107 and / or heater plate 131 more efficient in generating the humidity delivered to the patient 101. The heater plate 131 does not have to work as hard because it does not need to generate a high target temperature at the humidification chamber port 111. This is because the heated and insulated intake tube 103 better maintains the absolute humidity of the gas flowing from the humidifier chamber port 111 through the intake tube 103 .

[0162] Locating the heater wire 145 within the wall of the intake tube 103 also increases the efficiency with which the intake tube 103 maintains the relative humidity of the gas. The heater wire can heat the wall of the intake tube 103 rather than the gas flowing within the lumen of the intake tube 103, thereby reducing the relative humidity of the gas near the wall of the intake tube 103. If the intake tube 103 comprises a composite conduit having a spirally wound hollow body or "bubble" tube (described in more detail below), the heater wire 145 is below the insulating bubble (on the lumen side of the inner wall), thereby reducing heat loss to the outside through the wall of the intake tube 103.

[0163] The smooth bore intake tube 103 promotes laminar gas flow, creating a more parabolic wavefront across the lumen of the intake tube 103 with gas near the center of the lumen having a higher velocity than gas near the wall of the intake tube 103. In this configuration, the high velocity gas has less time to transfer heat to adjacent lower velocity gas during its passage from the inlet 109 to the outlet 113. In conjunction with the inward direction of the heat generated by the heater wire, this configuration helps to further increase the heat retained by the gas flow.

[0164] The smooth bore intake tube 103 also does not provide pockets where vapor can become trapped or condensation can accumulate, as does a corrugated tube, and thus vapor carried by the gas is encouraged to remain in the vapor phase and exit the intake tube 103 and thus be delivered to the patient 101.

[0165] The corrugated expiratory tube 117 maximizes vapor removal and minimizes condensate formation. The expiratory tube 117 can be vapor permeable to facilitate diffusion of vapor through the walls of the expiratory tube 117 to the outside atmosphere. In some configurations, the expiratory tube 117 is vapor permeable and heated, and controlled heating along the tube facilitates diffusion of vapor through the walls of the expiratory tube 117 to the outside atmosphere. Vapor transferred to the outside atmosphere is not delivered to the gas source 105. The corrugated expiratory tube 117 creates turbulence in the portion of the gas flow adjacent the walls of the expiratory tube 117, increasing the residence time of the gas adjacent the walls within the corrugations. The increased residence time increases the opportunity for vapor diffusion through the walls of the expiratory tube 117. The increased residence time also reduces the temperature of the gas swirling within the "pockets" of each corrugation, increasing the relative humidity of these gases. The increased relative humidity increases the vapor pressure gradient across the walls of the expiratory tube 117, further increasing vapor diffusion through the walls.

[0166] As described below, the expiratory tube 117 may include a heater wire 155 wrapped around the center of the lumen of the expiratory tube 117. A heater wire positioned in this manner adds turbulence to the gas flow while minimizing condensation formation. More turbulence means better mixing of the gas, thereby moving water vapor to the outer wall of the expiratory tube 117. The corrugated expiratory tube 117 also provides "pockets" of the corrugation, which has the advantage of collecting any liquid that condenses from the vapor. Liquid trapped within the corrugation is liquid that is not delivered to the gas source 105. In other configurations, the heater wire may be positioned within the wall of the expiratory tube. The presence of the heater wire 155 within the expiratory tube 117 also minimizes condensation formation within the expiratory tube.

[0167] The combination of a smooth bore inspiratory tube 103 and a corrugated expiratory tube 117 allows the humidifier 107 to improve humidity performance. In both invasive and non-invasive ventilation, there is a contribution from the patient and a bias flow. In both, the expiratory tube 117 may function to reduce the amount of humidity returned to the gas source 105. The function of the expiratory tube 117 may be such that it sufficiently reduces the amount of humidity returned to the gas source 105.

[0168] The function of the expiratory tube can enable the humidifier 107 and inhalation tube 103 to deliver higher levels of humidity to the patient 101. If the expiratory tube 117 cannot sufficiently reduce the amount of humidity returned to the gas source 105, then the ability of the humidifier 107 and inhalation tube 103 to deliver higher levels of humidity to the patient 101 would need to be reduced or inhibited, since some of that excess humidity would be carried through the expiratory tube 117 to the gas source 105.

[0169] The inhalation tube 103 and the exhalation tube 117 are described in more detail below.

[0170] Intake pipe FIG. 2A shows a side plan view of a section of an intake pipe conduit 201. Generally, the conduit 201 includes a first elongate member 203 and a second elongate member 205. Member is a broad term and should be given its ordinary and accustomed meaning to those skilled in the art (i.e., not limited to a special or specialized meaning), including, but not limited to, integral parts, integral components, and separate components. The first elongate member 203 has a "bubble" profile, while the second elongate member 205 is a structural support or reinforcing member that adds structural support to the hollow body. As used herein, any reference to a "bubble" refers to an elongate hollow body having a shape in cross section defined by a wall with a hollow space therein. With reference to FIG. 2B, such shapes may include an oval or "D" shape. Such shapes may include, but are not limited to, an "O" shape and other regular and irregular shapes, both symmetrical and asymmetrical. As used herein, the term "bubble" may refer to the cross-sectional shape of the elongated wind or turn of the first elongated member 203, for example, taken at a cross-section of the wind or turn, as shown in FIG. 2B. The hollow body and structural support member may have a helical configuration as described herein. The conduit 201 may be used to form an intake tube 103 as described above, a coaxial tube as described below, or any other tube as described elsewhere in this disclosure.

[0171] The first elongated member 203 may include a hollow body that is spirally wound to at least partially form an elongated tube having a longitudinal axis LA-LA and a lumen 207 extending along the longitudinal axis LA-LA. A portion 211 of the first elongated member 203 forms at least a portion of the inner wall of the lumen 207. The first elongated member 203 may be a tube. Preferably, the first elongated member 203 is flexible. By flexible, we mean the ability to bend. Furthermore, the first elongated member 203 is preferably transparent or at least translucent or semi-opaque. A degree of light transparency allows a caregiver or user to inspect the lumen 207 for blockages or contamination or to see the presence of moisture (i.e., condensation). A variety of plastics, including medical grade plastics, are suitable for the body of the first elongated member 203. Suitable materials include polyolefin elastomers, polyether block amides, thermoplastic copolyester elastomers, EPDM-polypropylene blends and thermoplastic polyurethanes.

[0172] The hollow body structure of the first elongated member 203 contributes to the insulation of the conduit 201. An insulated conduit is desirable to prevent heat loss, as explained above, and allows the conduit 201 to deliver gas from the humidifier 107 to the patient 101 while maintaining a conditioned state of the gas with minimal energy consumption.

[0173] The second elongate member 205 is also helically wound and joined to the first elongate member 203 between adjacent turns of the first elongate member 203. The second elongate member 205 forms at least a portion of the lumen 207 of the elongate tube. The second elongate member 205 serves as structural support for the first elongate member 203. The second elongate member 205 can be wider at the base (proximal to the lumen 207) and narrower at the top. The second elongate member can be generally triangular, T-shaped, or Y-shaped. However, any shape that matches the contour of the corresponding first elongate member 203 is suitable.

[0174] Preferably, the second elongate member 205 is flexible to facilitate bending of the tube. Desirably, the second elongate member 205 is less flexible than the first elongate member 203. This increases the ability of the second elongate member 205 to provide structural support to the first elongate member 203. The second elongate member 205 can be solid or mostly solid.

[0175] The second elongated member 205 may encapsulate or contain a conductive material such as a filament, specifically a filament used to generate heat or carry information from a sensor (not shown). The heating element may include a filament to minimize cold surfaces where condensation from the moisture-laden gas may form. The heating element may also be used to modify the temperature profile of the gas within the lumen 207 of the conduit 201. A variety of polymers and plastics, including medical grade plastics, are suitable for the body of the second elongated member 205. Suitable materials include polyolefin elastomers, polyether block amides, thermoplastic copolyester elastomers, EPDM-polypropylene blends, and thermoplastic polyurethanes. The first elongated member 203 and the second elongated member 205 may be made of the same material.

[0176] FIG. 2B shows a longitudinal cross-section of the upper portion of the conduit 201 of FIG. 2A. FIG. 2B has the same orientation as FIG. 2A. The first elongated member 203 may have a hollow body shape. The first elongated member 203 may form a plurality of hollow bubbles in the longitudinal cross-section. A portion 209 of the first elongated member 203 overlaps an adjacent wrap of the second elongated member 205. A portion 211 of the first elongated member 203 forms at least a portion of the wall of the lumen 207 (tube bore). Adjacent bubbles may be separated by a gap 213. A T-shaped second elongated member 205 as shown in FIG. 2B may help maintain the gap 213 between adjacent bubbles.

[0177] The first elongate member 203 defines a plurality of hollow bubbles in longitudinal cross section.

[0178] One or more conductive materials may be disposed within the second elongated member 205 for heating or sensing the gas flow. Two heating elements 215 may be enclosed within the second elongated member 205, one on each side of the vertical portion of the "T". The heating elements 215 include a conductive material such as an alloy of aluminum (Al) and / or copper (Cu) or a conductive polymer. Preferably, the material forming the second elongated member 205 is selected to be non-reactive with the metal in the heating element 215 when the heating element 215 reaches its operating temperature. The heating elements 215 may be spaced apart from the lumen 207 such that the elements are not exposed to the lumen 207. At one end of the composite tube, a pair of elements may be formed into a connected loop. Multiple filaments may be disposed within the second elongated member 205.

[0179] Table 2 shows some non-limiting sample dimensions and some non-limiting sample ranges of two different composite conduits described herein, one for use with infants and one for use with adults. Dimensions refer to the cross-section of the tube. In these tables, lumen diameter refers to the inside diameter of the tube. Pitch refers to the distance between two repeating points measured axially along the tube, i.e., the distance between the tips of adjacent vertical portions of the "T" of the second elongated member 205. Bubble width refers to the width (maximum outer diameter) of the bubble. Bubble height refers to the height of the bubble from the tube lumen. Bead height refers to the maximum height of the second elongated member 205 from the tube lumen (e.g., the height of the vertical portion of the "T"). Bead width refers to the maximum width of the second elongated member 205 (e.g., the width of the horizontal portion of the "T"). Bubble thickness refers to the thickness of the bubble wall.

[0180] [Table 3]

[0181] Tables 3 and 4 show the properties of a composite tubing as described herein (designated "A") having a heating element embedded within the second elongated member 205. For comparison, properties of a Fisher & Paykel model RT100 disposable corrugated tubing (designated "B") having a heating element spirally wound inside the bore of the tubing are also shown.

[0182] Measurements of resistance to flow (RTF) were performed according to Annex A of ISO 5367:2000(E). This publication specifies a normative list of apparatus, procedural steps and units for expressing the test results of flow resistance by measuring the pressure increase at the rated flow rate of the breathing tube. It includes variances for testing breathing tubes of 1 m length supplied ready for use or cut to length, and for testing each limb individually of a dual limb circuit containing a pair of breathing tubes integrally connected to a Y-piece. The result of the test is the difference between the pressure measured in the reservoir with the breathing tube attached to the reservoir opening and the pressure measured in the reservoir without the breathing tube attached to the reservoir opening.

[0183] The results are summarized in Table 3. As shown below, the RTF of the composite tube is lower than the RTF of a comparable sized Model RT100 tube.

[0184] [Table 4]

[0185] Condensate or "water drop" in the tube refers to the weight of condensate collected per day at a gas flow rate of 20 L / min and a room temperature of 18°C. Humidified air flows continuously from the chamber through the tube. The weight of the tube is recorded before and after each day of testing. Three consecutive tests are performed with the tube kept dry during each test. The results are shown in Table 4 below. The results showed that water drop was significantly lower for the composite tube than for a comparably sized Model RT100 tube.

[0186] [Table 5]

[0187] The composite tube 201 may include one or more heating filaments 215 disposed within the gas path. The heating filaments may be positioned in a helical configuration on the lumen wall (tube bore). The one or more heating filaments 215 may be disposed on the lumen wall by bonding, embedding, or the heating filaments are otherwise formed on a surface of the second elongate member 205 that forms the lumen wall when assembled. Thus, the method may include disposing one or more heating filaments 215 on the lumen wall.

[0188] Further details regarding composite conduits suitable for the intake pipe 103 are disclosed in the specifications and drawings of U.S. Patent Application Publication No. 14 / 123,485, published as U.S. Patent Application Publication No. 2014 / 0202462 A1, and U.S. Patent Application Publication No. 14 / 649,801, published as U.S. Patent Application Publication No. 2015 / 0306333 A1, the entire contents of which are incorporated herein by reference.

[0189] Expiratory tube As described above with respect to FIG. 1, the breathing circuit may utilize a vapor-permeable (i.e., breathable) expiratory tube to handle exhaled gases having a high level of relative humidity. Breathability is desirable to increase vapor diffusion and thereby prevent water droplets (condensation) within these components. Thus, the breathing circuit may include a vapor-permeable expiratory tube. Generally, the expiratory tube includes an inlet (for receiving the expiratory gas), an outlet (for discharging the received gas), and a sealing wall defining at least one gas passageway between the inlet and the outlet, at least a portion of the sealing wall being of a vapor-permeable material that allows the transmission of water vapor but substantially prevents the transmission of liquid water and bulk flow of breathing gas. The expiratory tube may be terminated by a first connector at the inlet and a second connector at the outlet, providing only one gas passageway in the length between the inlet and outlet connectors.

[0190] The wall, due to its breathability or vapor permeability, provides a water vapor path from the gas space within the tube to the area beyond the wall, which may be ambient air. Preferably, the vapor permeable portion of the containment wall is formed of a foam material. The tube may comprise an extruded corrugated conduit.

[0191] Exhalation tubes comprising vapor-permeable expanded polymers have been found to be advantageously breathable and robust. The exhalation tube may include a wall defining an interior space, at least a portion of said wall being of a vapor-permeable expanded material that allows the transmission of water vapor from gas within the space but prevents the transmission of liquid water. The entirety of the sealing wall may be formed of a foam material. Preferably, the wall is also impermeable to the bulk flow of gas within the space containing the breathing gas. Due to its vapor permeability, the wall forms a water vapor path from the gas space to the area beyond the wall.

[0192] Reference is now made to Figures 3A and 3B, which show an expiratory tube conduit 301. Figure 3A shows a side view of the conduit 301, and Figure 3B shows a cross-sectional view of the conduit 301 along the same side view as Figure 3A. In both Figures 3A and 3B, the horizontal axis is shown as line 303-303. The conduit wall, shown as wall 305 in Figure 3B, is a vapor permeable foam material. As shown, the conduit 301 is corrugated. The tube wall, shown as wall 305 in Figure 3B, is a breathable foam material, as described above.

[0193] The tube is a type of component, so the details of the components described above are also applicable to the tube described here. At least a portion of the sealing wall may include a breathable foam material that allows water vapor transmission but substantially prevents liquid water and bulk flow of breathing gas. The tube may be an extruded corrugated tube. The medical circuit tube may be used as a breathing tube or conduit or a tube or conduit for a limb of an air delivery system. For example, the tube may be an expiratory breathing tube or an exhaust conduit, respectively. The tube may also be part of a patient interface. The conduit 301 may be used to form an expiratory tube 117 as described above, a coaxial tube as described below, or any other tube as described elsewhere in this disclosure.

[0194] By incorporating highly breathable or vapor-permeable foamed or non-foamed materials, components can be manufactured that have both relatively high bending stiffness and high breathability. Foamed polymers allow water vapor to diffuse through them rapidly due to their high vapor permeability (breathability). This reduces the build-up of condensation in the expiratory tube by allowing water vapor from the humidified gas in the expiratory tube to permeate to the surrounding ambient air or other dryer gas on the other side of the component. Yet components formed from these foamed polymers are also rigid, self-supporting, shatter-resistant or semi-rigid, have relatively high resistance to crushing and resistance to buckling, and may not require additional reinforcement. Because foamed polymers allow the permeation of water vapor from gases but prevent the permeation of liquid water, foamed polymers are useful for forming components of medical circuits. Foamed polymers are also substantially impermeable to the bulk flow of gases so that they can be used to form components for delivering humidified gases. The foamed polymer may be selected such that its "bulk" properties (thickness, material, material formulation, modulus, air permeability and / or bulk stiffness) meet the requirements of the ISO 5367:2000(E) standard (i.e., tests for increased flow resistance) without additional reinforcement, yet is vapor permeable, ISO 5367:2000(E) being incorporated herein by reference in its entirety.

[0195] Preferably, the foamed polymer is a vapor-permeable foamed thermoplastic polymer.The vapor-permeable thermoplastic polymer can be a foamed thermoplastic elastomer (or TPE as defined by ISO 18064:2003(E)), such as (1) a copolyester thermoplastic elastomer (such as ARNITEL®, a copolyester thermoplastic elastomer with polyether soft segments, or other TPC or TPC-ET materials as defined by ISO 18064:2003(E)), or (2) a polyether block amide (such as PEBAX®, a polyamide thermoplastic elastomer with polyether soft segments, or other TPA-ET materials as defined by ISO 18064:2003(E)), or (3) a thermoplastic polyurethane (a TPU material as defined by ISO 18064:2003(E)), or (4) a foamed polymer blend, such as a TPE / polybutylene terephthalate (PBT, such as DURANEX® 500FP) blend. It has been found that the vapor-permeable TPE ARNITEL® VT3108 may be particularly suitable for foaming and molding components. In this material, the relationship between breathability and strength can be significantly improved by foaming the material as it is molded into a product or component. If the breathable thermoplastic polymer is an expanded TPE / PBT blend, the blend preferably comprises 80%-99% (or about 80%-99%) by weight of TPE and 20%-1% (or about 20%-1%) by weight of PBT. The porosity of the foamed material can be greater than 25% (or about 25%), such as 25-60% (or about 25-60%) or 30-50% (or about 30-50%). The foamed material can be structured such that no more than 5% (or about 5%) of the voids in the foamed material are greater than 500 μm in diameter.

[0196] The combination of permeability and elastic modulus for all previously known materials is given by the formula: 1n(P)=0.019(1n(M)). 2-0.71n(M)) + 6.5, where P is the permeability of the material in g mm / m2 / day measured according to ASTM E96 Procedure A (dry method at 23 °C and 90% relative humidity) and M is the Young's modulus of the material in MPa.

[0197] The breathing circuit may include an expiratory tube that includes a non-foam-based corrugated and / or vapor-permeable material. In some non-limiting configurations, the inner wall of the expiratory tube may include a spirally wrapped vapor-permeable tape, or the non-foam-based material may be extruded into a continuous tube. In some configurations, the inner wall of the expiratory tube includes a series of beads of various diameters. The beads of different diameters may be positioned along the inner wall of the expiratory tube to create a corrugated pattern. Alternatively, the corrugated structure may be created in the tube by methods known in the art, such as molding or stamping.

[0198] The wall may also include at least one reinforcing rib that reinforces the wall or at least one area of ​​localized thickening of the wall to reinforce the wall. The tube may include a number of reinforcing ribs disposed about the closure wall. These ribs may be co-extruded with the tube so as to be generally aligned with the longitudinal axis of the tube. Preferably, there are 3 to 8 reinforcing ribs, especially 3 to 5 reinforcing ribs.

[0199] Reference is now made to Figures 4A and 4B, which show a portion of a conduit 301 that may be used to form the expiratory tube 117. The conduit 301 may be manufactured from a foamed vapor-permeable material as described herein. The conduit 301 further includes a plurality of reinforcing ribs 403, which may be co-extruded with the conduit 301. The ribs 403 may be formed from the same foamed polymer as the conduit 301. Alternatively, the ribs 403 may be made from a different material than the conduit 301. This may be accomplished by co-extrusion. As shown in Figure 4A, the conduit 301 may be extruded with the ribs 403 in place and then corrugated to form the "dot-like" structure shown in Figure 4B. The conduit 301 may include 3-8 reinforcing ribs, for example 3-5 reinforcing ribs.

[0200] In particular, the ribs may be disposed about the circumference of the tubular shape. The ribs may be disposed circumferentially about an interior surface of the tubular shape. The ribs may be generally longitudinally aligned along the length of the tubular shape between the inlet and outlet.

[0201] Reference is now made to Figures 5A and 5B, which illustrate the configuration of corrugated, ribbed vapor permeable conduit 301. In Figure 5, raised ribs 403 are visible within the spaces between the ridges on the interior of conduit 301.

[0202] In addition to the above, a heater such as a resistive heater wire may be provided within the passageway of the conduit 301, within the wall of the conduit 301, or around the exterior of the outer wall surface of the conduit 301 to reduce or eliminate the formation of condensation within the tube. Figure 6 is a general view of a corrugated foamed polymer conduit 301 incorporating a heater wire 601 within the passageway of the conduit 301. Figure 7 is a general view of a corrugated foamed polymer conduit 301 incorporating a heater wire 601 around the exterior of the outer wall surface of the conduit 301. Figure 8 includes a schematic diagram of an expiratory tube 117 incorporating a heater wire 601 within the tube wall.

[0203] Further details regarding the expiratory tube are disclosed in the specification and drawings of U.S. Patent Application Publication No. 13 / 517,925, published as U.S. Patent Application Publication No. 2013 / 0098360A1, the entire contents of which are incorporated herein by reference.

[0204] Reference is now made to Figure 8, which illustrates a breathing circuit including an inhalation tube 103 and an exhalation tube 117. The characteristics of the inhalation tube 103 and the exhalation tube 117 are similar to those described above with respect to Figures 1-7. The inhalation tube 103 has an inlet 109 in communication with the humidifier 107 and an outlet 113 through which humidified gas is provided to the patient 101. The exhalation tube 117 also has an inlet 109 for receiving exhaled gas from the patient 101 and an outlet 113. As described above with respect to Figure 1, the outlet 113 of the exhalation tube 117 may exhaust the exhaled gas to the atmosphere, the gas source 105, an air scrubber / filter (not shown), or any other suitable location.

[0205] As discussed above with respect to Figures 1, 6 and 7, a heating wire 215 may be included in the inhalation tube 103 and / or a heating wire 601 may be included in the exhalation tube 117 to reduce the risk of condensation formation within the tubes by raising the temperature of the gas (mainly the gas near the tube wall) above the saturation temperature. It should be understood that the heating wires may desirably include a coiled or helical configuration and are shown as straight for conceptual purposes. The breathing circuit may include connectors (Y connector or Y-piece 801) for connecting the inhalation tube 103 and the exhalation tube 117 to a patient interface (not shown). Of course, it should be understood that other breathing circuit configurations are within the scope of the present disclosure.

[0206] The foregoing description includes preferred forms of the present invention. Modifications may be made thereto without departing from the scope of the present invention. Those skilled in the art will envision numerous structural modifications and widely differing embodiments and applications of the present invention without departing from the scope of the present invention, which is defined in the appended claims. The disclosures and descriptions herein are purely illustrative and are not intended to be in any sense limiting.

Claims

1. 1. A circuit kit for use in respiratory therapy of a patient, comprising: an inhalation tube configured to receive a humidified inhalation gas flow from a gas source and to supply the humidified inhalation gas flow to a patient interface, the inhalation tube including an inhalation inlet, an inhalation outlet, and an inner wall surrounding an inhalation central bore, the inner wall of the inhalation tube being smooth; an expiratory tube configured to receive an expiratory gas flow from a patient, the expiratory tube including an expiratory inlet, an expiratory outlet, and an inner wall surrounding an expiratory central bore, the inner wall of the expiratory tube being corrugated; a breathing circuit including the inhalation tube has an inner diameter of 9-13 mm and the exhalation tube has a nominal inner diameter of 13-19 mm; The expiratory tube is breathable. Circuit kit.

2. The circuit kit of claim 1 , further comprising a y-piece configured to couple the inhalation tube and the exhalation tube.

3. 3. The circuit kit of claim 1 or 2, further comprising a chamber for holding a quantity of water and for placement on the humidifier.

4. 4. The circuit kit of claim 1, further comprising a dry line for conveying flow from a ventilator or other gas source to the humidifier inlet.

5. The circuit kit according to any one of claims 1 to 4, wherein the expiratory tube has a nominal inner diameter of 14 mm to 18 mm.

6. The circuit kit according to any one of claims 1 to 5, wherein the inhalation tube or the exhalation tube has a length of 1.5m to 2.5m.

7. The circuit kit according to any one of claims 1 to 6, wherein the inhalation tube or the exhalation tube has a length of 1.6m to 2.5m.

8. 8. A circuit kit as claimed in any one of claims 1 to 7, wherein the intake pipe surrounds a heating element within the intake central bore or within the inner wall of the intake pipe.

9. The circuit kit according to claim 1 , wherein the expiratory tube includes a heating element.

10. 10. A circuit kit as claimed in any one of claims 1 to 9, wherein the intake pipe includes, in longitudinal cross section, a plurality of bubbles each having a flat surface forming at least a part of the inner wall of the intake pipe.

11. 11. The circuit kit of any one of claims 1 to 10, wherein the circuit kit is for use with a ventilator configured to deliver a tidal volume in the range of 50ml to 300ml.

12. 12. The circuit kit of any one of claims 1 to 11, wherein the circuit kit is for use with a ventilator configured to treat pediatric and adolescent patients.

13. 13. A circuit kit according to any one of claims 1 to 12, wherein the difference between the inner diameter of the inhalation tube and the nominal inner diameter of the expiratory tube is between 1 mm and 10 mm.

14. A circuit kit according to any one of claims 1 to 13, wherein the inner diameter of the inhalation tube is smaller than the nominal inner diameter of the expiratory tube by a value between 1 mm and 10 mm.

15. 15. A circuit kit according to any one of claims 1 to 14, wherein the inhalation tube and / or the exhalation tube may include multiple sections for accommodating other equipment such as a water trap, and / or an intermediate connector having one or more sensors, and / or a PCB, and / or a controller.

16. A system including a circuit kit according to any one of claims 1 to 15, further comprising a humidifier.

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