Medical tube and method of manufacturing

Abstract

The invention relates to a medical tube and a method of manufacture. A medical tube includes an elongate catheter having a first opening, a second opening, a longitudinal axis, a lumen extending along the longitudinal axis between the first opening and the second opening, and a corrugated wall formed of an extruded material extending between the first opening and the second opening and surrounding the lumen. The wall is harder in a first length of the conduit adjacent the first opening than in a second length of the conduit adjacent the second opening. The variable hardness of the tube wall may improve the heat distribution of the tube and improve the backflow of condensate into a humidifier that provides humidified gas to the tube.

Description

[0001] This application is a divisional application of invention patent application 202210728125.0, filed on June 24, 2022, entitled "Medical tube and manufacturing method". Technical Field

[0002] This disclosure generally relates to tubing suitable for medical use, and more specifically to tubing suitable for use in medical circuits for supplying and / or removing gas from a patient, such as in positive airway pressure (PAP), ventilators, anesthesia, ventilators, and blowing systems. Background Technology

[0003] In a medical circuit, various components deliver warm, humidified gas to the patient. For example, in some breathing circuits such as PAP or assisted breathing circuits, the gas inhaled by the patient is delivered from a heater-humidifier through an inspiratory tube. As another example, a tube can deliver humidified gas (usually CO2) into the abdominal cavity in an exhalation circuit. This can help prevent the patient's internal organs from becoming dehydrated and can reduce the amount of time required for postoperative recovery.

[0004] In these medical applications, these gases are preferably delivered under conditions of near-saturation humidity and at near body temperature (typically between 33°C and 37°C). Condensation, or “drizzle,” can form on the inner surface of the breathing tube as the high-humidity breathing gas cools and / or comes into contact with the relatively cool surface of the breathing tube. Tubes that insulate against heat loss and, for example, enable improved temperature and / or humidity control in medical circuits remain necessary.

[0005] Therefore, the object of the present invention is to provide a medical tube and / or a method of manufacturing a medical tube, which will at least partially solve the aforementioned problems or will at least provide useful options to industry or the public or both.

[0006] In this specification, references to patent specifications, other external documents, or other sources of information are made generally for the purpose of providing background for discussing the features of the invention. Unless otherwise expressly stated, references to such external documents should not be construed as an admission that such documents or sources of information are prior art or part of general common knowledge in the art within any jurisdiction.

[0007] Other aspects and advantages of the invention will become apparent from the following description, which is given by way of example only. Summary of the Invention

[0008] Medical tubes and breathing tubes, as well as methods of manufacturing such tubes, are disclosed herein in various embodiments.

[0009] In at least one embodiment, the medical tubing for providing humidifying gas to a patient may include an elongated catheter having a first opening configured in size and shape for connection to a humidifying gas source, a second opening configured in size and shape for connection to a patient interface, a longitudinal axis, an inner lumen extending along the longitudinal axis between the first and second openings, and a wall formed of an extruded material extending between the first and second openings and surrounding the inner lumen. The wall is harder in a first region of the catheter adjacent to the first opening than in a second region of the catheter adjacent to the second opening.

[0010] In at least one embodiment, the heated breathing tube may include a single corrugated squeeze catheter including a proximal patient end and a distal chamber end; and one or more heating elements on or in the catheter, wherein the catheter has a first region having a first hardness at the chamber end and a second region having a second hardness at the patient end, and the first hardness is greater than the second hardness.

[0011] In various embodiments, within the aforementioned medical tubing and / or heated breathing tubing, a first region is configured to extend vertically from the humidifying gas source. This vertical extension may define a reflux length. For example, the reflux length may be between approximately 350 mm and approximately 400 mm.

[0012] In various embodiments, the aforementioned medical tubing and / or heated breathing tubing has one, some, or all of the following characteristics, as well as those described elsewhere in this disclosure. The medical or breathing tubing may further include one or more conductive filaments in or on the catheter. At least one of the one or more conductive filaments may be a heating wire. At least one of the one or more conductive filaments may be a sensing wire. The catheter may be generally cylindrical. The wall may be corrugated. The extruded material may be foam. The foam may be a polymer foam. The foam may be a closed-cell foam. The extruded material may include one or more surface modifiers. The wall may have an average contact angle of less than 50 degrees (or about 50 degrees). The wall thickness in the first region may be between 0.5 mm and 2.0 mm (or about 0.5 mm and about 2.0 mm). The wall thickness in the second region may be between 0.1 mm and 1.0 mm (or about 0.1 mm and about 1.0 mm). The mass of the wall in the first region can be between 50 g / m and 110 g / m (or approximately 50 g / m and approximately 110 g / m). The mass of the wall in the second region can be between 20 g / m and 50 g / m (or approximately 20 g / m and approximately 50 g / m). The volume of the wall in the first region can be 1.0 cm³. 3 / m and 2.0cm 3 / m (or approximately 1.0cm) 3 / m and approximately 2.0cm 3The volume of the wall in the second region is between / m). 3 / m and approximately 1.0cm 3 The ratio of the flexural modulus of the wall in the first region to that in the second region can be between 10:1 and 250:1 (or approximately 10:1 to approximately 250:1). The wall stiffness in the third region of the conduit between the first and second regions can be between the wall stiffness in the first and second regions. The average wall thickness can be approximately 100 micrometers.

[0013] In various embodiments, the aforementioned medical tubing or heated breathing tubing (including any or all of the above-described characteristics) has one, some, or all of the following characteristics, as well as those described elsewhere in this disclosure. The medical or breathing tubing may further include a sheath surrounding at least a portion of the outer surface of an elongated conduit. The sheath may include an extruded material compressed around at least a portion of the outer surface of the elongated conduit. The sheath may include a material generally helically wound around at least a portion of the outer surface of the elongated conduit. The sheath may include a bushing material surrounding at least a portion of the outer surface of the elongated conduit. The sheath may include a sheath wall. The sheath wall may have a generally constant stiffness. The sheath wall may be stiffer in a first region of the sheath than in a second region of the sheath. The sheath wall may be stiffer near a first opening of the conduit than near a second opening of the conduit. The sheath wall may be stiffer near the second opening of the conduit than near the first opening of the conduit. The sheath wall may be stiffer near both the first and second openings of the conduit than in the intermediate region of the conduit.

[0014] One or all of the aforementioned medical tubing according to the foregoing embodiments can be incorporated into a breathing circuit or blowing system and other applications. The breathing tubing can be incorporated into a breathing circuit and other applications.

[0015] In at least one embodiment, a method of delivering humidified gas to a patient may include providing a single corrugated extrusion catheter including a proximal patient end, a distal chamber end, a plurality of heating elements on or therein the catheter wall, a first region adjacent to the chamber end having a first hardness, and a second region adjacent to the patient end having a second hardness, the first hardness being greater than the second hardness; connecting the chamber end of the catheter to a chamber, wherein the catheter in the first region extends vertically from the chamber; connecting the patient end of the catheter to a patient interface; and delivering humidified air through the catheter. In various embodiments, the catheter may have one, some, or all of the characteristics described above with respect to medical and respiratory tubes, and the characteristics described elsewhere in this disclosure.

[0016] In at least one embodiment, a method of manufacturing a tube or catheter according to one, some, or all of the above embodiments includes extruding a strip, wherein a first length of the strip is thicker, heavier, or stiffer than a second length of the strip; helically winding the extruded strip around a mandrel such that adjacent turns of the extruded strip touch or overlap, thereby forming an elongated catheter having a longitudinal axis and an inner lumen extending along the longitudinal axis; corrugating the elongated catheter and cooling the elongated catheter to form a medical tube having a wall surrounding the inner lumen, wherein the wall is stiffer in a first region of the catheter adjacent to a first end than in a second region of the catheter adjacent to a second end. As described above, the wall may have a thickness between 0.5 mm and 2.0 mm (or about 0.5 mm and about 2.0 mm in the first region). The wall in the second region may have a thickness between 0.1 mm and 1.0 mm (or about 0.1 mm and about 1.0 mm). The ratio of the flexural modulus of the wall in the first region to the flexural modulus of the wall in the second region may be between about 10:1 and about 250:1.

[0017] In various embodiments, the foregoing method may have one, some, or all of the tube or conduit characteristics described above, the following characteristics, and characteristics described elsewhere in this disclosure. The extruded tape may include foam. The foam may be a polymer foam. The polymer foam may be closed-cell. The extruded tape may include one or more surface modifiers. The surface of the wall facing the inner lumen may have a surface contact angle of less than 50 degrees (or about 50 degrees). The method may further include helically winding a reinforcing strip between adjacent turns of the extruded tape. The reinforcing strip may include one or more conductive filaments. The method may further include helically winding one or more conductive filaments around an elongated conduit.

[0018] In at least one embodiment, a method of manufacturing a tube or conduit according to one, some, or all of the foregoing embodiments includes extruding an elongated conduit having a longitudinal axis and an inner lumen extending along the longitudinal axis; and corrugating the elongated conduit and cooling the elongated conduit to form a medical tube having a wall surrounding the inner lumen, wherein the wall is stiffer in a first region of the conduit adjacent to a first end than in a second region of the conduit adjacent to a second end. In various embodiments, the foregoing method may have one, some, or all of the tube or conduit characteristics described above, the following characteristics, and characteristics described elsewhere in this disclosure. As explained above, the first region may be configured to extend vertically from a humidifying gas source. This vertical extension may define a reflux length. For example, the reflux length may be between 350 mm and 400 mm (or about 350 mm and about 400 mm). In some embodiments, the method may further include co-extruding one or more conductive filaments such that the one or more conductive filaments are disposed on or therein in the conduit.

[0019] As used in this specification, the term "comprising" means "consisting of at least part of...". When interpreting each expression in this specification that includes the term "comprising", multiple features may also exist in addition to one or more features that begin with that term. Related terms such as "comprising" will be interpreted in the same manner.

[0020] In a broader sense, the invention may also consist primarily of parts, elements, and features individually or collectively mentioned or indicated in the description of this application, and any or all combinations of any two or more of the said parts, elements, or features, and when a particular whole having a known equivalent in the field to which the invention relates is referred to herein, such known equivalents are considered to be incorporated herein as described individually.

[0021] The present invention is mainly based on the foregoing and also envisions several other constructions, of which only examples are given below. Attached Figure Description

[0022] Example embodiments of various features of the disclosed systems and methods will now be described with reference to the accompanying drawings. The drawings and associated descriptions are provided to illustrate multiple embodiments and do not limit the scope of this disclosure.

[0023] Figure 1 A schematic diagram of a medical circuit incorporating one or more medical tubes is shown.

[0024] Figures 2A to 2C The longitudinal section of the example composite pipe is shown.

[0025] Figure 3 The medical circuit with the reflux length of the demonstration tube is shown.

[0026] Figures 4A to 4E The diagram illustrates a test apparatus used to measure the flexural modulus of a tube.

[0027] Figure 5A To plot the test results for a tube sample with a mass of 100 g / m.

[0028] Figure 5B To plot the test results for a tube sample with a mass of 40 g / m.

[0029] Figure 5C for Figure 5A An enlarged version of the linear portion of the flexural test curve.

[0030] Figure 5D for Figure 5B An enlarged version of the linear portion of the flexural test curve.

[0031] Figures 6 to 7 The illustration shows an example of the placement of the heater wire.

[0032] Figure 8 This graph compares condensate accumulation in a uniform hardness tube with condensate accumulation in a variable hardness tube.

[0033] Figure 9 An example medical circuit according to at least one embodiment is shown.

[0034] Figure 10 An air blowing system according to at least one embodiment is shown.

[0035] Figure 11 This is a schematic illustration of a method for manufacturing a medical tube, which includes a feed hopper, a screw feeder toward a die head, and terminates at a corrugated plate mill.

[0036] Figure 12 This is a schematic diagram illustrating a method for manufacturing a medical tube by spiral forming.

[0037] Throughout these figures, reference numerals are reused to indicate the correspondence between referenced (or similar) elements. Furthermore, the first digit of each reference numeral indicates the figure in which the element first appears. Detailed Implementation

[0038] The following description, with reference to the accompanying drawings, details several illustrative embodiments for implementing the apparatus and methods described herein. The invention is not limited to these described embodiments.

[0039] Breathing circuit including one or more medical tubes

[0040] To understand this disclosure in more detail, please refer first to Figure 1 The figure illustrates a breathing circuit according to at least one embodiment, comprising one or more medical tubes. "Tube" is a broad term and is given its common and conventional meaning to those skilled in the art (that is, it is not limited to a specific or custom meaning), and includes (but is not limited to) non-cylindrical channels. The breathing circuit incorporates one or more variable-stiffness tubes, which can generally be defined as tubes having different stiffness at each end. This breathing circuit can be a continuous, variable, or two-stage positive airway pressure (PAP) system or another form of respiratory therapy.

[0041] It can be done as follows: Figure 1Gas is delivered in the circuit. Dry gas is delivered from the fan / blower 105 to the humidifier 107, which humidifies the dry gas. The humidifier 107 is connected via port 111 to the inlet 109 (the end for receiving humidified gas) of the inspiratory tube 103, thereby supplying humidified gas to the inspiratory tube 103. The inspiratory tube is a tube configured to deliver breathing gas to the patient and may be made of a variable stiffness tube, as described in more detail below. Gas flows through the inspiratory tube 103 to the outlet 113 (the end for discharging humidified gas) and then subsequently to the patient 101 through the patient interface 115 connected to the outlet 113.

[0042] The exhalation tube 117 is also connected to the patient interface 115. The exhalation tube is configured to move exhaled humidified gas away from the patient. Here, the exhalation tube 117 returns exhaled humidified gas from the patient interface 115 to the ventilator / blower 105.

[0043] In this example, dry gas enters the ventilator / blower 105 through vent 119. Fan 121 can improve airflow into the ventilator / blower by drawing air or other gas through vent 119. For example, fan 121 may be a variable speed fan, in which electronic controller 123 controls the fan speed. Specifically, the function of electronic controller 123 can be controlled by electronic master controller 125 in response to inputs from master controller 125 and a predetermined desired value (preset value) of pressure or fan speed set by the user via dial 127.

[0044] Humidifier 107 includes a humidification chamber 129 containing a volume of water 130 or other suitable humidifying liquid. Preferably, the humidification chamber 129 is removable from humidifier 107 after use. Removability makes it easier to sterilize or reposition the humidification chamber 129. However, the humidification chamber 129 portion of humidifier 107 can be a monolithic construction. The body of humidification chamber 129 can be formed of non-conductive glass or plastic material. But humidification chamber 129 can also include multiple conductive components. For example, humidification chamber 129 may include a highly thermally conductive substrate (e.g., an aluminum substrate) that contacts or is associated with a heater plate 131 on humidifier 107. For example, humidifier 107 can be a standalone humidifier, such as any of the humidifiers in the respiratory humidification range of Fisher & Paykel Healthcare Ltd. in Auckland, New Zealand.

[0045] The humidifier 107 may also include multiple electronic controls. In this example, the humidifier 107 includes an electronic analog or digital main controller 125. Preferably, the main controller 125 is a microprocessor-based controller that executes computer software commands stored in associated memory. In response to user-set humidity or temperature values ​​input via, for example, user interface 133, and other inputs, the main controller 125 determines when (or at what level) to power the heater plate 131 to heat the water 130 within the humidification chamber 129.

[0046] Any suitable patient interface 115 can be used. "Patient interface" is a broad term and is given its common and conventional meaning to those skilled in the art (that is, it is not limited to a specific or custom meaning) and includes (but is not limited to) masks (such as endotracheal masks, face masks, and nasal masks), cannulas, and nasal pillows. Temperature probe 135 can be attached to the inhalation tube 103 near or to the patient interface 115. Temperature probe 135 monitors the temperature near or at the patient interface 115. A heating filament (not shown) associated with the temperature probe can be used to adjust the temperature of the patient interface 115 and / or the inhalation tube 103 to raise the temperature of the inhalation tube 103 and / or the patient interface 115 above its saturation temperature, thereby reducing the chance of unwanted condensation.

[0047] exist Figure 1 In this configuration, exhaled humidified gas is returned from the patient interface 115 to the ventilator / blower 105 via an exhalation tubing 117. The exhalation tubing 117 can also be a variable stiffness tubing, as described in more detail below. However, the exhalation tubing 117 can also be a medical tubing, as previously known in the art. In either case, the exhalation tubing 117 may have an integrated temperature probe and / or heating filament (as described above with respect to the inhalation tubing 103) to reduce the chance of condensation. Furthermore, the exhalation tubing 117 does not need to return exhaled gas to the ventilator / blower 105. Alternatively, the exhaled humidified gas can be directly delivered to the ambient environment or to other auxiliary devices, such as an air scrubber / filter (not shown). In some embodiments, the exhalation tubing is omitted entirely.

[0048] Variable hardness tube

[0049] Figure 2AA longitudinal section of an example variable-thickness tube 201 is shown. Generally, the medical tube 201 includes an elongated catheter 203 having a first opening 205, a second opening 207, and a longitudinal axis LA-LA. In this example, the elongated catheter 203 has a generally cylindrical shape. However, "catheter" is a broad term and is given its common and conventional meaning to those skilled in the art (that is, it is not limited to a specific or customary meaning) and includes (but is not limited to) non-cylindrical channels. An inner lumen 209 extends along the longitudinal axis LA-LA between the first opening 205 and the second opening 207. The catheter 203 is stiffer near the first opening 205 than it is near the second opening 207.

[0050] The conduit 203 includes a wall 211 that extends between the first opening 205 and the second opening 207 and surrounds the lumen 209. In this example, the wall 211 is stiffer in a first region 213 of the conduit 203 adjacent to the first opening 205 than in a second region 215 of the conduit 203 adjacent to the second opening 207. The wall 211 may optionally be corrugated or have a corrugated profile. As shown in this example, the corrugated profile may include alternating outer crests (or annular protrusions) and inner troughs (or annular recesses). The outer crests may correspond to locations of the elongated conduit with the largest inner and outer radii, and the inner troughs may correspond to locations of the elongated conduit with the smallest inner and outer radii. Such corrugations may be in the form of annular corrugations or helical corrugations. Alternatively, the wall 211 may have a smooth or non-corrugated profile. Optionally, the first opening 205 is configured in size and shape for connection to a humidifying gas source, such as a humidifier as described above, and the second opening 207 is configured in size and shape for connection to a patient interface. For example, one or more ends may be configured for connection to a connection port facilitating connection to the patient interface and / or the humidifier. Other configurations may also be desirable. For example, in other embodiments, the first opening 205 may be configured for connection to a patient interface, while the second opening 207 may be configured for connection to a ventilator / blower, as described above.

[0051] As described in more detail below, tube 201 may optionally include one or more conductive (heating or sensing) filaments. The filaments may be optionally positioned in the following ways: typically in an unsecured helical manner within the cavity; typically combined with an external sheath positioned in close external contact with the tube wall to secure the conductive filaments in place and prevent heat loss; or embedded in the tube wall.

[0052] The increased stiffness at one end of the tube can lead to better management of condensate by improving "backflow." Furthermore, the increased stiffness is related to improved properties of the insulating wall surface (e.g., increased thickness, mass, and / or volume). Therefore, for unheated tubes or tubes with a heating filament placed within the lumen, the first end is preferably the humidifier end to better insulate the tube from heat loss where most condensation occurs. This configuration also increases the stiffness of the tube where it exits the humidifier, allowing it to maintain a more vertical position over a greater distance before bending towards the horizontal. In this way, more condensate flows back to the humidifier rather than into the breathing tube. The thinner tube at the patient end improves flexibility, reduces mass, and improves patient comfort.

[0053] For heating filaments placed externally (e.g., on the tube wall opposite to the radial direction of the inner lumen) or embedded in the wall, the second end is preferably a humidifier end to allow heat from the element to penetrate the tube more easily and heat the airflow. An insulating outer sheath (described below) is typically fitted to this type of tube to prevent heat loss. The stiffer tube at the patient end is compensated for by a thinner sheath to increase flexibility and reduce mass for improved user comfort.

[0054] Therefore, in use, the tubes according to various embodiments produce less condensate and are suitable for a wider range of environmental conditions under which the tubes can be used before condensate buildup becomes a substantial problem.

[0055] Generally, the total length of the tube can be between 1.0m and 3.0m (or about 1.0m and 3.0m) or between 1.0m and 2.0m (or about 1.0m and 2.0m). Preferably, the tube length is 1.5m (or about 1.5m) or 1.8m (or about 1.8m). Preferably, the average diameter of the inner cavity (taking into account the variability in diameter caused by the crests and troughs in the optional corrugations) is between 10mm and 30mm (or about 10mm and 30mm). Preferably, the inner cavity diameter is 20mm (or about 20mm) or 22mm (or about 22mm). In practice, it is considered here that the variable stiffness tube described herein can be used as a substitute for tubes previously used in the art, which typically have an average inner cavity diameter between 10mm and 30mm and a length varying between about 1m and 2.5m.

[0056] Preferably, the pipe is resistant to crushing, flow restriction during bending, kinking, changes in length and / or volume under internal pressure, and leakage (<25 mL / min at 6 kPa), has low flow resistance (pressure increase of less than 0.2 kPa at maximum rated flow), and is electrically safe. Preferably, the pipe can be bent around a 25 mm diameter metal cylinder without kinking, clogging, or collapse, as defined in the test of increased flow resistance with bending according to ISO 5367:2000(E).

[0057] hardness

[0058] Refer again Figure 2A Preferably, the first region 213 of the conduit 203 adjacent to the first opening 205 is harder than the second region 215 of the conduit 203 adjacent to the second opening 207. Various embodiments include one or more additional regions between the first region 213 and the second region 215 that have a different hardness characteristic than the first region 213 and the second region 215 (e.g., a hardness characteristic intermediate between the hardness characteristics of the first region 213 and the second region 215). For example, a three-region tube 201 can provide a better bend profile compared to a two-region tube 201. Figure 2B The diagram illustrates a schematic three-region tube 201. This example includes a third region 221 located between a first region 213 and a second region 215.

[0059] The first region 213 and / or the second region 215 can be an absolute distance, such as 5 cm or 10 cm (or approximately 5 cm or 10 cm). The first region 213 and / or the second region 215 can also represent a relative distance. In at least one embodiment, the first region 213 includes 10% - 30% (or approximately 10% - 30%) or 30% - 50% (or approximately 30% - 50%) of the total length of the tube 201 (wherein, for example, the total length of the tube 201 is the distance from the first opening 205 to the second opening 207, excluding the cuff or connector 223 or any other separate terminal piece attached to the end of the tube 201). For example, the first region 213 can include 33% (or approximately 33%) or 35% (or approximately 35%) of the total length of the tube 201 (wherein, for example, the total length of the tube 201 is the distance from the first opening 205 to the second opening 207). In at least one embodiment, the second region 215 comprises 5% - 15% (or about 5% - 15%), or 15% - 50% (or about 15% - 50%) of the total length of the tube 201 (where, for example, the total length of the tube 201 is the distance from the first opening 205 to the second opening 207). For example, its second region 215 may comprise 10% (or about 10%), or 15% (or about 15%) of the total length of the tube 201 (where, for example, the total length of the tube 201 is the distance from the first opening 205 to the second opening 207). In at least one embodiment of the standard 1.8 m pipe 201, a first region 213 is 0.3 m to 0.7 m (or about 0.3 m to 0.7 m) in length, and preferably 0.5 m or nearby; a second region 215 is 0.1 m to 0.2 m (or about 0.1 m to 0.2 m) in length, and preferably 1.15 m or nearby; and a third region 221, located between the first region 213 and the second region 215, is between 1.0 m and 1.5 m in length, and preferably 0.15 m or nearby. In any case, the first region 213 and the second region 215 represent the substantial length of the pipe 201.

[0060] The differences in hardness in these regions represent a significant deviation from the prior art. Typical prior art delivery tubes may incorporate extruded corrugated conduits. At a very localized level, such as within a corrugation pitch typically less than 1 cm, the hardness of the conduit will vary. The corrugating process can produce walls that are harder at the troughs of the corrugations than at the crests. However, between the two ends of the tube connector, the hardness characteristics across any substantial length are essentially the same as those over any other substantial length of the conduit. That is, these characteristics do not change substantially at the macroscopic level, as is the case in the embodiments described herein.

[0061] Some embodiments include the understanding that the hardness of the first region 213 can be defined based on the "reflow length". For example... Figure 3 As shown, when tube 201 is connected to humidifier 107 or other humidifying gas sources, tube 201 is generally upright at the connection point. In other words, the slope of the imaginary line drawn through the center of tube 201 is approximately infinite. Without some kind of support to hold tube 201 in this position, the flexibility of tube 201 naturally causes it to bend at a certain distance from the connection point. Therefore, as the distance from the connection point increases, the slope of the imaginary line through the center of tube 201 gradually decreases. At a certain distance from the connection point, the slope of the imaginary line reaches zero. After this distance, the slope of the imaginary line gradually becomes more negative. When the slope of the imaginary line is positive, the condensate collected on the wall 211 of the tube surrounding the inner cavity 209 can theoretically "reverse" back into humidifier 107 under gravity. Conversely, when the slope of the imaginary line is negative, the condensate will theoretically be discharged from humidifier 107.

[0062] Therefore, for an unsupported tube 201, the recirculation length 301 can be defined as the distance between the point of connection to the humidifier 107 (or other humidity source) and the point where the slope of an imaginary line passing through the center of tube 201 is zero. Generally, the recirculation length 301 is the length of tube 201 measured from the point of connection to the humidifier 107, where condensate collected on the wall 211 surrounding the inner cavity 209 will naturally flow back into the humidifier 107. The recirculation length 301 increases as the first region 213 becomes harder. If the first region 213 is less hard, then the recirculation length 301 decreases. In some embodiments, the recirculation length 301 is 350 mm to 400 mm (or about 350 mm to 400 mm), for example, 380 mm (or about 380 mm). Studies are conducted to evaluate the effect of hardness on the ability of tube 201 to recirculate condensate on the tube wall 211 into the humidifier 107. A thickly clad tube 201 was connected to an AIRVO humidifier manufactured by Fisher & Paykel Healthcare Ltd. in Auckland, New Zealand. The return length was measured to be 380 mm. To eliminate the isolation effect of the cladding and focus on the effect of the return length, an unclad tube was used. A metal frame was used to replicate the 380 mm return length to hold the tube in place. The AIRVO humidifier was then turned on and operated at a flow rate of 15 L / min. A small table fan was placed 40 cm away from the humidifier outlet and turned on at its highest setting. This unrealistic ventilation condition was imposed to amplify potential condensation. At the far end of the metal frame, the tube was allowed to take a horizontal position on a table. The AIRVO humidifier and fan were kept running for 16 hours. After this time, the tube was removed from the AIRVO humidifier and weighed.

[0063] By forming tube 201 such that a larger length is oriented upwards (or at least positively inclined) adjacent to the humidifying gas delivery device, condensate formed in this portion of tube 201 flows back into the humidifying gas delivery device. Some embodiments include the understanding that forming tube 201 with a suitable return length 301 provides this upward extension while avoiding the need for bulky or complex rigid connectors. See again Figure 2A Several characteristics can affect the stiffness of the conduit 203. For example, in at least one embodiment, the fact that the conduit 203 is stiffer near the first opening 205 than near the second opening 207 is caused by the wall 211 of the conduit 203 being thicker near the first opening 205 than near the second opening 207. Preferably, the first region 213 has an average wall 211 thickness of 0.5 mm to 2.0 mm (or about 0.5 mm to 2.0 mm), or 1.0 mm to 2.0 mm (or about 1.0 mm to 2.0 mm), or 1.1 mm to 1.6 mm (or about 1.1 mm to 1.6 mm), or 1.6 mm (or about 1.6 mm), or 1.58 mm (or about 1.58 mm), or 1.18 mm (or about 1.18 mm). Preferably, the second region 215 has an average wall thickness of 0.1 mm to 1.0 mm (or about 0.1 mm to 1.0 mm), or 0.1 mm to 0.7 mm (or about 0.1 mm to 0.7 mm), or 0.1 mm to 0.5 mm (or about 0.1 mm to 0.5 mm), or 0.2 mm to 0.7 mm (or about 0.2 mm to 0.7 mm), or 0.3 mm to 0.6 mm (or about 0.3 mm to 0.6 mm), or 0.30 mm (or about 0.30 mm), 0.33 mm (or about 0.33 mm), 0.37 mm (or about 0.37 mm), 0.50 mm (or about 0.50 mm), 0.53 mm (or about 0.53 mm), 0.54 mm (or about 0.54 mm), or 0.56 mm (or about 0.56 mm). The third region 211, located between the first region 213 and the second region 215, may have an average wall thickness of 0.5 mm to 1.0 mm (or about 0.5 mm to 1.0 mm), preferably 0.6 mm or nearby. In some embodiments, the average wall thickness in the first region 213 is at least 25% (or about 25%), at least 100% (or about 100%), or at least 200% (or about 200%) greater than that in the second region 215.

[0064] Another measure of thickness is the average thickness per unit length. Preferably, the ratio of the average wall thickness 211 in the first region 213 to the average wall thickness 211 in the second region 221 per unit length is 1.5:1 to 5.5:1 (or about 1.5:1 to 5.5:1), or 4.5:1 to 5.0:1 (or about 4.5:1 to 5.0:1), or 2.0:2.5 (or about 2.0:2.5). For example, the bellows 201 may be 4.8:1 (or about 4.8:1) measured at the crests and 2.2:1 (or about 2.2:1) measured at the troughs.

[0065] In at least one embodiment, the fact that the conduit 203 is stiffer near the first opening 205 than near the second opening 207 is due to the fact that the wall 211 of the conduit 203 has a greater mass near the first opening 207 than near the second opening 207. The ratio of the average wall 211 mass per unit length in the first region 213 to the average wall 211 mass of the conduit 201 in the second region 215 can be 1.5:1 to 1.9:1 (or about 1.5:1 to 1.9:1), or 1.5:1 to 2:1 (or about 1.5:1 to 2:1). The first region 213 may have an average wall mass of 50 g / m to 110 g / m (or about 50 g / m to 110 g / m), or 65 g / m to 100 g / m (or about 65 g / m to 100 g / m), or 65 g / m to 80 g / m (or about 65 g / m to 80 g / m), or 70 g / m (or about 70 g / m), or 75 g / m (or about 75 g / m). The second region 215 may have an average wall mass of 211 of 20 g / m to 50 g / m (or about 20 g / m to 50 g / m), or 30 g / m to 50 g / m (or about 30 g / m to 50 g / m), or 30 g / m to 45 g / m (or about 30 g / m to 45 g / m), or 35 g / m to 45 g / m (or about 35 g / m to 45 g / m), or 40 g / m (or about 40 g / m), or 42 g / m (or about 42 g / m). The third region 221, located between the first region 213 and the second region 215, may have an average wall mass of 211 of 45 g / m to 65 g / m (or about 45 g / m to 65 g / m), preferably 50 g / m or close to that. In some embodiments, the average wall mass 211 is at least 25% (or about 25%), at least 100% (or about 100%), or at least 200% (or about 200%) greater in the first region 213 than in the second region 215.

[0066] In at least one embodiment, the fact that the conduit 203 is stiffer near the first opening 205 than near the second opening 207 is due to the wall 211 of the conduit 203 having a larger volume near the first opening 207 than near the second opening 207. The ratio of the average wall 211 volume per unit length in the first region 213 to the average wall 211 volume in the second region 215 can be 1.5:1 to 3.5:1 (or about 1.5:1 to 3.5:1), or 2.0:1 to 3.0:1 (or about 2.0:1 to 3.0:1), or 2.5:1 to 2.6:1 (or about 2.5:1 to 2.6:1). The first region 213 can have a diameter of 1.0 cm. 3 / cm to 2.0 cm 3 / cm (or approximately 1.0 cm) 3 / cm to 2.0 cm 3 / cm), or 1.0 cm 3 / cm to 1.5cm 3 / cm (or approximately 1.0 cm) 3 / cm to 1.5 cm 3 / cm), or 1.20 cm 3 / cm (or approximately 1.20 cm) 3 / cm), or 1.17 cm 3 / cm (or approximately 1.17 cm) 3 The average wall volume 211 is 0.2 cm². The second region 215 can have a wall volume of 0.2 cm². 3 / cm to 1.0 cm 3 / cm (or approximately 0.2 cm) 3 / cm to 1.0 cm 3 / cm), or 0.40 cm 3 / cm to 0.55 cm 3 / cm (or approximately 0.40 cm) 3 / cm to 0.55 cm 3 / cm), or 0.45 cm 3 / cm (or approximately 0.45 cm) 3 / cm), or 0.50 cm 3 / cm (or approximately 0.50 cm) 3 The average wall 211 volume is ( / cm). In some embodiments, the average wall 211 volume in the first region 213 is at least 25% (or about 25%), at least 100% (or about 100%), or at least 200% (or about 200%) larger than that in the second region 215.

[0067] In at least one embodiment, the fact that the conduit 203 is stiffer near the first opening 205 than near the second opening 207 is caused by the wall 211 having a greater flexural modulus near the first opening 205 than near the second opening 207.

[0068] Figures 4A to 4E The illustration shows a testing apparatus used to measure the flexural modulus of a tube. The apparatus shown includes commercially available Instron machines.

[0069] like Figure 4A As shown, in order to test tube 201, plug 401 is inserted into the opening of tube 201 sample.

[0070] like Figure 4B As shown, plug 401 is attached to arm 403 of test wheel 405. Tube 201 is wound around test wheel 405 (which has a diameter of 78 mm) and secured by support wheel 407 with a diameter of 75 mm. Support wheel 407 contacts tube 201 to fix its position. It does not crush the tube 201 sample. The position of support wheel 407 is adjusted accordingly by adjusting the position of screw 409 along slot 411 in support frame 413 of support wheel 407.

[0071] like Figure 4C As shown, a rope 415 is attached to a test wheel 405. Starting from a point where the arm 403 of the test wheel 405 is adjacent to the support wheel 407 and the tube 201 is in an unbent condition, the rope 415 is then pulled at a constant rate of 250 mm per minute for a distance of 100 mm. The tensile load on the rope 415 is recorded as a function of distance.

[0072] Regarding the pipe axis of pipe 201 ( Figure 4D and 4E The test is repeated while rotating (as shown in the diagram) toward each of the four orientations to account for asymmetry in the shape of the tube 201. The test according to this process provides data on the flexural characteristics of the tube 201. Testing the tube 201, which may have different flexural moduli at multiple locations along the tube 201, includes testing each region of the tube 201 by cutting out regions, mounting regions, and performing tests according to this process.

[0073] For the tested segment, the flexural modulus is calculated as the gradient of the load generated by the test with respect to the linear portion of the elongation curve. The flexural modulus of the test segment is the average flexural modulus calculated for each of the four orientations. For example, Figure 5A The figure shows the flexural test data for four orientations of a section of a corrugated pipe with a pipe mass of 100 g / m. Figure 5BThe figure illustrates the flexural test data for four orientations of a section of a corrugated pipe with a pipe mass of 40 g / m.

[0074] Figure 5C Only the illustration is shown. Figure 5A The linear portion of the curve has the best-fit line for each orientation of the tube. The best-fit line for the tube in the first orientation has a gradient of 0.3377 N / mm. The best-fit line for the tube in the second orientation has a gradient of 0.3652 N / mm. The best-fit line for the tube in the third orientation has a gradient of 0.342 N / mm. The best-fit line for the tube in the fourth orientation has a gradient of 0.3506 N / mm. The average gradient, and therefore the flexural modulus calculated for this tube portion based on this test, is 0.3488 N / mm.

[0075] Figure 5D The diagram shows Figure 5B The magnified portion of the curve shows the best-fit line for each orientation of the tube. The best-fit line for the tube in the first orientation has a gradient of 0.0208 N / mm. The best-fit line for the tube in the second orientation has a gradient of 0.0194 N / mm. The best-fit line for the tube in the third orientation has a gradient of 0.0076 N / mm. The best-fit line for the tube in the fourth orientation has a gradient of 0.0103 N / mm. The average gradient, and therefore the flexural modulus calculated for this tube section based on this test, is 0.01452 N / mm.

[0076] These tests show that the corrugated pipe portion with a tube mass of 40 g / m has a tested flexural modulus of approximately 0.015 N / mm, while the corrugated pipe portion with a tube mass of 100 g / m has a tested flexural modulus of 0.349 N / mm. Therefore, the flexural modulus of the 100 g / m sample is more than 20 times that of the 40 g / m sample.

[0077] As defined by the aforementioned test method, the ratio of the flexural modulus per unit length in the first region to that in the second region can be 10:1 to 250:1 (or about 10:1 to 250:1), 100:1 to 220:1 (or about 100:1 to 220:1), or 170:1 to 200:1 (or about 170:1 to 200:1), or 188:1 (or about 188:1), or 185:1 (or about 185:1). In some embodiments, the average flexural modulus in the first region is at least 25% (or about 25%), at least 100%, or at least 200% greater than that in the second region.

[0078] wall composition

[0079] In at least one embodiment, the wall is formed from an extrusion comprising one or more polymers. Preferred polymers include linear low-density polyethylene (LLDPE), low-density polyethylene (LDPE), polypropylene (PP), polyolefin plastic (POP), ethylene vinyl acetate (EVA), plasticized polyvinyl chloride (PVC), or blends of two or more of these materials. The polymer forms at least 98.4 (or about 98.4), 98.5 (or about 98.5), 98.6 (or about 98.6), 98.7 (or about 98.7), 98.8 (or about 98.8), 98.9 (or about 98.9), 99.0 (or about 99.0), 99.1 (or about 99.1), 99.2 (or about 99.2), 99.3 (or about 99.3), 99.4 (or about 99.4), 99.5 (or about 99.5), 99.6 (or about 99.6), 99.7 (or about 99.7), 99.8 (or about 99.8), or 99.9 (or about 99.9) weight percentages (by weight) of the total extrudate. In a specific embodiment, the extrudate comprises 99.488 (or about 99.488) wt% or about 99.49 (or about 99.49) wt% LLDPE.

[0080] The extrudate may optionally include one or more surface modifiers. A surface modifier is an additive, either alone or in combination with another substance, to affect the surface properties of the material. This agent can help increase the surface energy (or wettability) of the wall surface. Increased surface energy can advantageously promote a reduced contact angle between droplets or water droplets of condensate or liquid that can accumulate on the surface. Specifically, droplets or water droplets can diffuse across a larger surface area of ​​the wall and, therefore, are more likely to re-evaporate into the airflow passing through the cavity.

[0081] Including surface modifiers in bellows can be particularly advantageous. In bellows, small droplets or water droplets of condensate are more likely to form in the lower-temperature sections of the bellows. These lower-temperature sections are typically the parts of the bellows closest to or most exposed to the ambient conditions surrounding the pipe. Modifying the surface properties of the pipe wall allows these small droplets or water droplets to diffuse across the pipe surface and, in doing so, move towards warmer regions. This migration of the droplets towards warmer regions and towards areas of the pipe exposed to larger or faster airflows can achieve an increased reevaporation rate.

[0082] Suitable surface modifiers include glyceryl monostearate (GMS), ethoxylated amines, sodium alkyl sulfonates, and diethanolamide laurate, as well as additives containing these substances. MLDNA-418, supplied by Clariant (New Zealand) Ltd. and marketed as “418 LD Antistatic Masterbatch,” is a surface modifier masterbatch containing 5 (±0.25)% glyceryl monostearate (CAS No. 123-94-4) as the active ingredient. Preferably, the surface modifier comprises at least about 0.05 (or about 0.05), 0.1 (or about 0.1), 0.15 (or about 0.15), 0.2 (or about 0.2), 0.25 (or about 0.25), 0.3 (or about 0.3), 0.35 (or about 0.35), 0.4 (or about 0.4), 0.45 (or about 0.45), 0.5 (or about 0.5), 1.1 (or about 1.1), 1.2 (or about 1.2), 1.3 (or about 1.3), 1.4 (or about 1.4), or 1.5 (or about 1.5) wt% of the total extrudate. For example, in at least one embodiment, the extrudate comprises 0.25 wt% (or about 0.25 wt%) of the surface modifier. As another example, in at least one embodiment, the extrudate comprises 0.5 wt% (or about 0.5 wt%) of the surface modifier.

[0083] Other methods can also be used to increase surface energy and reduce contact angle. Suitable methods include physical, chemical, and radiation methods. Physical methods include, for example, physisorption and Langmuir-Blodget membranes. Chemical methods include oxidation by strong acids, ozone treatment, chemisorption, and flame treatment. Radiation methods include plasma (glow discharge), corona discharge, photoactivation (UV), lasers, ion beams, electron beams, and gamma irradiation.

[0084] By selecting a suitable surface modification method or surface modifier, it is possible to provide a catheter wall having a degree of less than 50 (or about 50), 45 (or about 45), 40 (or about 40), 35 (or about 35), 30 (or about 30), 25 (or about 25), 20 (or about 20) degrees. The surface characteristics of the contact angle, such as that of a surface, can be measured using an angle measuring device (e.g., a goniometer). For example, a contact angle less than 35°... (or approximately 35) The surface properties of the tube wall, including the contact angle, provide useful results.

[0085] Table 1 below shows the contact angle measurements for different LLDPE samples, including those treated with surface modifiers and those treated with radiation. The contact angle measurements were based on the static droplet shape test method according to ASTM standard D7334, 2008, "Standard Practice for the Wetness of Coatings, Substrates and Pigments by Advance Contact Angle Measurement".

[0086] Table 1

[0087]

[0088] Compared to other surface modification methods tested, the sample with 5% MLDNA-418 surface modifier produced the lowest measured contact angle.

[0089] Foam

[0090] In some embodiments, the tube wall described above can be formed from a polymer foam. The foam is a solid material having gas voids dispersed throughout the foam. The voids can be open-cell or mesh-like (such that most (e.g., 51%–100%) of the voids are interconnected with other voids). The voids can also be closed-cell, such that most (e.g., 80%, 90%, or more) of the cells are not interconnected with other voids. Foams with open-cell voids can be advantageous because they are generally sparser, require less material, and are therefore cheaper to produce than those with closed-cell voids. However, preferably, the voids are closed-cell, which improves and better controls the insulating properties of the wall. Foams with closed-cell voids can also have the additional advantage of being easier to manufacture than foams with open-cell voids.

[0091] In embodiments that include a foam wall, the foam wall is preferably a monolithic polymer foam, for example, formed by extrusion of a single extruder.

[0092] Compared to the level of insulation provided by non-foam walls, foam walls can advantageously provide an improved level of insulation for the lumen. Therefore, in at least one embodiment, the wall insulates the contents of the elongated conduit (e.g., humidifying gas flowing through an airflow channel) from the possible cooling effects of the environment surrounding the medical tube (e.g., from the ambient air surrounding the breathing circuit or laparoscopic ventilation system). The environment surrounding the medical tube is, for example, a hospital ward or room, an operating room, a home bedroom, or other location where the patient may be located.

[0093] In various embodiments, the foam wall has or provides a thermal conductivity of 0.2 W / mK to 0.4 W / mK (watts per meter Kelvin) (or about 0.2 W / mK to 0.4 W / mK). However, it should be understood that other levels of thermal conductivity can be advantageously achieved with the foam wall, and thermal conductivityes of 0.15 W / mK to 0.35 W / mK (or about 0.15 to 0.35 W / mK) or 0.25 W / mK to 0.45 W / mK (W / mK) have also been considered.

[0094] Example methods for forming foam walls include adding a chemical foaming agent to the extrudate. Chemical foaming agents are sometimes also referred to as foaming agents. Chemical foaming agents enable foaming of the extrudate material as part of or after the extrusion process, which is described in more detail below. The chemical foaming agent may include at least 0.005 (or about 0.005), 0.006 (or about 0.006), 0.007 (or about 0.007), 0.008 (or about 0.008), 0.009 (or about 0.009), 0.01 (or about 0.10), 0.011 (or about 0.011), 0.012 (or about 0.012), 0.013 (or about 0.013), 0.014 (or about 0.014), 0.015 (or about 0.015), 0.016 (or about 0.016), 0.017 (or about 0.017), 0.018 (or about 0.018), 0.019 (or about 0.019), or 0.02 (or about 0.02) by weight of the total extrudate. For example, a chemical blowing agent may comprise 0.01 to 0.012 (or about 0.01 to 0.012) wt% of the total extrudate. As part of the chemical blowing extrusion process, the polymer component of the extrudate is mixed with the chemical blowing agent. Some preferred chemical blowing agents include calcium oxide. For example, MHYNA-CF20E, supplied by Clariant (New Zealand) Ltd under the product name Hydrocerol CF20E, is a chemical blowing agent in the form of a blowing agent masterbatch containing about 0.5% to 1% calcium oxide as an active ingredient.

[0095] During the chemical foam extrusion process, the polymer resin component and the chemical foaming agent are mixed and melted. The chemical foaming agent decomposes and releases gas, which is dispersed in the polymer (or masterbatch or extrudate) melt and expands after exiting the die of the extruder.

[0096] It should also be understood that other foaming techniques, such as physical rather than chemical foaming methods, can be used to form foam walls. Physical foaming methods involve introducing gas directly into the extrudate while under pressure. As the extrudate is compressed, the pressure decreases, causing the gas to expand. For example, one such physical foaming technique involves foaming or injecting gas into the extrudate at or near the extrusion point. Such gases may include nitrogen, carbon dioxide, pentane, or butane.

[0097] jacket

[0098] In some embodiments, the elongated catheter 203 may further include a sheath 227, such as Figure 2C As shown in the diagram. Sheath 227 is a component that partially or completely surrounds wall 211. Sheath 225 may be secured to the wall 211 of conduit 203 at a location along wall 211 or may be secured only to the end of conduit 201. Sheath 227 can be used to secure conductive filaments (described below) in place and / or prevent heat loss due to cold airflow impacting the conduit wall 211.

[0099] Although the sheath 227 can be incorporated into the conduit 203, which includes a smooth wall (not shown) or a corrugated wall 211, it can be particularly advantageous to include the sheath 227 together with a corrugated wall. The sheath can trap air between adjacent outer crests (or annular protrusions) of the corrugations. This can help with further isolation of gas passing through the inner cavity 209.

[0100] For the delivery pipe with sleeve 227, sleeve 227 can be applied around wall 211 as an extruded outer layer, as packaging material around wall 211, or as a bushing that is slidable or pulled into position around wall 211. This sleeve 227 can be formed from a material similar to wall 211 (described above), such as LLDPE. Sleeve 227 can help further improve the thermal properties of pipe 201.

[0101] The sheath 227 can have any required thickness, but the thickness and the material used should be balanced with the need to maintain the flexibility of the catheter 203. In one embodiment, the sheath 227 may have an average wall thickness of 100 micrometers (or about 100 micrometers).

[0102] However, the average thickness per unit length, average mass per unit length, average volume per unit length, or flexural modulus can vary macroscopically along the length of the sheath 227. In some embodiments, the characteristic measurement may be greater in a region of the sheath 227 adjacent to one end of the tube 201 than in a region of the sheath 227 adjacent to the other end. In other embodiments, the characteristic measurement may vary gradually along the length of the sheath 227. In other embodiments, the characteristic measurement may have a dissimilar transition along the length of the sheath 227. In some embodiments, the measurement or characteristic may be greater in a region adjacent to one end of the tube 201 than in a region along the middle length of the tube 201, and may be greater in a region adjacent to the other end of the tube 201 than in a region along the middle length of the tube 201.

[0103] For example, the outer sheath 227 can be thicker at the humidifier end of the tube 201 to better isolate the tube 201 and prevent heat loss where most condensation is likely to occur. The thicker sheath 227 at the humidifier end also increases the rigidity of the tube 201, allowing it to maintain a more vertical position over a greater distance before bending towards the horizontal, thereby increasing the backflow length (not shown). In this way, more condensation returns to the humidifier (not shown) rather than entering the breathing tube 201. The thinner sheath 227 at the patient end increases flexibility and reduces mass to improve user comfort.

[0104] When the sheath 227 is compressed around the wall 211, this compression can be, for example, a continuous step of the initial compression of the wall 211, that is, a compression step after the formation of the wall 211. Furthermore, when the outer sheath 227 is, for example, a wrapping around the wall 211, the sheath 227 is constructed in place by a strip or band of length spirally wound around the wall 211. Moreover, when the outer sheath 227 is pre-formed as a hollow tube, it can be fitted around the outer periphery of the wall 211.

[0105] conductive filaments

[0106] In some embodiments, tube 201 may further include one or more conductive filaments. These conductive filaments may be heating filaments and / or sensing filaments.

[0107] The filament can be, for example, taken in the form of a thread or band on or within the wall of a catheter. Figure 6 The illustration shows an example placement of the heater wire 601 within the inner cavity 209 of tube 201. Although the filament may be within the inner cavity 209, it may also be desirable to remove the filament from the airflow path. For example, the filament may be placed on or inside a wall opposite to the radial direction of the inner cavity. Figure 7The illustration shows the placement of heater lines 601 around the outer surface of wall 211. This placement reduces the risk of ignition in the oxygen-enriched flow and also improves laminar airflow.

[0108] The materials used for these filaments include conductive metals such as copper or aluminum, or PTC (positive temperature coefficient) type materials. Aluminum is less conductive than copper, but it can be an economical choice, although it has a larger wire diameter for the same resistance. Although the applied loop voltage is inherently safe (less than 50 V), for corrosion resistance and electrical safety in the event of damage to the wall or sheath, the wire is ideally self-insulated, either by enamel coating or by anodizing in the case of aluminum.

[0109] In some embodiments, the filament may be placed on the outer surface of wall 211 (radially outward from inner cavity 209), and a plastic sheath 227 may be mounted around the filament. In this configuration, the sheath 227 can help confine the filament in place. Furthermore, the sheath may also be included when the filament is placed within inner cavity 209 or wall 211. As explained above, the outer sheath 227 isolates the filament from heat loss. However, the outer sheath 227 may be used regardless of whether the filament is included.

[0110] Comparison with uniform hardness tubes

[0111] Figure 8 Condensation accumulation in a uniform hardness tube was compared with that in a variable hardness tube. In this experiment, three uniform hardness tubes and one variable hardness tube were connected in a loop with a humidifying gas source and placed in a test chamber with a flow of cold air, simulating a typical hospital ward with conditioned air flowing through the loop. Condensation accumulated over a 16-hour period was collected and weighed. The results indicated that increasing the wall mass in the uniform thickness tube from 50 g / m to 63 g / m to 74 g / m reduced condensation accumulation. The variable hardness tube, made of three sections with a mass of 74 g / m at the first end, 63 g / m in the middle region, and 50 g / m at the second end, unexpectedly accumulated less condensation than the 74 g / m tube.

[0112] One explanation for the unexpected performance improvement of the variable stiffness tube compared to the stiffest uniform thickness tube may be the interaction with the humidifier, which acts as the humidifying gas source. The MR850 humidifier, manufactured by Fisher & Paykel Healthcare Ltd. in Auckland, New Zealand, detects the patient-end temperature and controls the heating plate beneath the chamber and the heating filament within the tube. The algorithm used by the humidifier involves introducing gas into the tube at 37°C to fully saturate it, then heating the tube so that the temperature sensed at the end of the tube measures 40°C. Because the 50 / 63 / 74 g / m variable stiffness tube has a relatively thinner wall at the patient end, the temperature there is lower than at the patient end of a 74 g / m uniform wall tube. Therefore, the humidifier's control algorithm directs more power to the heating plate and heating filament with the variable stiffness sample, resulting in less condensation at the humidifier end of the tube.

[0113] Components in medical circuits

[0114] Next reference Figure 9 The figure illustrates an example medical circuit according to at least one embodiment. The circuit includes a variable stiffness tube for an inspiratory tube 103 as described above. The characteristics of the inspiratory tube 103 are similar to those described above. The inspiratory tube 103 has an inlet 109 communicating with a humidifying gas source 115 and an outlet 113 through which humidifying gas is supplied to the patient 101. As described above, a heater wire 601 may be placed within the inspiratory tube 103 to reduce the risk of condensation in the tube by maintaining the tube wall temperature above the dew point temperature.

[0115] exist Figure 9 The system also includes an exhalation tubing 117. The exhalation tubing 117 has an inlet 109 and an outlet 113, the inlet receiving humidified exhaled gas from the patient. (As mentioned above...) Figure 1 As described, the outlet 113 of the exhalation tube 117 can discharge exhaled gas to the atmosphere, to the ventilator / blower unit 115, to the air scrubber / filter (not shown), or to any other suitable location.

[0116] However, the exhalation tubing is optional. The inhalation tubing 103 according to the above embodiment can be used with other forms of respiratory support, such as a stand-alone blower humidifier without an expiratory return path. Examples of such products include humidified CPAP delivery products and COPD treatment products from Fisher & Paykel Healthcare Ltd. of Cranton, New Zealand. In these systems, the combined blower / humidifier supplies humidified gas to the connected delivery tubing. The delivery tubing supplies this gas to a patient interface connected to the patient end of the delivery tubing. The patient interface is typically a full-face mask, nasal mask, nasal pillow for CPAP treatment, a nasal needle or nasal cannula for COPD treatment, or a tracheal connector for intubated patients, where the device can be used to assist in the transition to full ventilation.

[0117] Components of the air blowing system

[0118] Laparoscopic surgery, also known as minimally invasive surgery (MIS) or keyhole surgery, is a modern surgical technique in which procedures in the abdomen are performed through smaller incisions (typically 0.5 cm to 1.5 cm) compared to the larger incisions required in conventional surgical procedures. Laparoscopic surgery involves procedures within the abdominal or pelvic cavity. During laparoscopic surgery with inhalation, it may be desirable for the inhaled gas (usually CO2) to be humidified before being delivered into the abdominal cavity. This helps prevent the patient's internal organs from becoming dehydrated and can reduce the amount of time required for postoperative recovery. Inhalation systems generally consist of multiple humidifier chambers containing a certain amount of water. The humidifier typically includes a heater plate that heats the water to produce water vapor, which is then passed through the introduced gas to humidify it. This gas containing water vapor is then expelled from the humidifier.

[0119] Next reference Figure 10 The figure illustrates a blowing system 1001 according to at least one embodiment. The blowing system 1001 includes a blower 1003 that generates a flow of blowing gas at atmospheric pressure for delivery to the abdominal or peritoneal cavity of a patient 1005. The gas is passed to a humidifier 1007 (including a heater base 1009 and a humidifier chamber 1011), wherein the chamber 1011 contacts the heater base 1009 in use, such that the heater base 1009 provides heat to the chamber 1011. In the humidifier 1007, the blowing gas is passed through the chamber 1011, such that the blowing gas is humidified to a suitable moisture level.

[0120] System 1001 includes a delivery conduit 1013 connecting a humidifier chamber 1011 to the peritoneal cavity or surgical site of a patient 1005. The conduit 1013 is a variable stiffness tube as described above. The conduit 1013 has a first end and a second end, the first end being connected to an outlet of the humidifier chamber 1011 and receiving humidified gas from the chamber 1011. The second end of the conduit 1013 is placed in the surgical site or peritoneal cavity of the patient 1005, and the humidified blowing gas travels from the chamber 1011, through the conduit 1013, and into the surgical site to blow air into and inflate the surgical site or peritoneal cavity. The system also includes a controller (not shown) that regulates the amount of humidity supplied to the gas by controlling the power supplied to the heater base 1009. The controller can also be used to monitor water in the humidifier chamber 1011. A smoke extraction system 1015 is shown leading to the exterior of the body cavity of the patient 1005.

[0121] The smoke extraction system 1015 can be used in conjunction with the air blowing system 1001 described above, or it can be used with other suitable air blowing systems. The smoke extraction system 1015 includes an exhaust or venting branch 1017, an exhaust assembly 1019, and a filter 1021. The exhaust branch 1017 connects the filter 1021 to the exhaust assembly 1019, which is located in or adjacent to the surgical site or peritoneal cavity of the patient 1005 during use. The exhaust branch 1017 is a self-supporting tube with two open ends (that is, the tube is capable of supporting its own weight without collapsing): a surgical site end and an outlet end.

[0122] At least one embodiment includes the understanding that using a variable stiffness tube as a conduit 1013 allows for the delivery of humidifying gas to the patient 1005 surgical site with minimal heat loss. This can advantageously reduce the overall energy consumption of the blowing system because less heat input is required to compensate for heat loss.

[0123] Manufacturing method

[0124] The conduit, sheath, or both of these can be manufactured according to multiple processes adapted to provide variations in hardness within the conduit. The conduit and sheath can be formed by the same manufacturing method or by different manufacturing methods. In some manufacturing methods, the conduit and sheath can be integrated during the manufacturing process, such that the sheath is attached to the conduit at numerous locations along the length of the conduit or along a continuous helix along the length of the conduit. Alternatively, the sheath can freely surround the conduit and be attached to the conduit only at or near the end connector.

[0125] Typically, the conduit, sheath, or both can be made from one or more extruded polymer components. The properties of the extrudate (including composition, surface modifiers, methods for increasing surface energy, and foaming agents) are described above.

[0126] refer to Figure 11 A first manufacturing method is described. This method includes extruding an elongated conduit having a longitudinal axis, an inner cavity extending along the longitudinal axis, and a wall surrounding the inner cavity, wherein the wall is stiffer in a first length of the conduit than in a second length. The method may also include corrugating the elongated conduit, for example using a corrugating die. More specifically, the process involves mixing or providing a masterbatch of extrudate material (i.e., material for extrusion), feeding the masterbatch into an extrusion die, extruding the extrudate as described above, and (optionally) feeding the elongated conduit into a corrugated plate mill using an endless chain of a die block to form a corrugated tube.

[0127] Figure 11 The diagram generally illustrates an arrangement in which a feed hopper 1101 is provided for receiving raw components or materials (e.g., masterbatch and other materials), which will be conveyed in direction A toward a die head 1107 via a screw feeder 1103 driven by an electric motor 1105. A molten tube 1109 is extruded from a die head 1111. Conductive filaments may optionally be co-extruded on or within the molten tube 1109. The method may further include one or more screw extrusion processes that progressively increase the material layer to produce portions of varying hardness along the tube. Such screw extrusion processes are described in more detail below.

[0128] Extrusion presses, such as Welex extrusion presses equipped with 12-16 mm annular dies and typically with a gap of 0.5-1.0 mm, have been found suitable for rapid, low-cost tube production. Similar extrusion machines are supplied by Kuhne (Germany), AXON AB Plastics Machinery (Sweden), AMUT (Italy), and Battenfeld (Germany and China). Corrugated sheet mills, such as those manufactured and supplied by Unicor® (Hasford, Germany), have been found suitable for corrugated sheet forming steps. Similar machines are supplied by OLMAS (Callatabria Enza, Italy), Qingdao HUASU Machinery Manufacturing Co., Ltd. (Jiaozhou, Qingdao, China), or Top Industries (Chengdu) Co., Ltd. (Chengdu, China).

[0129] During manufacturing, the molten tube 1109 is passed between a series of rotating dies / blocks on a corrugated plate mill after exiting the extrusion die 1111, forming a corrugated tube. The molten tube is formed by a vacuum applied to the outside of the tube via slots and channels passing through these blocks and / or pressure applied to the inside of the tube via an air channel passing through the center of the extrusion die mandrel. If internal pressure is applied, a specially shaped long internal rod may be required extending from the die mandrel and closely conforming to the inside of the corrugations to prevent air pressure from escaping along the tube at both ends. Different wall thicknesses can be obtained by varying the corrugated plate mill speed. Slower corrugated plate mill speeds result in thicker walls, while faster speeds result in thinner walls.

[0130] The tube may also include a flat clamping area for connection to the end connector fitting. Therefore, during manufacturing, molded plastic end connector fittings can be permanently fixed and / or airtight by friction fitting, adhesive bonding, overmolding, or by thermal or ultrasonic welding.

[0131] Another suitable method for manufacturing tubes according to the embodiments described herein involves helical forming, such as... Figure 12 As shown in the diagram. Generally, the method involves extruding a tape, wherein a first length of the tape is more rigid than a second length of the tape; and helically winding the extruded tape around a mandrel such that adjacent turns of the extruded tape touch or overlap, thereby forming an elongated conduit having a longitudinal axis, an inner lumen extending along the longitudinal axis, and a wall surrounding the inner lumen, wherein the wall is more rigid in the first length of the conduit than in the second length of the conduit. The method may also optionally include corrugating the elongated conduit.

[0132] The extrusion process involves mixing or providing a masterbatch of extrudate material (i.e., the material used for extrusion), feeding the masterbatch into an extrusion die, and extruding the extrudate into a strip.

[0133] Subsequently, the extruded or pre-formed tape is wound into a spiral shape such that within each turn, one edge of the tape overlaps the edge of the previous turn and lies beneath the edge of the subsequent turn. Such helically wound conduits can be made using a single helically arranged tape or multiple staggered helically arranged tapes. In some embodiments, a reinforcing strip covers the overlap between the turns of the tape. This strip can provide the conduit with helical reinforcement against crushing and can also provide a source of thermal, chemical, or mechanical adhesive for fusing or joining the overlapping portions of the tape. In some instances, double-walled conduits can be constructed by placing additional tape, or portions of the same tape, on the outer side and supported on a helical ridge formed by the strip.

[0134] In this method, the hardness of the tube depends on the hardness of the strip, and the hardness of the tube can be adjusted by changing the thickness, mass, volume, flexural modulus, etc. of the strip. Based on this process, a tube with a variable wall thickness along its length can be constructed by changing the thickness of the strip, such that, for example, in a first region, the strip can have a greater thickness than in another region, where this thickness can be slightly thinner, and in a second region, the thickness can be even thinner.

[0135] Another suitable method for helical forming involves extruding a strip having generally uniform hardness; winding the extruded strip helically around a mandrel such that adjacent turns of the extruded strip touch or overlap, thereby forming an elongated conduit having a longitudinal axis, an inner cavity extending along the longitudinal axis, and a wall surrounding the inner cavity, wherein the wall is harder in a first length of the conduit than in a second length. The method may include corrugating the elongated conduit to provide a conduit with a wall of variable hardness. For example, the corrugated mill speed can be varied to obtain different wall thicknesses. Slower corrugated mill speeds result in thicker walls, and faster speeds result in thinner walls.

[0136] Figure 12 The image shows the melt extrusion tube 1201 exiting the extruder die 1203 before being passed to the corrugated plate mill 1205. After exiting the corrugated plate mill 1205, the heater wire 601 is wound around the outside of the formed tubular component 201.

[0137] The above reference Figure 12 One advantage of the preferred type of pipe manufacturing described is that some of the die blocks B can include end clamp features simultaneously formed as tubular components 201. Manufacturing speed can be significantly increased by reducing complexity and eliminating secondary manufacturing processes. While this method represents an improvement over the individual clamp forming process, a disadvantage of prior art flat clamps is that the corrugated mill must slow down to increase the pipe wall thickness in this region (the extruder continues at the same speed). Increasing the clamp thickness allows for the use of clamp adapter fittings to achieve increased clamp strength and sealing properties. Furthermore, during the limited contact time with the corrugated mill block, the heat of the molten polymer in this thicker region is difficult to remove, which becomes a significant limiting factor for the maximum operating speed of the pipe production line.

[0138] The foregoing description of the invention includes its preferred form. Modifications may be made thereto without departing from the scope of the invention. Many variations in construction, as well as a wide range of different embodiments and applications of the invention, will be apparent to those skilled in the art as to their own existence without departing from the scope of the invention as defined in the appended claims. The disclosure and description herein are merely illustrative and are not intended to be limiting in any sense.

Claims

1. A medical tube for delivering humidifying gas to a patient, comprising: A slender conduit has: a first opening as a humidifying gas inlet for receiving humidifying gas, a second opening as a humidifying gas outlet for discharging humidifying gas, a longitudinal axis, an inner cavity extending along the longitudinal axis between the first and second openings, and a conduit wall formed of an extruded material, extending between the first and second openings and surrounding the inner cavity. The catheter wall is harder near the first opening than near the second opening.

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