Medical tube and method of manufacture

Abstract

The present invention relates to medical tubes and methods of manufacture. A medical tube includes an elongated conduit 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 stiffer 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 stiffness of the tube wall can improve heat distribution of the tube and improve condensate return into a humidifier that provides humidified gas to the tube.

Description

[0001] This application is a divisional application of the invention patent application 201811053333.5, filed on September 11, 2018, entitled "Medical Tubing and Manufacturing Method". TECHNICAL FIELD

[0002] The present disclosure relates generally to tubing suitable for medical use, and in particular to tubing for use in medical circuits suitable for providing gases to and / or removing gases from a patient, such as in positive airway pressure (PAP), respirators, anesthesia, ventilators, and insufflation systems. BACKGROUND

[0003] In medical circuits, various components deliver warm, humidified gases to a patient. For example, in some respiratory circuits, such as PAP or assisted breathing circuits, gases inhaled by a patient are delivered from a heater-humidifier through an inspiratory tube. As another example, a tube can deliver humidified gases, typically C02, into the abdominal cavity in an insufflation circuit. This can help prevent "dehydration" of the patient's internal organs, and can reduce the amount of time needed for post-surgical recovery.

[0004] In these medical applications, the gases are preferably delivered at conditions having a humidity close to saturation and at a temperature close to body temperature, typically at a temperature between 33°C and 37°C. Condensation or "rainout" can form on the interior surface of the breathing tube as the high humidity breathing gases cool and / or come into contact with the relatively cooler breathing tube surface. There remains a need for tubing that insulates against heat loss and, for example, achieves improved temperature and / or humidity control in medical circuits.

[0005] It is therefore an object of the present invention to provide medical tubing and / or a method of manufacturing medical tubing that will at least go some way to addressing the foregoing problems or that will at least provide a useful choice to the industry or the public or both.

[0006] In this specification where a document, act or other item of prior art is referred to this is generally for the purpose of providing a context for discussion. Unless specifically stated otherwise, reference to such an item of prior art is not, and should not be taken as, an acknowledgement or admission that in any jurisdiction such an item of prior art was, is or is commonly used as prior art against a present application.

[0007] Other aspects and advantages of the present invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, which illustrate, by way of example, the principles of the invention. SUMMARY

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

[0009] In at least one embodiment, a medical tube for providing humidified gas to a patient can include an elongated conduit having a first opening sized and shaped for connection to a source of humidified gas, a second opening sized and shaped for connection to a patient interface, a longitudinal axis, a 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 lumen. The wall is stiffer in a first region of the conduit proximate the first opening than in a second region of the conduit proximate the second opening.

[0010] In at least one embodiment, a heated respiratory tube can include a single corrugated extruded conduit including a proximal patient end and a distal chamber end, and one or more heating elements on or in the conduit, wherein the conduit has a first region having a first stiffness at the chamber end and a second region having a second stiffness at the patient end, and the first stiffness is greater than the second stiffness.

[0011] In various embodiments, in the foregoing medical tube and / or heated respiratory tube, the first region is configured for vertical extension from the source of humidified gas. The vertical extension can define a backflow length. For example, the backflow length can be between about 350 mm and about 400 mm.

[0012] In various embodiments, the foregoing medical tube and / or heated respiratory tube has one, some, or all of the following properties, as well as the properties described elsewhere in this disclosure. The medical or respiratory tube can further include one or more conductive filaments in or on the conduit. At least one of the one or more conductive filaments can be a heating filament. At least one of the one or more conductive filaments can be a sensing wire. The conduit can be generally cylindrical. The wall can be corrugated. The extruded material can be a foam. The foam can be a polymer foam. The foam can be a closed cell foam. The extruded material can include one or more surface modifiers. The wall can have an average contact angle of less than 50 degrees (or about 50 degrees). The thickness of the wall in the first region can be between 0.5 mm and 2.0 mm (or about 0.5 mm and about 2.0 mm). The thickness of the wall in the second region can 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 about 50 g / m and about 110 g / m). The mass of the wall in the second region can be between 20 g / m and 50 g / m (or about 20 g / m and about 50 g / m). The volume of the wall in the first region can be between 1.0 cm 3 / m and 2.0 cm 3 / m (or about 1.0 cm 3 / m and about 2.0 cm 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 of 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 foregoing embodiments includes extruding a strip, where a first length of the strip is thicker, heavier, or stiffer than a second length of the strip; winding the extruded strip in a helical manner 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 internal 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 internal lumen, where the wall is stiffer in a first region of the catheter proximate a first end than in a second region of the catheter proximate a second end. As noted above, the wall can have a thickness between 0.5 mm and 2.0 mm (or between about 0.5 mm and about 2.0 mm in the first region). The wall in the second region can have a thickness between 0.1 mm and 1.0 mm (or between 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 can be between or about 10: 1 and about 250: 1.

[0017] In various embodiments, the foregoing methods can have one, some, or all of the tube or catheter properties described above, below, and elsewhere in the present disclosure. The extruded strip can include a foam. The foam can be a polymeric foam. The polymeric foam can be closed cell. The extruded strip can include one or more surface modifiers. The wall can have a surface contact angle facing the internal lumen of less than 50 degrees (or about 50 degrees). The method can further include winding a reinforcing strip in a helical manner between adjacent turns of the extruded strip. The reinforcing strip can include one or more conductive filaments. The method can further include winding the one or more conductive filaments in a helical manner around the elongated catheter.

[0018] In at least one embodiment, a method of manufacturing a tube or catheter according to one, some, or all of the foregoing embodiments includes extruding an elongated catheter having a longitudinal axis and an internal lumen extending along the longitudinal axis; and corrugating the elongated catheter and cooling the elongated catheter to form a medical tube having a wall surrounding the internal lumen, where the wall is stiffer in a first region of the catheter proximate a first end than in a second region of the catheter proximate a second end. In various embodiments, the foregoing methods can have one, some, or all of the tube or catheter properties described above, below, and elsewhere in the present disclosure. As noted above, the first region can be configured for vertical extension from a source of humidified gas. The vertical extension can define a backflow length. For example, the backflow length can be between 350 mm and 400 mm (or between about 350 mm and about 400 mm). In certain embodiments, the method can further include co-extruding one or more conductive filaments such that the one or more conductive filaments are disposed on or in the catheter.

[0019] The term "comprising" as used in this specification means "at least comprising". When interpreting each statement in this specification that includes the term "comprising", features other than that or those prefaced by the term "comprising" can also be present. Related terms such as "comprise" and "comprises" are to be interpreted in the same manner.

[0020] Broadly speaking, the present application can also mainly consist in the parts, elements and features referred to or indicated in the specification of the application, individually or collectively, and any combination of any two or more of said parts, elements or features and any combination of any of the parts, elements or features with other

[0021] The present application mainly consists in the foregoing and also envisages a number of configurations, only examples of which are given below. BRIEF DESCRIPTION OF DRAWINGS

[0022] Example implementations of various features of the disclosed systems and methods will now be described with reference to the following figures. The drawings described below are provided for purposes of illustration only and merely depict example implementations of the disclosure.

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

[0024] Figures 2A to 2C A longitudinal cross-section of an example composite tube is shown.

[0025] Figure 3 A medical circuit demonstrating the backflow length of a tube is shown.

[0026] Figures 4A to 4E A test apparatus for measuring the flexural modulus of a tube is illustrated.

[0027] Figure 5A A graph of test results for a tube sample having a mass of 100 g / m is plotted.

[0028] Figure 5B A graph of test results for a tube sample having a mass of 40 g / m is plotted.

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

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

[0031] Figures 6 to 7 An example placement of heater wires is illustrated.

[0032] Figure 8 A graph for comparing condensate accumulation in a uniform durometer tube to condensate accumulation in a variable durometer tube.

[0033] Figure 9 An example medical circuit is shown in accordance with at least one embodiment.

[0034] Figure 10 A gas insufflation system is shown in accordance with at least one embodiment.

[0035] Figure 11 A schematic illustration of a manufacturing method for a medical tube including a feed hopper, a spiral feeder toward a die, and ending with a corrugator is shown.

[0036] Figure 12 A schematic illustration of a spiral forming manufacturing method for a medical tube is shown.

[0037] Throughout these drawings, reference numbers can be re-used to indicate correspondence between referenced steps and elements. In addition, the first digit of each reference number typically indicates the figure in which the element first appears. DETAILED DESCRIPTION

[0038] The details of several illustrative embodiments regarding the apparatus and methods taught herein are described below with reference to the drawings. The invention is not limited to these described embodiments.

[0039] Respiratory circuit including one or more medical tubes

[0040] For a more detailed understanding of the present disclosure, reference is first made to Figure 1 The figure illustrates a respiratory circuit including one or more medical tubes in accordance with at least one embodiment. Tube is a broad term and to one of ordinary skill in the art gives it its ordinary and customary meaning (i.e., it is not limited to a special or custom definition) and includes, without limitation, a non-cylindrical passage. The respiratory circuit incorporates one or more variable durometer tubes, which can be generally defined as a tube having dissimilar durometer at each end of the tube. The respiratory circuit can be a continuous, variable, or bi-level positive airway pressure (PAP) system or another form of respiratory therapy.

[0041] The following can be performed in Figure 1The dry gases are passed from a blower / fan 105 to a humidifier 107, which humidifies the dry gases. The humidifier 107 is connected to an inlet 109 (the end for receiving humidified gases) of an inspiratory tube 103 via a port 111, thereby supplying humidified gases to the inspiratory tube 103. The inspiratory tube is a tube configured to deliver breathing gases to a patient, and can be made of a variable stiffness tube, as described in more detail below. The gases flow through the inspiratory tube 103 to an outlet 113 (the end for expelling humidified gases), and then to the patient 101 through a patient interface 115 connected to the outlet 113.

[0042] An expiratory tube 117 is also connected to the patient interface 115. The expiratory tube is a tube configured to move exhaled humidified gases away from the patient. Here, the expiratory tube 117 returns exhaled humidified gases from the patient interface 115 to the blower / fan 105.

[0043] In this example, dry gases enter the blower / fan 105 through a vent 119. A fan 121 can improve the flow of gases into the blower / fan by drawing air or other gases through the vent 119. For example, the fan 121 can be a variable speed fan, where an electronic controller 123 controls the fan speed. In particular, the function of the electronic controller 123 can be controlled by an electronic main controller 125 in response to inputs from the main controller 125 and a predetermined desired value (preset value) of pressure or fan speed set by a user via a dial 127.

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

[0045] The humidifier 107 can also include a number of 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 an associated memory. In response to humidity or temperature values set by a user, input via, for example, a user interface 133, and other inputs, the main controller 125 determines when (or at what level) to energize the heater plate 131 in order to heat the water 130 within the humidification chamber 129.

[0046] Any suitable patient interface 115 can be incorporated. The patient interface is a broad term and includes, without limitation, masks (such as tracheal masks, face masks, and nasal masks), cannulae, and nasal pillows, to one of ordinary skill in the art gives it its ordinary and customary meaning (i.e., it is not limited to a special or custom meaning), and includes, without limitation, hoods, cannulae, and nasal pillows. A temperature probe 135 can be connected to the inspiratory tube 103 proximate the patient interface 115, or to the patient interface 115. The temperature probe 135 monitors the temperature proximate 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 inspiratory tube 103 in order to raise the temperature of the inspiratory tube 103 and / or patient interface 115 above the saturation temperature, thereby reducing the chance of unwanted condensation.

[0047] In Figure 1 exhaled humidified gases are returned from the patient interface 115 to the ventilator / blower 105 via an expiratory tube 117. The expiratory tube 117 can also be a variable stiffness tube, as described in greater detail below. However, the expiratory tube 117 can also be a medical tube, as previously known in the art. In either case, the expiratory tube 117 can have a temperature probe and / or heating filament integrated with it (as described above with respect to the inspiratory tube 103), thereby reducing the chance of condensation. Furthermore, the expiratory tube 117 need not return the exhaled gases to the ventilator / blower 105. Alternatively, the exhaled humidified gases can be passed directly to the ambient environment or to other ancillary equipment, such as an air scrubber / filter (not shown). In certain embodiments, the expiratory tube is omitted altogether.

[0048] Variable Stiffness Tube

[0049] Figure 2AA longitudinal cross-section of an example variable thickness tube 201 is shown. In general, the medical tube 201 includes an elongated conduit 203 having a first opening 205, a second opening 207, and a longitudinal axis LA— LA. In this example, the elongated conduit 203 has an overall cylindrical shape. However, "conduit" is a broad term and is to be given its ordinary and customary meaning to a person of ordinary skill in the art (i.e., it is not to be limited to a special or customized meaning), and includes, without limitation, a non-cylindrical passage. An internal lumen 209 extends along the longitudinal axis LA— LA between the first opening 205 and the second opening 207. The conduit 203 is stiffer adjacent the first opening 205 than it is adjacent 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 internal lumen 209. In this example, the wall 211 is stiffer in a first region 213 of the conduit 203 adjacent the first opening 205 than it is in a second region 215 of the conduit 203 adjacent the second opening 207. The wall 211 can optionally be corrugated, or have a corrugated profile. As shown in this example, the corrugated profile can include alternating external peaks (or annular protrusions) and internal valleys (or annular recesses). The external peaks can correspond to locations of the elongated conduit having a maximum internal radius and a maximum external radius, and the internal valleys can correspond to locations of the elongated conduit having a minimum internal radius and a minimum external radius. Such corrugations can have an annular corrugation or a helical corrugation form. Alternatively, the wall 211 can have a smooth or non-corrugated profile. Optionally, the first opening 205 is configured in size and shape for connection to a source of humidified gases, 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 can be configured for connection to a connection port that facilitates connection to a patient interface and / or a humidifier. Other configurations can also be desirable. For example, in other embodiments, the first opening 205 can be configured for connection to a patient interface, while the second opening 207 can be configured for connection to a ventilator / blower, as described above.

[0051] As described in greater detail below, the tube 201 can optionally include one or more conductive (heating or sensing) filaments. Optional locations for the filaments are: typically placed within the internal lumen in an unfixed helical manner; typically placed in close external contact with the tube wall in conjunction with an external sheath in order to fix the conductive filaments in place and prevent heat loss; or embedded in the tube wall.

[0052] The increased stiffness of the tube at one end can result in better management of condensate by improving "run-back". In addition, the increased stiffness is associated with improved properties of the insulating surface of the wall (e.g. increased thickness, mass and / or volume). Thus, for unheated tubes or tubes with heating filaments placed within the lumen, the first end is preferably the humidifier end so that the tube is better insulated from heat loss where most condensation occurs. This configuration also increases the stiffness of the tube where it exits the humidifier, so that the tube can maintain a more upright position over a greater distance before bending towards horizontal. In this way, more condensate runs 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 on the outside (e.g. on the tube wall diametrically opposite the lumen) or embedded in the wall, the second end is preferably the humidifier end so that heat from the element more easily penetrates the tube and heats the airflow. An insulating outer sheath (as described below) will typically be fitted to this type of tube to prevent heat loss. The stiffer tube at the patient end is compensated for by a thinner sheath so as to increase flexibility and reduce mass to improve user comfort.

[0054] Thus, in use, the tubes according to various embodiments produce less condensate and a greater range of environmental conditions over which they can be used before condensate build-up becomes a substantial problem.

[0055] In general, the total length of the tube can be between 1.0 and 3.0 m (or about 1.0 and 3.0 m) or between 1.0 and 2.0 m (or about 1.0 and 2.0 m). Preferably, the length of the tube is 1.5 m (or about 1.5 m) or 1.8 m (or about 1.8 m). Preferably, the average diameter of the lumen (allowing for variability in diameter caused by peaks and troughs in optional corrugations) is between 10 and 30 mm (or about 10 and 30 mm). Preferably, the lumen diameter is 20 mm (or about 20 mm) or 22 mm (or about 22 mm). Indeed, it is contemplated herein that the variable stiffness tubes described herein can be used as a replacement for tubes previously used in the art, which typically have an average lumen diameter of between 10 and 30 mm and a length varying between about 1 and 2.5 m.

[0056] It is also preferred that a roller resistant, kink resistant, crush resistant, twist resistant, collapse resistant, leak resistant (at 6 kPa < 25 mL / min) tube has a low flow resistance (an increase in pressure at maximum rated flow of less than 0.2 kPa) and is power safe. Preferably, the tube can be bent around a 25 mm diameter metal cylinder without kinking, occlusion, or collapse, as defined in the Test for Increase in Flow Resistance with Bending according to ISO 5367:2000(E).

[0057] Hardness

[0058] Referring again to Figure 2A , preferably the first region 213 of the conduit 203 adjacent the first opening 205 is stiffer than the second region 215 of the conduit 203 adjacent the second opening 207. Various embodiments include one or more additional regions having a stiffness characteristic different from that of the first region 213 and the second region 215, for example a stiffness characteristic intermediate that of the first region 213 and the second region 215, between the first region 213 and the second region 215. For example, a three-region tube 201 can give better bending profiles than a two-region tube 201. In Figure 2B An illustrative three-region tube 201 is shown in FIG. 1 1. This example includes a third region 221 intermediate the first region 213 and the 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 about 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 comprises 10-30% (or about 10-30%) or 30-50% (or about 30-50%) 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, excluding a cuff or connector 223 or any other separate end component attached to the end of the tube 201). For example, the first region 213 can comprise 33% (or about 33%) or 35% (or about 35%) 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, 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 205). For example, the second region 215 can 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 a standard 1.8 m tube 201, the 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 thereabout, the second region 215 is 0.1 m to 0.2 m (or about 0.1 to 0.2 m) in length and preferably 1.15 m or thereabout, and the third region 221, which is intermediate the first region 213 and the second region 215, is between 1.0 m to 1.5 m in length and preferably 0.15 m or thereabout. In any case, the first region 213 and the second region 215 represent a substantial length of the tube 201.

[0060] The difference in hardness in these regions represents a significant departure from the prior art. A typical prior art delivery tube can incorporate an extruded corrugated conduit. At an extremely local level, for example within the pitch of the corrugations, which is typically less than 1 cm, the hardness of the conduit will vary. The corrugation forming process can produce a wall that is harder at the troughs of the corrugations than at the peaks. However, between the two ends of the tube connector, the hardness properties across any substantial length are substantially the same as any other substantial length of the conduit. That is, these properties do not substantially vary at a macro level, which is the case in the embodiments described herein.

[0061] Certain embodiments include the recognition that the hardness of the first region 213 can be defined in terms of a "backflow length." As Figure 3As shown in FIG. 3, when the tube 201 is engaged with the humidifier 107 or other source of humidified gas, the tube 201 is generally upright at the point of engagement. In other words, the slope of an imaginary line drawn through the center of the tube 201 is approximately infinite. Without some kind of support holding the tube 201 in this position, the flexibility of the tube 201 naturally causes it to bend at some distance from the point of engagement. Thus, as the distance from the point of engagement increases, the slope of the imaginary line through the center of the tube 201 gradually decreases. At some distance from the point of engagement, the slope of the imaginary line reaches zero. Beyond this distance, the slope of the imaginary line gradually becomes more negative. When the slope of the imaginary line is positive, condensate collected on the wall 211 of the tube around the inner lumen 209 can theoretically "drain back" into the humidifier 107 under the force of gravity. Conversely, when the slope of the imaginary line is negative, condensate will theoretically drain away from the humidifier 107.

[0062] Thus, for an unsupported tube 201, the drain back length 301 can be defined in terms of the distance between the point of connection to the humidifier 107 (or other source of humidity) and the point at which the slope of the imaginary line through the center of the tube 201 is zero. Generally, the drain back length 301 is the length of the tube 201 measured from the point of connection to the humidifier 107 at which condensate collected on the wall 211 around the inner lumen 209 will naturally drain back into the humidifier 107. The drain back length 301 increases as the first region 213 becomes stiffer. If the first region 213 is less stiff, the drain back length 301 decreases. In certain embodiments, the drain back length 301 is 350 mm to 400 mm (or about 350 mm to 400 mm), for example, 380 mm (or about 380 mm). Studies were conducted to assess the effect of stiffness on the ability of the tube 201 to drain back condensate on the wall 211 into the humidifier 107. Tubes 201 with thicker cladding were connected to an AIRVO humidifier manufactured by Fisher & Paykel Healthcare Limited of Auckland, New Zealand. The drain back length was measured to be 380 mm. To eliminate the insulating effect of the cladding and focus on the effect of the drain back length, tubes without cladding were used. A stand was used to replicate the 380 mm drain back length in order to hold the tube in place. The AIRVO humidifier was then turned on and run at a flow rate of 15 L / min. A small table fan was placed 40 cm away from the humidifier outlet and turned on to the highest setting. This unrealistic ventilation condition was imposed to exaggerate the possible condensation. At the far end of the stand, the tube was allowed to take a horizontal position resting on a table. The AIRVO humidifier and fan were left running for 16 hours. After this time, the tube was removed from the AIRVO humidifier and weighed.

[0063] By forming the tube 201 such that the greater length is oriented upward (or at least positively inclined) adjacent the humidified gas delivery device, condensate formed in this portion of the tube 201 flows back into the humidified gas delivery device. Certain embodiments include the recognition that forming the tube 201 with a suitable backflow length 301 provides this upward extension while avoiding the need for a bulky or complex rigid connector. Again with reference to Figure 2A A number of characteristics can influence the stiffness of the conduit 203. For example, in at least one embodiment, the fact that the conduit 203 is stiffer adjacent the first opening 205 than it is adjacent the second opening 207 results from the wall 211 of the conduit 203 being thicker adjacent the first opening 205 than it is adjacent 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 211 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 intermediate the first region 213 and the second region 215 can have an average wall 211 thickness of 0.5 mm to 1.0 mm (or about 0.5 mm to 1.0 mm), preferably 0.6 mm or thereabout. In certain embodiments, the average wall 211 thickness is at least 25% (or about 25%) greater, at least 100% (or about 100%) greater, or at least 200% (or about 200%) greater in the first region 213 than in the second region 215.

[0064] Another example measure of thickness is average thickness per unit length. Preferably, the ratio of average wall 211 thickness in the first region 213 to average wall 211 thickness 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 the example bellows 201, the ratio can be 4.8: 1 (or about 4.8: 1) measured at the peaks and 2.2: 1 (or about 2.2: 1) measured at the valleys.

[0065] In at least one embodiment, the fact that the conduit 203 is stiffer adjacent the first opening 205 than it is adjacent the second opening 207 is caused by the wall 211 of the conduit 203 having a greater mass adjacent the first opening 207 than it does adjacent the second opening 207. The ratio of average wall 211 mass in the first region 213 to average wall 211 mass of the conduit 201 in the second region 215 per unit length 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 can have an average wall 211 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 can have an average wall 211 mass 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). A third region 221 intermediate the first region 213 and the second region 215 can have an average wall 211 mass of 45 g / m to 65 g / m (or about 45 g / m to 65 g / m), preferably 50 g / m or thereabout. In certain embodiments, the average wall 211 mass 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 adjacent the first opening 205 than it is adjacent the second opening 207 is caused by the walls 211 of the conduit 203 having a greater volume adjacent the first opening 207 than adjacent the second opening 207. The ratio of the average wall 211 volume in the first region 213 to the average wall 211 volume in the second region 215 per unit length 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 an average wall 211 volume of 1.0 cm 3 / cm to 2.0 cm 3 / cm (or about 1.0 cm 3 / cm to 2.0 cm 3 / cm), or 1.0 cm 3 / cm to 1.5 cm 3 / cm (or about 1.0 cm 3 / cm to 1.5 cm 3 / cm), or 1.20 cm 3 / cm (or about 1.20 cm 3 / cm), or 1.17 cm 3 / cm (or about 1.17 cm 3 / cm). The second region 215 can have an average wall 211 volume of 0.2 cm 3 / cm to 1.0 cm 3 / cm (or about 0.2 cm 3 / cm to 1.0 cm 3 / cm), or 0.40 cm 3 / cm to 0.55 cm 3 / cm (or about 0.40 cm 3 / cm to 0.55 cm 3 / cm), or 0.45 cm 3 / cm (or about 0.45 cm 3 / cm), or 0.50 cm 3 / cm (or about 0.50 cm 3 / cm). In certain embodiments, the average wall 211 volume 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.

[0067] In at least one embodiment, the fact that conduit 203 is stiffer adjacent to first opening 205 than it is adjacent to second opening 207 is caused by wall 211 having a greater modulus of deflection adjacent to first opening 205 than it does adjacent to second opening 207.

[0068] Figures 4A to 4E A test apparatus for measuring the modulus of deflection of a tube is illustrated. The illustrated apparatus includes a commercially available Instron machine.

[0069] As Figure 4A To test tube 201, plug 401 is inserted into the opening of tube 201 sample as shown in

[0070] As Figure 4B Plug 401 is attached to arm 403 of test wheel 405 as shown in Tube 201 is wrapped around test wheel 405 (which has a diameter of 78 mm) and is secured by support wheel 407 which has a diameter of 75 mm. Support wheel 407 touches tube 201 to secure its position. It does not crush 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] As Figure 4C A string 415 is attached to test wheel 405 as shown in From the point where arm 403 of test wheel 405 is adjacent to support wheel 407 and tube 201 is in an un-deflected condition, string 415 is then pulled a distance of 100 mm at a constant rate of 250 mm per minute. The tensile load on string 415 is recorded as a function of distance.

[0072] The test is repeated with tube 201 rotated about the tube axis (shown in Figure 4D and 4E ) towards each of four orientations to account for asymmetries in the shape of tube 201. The tests according to this procedure provide data for the deflection properties of tube 201. Testing tube 201 with a modulus of deflection that can be different at multiple locations along tube 201 includes testing each of the regions of tube 201 by cutting out the regions, mounting the regions, and testing according to this procedure.

[0073] For the section being tested, the modulus of deflection is calculated as the gradient of the linear portion of the load versus extension curve produced by the test. The modulus of deflection for the test section is the average modulus of deflection calculated for each of the four orientations. For example, Figure 5A Modulus of deflection test data for four orientations of a section of corrugated tube having a tube mass of 100 g / m is illustrated; Figure 5BFour directional flex test data for a section of corrugated pipe having a tube mass of 40 g / m are illustrated.

[0074] Figure 5C Only the linear portion of the curve for Figure 5A is illustrated, with a 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 thus the flex modulus calculated for this tube section according to this test, is 0.3488 N / mm.

[0075] Figure 5D An enlarged portion of the curve in Figure 5B is illustrated, with a 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 thus the flex modulus calculated for this tube section according to this test, is 0.01452 N / mm.

[0076] As can be seen from these tests, a section of corrugated pipe having a tube mass of 40 g / m has a test flex modulus of about 0.015 N / mm, while a section of corrugated pipe having a tube mass of 100 g / m has a test flex modulus of 0.349 N / mm. Thus, the flex modulus of the 100 g / m sample is over 20 times the flex modulus of the 40 g / m tube.

[0077] As defined by the foregoing test method, the ratio of the flex modulus in the first region to the flex modulus in the second region per unit length 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 certain embodiments, the average flex modulus is at least 25% (or about 25%) greater, at least 100% greater, or at least 200% greater in the first region than in the second region.

[0078] Wall composition

[0079] In at least one embodiment, the wall is formed from an extrudate 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 a blend 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) percent by weight (wt. %) of the total extrudate. In particular embodiments, the extrudate comprises 99.488 (or about 99.488) wt. % or about 99.49 (or about 99.49) wt. % LLDPE.

[0080] The extrudate can also optionally include one or more surface modifiers. Surface modifiers are additives that either alone or in combination with another substance affect the properties of the surface of a material. This agent can help increase the surface energy (or wettability) of the surface of the wall. Increasing the surface energy can advantageously promote a reduced contact angle between droplets or beads of condensate or liquid that can accumulate on the surface. In particular, the droplets or beads can spread over a larger surface area of the wall and thus, are more likely to re-evaporate into the airflow flowing through the lumen.

[0081] It can be particularly advantageous to include a surface modifier in a bellows. In a bellows, small droplets or beads of condensate are more likely to form in the portion of the bellows that is at a low temperature location. The low temperature location is typically the portion of the bellows that is closest to or most exposed to the ambient conditions surrounding the tube. Altering the surface properties of the tube wall can cause the small droplets or beads that form at the low temperature location to spread over the tube surface and, in doing so, move toward areas of warmer temperature. This migration of the movement of the small droplets toward areas of warmer temperature and toward areas of the tube that are exposed to greater or faster airflow flow can result in an increased rate of re-evaporation.

[0082] Suitable surface modifiers include glycerol monostearate (GMS), ethoxylated amines, sodium alkyl sulfonate salts, and lauric diethanolamide, and additives including these. MLDNA-418 supplied by Clariant (New Zealand) Limited and product name "418 LD Antistatic Masterbatch" is a surface modifier masterbatch with 5 (+ / - 0.25)% glycerol 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) weight percent of the total extrudate. For example, in at least one embodiment, the extrudate comprises 0.25 weight percent (or about 0.25 weight percent) of the surface modifier. As another example, in at least one embodiment, the extrudate comprises 0.5 weight percent (or about 0.5 weight percent) of the surface modifier.

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

[0084] By selecting a suitable surface modification method or surface modifier, it is possible to provide a conduit wall having a surface property contact angle 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 (°) as measurable by an angle measuring device such as a goniometer. For example, a tube wall having a surface property contact angle of less than 35° (or about 35°) provides useful results.

[0085] Table 1 below shows contact angle measurements for different LLDPE samples, including samples treated with surface modifiers and samples treated with radiation. The contact angle measurements are based on a static drop shape test method according to ASTM Standard D7334, 2008, "Standard Practice for Surface Wettability of Coatings, Substrates, and Pigments by the

[0086] Table 1

[0087]

[0088] The sample with 5% ML DNA-418 surface modifier produced the lowest measured contact angle compared to the other surface modification methods tested.

[0089] Foam

[0090] In certain embodiments, the tube wall described above can be formed from a polymeric foam. A foam is a solid material with gas voids interspersed throughout the foam. The voids can be open or reticulated (such that a majority (e.g., 51-100%) of the voids are interconnected with other voids). The voids can also be closed, such that a majority (e.g., 80%, 90% or more) of the cells are not interconnected with other voids. Foams with open voids can be advantageous because they are generally less dense, require less material, and thus are less expensive to produce than closed voids. Preferably, however, the voids are closed, which improves and better controls the insulating properties of the wall. Foams with closed voids can have the additional advantage of being easier to manufacture than foams with open voids.

[0091] In embodiments including a foam wall, the foam wall is preferably a monolithic polymeric foam, e.g., formed from the extrusion of a single extrudate.

[0092] A foam wall can advantageously provide an improved level of thermal insulation to the internal lumen compared to the level of thermal insulation provided by a non-foam wall. Thus, in at least one embodiment, the wall thermally insulates the contents of the elongated conduit (e.g., humidified gas flowing through the gas flow passage, etc.) from the potentially cooling effects of the environment surrounding the medical tube (e.g., isolated from ambient air surrounding a breathing circuit, or a laparoscopic insufflation system). The environment surrounding the medical tube is, for example, a hospital room or room, an operating room, a home bedroom, or other location where a patient can be located.

[0093] In various embodiments, the foam wall has or provides a thermal conductivity of 0.2 W / m-K to 0.4 W / m-K (or about 0.2 W / m-K to 0.4 W / m-K). However, it should be appreciated that the foam wall can beneficially achieve other levels of thermal conductivity, and thermal conductivities of 0.15 W / m-K to 0.35 W / m-K (or about 0.15 to 0.35 W / m-K) or 0.25 W / m-K to 0.45 W / m-K (W / m-K) are also contemplated.

[0094] An example method for forming the foam wall includes adding a chemical blowing agent to the extrudate. The chemical blowing agent is sometimes also referred to as a blowing agent. The chemical blowing agent enables foaming of the extrudate material as part of the extrusion process or to enable foaming of the extrudate material after the extrusion process, which is described in more detail below. The chemical blowing agent can 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) percent by weight of the total extrudate. For example, the chemical blowing agent can include 0.01 to 0.012 (or about 0.01 to 0.012) percent by weight of the total extrudate. As part of the chemical blowing extrusion process, the polymeric components of the extrudate are mixed with the chemical blowing agent. Some preferred chemical blowing agents include calcium oxide. For example, MHYNA-CF20E, supplied by Clariant (New Zealand) Limited under the product name Hydrocerol CF20E, is a chemical blowing agent in the form of a blowing agent masterbatch having about 0.5-1% calcium oxide as the active ingredient.

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

[0096] It should also be appreciated that other foaming techniques can be used to form the foam wall, such as by physical rather than chemical blowing methods. Physical blowing methods include directly introducing a gas into the extrudate while under pressure. As the extrudate is extruded, the pressure decreases, causing the gas to expand. For example, one such physical blowing technique includes foaming or injecting a gas into the extrudate at or near the point of extrusion. Such a gas can include nitrogen, carbon dioxide, pentane, or butane.

[0097] Sheath

[0098] In certain embodiments, the elongate conduit 203 can further include a sheath 227, as Figure 2CA sheath 227 is a member that partially or completely surrounds the wall 211. The sheath 225 can be affixed to the wall 211 of the conduit 203 at a location along the wall 211 or can be affixed only to the end of the tube 201. The sheath 227 can serve to secure conductive filaments (described below) in place and / or to prevent heat loss due to the impingement of cold air flow on the tube wall 211.

[0099] While the sheath 227 can be incorporated into a conduit 203 that includes a smooth wall (not shown) or a corrugated wall 211, it can be particularly advantageous to incorporate this sheath 227 with a corrugated wall. The sheath can trap air between adjacent outer peaks (or annular protrusions) of the corrugations. This can help to further isolate the gas passing through the lumen 209.

[0100] For a delivery tube incorporating a sheath 227, the sheath 227 can be applied around the wall 211 as an extruded outer layer, as a wrapping material around the wall 211, or as a bushing that is slid or pulled into place around the wall 211. This sheath 227 can be formed of a similar material as the wall 211 (described above), such as LLDPE. The sheath 227 can help to further improve the thermal performance of the tube 201.

[0101] The sheath 227 can have any necessary thickness, but the thickness and the material used should be balanced with the need to maintain the flexibility of the conduit 203. In one embodiment, it is contemplated that the sheath 227 can have an average wall thickness of 100 microns (or about 100 microns).

[0102] However, the average thickness per unit length, the average mass per unit length, the average volume per unit length, or the flexural modulus can vary on a macroscopic level along the length of the sheath 227. In some embodiments, a property measurement can be greater at one region of the sheath 227 proximate one end of the tube 201 than at a region of the sheath 227 proximate the other end. In other embodiments, a property measurement can vary gradually along the length of the sheath 227. In other embodiments, a property measurement can have a distinct transition moving along the length of the sheath 227. In certain embodiments, a measurement or property can be greater at a region proximate one end of the tube 201 than in a region at a middle length portion of the tube 201, and can be greater at a region proximate the other end of the tube 201 than at a region at a middle portion of the tube 201.

[0103] For example, the outer jacket 227 can be thicker at the humidifier end of the tube 201 in order to better insulate the tube 201 and prevent heat loss where most condensation is likely to occur. The thicker jacket 227 at the humidifier end can also increase the stiffness of the tube 201 so that it maintains a more upright position over a greater distance before bending towards horizontal, thereby increasing the length of the return flow (not shown). In this way, more condensation returns to the humidifier (not shown) rather than into the breathing tube 201. The thinner jacket 227 at the patient end can increase flexibility and reduce mass to improve user comfort.

[0104] When the jacket 227 is extruded around the wall 211, for example, this extrusion can be a continuous step of the initial extrusion of the wall 211, that is, a post-formation extrusion step of the wall 211. Furthermore, when the outer jacket 227 is, for example, a wrap around the wall 211, the jacket 227 is constructed in place by a band or ribbon that is wound in a helical manner around the length of the wall 211. Still further, when the outer jacket 227 is preformed as a hollow tube, it can be slipped in place around the outside of the wall 211.

[0105] Conductive filaments

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

[0107] The filaments can, for example, take the form of wires or ribbons on or in the wall of the conduit. Figure 6 An example placement of the heater wire 601 within the inner lumen 209 of the tube 201 is illustrated. Although the filaments can be within the inner lumen 209, it can also be desirable to move the filaments out of the airflow path. For example, the filaments can be placed on or inside the wall diametrically opposite the inner lumen. Figure 7 Placement of the heater wire 601 around the outer surface of the wall 211 is illustrated. Such placement can reduce the risk of ignition in the oxygen-enriched airflow and also improve stratified airflow.

[0108] The material of such filaments is a conductive metal including copper or aluminum, or a PTC (positive temperature coefficient) type of material. Aluminum is less conductive than copper, but can be an economical choice, only with a larger wire diameter at the same electrical resistance. Although the applied circuit voltage is intrinsically safe (less than 50 V), in order to be resistant to corrosion and electrically safe in case of damage to the wall or jacket, the wire will desirably be self-insulated either by a vitreous enamel coating, or by anodization in the case of aluminum.

[0109] In certain embodiments, a filament can be placed on the outer surface of the wall 211 (radially outward from the lumen 209), and a plastic sheath 227 can be installed around the filament. In this configuration, the sheath 227 can help to keep the filament in place. In addition, a sheath can also be included when the filament is placed in the lumen 209 or in the wall 211. As explained above, the isolation of the outer sheath 227 prevents heat loss. However, the outer sheath 227 can be employed regardless of whether the filament is also included.

[0110] Comparison with uniform stiffness tubes

[0111] Figure 8 Condensate accumulation in uniform stiffness tubes was compared with condensate accumulation in variable stiffness tubes. In this experiment, three uniform stiffness tubes and one variable stiffness tube were connected in a circuit with a source of humidified gas and placed in a test chamber with a flow of cold air, simulating a typical hospital ward with conditioned air flowing through the circuit. Condensate accumulated over a 16 hour period was collected and weighed. The results indicated that increasing the mass of the wall in a uniform thickness tube from 50 g / m to 63 g / m to 74 g / m reduced condensate accumulation. A variable stiffness tube made with three sections having 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 condensate than the 74 g / m tube.

[0112] One explanation for the unexpected performance improvement of the variable stiffness tube over the stiffest uniform thickness tube can be the interaction with the humidifier that acts as the source of humidified gas. The MR850 humidifier, manufactured by Fisher & Paykel Healthcare Limited in Auckland, New Zealand, detects the patient end temperature and controls the heater plate under the chamber and the heating filament in the tube. The algorithm used by the humidifier includes putting the gas into the tube fully saturated at 37°C, 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 thin wall at the patient end, the temperature is lower at the patient end than it is at the patient end of the 74 g / m uniform wall tube. Therefore, the control algorithm of the humidifier puts more power into the heater plate and heating filament with the variable stiffness sample, resulting in less condensation at the humidifier end of the tube.

[0113] Components in a medical circuit

[0114] Reference will now be made Figure 9FIG. 1 illustrates an example medical circuit, according to at least one embodiment. The circuit includes a variable stiffness tube for the inspiratory tube 103 as described above. The properties of the inspiratory tube 103 are similar to the tube described above. The inspiratory tube 103 has an inlet 109 in communication with the source of humidified gases 115, and an outlet 113 through which humidified gases are provided to the patient 101. As described above, a heater wire 601 can be placed within the inspiratory tube 103 to reduce the risk of condensation rain in the tube by maintaining the tube wall temperature above the dew point temperature.

[0115] In Figure 9 addition, an expiratory tube 117 is provided. The expiratory tube 117 also has an inlet 109 that receives exhaled humidified gases from the patient, and an outlet 113. As described above with respect to Figure 1 the inspiratory tube 103, the outlet 113 of the expiratory tube 117 can exhaust the exhaled gases to the atmosphere, to the ventilator / blower unit 115, to an air washer / filter (not shown), or to any other suitable location.

[0116] However, the expiratory tube is optional. The inspiratory tube 103 according to the embodiments described above can be used with other forms of respiratory support, for example, with a standalone blower humidifier that does not have an expiratory return path. Examples of such products include the humidified CPAP delivery products and COPD therapy products of Fisher & Paykel Healthcare Limited of Auckland, New Zealand. In these systems, a combined blower / humidifier supplies humidified gases to a connected delivery tube. The delivery tube supplies these gases to a patient interface on a patient end connected to the delivery tube. The patient interface is typically a full face mask for CPAP therapy, a nasal mask, a nasal pillows, a nasal cannula or a tracheal connector for intubated patients for COPD therapy, where the device can be used to assist in the transition to full ventilation.

[0117] Components of a insufflation system

[0118] Laparoscopic surgery, also known as minimally invasive surgery (MIS) or keyhole surgery, is a modern surgical technique where operations are performed through small incisions (usually 0.5 to 1.5 cm) as opposed to the large incisions required in traditional surgical procedures. Laparoscopic surgery involves operations inside the abdominal or pelvic cavities. During laparoscopic surgery with insufflation, it can be desirable for the insufflation gas (typically C02) to be humidified before being delivered into the abdominal cavity. This can help to prevent "dehydration" of the patient's internal organs, and can reduce the amount of time required for post-operative recovery. An insufflation system generally includes a plurality of humidifier chambers that hold a quantity of water inside. The humidifier generally includes a heater plate that heats the water to produce water vapour that is transferred into incoming gases to humidify the gases. The gases with water vapour are delivered out of 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 catheter, the sheath, or both of the delivery tube can be manufactured according to a number of processes adapted to provide a variation in stiffness in the tube. The catheter and sheath can be formed by the same manufacturing method, or by different manufacturing methods. In some manufacturing methods, the tube and sheath can be integrated during the manufacturing method, such that the sheath is connected to the catheter at a number of locations along the length of the tube or along one continuous spiral along the length of the tube. Alternatively, the sheath can be free to surround the catheter and only connect the catheter at or adjacent to the end connectors.

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

[0126] Reference is made to Figure 11 A first manufacturing method is described. The method includes extruding an elongate catheter having a longitudinal axis, an inner lumen extending along the longitudinal axis, and a wall surrounding the inner lumen, wherein the wall is stiffer in a first length of the catheter than in a second length of the catheter. The method can further include corrugating the elongate catheter, for example with a corrugation forming die. More specifically, the process involves mixing or providing a masterbatch of extrudate material (i.e., the material for extrusion), feeding the masterbatch into an extrusion die, extruding the extrudate as described above, and feeding the elongate catheter into a corrugator to form a corrugated tube using a endless chain of die blocks (optionally).

[0127] Figure 11 A setup is generally illustrated, in which a hopper 1101 is provided for receiving raw ingredients or materials (e.g., a masterbatch and other materials), which will be passed through a screw feeder 1103 driven by a motor 1105 in a direction A towards a die 1107. A molten tube 1109 is extruded from the die 1111. Conductive filaments can optionally be co-extruded on or in the molten tube 1109. The method can further include one or more spiral extrusion processes that gradually add layers of material to produce portions of different stiffness along the tube. Such spiral extrusion processes are described in more detail below.

[0128] It has been found that extruders, such as Welex extruders equipped with 30-40 mm diameter screws and typically having 0.5-1.0 mm gaps, 12-16 mm annular dies, are suitable for rapid production of low cost tubes. Similar extrusion machines are provided by Kuhne (Germany), AXON AB Plastic Machinery (Sweden), AMUT (Italy), and Battenfeld (Germany and China). It has been found that, for example, by using a 30 mm diameter screw with a 0.5 mm gap, a 12 mm diameter tube can be produced at a rate of 1.5 kg / hr, which is a rate of 0.5 kg / min. The tube can be produced at a rate of 0.5 kg / min, which is a rate of 1.5 kg / hr. Corrugated sheet rolling machines such as those manufactured and supplied by Hoesch-Fortuna (Germany) are suitable for the corrugation step. Similar machines are provided by OLMAS (Carate Brianza, Italy), Qingdao HUASU Machinery Manufacturing Co., Ltd. (Qingdao, China), or Top Industrial (Chengdu) Co., Ltd. (Chengdu, China).

[0129] During manufacture, the molten tube 1109 is transferred between a series of rotating dies / blocks on a corrugated sheet rolling machine after exiting the extruder die 1111 and formed into a corrugated tube. The molten tube is formed by vacuum applied to the outside of the tube via slots and channels through the blocks and / or pressure applied to the inside of the tube via an air channel through the center of the extruder die core rod. If internal pressure is applied, a specially shaped long internal rod can be needed to extend from the die core rod and closely conform to the inside of the corrugations to prevent air pressure from escaping at both ends along the tube. The corrugated sheet rolling machine speed can be varied to obtain different wall thicknesses. Slower corrugated sheet rolling machine speeds give thicker walls, and faster speeds give thinner walls.

[0130] The tube can also include a flat collar region for connection to an end connector fitting. Thus, during manufacture, a molded plastic end connector fitting can be made permanently fixed and / or airtight by friction fit, adhesive bond, overmolding, or by heat or ultrasonic welding.

[0131] Another suitable method for manufacturing a tube according to the embodiments described herein involves spiral forming, as shown in Figure 12 Generally, the method includes extruding a strip of tape, where a first length of the tape is stiffer than a second length of the tape; winding the extruded tape in a spiral manner around a mandrel such that adjacent turns of the extruded tape touch or overlap, thereby forming an elongated conduit having a longitudinal axis, an internal lumen extending along the longitudinal axis, and a wall surrounding the internal lumen, where the wall is stiffer in the first length of the conduit than in the second length of the conduit. The method can also include optionally 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 in a spiral such that, within each turn, one edge of the tape overlaps the edge of the previous turn and underlaps the edge of the subsequent turn. Such a conduit wound in a spiral can be made with a single spirally disposed tape or with multiple spirally disposed tapes interleaved. In certain embodiments, a strip of reinforcement overlies the overlaps between turns of the tape. The strip can provide a spiral reinforcement against crushing for the tube and can also provide a source of heat, chemical or mechanical adhesive for fusing or joining the overlapped portions of the tape. In some instances, a double-walled conduit can be constructed by placing additional tape, or portions of the same tape, on the outside and supported on the spiral ridges formed by the strip.

[0134] In this method, the stiffness of the tube depends on the stiffness of the tape, and the stiffness of the tube can be adjusted by varying the thickness, mass, volume, flexural modulus, etc. of the tape. A tube with a variable wall thickness along the length of the tube can be constructed according to this process by varying the thickness of the tape such that, for example, in a first region the tape can have a greater thickness than in another region, where the thickness can be slightly thinner, and in a second region the thickness can be thinner.

[0135] Another suitable method for spiral forming includes extruding a tape having a generally uniform stiffness; winding the extruded tape in a spiral 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 stiffer in a first length of the conduit than in a second length of the conduit. The method can include corrugating the elongated conduit to provide a conduit having a variable stiffness wall. For example, the corrugator speed can be varied to obtain different wall thicknesses. A slower corrugator speed gives a thicker wall, and a faster speed gives a thinner wall.

[0136] Figure 12 Extruded molten tube 1201 exiting the die 1203 of the extruder prior to passing into the corrugator 1205 is shown in FIG. 12B. After exiting the corrugator 1205, heater wires 601 are wound around the outside of the formed tubular member 201.

[0137] The above references Figure 12One advantage of the described preferred type of pipe manufacture is that some of the die blocks B can include end collar features that are simultaneously formed as part of the tubular member 201. Manufacturing speed can be significantly increased by the reduction in complexity and elimination of secondary manufacturing processes. While this method is an improvement over separate collar forming processes, the disadvantage of prior art flat collars is that the corrugator mill must slow down to increase the wall thickness of the pipe in this area (the extruder continues at the same speed). The increased collar thickness is to achieve increased hoop strength and sealing properties with the collar adapter fittings. Additionally, the heat of the molten polymer in this thicker area is difficult to remove during the limited contact time with the corrugator mill blocks and this becomes a significant limiting factor on the maximum operating speed of the pipe production line.

[0138] The foregoing description of the application has included the preferred form of variou s embodiments. Modifications can be made to this general description as well as to the sub- claims below. Such modifications are not to be regarded as a departure from the scope of the application, but as included within the present application: The application relates to all that fall within the scope of the claims below. The disclosure and description are only illustrative. Changes can be made in the matter within the scope of the application.

Claims

1. A medical tube for providing humidified gas to a patient, comprising: an elongate conduit having a first opening as a humidified gas inlet for receiving humidified gas, a second opening as a humidified gas outlet for discharging humidified gas, a longitudinal axis, a lumen 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 lumen, wherein the conduit wall is stiffer adjacent the first opening than adjacent the second opening; wherein the conduit wall adjacent the first opening is configured to extend vertically upward from a source of humidified gas, and the conduit wall adjacent the first opening is capable of defining a backflow length.

2. The medical tube of claim 1, further comprising one or more conductive filaments in or on the conduit.

3. The medical tube of claim 2, wherein, At least one of the one or more conductive filaments is a heating filament.

4. The medical tube of claim 2, wherein, At least one of the one or more conductive filaments is a sensing wire.

5. The medical tube of claim 1, wherein, The conduit is generally cylindrical.

6. The medical tube of claim 1, wherein, The conduit wall is corrugated.

7. The medical tube of claim 1, wherein, The extruded material is a foam.

8. The medical tube of claim 7, wherein, The foam is a closed cell foam.

9. The medical tube of claim 1, wherein, The extruded material includes one or more surface modifiers.

10. The medical tube of claim 1, wherein, The conduit wall has an average contact angle of less than 50 degrees.

11. The medical tube of claim 1, wherein, The thickness of the conduit wall adjacent the first opening is between 0.5 mm and 2.0 mm, and the thickness of the conduit wall adjacent the second opening is between 0.1 mm and 1.0 mm.

12. The medical tube of claim 1, wherein, The mass of the conduit wall adjacent the first opening is between 50 g / m and 110 g / m, and the mass of the conduit wall adjacent the second opening is between 20 g / m and 50 g / m.

13. The medical tube of claim 1, wherein, The volume of the conduit wall adjacent the first opening is between 1.0 cm 3 / m and 2.0 cm 3 / m, and the volume of the conduit wall adjacent the second opening is between 0.2 cm 3 / m and 1.0 cm 3 / m.

14. The medical tube of claim 1, wherein, The ratio of the flexural modulus of the conduit wall adjacent the first opening to the flexural modulus of the conduit wall adjacent the second opening is between 10: 1 and 250:

1.

15. The medical tube of claim 1, wherein, The stiffness of the conduit wall in a middle region of the conduit between the first and second openings is intermediate the stiffness of the conduit wall adjacent the first opening and the stiffness of the conduit wall adjacent the second opening.

16. The medical tube of claim 1, further comprising a sheath surrounding at least a portion of an outer surface of the elongate conduit.

17. The medical tube of claim 16, wherein, The sheath includes an extruded material extruded around at least a portion of the outer surface of the elongate conduit.

18. The medical tube of claim 16, wherein, The sheath includes a material wound generally in a helical manner around at least a portion of the outer surface of the elongate conduit.

19. The medical tube of claim 16, wherein, The sheath includes a sleeve material sleeved around at least a portion of the outer surface of the elongate conduit.

20. The medical tube of claim 16, wherein, The sheath includes a sheath wall having a generally constant stiffness.

21. The medical tube of claim 1, wherein, The average conduit wall thickness is about 100 microns.

22. A breathing circuit comprising the medical tube of any one of claims 1 to 21.

23. A blower system comprising the medical tube of any one of claims 1 to 21.

24. A heated breathing tube, comprising: a single corrugated extruded conduit including a proximal patient end and a distal chamber end; one or more heating elements on or in the conduit; and a conduit wall; wherein the conduit wall has a first stiffness adjacent the chamber end, the conduit wall has a second stiffness adjacent the patient end, the first stiffness is greater than the second stiffness; wherein the conduit wall adjacent the chamber end is configured to extend vertically upward from a source of humidified gas, and the conduit wall adjacent the chamber end is capable of defining a backflow length. ​ 25. The breathing tube of claim 24, wherein, The conduit wall has a thickness of between 0.5 mm and 2.0 mm proximate the chamber end and between 0.1 mm and 1.0 mm proximate the patient end.

26. The breathing tube of claim 24, wherein, The ratio of the flexural modulus of the conduit wall proximate the chamber end to the flexural modulus proximate the patient end is between 10:1 and 250:

1.

27. The breathing tube of claim 24, wherein, The conduit is generally cylindrical.

28. The breathing tube of claim 24, wherein, The extruded conduit comprises a polymer foam.

29. The breathing tube of claim 28, wherein, The polymer foam is a closed cell foam.

30. The breathing tube of claim 24, wherein, The extruded conduit comprises one or more surface modifiers.

31. The breathing tube of claim 24, wherein, The conduit wall has a contact angle of less than 50 degrees.

32. The breathing tube of claim 24, wherein, The chamber end of the breathing tube is configured to define a backflow length of between 350 mm and 400 mm.

33. The breathing tube of claim 24, wherein, The mass of the conduit wall proximate the chamber end is between 50 g / m and 110 g / m and the mass of the conduit wall proximate the patient end is between 20 g / m and 50 g / m.

34. The breathing tube of claim 24, wherein, The volume of the conduit wall adjacent the chamber end is between 1.0 cm 3 / m and 2.0 cm 3 / m, and the volume of the conduit wall adjacent the patient end is between 0.2 cm 3 / m and 1.0 cm 3 / m.

35. The breathing tube of claim 24, wherein, The conduit has an intermediate region between the chamber end and the patient end and the conduit stiffness in the intermediate region is intermediate the conduit wall stiffness proximate the chamber end and the conduit wall stiffness proximate the patient end.

36. The breathing tube of claim 24, further comprising a sheath surrounding at least a portion of the outer surface of the conduit.

37. The breathing tube of claim 36, wherein, The sheath comprises an extruded material extruded around at least a portion of the outer surface of the conduit.

38. The breathing tube of claim 36, wherein, The sheath comprises a material wound generally in a helical manner around at least a portion of the outer surface of the conduit.

39. The breathing tube of claim 36, wherein, The sheath comprises a sleeve material sleeved around at least a portion of the outer surface of the conduit.

40. The breathing tube of claim 36, wherein, The sheath comprises a sheath wall having a generally constant stiffness.

41. The breathing tube of claim 36, wherein, The sheath comprises a sheath wall that is stiffer in a first region of the sheath than in a second region of the sheath.

42. The breathing tube of claim 41, wherein, The sheath wall is stiffer proximate the chamber end of the conduit than proximate the patient end of the conduit.

43. The breathing tube of claim 41, wherein, The sheath wall is stiffer proximate the patient end of the conduit than proximate the chamber end of the conduit.

44. The breathing tube of claim 41, wherein, The sheath wall is stiffer proximate the chamber end and the patient end of the conduit than in the intermediate region of the conduit.

45. The breathing tube of claim 24, wherein, The average wall thickness is about 100 microns.

46. A breathing circuit comprising the heated breathing tube of any one of claims 24-45.

47. A humidification system, the humidification system comprising: a humidifier configured to provide a source of humidified gas; a medical tube for providing the humidified gas to a patient, the medical tube comprising: an elongate conduit having a first opening as a humidified gas inlet for receiving the humidified gas from the humidifier, a second opening as a humidified gas outlet for expelling the humidified gas, a longitudinal axis, an internal lumen extending along the longitudinal axis between the first opening and the second opening, and a conduit wall extending between the first opening and the second opening and surrounding the internal lumen; wherein the conduit wall comprises a stiffened region proximate the first opening; wherein the medical tube is connected to the humidifier, the conduit wall proximate the first opening is configured to extend upwardly from the source of humidified gas so as to be able to define a backflow length, the backflow length being configured to cause any condensate formed to backflow to the humidifier.

48. The humidification system of claim 47, wherein, The backflow length is between 350 mm and 400 mm.

49. A medical tube for providing a humidified gas to a patient, comprising: an elongate conduit; a first opening sized and shaped to be connected to a source of humidified gas; a second opening configured to be connected to a patient interface; an internal lumen extending along a longitudinal axis of the medical tube between the first opening and the second opening; the wall, extending between the first opening and the second opening; wherein the conduit first region adjacent the first opening is stiffer than the conduit second region adjacent the second opening; wherein the conduit wall adjacent the first opening is configured to extend vertically upward from the source of humidified gas, and the conduit wall adjacent the first opening is capable of defining a backflow length.

50. The medical tube of claim 49, further comprising one or more conductive filaments.

51. The medical tube of claim 50, wherein, The conductive filaments are within the lumen, disposed on an exterior of the wall, or embedded in the wall.

52. The medical tube of claim 50 or 51, wherein, At least one of the one or more conductive filaments is a heating filament.

53. The medical tube of claim 50 or 51, wherein, At least one of the one or more conductive filaments is a sensing wire.

54. The medical tube of claim 49, further comprising a sheath surrounding at least a portion of an outer surface of the elongate conduit.

55. The medical tube of claim 54, wherein, The sheath comprises a jacket material that sheaths at least a portion of the outer surface of the elongate conduit.

56. The medical tube of claim 54 or 55, wherein, The sheath comprises a sheath wall having a generally constant stiffness.

57. The medical tube of claim 54 or 55, wherein, The sheath comprises a sheath wall that is stiffer in a sheath first region adjacent the first opening than in a sheath second region adjacent the second opening.

58. The medical tube of claim 49, wherein, The elongate conduit is formed from an extruded tape, the reinforcing strip being wrapped in a helical manner between adjacent turns of the extruded tape.

59. The medical tube of claim 58, wherein, The reinforcing strip comprises one or more conductive filaments.

60. The medical tube of claim 49, wherein, The wall has a smooth profile.

61. The medical tube of claim 49, wherein, The medical tube has a length between 1.0 m and 3.0 m.

62. The medical tube of claim 49, wherein, The medical tube has a length between 1.0 m and 2.0 m.

63. The medical tube of claim 49, wherein, The medical tube has a length of about 1.8 m.

64. The medical tube of claim 49, wherein, The lumen has a diameter between 10 mm and 30 mm.

65. The medical tube of claim 49, wherein, The wall has a greater modulus of flexure adjacent the first opening than adjacent the second opening.

66. The medical tube of claim 49, wherein, The second opening is configured to be connected to a connection port that facilitates connection to a patient interface.

67. The medical tube of claim 49, wherein, The wall is formed from an extrudate comprising one or more polymers.

68. The medical tube of claim 67, wherein, The wall is formed from one or more polymers selected from linear low density polyethylene (LLDPE), low density polyethylene (LDPE), polypropylene (PP), polyolefin plastic (POP), ethylene vinyl acetate (EVA), plasticized polyvinyl chloride (PVC), a blend of two or more of these materials.

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