WO2012077052A1

WO2012077052A1 - Proximal humidifier comprising hydrophobic membrane

Info

Publication number: WO2012077052A1
Application number: PCT/IB2011/055493
Authority: WO
Inventors: Mabini Arcilla
Original assignee: Koninklijke Philips Electronics N.V.
Priority date: 2010-12-08
Filing date: 2011-12-06
Publication date: 2012-06-14

Abstract

A humidifier (105) for use in a patient ventilation circuit comprises: an inlet (201) configured to receive a gas from a ventilator (101); an outlet (202) configured to provide a humidified gas to a patient; a chamber (203) disposed between the inlet (201) and the outlet (202); a reservoir (204) substantially surrounding the chamber (203) and configured to hold a liquid (205); and a hydrophobic membrane (208) disposed between the reservoir (204) and the chamber (203). Vapor (209) of the liquid passes through the hydrophobic membrane (208) and into the chamber (203).

Description

PROXIMAL HUMIDIFIER COMPRISING HYDROPHOBIC MEMBRANE

BACKGROUND

[0001] The upper airway normally warms and humidifies inspired air during normal breathing. Often, a patient requires ventilation that is either invasive or noninvasive. During invasive ventilation, the air no longer passes through the laryngeal, nasal and pharyngeal cavities but passes directly into the bronchi. Invasive ventilation normally involves the use of an endotracheal tube that bypasses the upper airway and so the upper airway cannot contribute to heating and

humidification of the gases delivered to the patient. This may lead to bronchial inflammation, damage to respiratory epithelium and ciliary cells, and endotracheal tube occlusions due to secretions. During noninvasive ventilation, the nasal mucosa may not be able to adequately warm and humidify the inspired gas. This can lead to thick mucus with an increase in airway resistance and reduced lung compliance.

[0002] Humidifiers may be used to add moisture to the air delivered to a patient on an invasive ventilator or a

noninvasive ventilator. Generally, there are two types of humidifiers, passive humidifiers and heated humidifiers.

Passive humidifiers comprise heat and moisture exchangers (HME) . The humidity of an HME is maintained by the air exhaled by the patient, and normally no water source or heating elements are used. While comparatively inexpensive, known passive humidifiers are not able to reliably maintain suitable temperature and humidity for high flow of inspired gas .

[0003] Known heated humidifiers comprise a heating plate that heats and evaporates water in the path of gas flow. However, known heated humidifiers are located comparatively far away from the endotracheal tube or mask, and the heated and

humidified gas cools down in the tubing in the patient circuit as it is delivered to the patient. Depending on the ambient temperature, the dew point is reached and there is

condensation or "rain-out" in the tubing. This condensation can result in bacterial growth and a reduced humidity level in the air delivered to the patient.

[0004] To prevent condensation in the tubing, known heated humidifiers incorporate a heated wire along the patient circuit. The heated wire reduces the condensation of water within the tubing along the patient circuit. However, heated wires can increase the temperature of the gas and ultimately reduce the humidity of the gas delivered to the patient.

[0005] What is needed is a humidifier that overcomes at least the shortcomings of known humidifiers discussed above.

SUMMARY

[0006] In a representative embodiment, a humidifier for use in a patient ventilation circuit comprises an inlet configured to receive a gas from a ventilator; an outlet configured to provide a humidified gas to a patient; a chamber disposed between the inlet and the outlet; a reservoir disposed about the chamber and configured to hold a liquid; and a hydrophobic membrane disposed between the reservoir and the chamber. Vapor of the liquid passes through the hydrophobic membrane and into the chamber.

[0007] In another representative embodiment, a ventilation system comprises a ventilator; a patient circuit comprising an inspiration tube and a respiration tube; and a humidifier connected to the patient circuit. The humidifier comprises an inlet configured to receive a gas from a ventilator; an outlet configured to provide a humidified gas to a patient; a chamber disposed between the inlet and the outlet; a reservoir

disposed about the chamber and configured to hold a liquid; and a hydrophobic membrane disposed between the reservoir and the chamber. Vapor of the liquid passes through the

hydrophobic membrane and into the chamber.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008] The representative embodiments are best understood from the following detailed description when read with the

accompanying drawing figures. The dimensions of features in the drawing figures may be arbitrarily increased or decreased for clarity of discussion. Wherever applicable and practical, like reference numerals refer to like elements.

[0009] FIG. 1 is a simplified schematic diagram of a

ventilation system in accordance with a representative

embodiment .

[0010] FIG. 2 is a simplified cross-sectional view of a humidifier in accordance with a representative embodiment.

[0011] FIG. 3 is a perspective view of a humidifier in accordance with a representative embodiment.

[0012] Fig. 4 is a cross-sectional view of a humidifier in accordance with a representative embodiment.

DETAILED DESCRIPTION

[0013] In the following detailed description, for purposes of explanation and not limitation, representative embodiments disclosing specific details are set forth in order to provide a thorough understanding of embodiments according to the present teachings. However, it will be apparent to one having had the benefit of the present disclosure that other embodiments according to the present teachings that depart from the specific details disclosed herein remain within the scope of the appended claims. Moreover, descriptions of well- known devices and methods may be omitted so as not to obscure the description of the example embodiments. Such methods and devices are within the scope of the present teachings.

[0014] Unless otherwise noted, when a first device is said to be connected to a second device, this encompasses cases where one or more intermediate devices may be employed to connect the two devices to each other. However, when a first device is said to be directly connected to a second device, this encompasses only cases where the two devices are connected to each other without any intermediate or intervening devices.

[0015] FIG. 1 is a simplified schematic diagram of a

ventilation system 100 in accordance with a representative embodiment. The ventilation system 100 comprises a ventilator 101, which is connected to an inspiration tube 102 and a respiration tube 103. The ventilator 101 is a known device. For example, the ventilator 101 may be one of a variety of ventilators commercially available from Koninklijke Philips Electronics N.V., Eindhoven, The Netherlands. The ventilator 101 comprises hardware and software useful in effecting ventilation of a patient and may include monitors and alarms useful toward that end. Many of the details of the ventilator 101 are not germane to the description of the representative embodiments, and are not discussed herein.

[0016] The inspiration tube 102 and the respiration tube 103 are connected to a Y-branch ("branch") 104 or other suitable inspiratory limb (not shown) . The branch 104 (or other suitable inspiratory limb) is connected directly to a

humidifier 105. The humidifier 105 is also connected directly to a patient interface 106 that is adapted for invasive or non-invasive patient ventilation. For example, the patient interface 106 may comprise an endotracheal tube for invasive patient ventilation, or a mask for non-invasive patient ventilation. As described more fully below, directly

connecting the humidifier 105 of the representative

embodiments to the patient interface 106 and to the branch 104 beneficially allows for the humidification and heating of gas delivered to the patient with minimal condensation in the inspiration tube 102 or the respiration tube 103, and minimal cooling of the gas delivered to the patient. Furthermore, directly connecting the humidifier 105 to the patient

interface 106 and to the branch 104 (or other inspiratory limb) reduces resistance in the flow path of the ventilation system 100 and does not significantly impact the compliance of the ventilation system 100.

[0017] A sensor 107 is optionally provided at the humidifier 105. The sensor 107 may be a temperature sensor, or a

humidity sensor, or both, for determining the temperature and/or humidity of the gas passing through the humidifier 105. Temperature data, or humidity data, or both, can be provided to a humidity controller 108. The humidity controller 108 may be implemented in whole or in part by a processing device, such as a processor or central processing unit (CPU) ,

application specific integrated circuits (ASICs) , field- programmable gate arrays (FPGAs) , or combinations thereof, using software, firmware, hard-wired logic circuits, or combinations thereof. When using a processor or CPU, a memory is included for storing executable software/firmware and/or executable code that enables performance of the various functions of the humidity controller 108. The memory may be any number, type and combination of nonvolatile read only memory (ROM) and volatile random access memory (RAM) , and may store various types of information, such as computer programs and software algorithms executable by the processor or CPU. The memory may include any number, type and combination of tangible computer readable storage media, such as a disk drive, an electrically programmable read-only memory (EPROM) , an electrically erasable and programmable read only memory (EEPROM) , a CD, a DVD, a universal serial bus (USB) drive, and the like.

[0018] Among other functions, the humidity controller 108 is configured to adjust the humidity and the temperature of the gas delivered by the humidifier 105 based on data received from the sensor 107. As described more fully below, the humidity level of the gas from the humidifier 105 is adjusted by controlling the flow of liquid (e.g., water or aqueous solution) to the humidifier 105 and the temperature of the liquid in the humidifier 105. The temperature of the gas in the humidifier 105 may be controlled by controlling a heater (not shown in Fig. 1) that is used to heat liquid in a reservoir (not shown in Fig. 1) of the humidifier 105.

[0019] The ventilation system 100 also comprises an outer reservoir 109 (e.g., a water bag) for holding liquid to be delivered to the humidifier 105. A valve 110 is provided between the outer reservoir 109 and the humidifier 105 to regulate fluid flow as needed. The valve 110 is controlled by the humidity controller 108 to control the flow of liquid to the humidifier 105. In this way, together with control of the heater, the humidity of the air from the humidifier 105 delivered to the patient is controlled. Illustratively, the valve 110 is a so-called "pinch valve." A tube 111 provides liquid (e.g., water or aqueous solution) from the outer reservoir 109 to the humidifier 105.

[0020] It is emphasized that the control by the humidity controller 108 of the fluid flow to the humidifier 105 and the temperature of the air delivered by the humidifier 105 is illustrative. Alternatively, the control of the temperature and humidity at the humidifier 105 may be provided through an integrated controller (not shown) and suitable power supply that are provided in the ventilator 101. Like the humidity controller 108, the integrated controller at the ventilator 101 may be implemented in whole or in part by a processing device, such as a processor or central processing unit (CPU) , application specific integrated circuits (ASICs) , field- programmable gate arrays (FPGAs) , or combinations thereof, using software, firmware, hard-wired logic circuits, or combinations thereof. A memory is also included for storing executable software/firmware and/or executable code that enables performance of the various functions of the integrated controller. Similarly, the integrated controlled is

configured to adjust the humidity and the temperature of the gas delivered by the humidifier 105 based on data received from the sensor 107. As described more fully below, the humidity level of the gas from the humidifier 105 is adjusted by controlling the flow of liquid (e.g., water or aqueous solution) to the humidifier 105 and the temperature of the liquid in the humidifier 105. The temperature of the gas in the humidifier 105 may be controlled by controlling a heater (not shown in Fig. 1) that is used to heat liquid in a

reservoir (not shown in Fig. 1) of the humidifier 105.

[0021] FIG. 2 is a simplified cross-sectional view of

humidifier 105 in accordance with a representative embodiment. The humidifier 105 comprises an inlet 201, an outlet 202 and a chamber 203 disposed between the inlet 201 and the outlet 202. The inlet 201 is connected directly to the branch 104 (or other suitable inspiratory limb) , and the outlet 202 is connected directly to the patient interface 106. As described more fully herein, gas (e.g., oxygen) is provided at the inlet 201, and flows through the chamber 203 where it is heated and humidified before exiting the outlet 202. The heated and humidified gas from the outlet 202 is provided to the patient (not shown) in an invasive manner (e.g., through an

endotracheal tube) or in a non-invasive manner (e.g., through a mask) .

[0022] The humidifier 105 comprises a reservoir 204 configured to hold a liquid (e.g., water or aqueous solution) 205. The liquid 205 is provided through an inlet 206, which is

connected to another reservoir (e.g., outer reservoir 109). The pressure of the liquid 205 is maintained above the

pressure in the chamber 203, illustratively by a gravity feed or a pump (not shown) . The reservoir 204 substantially surrounds the chamber 203. In a representative embodiment, the chamber 203 is substantially cylindrical and the reservoir 204 is disposed annularly around the chamber 203. It is emphasized that the cylindrical shape of the chamber 203 and the surrounding reservoir 204 is merely illustrative and that other geometrical configurations are contemplated. For example, the chamber 203 may be of elliptical cross-section with the reservoir 204 of similar shape surrounding the chamber 203. Furthermore, the shape of the chamber 203 and the shape of the reservoir 204 do not have to be the same so long as the reservoir 204 substantially surrounds the chamber 203 to effect delivery of heated and humidified gas to the chamber 203 in a manner described below.

[0023] In a representative embodiment, the reservoir 204 is made of a thermally conductive material such as aluminum or copper. As should be appreciated by one of ordinary skill in the art, copper provides beneficial bacteria resistant properties. A heater 207 is provided in a contacting manner with the reservoir 204 and may surround the reservoir 204.

The heater 207 may cover but does not necessarily cover the entire area of the outer surface of the reservoir 204.

Generally, the reservoir 204 is disposed around the chamber 203 and the heater 207 is disposed around the reservoir 204. For example, in accordance with a representative embodiment, the reservoir 204 is substantially cylindrical and the heater 207 is provided concentrically around the outer cylindrical surface of the reservoir 204.

[0024] The heater 207 is illustratively a ceramic heater such as a piezo ceramic heating element, known to one of ordinary skill in the art. Alternatively, the heater 207 may be an insulated etched foil heater or insulated wound wire heater. Generally, the heater 207 may be any suitable mechanically flexible heating element. The heater 207 provides a

comparatively large heating surface and the volume of liquid 205 in the reservoir 204 is comparatively small. As such, the humidifier 105 beneficially has a comparatively fast response rate .

[0025] The heater 207 is selected to heat the liquid 205 in the reservoir 204 to a temperature approaching its boiling point. The heater 207 is connected to an electrical source (not shown in Fig. 2) and may be controlled by the humidity controller 108. Alternatively, the humidifier 105 may be a stand-alone device and therefore not connected to humidity controller 108. In such an embodiment, a separate power supply is connected to the heater 207 to provide power to the heater 207. Still alternatively, the control of the

temperature and humidity at the humidifier 105 may be provided through an integrated controller at the ventilator 101.

[0026] The humidifier 105 comprises a hydrophobic membrane 208 disposed between the reservoir 204 and the chamber 203. In a representative embodiment, the chamber 203, the hydrophobic membrane 208 and the reservoir 204 are co-cylindrical. It is emphasized that this is merely illustrative, and the cross- sectional shape of the humidifier 105 may be other than circular. More generally, the hydrophobic membrane 208 substantially surrounds the chamber 203, and the reservoir 204 substantially surrounds the hydrophobic membrane 208.

[0027] Liquid 205 is heated in the reservoir 204 by the heater 207. A portion of the liquid near the interface of the hydrophobic membrane 208 and the liquid 205 reaches the vapor phase and is emitted as a gas (vapor) 209 through the

hydrophobic membrane 208. However, the hydrophobic membrane 208 will not allow water (or aqueous solution) in the liquid state to pass and enter the chamber 203. Thus, gas 209 but not liquid 205 traverses the hydrophobic membrane 208 and enters the chamber 203. The gas 209 heats and humidifies the (dry) gas provided at the inlet 201 as it flows through the chamber 203. The humidified air is then delivered to the outlet 202, which is connected directly to the patient

interface 106. Thus, heated and humidified gas is provided to the patient. Moreover, because the outlet 202 of the

humidifier 105 is directly connected to the patient interface 106 (e.g., endotracheal tube or mask), cooling and

condensation due to interaction with the ambient is

beneficially reduced.

[0028] In a representative embodiment, the hydrophobic

membrane 208 comprises polytetrafluoroethylene (PTFE) or other suitable material substance that allows water (or aqueous solution) in the gaseous phase to traverse into the chamber 203, but does not allow water (or other aqueous solution) in the liquid phase to pass into the chamber 203. In certain embodiments, the hydrophobic membrane 208 comprises extended PTFE (ePTFE) , commercially available from W.L. Gore &

Associates, Inc., Elkton, MD, USA, for example. In a

representative embodiment, hydrophobic membrane 208 is a comparatively thin layer of PTFE or ePTFE, having a thickness of approximately 0.002 mm to approximately 0.2mm.

[0029] FIG. 3 is a perspective view of humidifier 105 in accordance with a representative embodiment. The humidifier 105 comprises an outer housing 301 disposed around the

reservoir 204 (not shown in Fig. 3) . In an embodiment, the outer housing 301 forms a co-cylindrical assembly with the reservoir 204, the heater 207, the hydrophobic membrane 208 and the chamber 203 shown in FIG. 2. The outer housing 301 is illustratively plastic or other suitable polymer and provides thermal and electrical insulation to the patient. Again, it is emphasized that the cylindrical shape of the humidifier 105 is merely illustrative and that other cross-sectional shapes (e.g., elliptical) are contemplated.

[0030] Referring to Figs. 1-3, the tube 111 is connected between the outer reservoir 109 and the inlet 206 of the humidifier 105. The tube 111 provides liquid 205 to the reservoir 204 for heating and vaporization to provide gas 209 to the chamber 203. The flow of liquid from the outer

reservoir 109 to the inlet 206 may be controlled by the humidity controller 108 (or other controller) in order to maintain the humidity of air delivered to the patient at a desired level.

[0031] An electrical connection 302 is provided through the outer housing 301. The electrical connection 302 provides power to the heater 207. The electrical connection 302 may also provide signals from sensors (e.g., temperature and humidity sensors) of the humidifier 105 to the humidity controller 108 or to a controller at the ventilator 101. In response to these signals, the humidity controller 108 may adjust the flow of liquid to the reservoir 204, or the degree of heating provided by the heater 207, or both, in order to provide air of suitable temperature and humidity to the patient .

[0032] As noted above, the inlet 201 of the humidifier 105 is directly connected to the branch 104 or other inspiratory limb, and the outlet 202 of the humidifier 105 is connected directly to the patient interface 106. Notably, the

humidifier 105 may be located in an isolette (not shown) in a neonatal intensive care unit (NICU) .

[0033] The direct connection of the humidifier 105 to the branch 104, other inspiratory limb or isolette, and to the patient interface 106 beneficially reduces compliance and resistance along the patient circuit of the ventilation system 100 compared to known humidifiers. To this end, the heated and humidified gas leaving known heated humidifiers cools down in the patient circuit before it is delivered to the patient. Depending on the ambient temperature, the dew point may be reached, resulting in formation of condensation or "rain-out" in the tubing of the patient circuit. This condensation can lead to bacterial growth, and gas of insufficient humidity and temperature can be delivered to the patient. By contrast, the humidifier 105 of the representative embodiments heats and humidifies the gas delivered to the patient proximal to the patient interface 106 and substantially eliminates the problem of condensation in the tubing and therefore the need to use heated-wire circuits in the tubing of the patient circuit.

[0034] The humidifier 105 of the representative embodiments does not substantially add to the resistance or the compliance of the patient circuit. Notably, the use of known passive HME devices adds resistance to the patient circuit and can lead to an increase in the effort to breathe by the patient.

Similarly, known heated humidifiers use a chamber filled with water that introduces additional compliance in the circuit. With minimal addition of resistance, compliance and deadspace in the patient circuit, the humidifier 105 is beneficial in therapies such as neonatal ventilation and high frequency ventilation .

[0035] Fig. 4 is a cross-sectional view of humidifier 105 in accordance with a representative embodiment. Many of the details provided in the description of humidifier 105 in representative embodiments above are common to the description of the present representative embodiment, and thus are not repeated to avoid obscuring the description of the present representative embodiment.

[0036] The humidifier 105 comprises supports 401 disposed circumferentially about the chamber 203. The supports 401 are disposed between the chamber 203 and the hydrophobic membrane 208 and provide structural support to the hydrophobic membrane 208 to prevent "sagging" of the hydrophobic membrane 208 due to the weight of the liquid 205 disposed in the reservoir 204. The supports 401 illustratively comprise a screen or mesh that can be made of metal or a suitable polymer material.

[0037] A sensor 402 is provided in the chamber 203. The sensor 402 comprises one or more of a temperature sensor and a humidity sensor. In a representative embodiment, the sensor 402 is a known capacitive-type humidity sensor that has a temperature sensing capability. Alternatively, the sensor 402 may be a thermocouple sensor with a digital output that can be close loop with the humidity controller 108 to control the humidity level, or the temperature of the gas, or both.

[0038] Data from the sensor 402 are provided to humidity controller 108. Based on these data the humidity controller 108 is configured to adjust the degree of heating of the liquid 205 in the reservoir 204 by the heater 207, and to adjust the flow of liquid from the outer reservoir 109 to the reservoir 204 to maintain the temperature and the humidity of the gas provided at the outlet 202 at desired levels.

[0039] While representative embodiments are disclosed herein, one of ordinary skill in the art appreciates that many variations that are in accordance with the present teachings are possible and remain within the scope of the appended claims. The invention therefore is not to be restricted except within the scope of the appended claims.

Claims

1. A humidifier (105) for use in a patient ventilation circuit, comprising:

an inlet (201) configured to receive a gas from a

ventilator (101);

an outlet (202) configured to provide a humidified gas to a patient;

a chamber (203) disposed between the inlet (201) and the outlet (202);

a reservoir (204) substantially surrounding the chamber

(203) and configured to hold a liquid (205) ; and

a hydrophobic membrane (208) disposed between the

reservoir (204) and the chamber (203), wherein vapor (209) of the liquid (205) passes through the hydrophobic membrane (208) and into the chamber (203) .

2. The humidifier (105) as claimed in claim 1, further comprising a heater (207) in contact with the reservoir (204) and configured to heat the liquid (205) to approximately a boiling point of the liquid.

3. The humidifier (105) as claimed in claim 1, wherein the chamber (203) is substantially cylindrical and the

reservoir (204) is disposed substantially annularly around the chamber (203) .

4. The humidifier (105) as claimed in claim 1, further comprising another (206) inlet connected to the reservoir

(204) and configured to provide the liquid (205) to the reservoir (204) .

5. The humidifier (105) as claimed in claim 1, wherein the hydrophobic membrane comprises polytetrafluorethylene (PTFE) .

6. The humidifier (105) as claimed in claim 1, wherein the inlet (201) is directly connected to a Y-branch (104) of the patient ventilation circuit.

7. The humidifier (105) as claimed in claim 1, wherein the outlet (202) is directly connected to an endotracheal tube .

8. The humidifier (105) as claimed in claim 1, wherein the outlet is directly connected to a respiration mask.

9. The humidifier (105) as claimed in claim 1, further comprising a temperature sensor (402) in contact with the chamber (203) .

10. The humidifier (105) as claimed in claim 1, further comprising a humidity sensor (402) in contact with the chamber (203) .

11. A ventilation system (100), comprising:

a ventilator (101);

a patient circuit comprising an inspiration tube (102) and a respiration tube (103); and

a humidifier (105) connected to the patient circuit, the humidifier (105) comprising:

an inlet (201) configured to receive a gas from a

ventilator (101);

an outlet (202) configured to provide a humidified gas to a patient;

a chamber (203) disposed between the inlet (201) and the outlet (202);

a reservoir (204) substantially surrounding the chamber (203) and configured to hold a liquid (205) ; and

a hydrophobic membrane (208) disposed between the

12. The ventilation system (100) as claimed in claim 11, wherein the humidifier (105) further comprises a heater (207) in contact with the reservoir (204) and configured to heat the liquid (205) to approximately a boiling point of the liquid.

13. The ventilation system (100) as claimed in claim 11, wherein the chamber (203) is substantially cylindrical and the reservoir (204) is disposed substantially annularly about the chamber (204) .

14. The ventilation system (100) as claimed in claim 11, wherein the humidifier (105) further comprises another inlet (206) connected to the reservoir (204) and configured to provide the liquid (205) to the reservoir.

15. The ventilation system (100) as claimed in claim 11, wherein the hydrophobic membrane (208) comprises

polytetrafluorethylene (PTFE) .

16. The ventilation system (100) as claimed in claim 11, wherein the inlet (201) is directly connected to a Y-branch (104) of the patient ventilation circuit.

17. The ventilation system (100) as claimed in claim 11, wherein the outlet (202) is directly connected to an

endotracheal tube.

18. The ventilation system (100) as claimed in claim 11, wherein the outlet (202) is directly connected to a

respiration mask.

19. The ventilation system (100) as claimed in claim 11, wherein the humidifier (105) further comprises a temperature sensor and/or a humidity sensor (402) in contact with the chamber (203) .

20. The ventilation system (100) as claimed in claim 19, further comprising a humidity controller (108) configured to adjust a humidity of the humidified gas.