WO2001002043A1

WO2001002043A1 - Method and apparatus for delivering humidified air to a face mask

Info

Publication number: WO2001002043A1
Application number: PCT/CA2000/000726
Authority: WO
Inventors: C. Bruce Hewson; Benjamin Wiens
Original assignee: J & M Distributors Ltd.
Priority date: 1999-07-01
Filing date: 2000-06-16
Publication date: 2001-01-11
Also published as: AU5383400A; US6435180B1

Abstract

A humidifier (12) comprising: (a) an inlet (32) for receiving a supply of intake air; (b) a first chamber (27) for holding a first volume of said intake air; (c) a second chamber (29) for holding a second volume of said intake air, wherein said second volume of air is passed over the surface of water (31) contained within said second chamber (29); (d) a heather (58) for heating said water and said second volume of air within said second chamber (29); (e) a mixing conduit (84) for receiving and mixing together separate first and second streams of air discharged from said first and second chambers (27, 29) respectively; and (f) an adjustable regulator (96) for regulating the amount of said second stream of air passing into said mixing conduit (84).

Description

METHOD AND APPARATUS FOR DELIVERING HUMIDIFIED AIR TO A FACE MASK

Technical Field

This application relates to a humidifier for delivering a supply of heated, humidified air through an elongated conduit to a mask worn by a patient. The humidifier is designed for use by a patient during sleep to treat chronic breathing disorders such as allergic rhinitis. The relative humidity of the air stream is regulated to ensure that it will not condense to form water droplets within the interior of the conduit.

Background

The air passageways in patients suffering from chronic breathing disorders, such as asthma, rhinitis, bronchitis, sinusitis and the like, are often in a persistent post-traumatically inflamed state. One method of treating such conditions is to supply heated, pollutant-free, humidified air to the patient at night while he or she is sleeping. This enables the patient's air passageways to rest and partially recover from the inflammation. The patient is then able to resume a normal life during waking hours.

Breathing tents surrounding all or a portion of the patient's bed for delivering heated, humidified air to the patient during sleep are well-known in the prior art. However, such tents are not desirable since they often result in overheating of the patient and cause excess perspiration. A more effective means for delivering humidified air to a patient during sleep is through a face mask. Typically, the mask is connected to a bedside humidifier apparatus by an elongate conduit. One problem which has arisen with such devices is the tendency for the humidified air to condense as water vapour within the conduit. The water vapour then drips into the face mask, repeatedly rousing the patient from sleep.

Relative humidity is a percentage expression of the actual water vapour content of a gas as compared to its capacity to carry water at any given temperature. The capacity of a gas to hold water in its vaporous state increases with molecular velocity as the temperature of the gas rises. For example, as the temperature of air drops, its capacity to hold moisture also declines proportionately and hence the relative humidity increases. When the air temperature drops below the dew point, the excess vapour condenses as water droplets. Condensation of water vapour or "condensate rainout" can result from a drop in the temperature of humidified air as it passes through a conduit.

One approach for addressing this problem is to uniformly heat the air tiavelling through the conduit by means of electric wires wound around the conduit and controlled by a temperature sensor. For example, U.S. Patent No. 3,638,926 describes a humidification system wherein the tube interconnecting the humidifier and the patient is heated at least partially along its length by means of electric elements embedded within the wall of the tube. The primary drawback of heated wire systems is expense. Heated wire systems, such as those used in hospitals, tend to be about twice as expensive as conventional humidifiers. Another approach for contiolling water vapour condensation is to raise the temperature of the humidified air introduced into the conduit inlet to a temperature above the preferred outlet temperature. The inlet temperature is calibrated to take into account the anticipated heat drop along the length of the conduit and the corresponding increase in relative humidity. For example, in the '926 patent referred to above, the air leaving the humidifier is preferably at 35.5°C. (i.e. approximately body temperature) and is between 85 - 100% saturated. The air temperature is then increased to 47.8°C. to compensate for an anticipated temperature drop of about 10°C. along the length of the delivery hose. This avoids condensation of water vapour between the humidifier and the mask worn by the patient.

One drawback of the '926 system described above is that the humidified air is not heated and maintained at a temperature sufficient to sterilize the air supply to kill all air-borne bacteria or viruses before delivery to the patient. Moreover, the '926 system is reliant upon the use of supplementary heated wires in the delivery hose to reduce the magnitude of the heat drop.

The need has therefore arisen for a humidification system which delivers substantially sterile air to a patient for inhalation during sleep in a cost-effective manner. The air is delivered at a preferred temperature and humidity to avoid the disadvantages of vapour condensation within the air delivery conduit. Summary of Invention

In accordance with the invention, an apparatus and method for delivering humidified air through a conduit to a patient for inhalation during sleep is disclosed. The conduit has an inlet connected to a humidifier and an outlet connected to a breathing mask worn by the patient.

The applicant's apparatus comprises a humidifier having an inlet for receiving a supply of intake air; a first chamber for holding a first volume of the intake air; a second chamber for holding a second volume of the intake air, wherein the second volume of air is passed over the surface of water contained within the second chamber; a heater for heating the water and the second volume of air within the second chamber; a discharge conduit for receiving and mixing together separate first and second streams of air discharged from the first and second chambers respectively; and an adjustable regulator for regulating the amount of the second stream of air passing into the discharge conduit.

Preferably the second chamber is located within the first chamber and the first chamber surrounds the second chamber. The heater is disposed so that it also heats the first volume of air in the first chamber. Advantageously, the first and second air streams are heated to approximately the same temperature. The second container may consist of a container and a removable lid for covering the container, wherein the intake air passes from the first chamber into the second chamber through an opening defined between the container and the lid. The humidifier preferably includes a first compartment and a second compartment, wherein the first and second chambers are located in the first compartment and wherein the discharge conduit extends from the first compartment into the second compartment. The humidifier also includes an air outlet port connectable to the face mask and a fan mounted in the second compartment for conveying air from the discharge conduit to the air outlet port. Preferably, the first compartment is located above the second compartment and the heater is disposed in a lower portion of the first compartment.

The air inlet consists of a inlet conduit extending through the second compartment into the first compartment. The inlet conduit has an open upper end to discharge the intake air into the first chamber. The second chamber is located between the inlet conduit and the discharge conduit. The inlet conduit and discharge conduit are preferably disposed on opposite sides of the humidifier.

The discharge conduit comprises a first tube having an open upper end in communication with the first chamber and a second tube having an upper portion in communication with the second chamber and a lower portion extending within the first tube. The adjustable regulator comprises a valve for regulating flow of the second air stream into the second tube.

The applicant has also developed a method for delivering humidified air through an unheated conduit to a patient, the conduit having an inlet connected to a humidifier and an outlet connected to a breathing mask worn by the patient. The appUcant's method comprises the steps of:

(a) heating a first volume of air in the humidifier to form a supply of heated dry air;

(b) heating a volume of water in the humidifier and passing a second volume of air over the surface of the water to form a supply of heated moisture-laden air;

(c) adjustably mixing the heated dry air and the moisture-laden air together in the humidifier to form a stream of heated humidified air;

(d) conveying the heated humidified air from the humidifier through the conduit to the mask,

wherein the temperature and relative humidity of the humidified air is adjusted to substantially prevent condensation of the humidified air in the conduit.

Preferably, the temperature of the humidified air while resident within the conduit decreases to less than 40 °C and the relative humidity of the humidified air while resident within the conduit increases to greater than 80 % . Brief Description of Drawings

In drawings which describe embodiments of the invention but which should not be construed as restricting the spirit or scope of the invention in any way,

Figure 1 is an isometric view of the applicant's invention showing the humidifier, air delivery conduit and face mask interconnected.

Figure 2 is an exploded isometric view of the applicant's humidifier.

Figure 3 is a front isometric fragmented view of the applicant's humidifier.

Figure 4 is a rear isometric fragmented view of the applicant's humidifier.

Figure 5 is a bottom plan view of the applicant's humidifier.

Figure 6 is a side elevation of the applicant's humidifier in its assembled configuration.

Figure 7 is a top plan view the applicant's humidifier showing the outline of the water container and Ud in phantom outline. Figure 8 is a front elevational view of the appUcant's humidifier.

Figure 9 is a sectional view of the appUcant's humidifier taken along section Une 9 - 9 of Figure 7 and looking in the direction of the arrows.

Figure 10 is a top plan view of a bottom compartment of the appUcant's humidifier housing an electric fan for blowing humidified air through an exhaust conduit to an air outlet.

Figure 11 is an enlarged, cross-sectional view of the adjustable regulator valve for regulating the volume of moisture-laden air entering the discharge conduit.

Detailed Description of the Preferred Embodiment

Figure 1 iUustrates an apparatus 10 for deUvering heated, humidified air to a patient at a controUed rate for inhalation during sleep. Apparatus 10 includes a humidifier 12 for providing a supply of hurnidified air; a mask 20 for wear by the patient; and an elongate conduit 14 having an inlet 16 connectable to humidifier 12 and an outlet 18 connectable to mask 20. The invention is configured to prevent condensation of water vapour within conduit 14.

As shown best in Figures 2 - 4, humidifier 12 includes a housing 22 comprising a lower compartment 24 and an upper compartment 26. Lower compartment 24 includes a bottom panel 28 having a central grille 30 and an air inlet 32 formed therein. Bottom panel 28 is supported a short distance above a support surface by feet 33 (Figures 5 and 6).

An electric fan is mounted within lower compartment 24 and is controUed by a switch 36 connected to a front electronics panel 35 of lower compartment 24. Fan 40 is connectable to a power supply by a cord 41. An on/ off indicator Ught 37 is also connected to panel 35 adjacent to switch 36.

An air exhaust conduit 42 is mounted adjacent to fan 40 within lower compartment 24 (Figure 10). Exhaust conduit 42 has a generaUy conical body 44 which tapers to a narrow end 46 for discharging humidified air through an outlet 43 into conduit 14 (Figure 1). Fan 40 is preferably a relatively quiet blade fan although any suitable fan capable of drawing intake air through inlet 32 and expelling humidified air through exhaust conduit 42 could be substituted. As described further below, lower compartment 24 includes a baffle 38 for ensuring that humidified air flowing downwardly into lower compartment 24 is drawn into fan 40 and is expeUed into exhaust conduit 42 (Figures 4 and 10).

The upper compartment 26 of housing 22 rests on a narrow ledge formed on the perimeter of lower compartment 24. As shown best in Figures 2 and 3 , upper compartment 26 includes a bottom panel 47 and an air intake conduit 48 which is aUgnable with air inlet 32. Conduit 48 has an open upper end 49 in communication with upper compartment 26. Thus, fresh intake air drawn into humidifier 12 may pass through air inlet 32 and conduit 48 for deUvery to the interior of upper compartment 26. A circular support 50 having a pluraUty of apertures 52 formed therein is provided in a central portion of upper compartment 26

(Figure 2). A pluraUty of aUgnment posts 54 are spaced around the perimeter of support 50 to assist in aUgning a water container 66 as discussed further below.

A heating element 58 comprising a lower panel 60, a heating coil 62 and an upper panel 68 is positionable on support 50. Lower panel 60 has apertures 64 formed therein for ventilation purposes to permit some heat to escape downwardly through apertures 52 into housing lower compartment 24. This enables some pre-heating of the intake air passing through air inlet 32 within housing lower compartment 24. The temperature in lower compartment 24 is, however, not increased to a significant degree to avoid overheating of the fan motor.

A water container 66 comprising a bottom panel 69, a cylindrical sidewall 70 and a removable Ud 72 is removably positionable on heating element 58 within housing upper compartment 26. Container sidewall 70 includes a flanged rim 74 extending around its perimeter. As shown best in Figure 9 , Ud 70 has a mating rim 76 having a pluraUty of spaced ribs 78 formed thereon. When Ud 72 is placed on container sidewaU 70, ribs 78 maintain smaU vent(s) therebetween to permit the entry of intake air into container 66. The number, size and position of such vents may vary without departing from the invention.

Container 66 essentially defines two discrete air chambers within upper compartment 26, namely a first chamber 27 surrounding container 66 (Figure 4) and a second chamber 29 within the interior of container 66 between the surface of the heated water 31 and the overlying lid 72 (Figure 9). Accordingly, intake air drawn into humidifier 12 through the open end 49 of conduit 48 is either heated in the first chamber 27 surrounding container 66 or it passes into second chamber 29 as discussed above where it passes over the surface of the heated water 31 gathering moisture (Figure 9). Preferably the temperature of the relatively dry air in first chamber 27 and the moisture-laden air in second chamber 29 is approximately the same (due to uniform heating of upper compartment 26 by heating element 58). First and second chambers are preferably heated to a temperature within the range of 65 - 80° C.

As shown best in Figure 2, removable container Ud 72 includes a pair of spaced-apart depressions 92 which serve as finger and thumb holds for lifting Ud 72 clear of container 66. Housing 22 similarly includes a removable cover 94 having spaced-apart depressions 92 which may register with the depressions in Ud 72 (Figure 9) when humidifier 12 is assembled. As shown in Figure 9, cover 94 rests on the upper edges of upper compartment 26 to enclose air chamber 27.

As shown best in Figures 4 and 9 , container Ud 72 includes a lateral extension 80 which discharges the moisture-laden air from container 66 into a downtube 82, which is in turn in communication with a mixing conduit 84. Conduit 84 extends between upper and lower compartments 24, 26 through panel 47 and includes an open upper end 86 which receives the heated air from downtube 82. Thus, two separate streams of heated air are mixed together in mixing conduit 84 to form a humidified air stream, namely a first volume of relatively dry heated air from first chamber 27 and a second volume of relatively moisture-laden air from second chamber 29.

The rate and volume of moisture-laden air entering downtube 82 is regulated by a valve assembly 96 mounted at the end of Ud lateral extension 80. As shown best in Figure 11, valve assembly 96 comprises an adjustment knob 98 which is threadedly coupled to a valve 100. Adjustment knob 98 may be rotated to vary the degree of extension of valve 100 and hence the size of the opening leading into downtube 82. For example, when valve 100 is fully extended it covers the upper end of downtube 82 entirely, thereby preventing entry of moisture-laden air from second chamber 29 of container 66 into downtube 82.

The various components of humidifier 12 shown exploded apart in Figure 2 are designed to fit compactly together without fasteners for ease of assembly and disassembly (for example, for cleaning purposes). In use, container 66 is partiaUy fiUed with water 31 and humidifier 12 is assembled as shown in Figure 2. The inlet end 16 of air deUvery conduit 14 is plugged into outlet 43 of humidifier 12. The outlet end 18 of conduit 14 is connected to face mask 20 (Figure 1).

The operation of humidifier 12 is activated by moving switch 36 to the "on" position after connecting cord 41 to an electrical power supply. This activates fan 40 and causes heating coil 62 to heat up. Coil 62 is preferably set to heat water 31 and the surrounding air within chambers 27, 29 of upper compartment 26 to a temperature within the range of 65 - 80° C. A temperature sensor (not shown) may be mounted near the discharge end of mixing conduit 84 for regulating the temperature of the discharged air stream and for preventing overheating of coil 62.

The operation of fan 40 causes heated air to be drawn down through conduit 84 from upper compartment 26 to lower compartment 24 where fan 40 is housed. This creates a partial vacuum in upper compartment 26 after Ud 94 has been secured. As a result, fresh intake air is continuously drawn up through inlet 32 and intake conduit 48. The intake air is partially heated as it flows upwardly through inlet 32 and conduit 48 due to the operation of heating coil 62.

The intake air passes through the upper end 49 of conduit 48 into chamber 27 of upper compartment 26 (Figure 4). Chamber 27 surrounds container 66. Some of the intake air is drawn into container 66 through small vent(s) defined between container rim 74 and the corresponding rim 76 of container Ud 72 (Figure 9).

The intake air which does not pass into container 66 is circulated within air chamber 27 where it increases in temperature before exiting downwardly into mixing conduit 84. The residence time of the air within chamber 27 is maximized by positioning mixing conduit 84 at a location opposite from the location of intake conduit 48.

Humidifier 12 has a heated, "pass-over" design. That is, the intake air drawn into container 66 flows through air chamber 29 above the surface of heated water 31, causing the air to become moisture-laden

(Figure 9). After passing over water 31, the heated, moisture-laden air may be discharged into downtube 82. As discussed above, the volume of moisture-laden air entering downtube 82 is regulated by valve assembly 96 mounted at the end of Ud lateral extension 80. As shown in Figure 11, valve assembly 96 may be manually adjusted by turning adjustment knob 98. Adjustment knob 98 is threadedly coupled to valve 100 which directly overUes the opening into downtube 82.

Preferably valve assembly 96 is set so that a relatively smaU amount of moisture-laden air flows through downtube 82 into mixing conduit 84. The relatively dry air stream from air chamber 27 and the relatively moisture-laden air from air chamber 29 mix together in mixing conduit 84 to form a humidified air stream which is drawn downwardly into fan 40 located in lower compartment 24. Baffle 38 is positioned to ensure that substantiaUy aU of the downwardly flowing humidified air discharged from the lower end of mixing conduit 84 is drawn into fan 40 and is not dispersed into other portions of lower compartment 24 (Figure 4).

Fan 40 blows the humidified air through exhaust conduit 42 and humidifier outlet 43 into conduit 14. Fan 40 is set to ensure a comfortable air flow rate through mask 20 (normally 15 - 20 Utres per minute). Preferably, the temperature of the humidified air discharged from outlet 43 is within the range of 45 - 57° C. and has a relative humidity within the range of 25 - 55%.

Humidifier 12 is essentiaUy seU-steriUzing since Uve microorganisms are kiUed at temperatures above 45° for prolonged periods. A filter (not shown) may be mounted in air inlet 32 for filtering air-borne particles, such as poUen, dust or house mites. OptionaUy, a supplementary temperature sensor (not shown) may be mounted at the narrow end 46 of exhaust conduit 42 to trigger shut-off of heating coil 62 if the temperature of the discharged humidified air stream rises above a safe level (i.e. above approximately 65°).

Conduit 14 preferably comprises smooth bore CPAP-type hose and is three to six feet in length. The temperature of the humidified air stream drops significantly as it passes through conduit 14 between humidifier 12 and mask 20. By the time the air stream has reached mask 20 the temperature is preferably within the range of 30 - 35° (i.e. sUghtly less than body temperature) and the relative humidity has increased to approximately 90 - 100%. The relative humidity of the air discharged from humidifier 12 can be easily adjusted depending upon the length of conduit 14 and the ambient room temperature by adjusting valve assembly 96. This is important to ensure that, whatever the operating conditions, the temperature drop over the length of conduit 14 does not result in condensation of water vapour within conduit 14 (i.e. upstream from mask 20).

As wiU be apparent to those skilled in the art in the Ught of the foregoing disclosure, many alterations and modifications are possible in the practice of this invention without departing from the spirit or scope thereof. Accordingly, the scope of the invention is to be construed in accordance with the substance defined by the foUowing claims.

Claims

WHAT IS CLAIMED IS:

1. A humidifier comprising:

(a) an inlet for receiving a supply of intake air;

(b) a first chamber for holding a first volume of said intake air;

(c) a second chamber for holding a second volume of said intake air, wherein said second volume of air is passed over the surface of water contained within said second chamber;

(d) a heater for heating said water and said second volume of air within said second chamber;

(e) a mixing conduit for receiving and mixing together separate first and second streams of air discharged from said first and second chambers respectively; and

(f) an adjustable regulator for regulating the amount of said second stream of air passing into said mixing conduit.

2. The humidifier of claim 1, wherein said second chamber is located within said first chamber.

3. The humidifier of claim 2, wherein said first chamber surrounds said second chamber.

4. The humidifier of claim 2, wherein said heater heats said first volume of air in said first chamber.

5. The humidifier of claim 4, wherein said first and second air streams are heated to approximately the same temperature.

6. The humidifier of claim 5, wherein said second chamber comprises a container and a removable Ud for covering said container, and wherein said intake air passes from said first chamber into second chamber through an opening defined between said container and said Ud.

7. The humidifier of claim 4, further comprising a first compartment and a second compartment, wherein said first and second chambers are located in said first compartment and wherein said mixing conduit extends from said first compartment into said second compartment.

8. The humidifier of claim 7, comprising an air outlet port connectable to a face mask, said humidifier further comprising a fan mounted in said second compartment for conveying air from said mixing conduit to said air outlet port.

9. The humidifier of claim 8, wherein said first compartment is located above said second compartment and wherein said heater is disposed in a lower portion of said first compartment.

10. The humidifier of claim 9, wherein said air inlet comprises an air inlet conduit extending through said second compartment into said first compartment.

11. The humidifier of claim 10, wherein said air inlet conduit has an open upper end located at a position opposite from the location of said mixing conduit.

12. The humidifier of claim 11, wherein said second chamber is disposed between said open upper end of said inlet conduit and said mixing conduit.

13. The humidifier of claim 12, wherein said mixing conduit comprises a first tube having an open upper end in communication with said first chamber and a second tube having an upper portion connected to said second chamber and a lower portion extending within said first tube.

14. The humidifier of claim 13, wherein said adjustable regulator comprises a valve for regulating flow of said second air stream into said second tube.

15. The humidifier of claim 12, wherein said heater heats said intake air as it passes through said intake conduit.

16. The humidifier of claim 7, further comprising a housing for enclosing said first and second compartments, wherein said housing comprises a removable cover for enclosing said first chamber.

17. A method of deUvering humidified air through an unheated conduit to a patient, said conduit having an inlet connected to a humidifier and an outlet connected to a breathing mask worn by said patient, said method comprising the steps of:

(a) heating a first volume of air in said humidifier to form a supply of heated dry air;

(b) heating a volume of water in said humidifier and passing a second volume of air over the surface of said water to form a supply of heated moisture-laden air;

(c) adjustably mixing said heated dry air and said moisture-laden air together in said humidifier to form a stream of heated humidified air;

(d) conveying said heated humidified air from said humidifier through said conduit to said mask,

wherein the temperature and relative humidity of said humidified air is adjusted to substantially prevent condensation of said humidified air in said conduit.

18. The method of claim 17, wherein the temperature of said humidified air while resident within said conduit decreases to less than 40 °C and the relative humidity of said humidified air while resident within said conduit increases to greater than 80%.

19. The method of claim 18, wherein the temperature of said humidified air at said conduit inlet is within the range of 45 - 57° C and the relative humidity of said humidified air at said conduit inlet is within the range of 25 - 55%.

20. The method of claim 19, wherein the temperature of said humidified air at said conduit outlet is within the range of 30 - 35° C and the relative humidity of said humidified air at said conduit outlet is greater than 90%.

21. The method of claim 17, wherein said first and second volumes of air are heated to approximately the same temperature.

22. The method of claim 17, wherein said first and second volumes of air are heated within said humidifier to a temperature within the range of 65 - 80° C.