Abstract:
The present invention encompasses the inclusion of non-heat, active-force humidifiers into CPAP devices. These humidifier modules use for example ultrasonics, atomization, and nebulization to increase the relative humidity of the air being delivered to the patient. Humidity is important in CPAP devices because it is vital to patient comfort and optimum health. All of these various, non-heat active humidifier modules are components or attachments to a CPAP device, and all optionally employ various procedures and devices for dealing with excess condensation. Most importantly, these humidification modules avoid the main problems associated with heat-requiring humidifiers, such as the added cost and time needed to operate these humidifiers, the excess condensation produced, and the increased likelihood of microbial growth.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to improved humidification devices for use in continuous positive airway pressure (CPAP) systems. These devices actively humidify air without the need to substantially increase water temperature. The present invention additionally relates to a method for delivering air humidified by non-heat-based humidifiers to airflow delivered to the subject with a CPAP system. The present invention may include a device to collect condensation from the humidified air and recycle the liquid for reutilization in the humidifier. 
     2. Technical Background 
     Continuous positive airway pressure (CPAP) devices are used to relieve partial or complete upper airway obstructions in a subject during sleep. A condition known as sleep apnea results when airflow is halted for more than ten seconds during sleep. Sleep apnea leads to decreased blood oxygenation and disrupts sleep. The procedure for administering CPAP treatment has been well documented. An early description can be found in U.S. Pat. No. 4,944,310 (Sullivan). CPAP treatment acts as a pneumatic splint of the airway by applying positive pressure, usually in the range 4 to 20 cm H 2 O. The air is supplied to the airway by a motor driven blower whose outlet passes via an air delivery hose to a nose and/or mouth mask sealed to a patient&#39;s face. An exhaust port is provided in the delivery tube proximate to the mask. CPAP pressure is increased on the detection of pre-defined patterns to provide increased airway pressure to subvert, ideally, the occurrence of the obstructive episodes and the other forms of breathing disorders. 
     Humidification is an important aspect of the CPAP procedure. The high airflow generated from the CPAP device removes moisture from a subject&#39;s nasal cavity, leaving a feeling of dryness and congestion. This dryness is uncomfortable and prevents many users from using the CPAP. In addition to dryness, non-humidified CPAP air may cause bleeding, swelling, excess mucous, congestion, or sneezing. The irritation also creates a very fertile ground for infections. The irritation may be cumulative, building up over time. The only way to reduce the irritation is to add moisture. Humidification therefore can be an important part of CPAP treatment. Besides humidification, water soluble lotions, solutions, or sprays for the nose and prescribed medications such as Nasonex and Flonase can be used to alleviate problems associated with CPAP air. 
     The prior art includes many references to humidification devices requiring heat (heat-based humidifiers). An example of this is found in U.S. Pat. No. 6,877,510 (Nitta). Heat-based humidifiers, such as heat vaporization humidifiers, heat the liquid as well as the airflow, increasing the maximum amount of water vapor the air can hold. They can also be adjusted to produce more or less moisture by altering the amount of heat applied. Also, the water chamber can be much smaller than in a passive humidifier. An integrated heat-based humidifier, however, cannot be heated as high as a stand-alone heated-based humidifier, due to the close proximity of the heating element to the CPAP. Also, as described below, heat-based humidifiers may produce more condensation than non-heat-based humidifiers, due to a higher temperature difference between the CPAP air and the ambient room temperature. Because of this, these humidifiers are sometimes set at lower constant humidification levels throughout the night, which reduces condensation during the coldest part of the night but prevents optimal humidification at the start and end of the night when temperatures are higher. Other main drawbacks of heat-based humidifiers are that they consume much or more electric power because of the high amount of heat needed to operate, and they require more time to begin humidification than non-heat-based humidifiers because of the need to substantially heat the humidifying liquid. Also, microbial growth is greater in heat-based humidifiers, increasing the risk of patient exposure to, for example, bacteria, yeasts, and molds. Finally, the components of heat-based humidifiers may have to be replaced more often than in non-heat-based humidifiers, as steam canisters need to be replaced every so often and can usually only be purchased from the original manufacturer of the steam humidifier. This increases time and costs associated with maintaining heat-based humidifiers as opposed to non-heat-based humidifiers. 
     The prior art also describes passive or “passover” humidifiers, which do not require heat. An example of this as integrated into a CPAP device is shown in U.S. Pat. No. 6,827,340 (Austin). These humidifiers are quite simple and, for the most part, self-regulating. They rely on the fact that an air stream passing over a reservoir of liquid or past a wick saturated with that liquid will pick up whatever moisture it can as it “passes over” the liquid. The higher the relative humidity, the harder it is for the air stream to pick up moisture, which is why these humidifiers are self-regulating (as humidity increases the humidifier&#39;s water-vapor output naturally decreases due to the decreasing difference in vapor pressure). Although these humidifiers are simple and do not require a heat source, there is no way to increase or decrease the amount of air humidification should this level be too low or high. Also, when integrated into a CPAP device, the surface area of the water used to humidify the air is necessarily smaller, resulting in lower humidification levels. As a result, this humidifier is only feasible in CPAPs set at lower-end pressures, as higher-end pressures will not produce adequate humidification levels. Conversely, increasing the surface area of the water contacting the air will increase the size of the humidifier, to the point where it would be difficult to integrate it into the CPAP. In these cases, the humidifier must be a separate attachment, not part of the CPAP system itself. Also, because of the larger size, these humidifiers may suffer from fill and spill problems because of the large size of the reservoir tank. 
     Condensation is a problem for any humidifier in a CPAP system. Because the greater the temperature difference between the ambient room temperature and the CPAP air the more condensation is produced, heat-based humidifiers are more susceptible to condensation than other humidifiers, since the air they produce is hotter than air produced in “cold” humidifiers. This is especially a problem at night, when the ambient temperature usually decreases in relation to the temperature of the humidifier. Condensation produces an accumulation of water in the CPAP tubing. This water produces a disruptive gurgling noise and added resistance to the CPAP circuit that results in large, transient fluctuations in mask pressure. Also, as little as 10 ml of condensate can cause an inspiratory pressure drop of up to 5.6 cm H 2 O. Thus, preventing the formation of condensate in the CPAP tubing is vital to ensuring CPAP therapy remains effective and tolerable. Some CPAP devices with heat-based humidifiers use heated CPAP tubing to prevent condensation, but this can be dangerous. See U.S. Pat. No. 5,537,996 (McPhee). Others use sensors which detect the ambient temperature and adjust heat output accordingly, so that the temperature of the CPAP air is never substantially greater then the temperature of the ambient air, minimizing condensation. See U.S. Pat. No. 5,558,084 (Daniell). 
     It is an object of the present invention to avoid the drawbacks of heat-based humidifiers and passive humidifiers in CPAP systems. It is further an object of the present invention to produce an integrated, compact, adjustable, cost-effective humidifier for use in CPAP systems. It is even further an object of the present invention to be less susceptible to contaminant growth because it operates at lower temperatures, creating a less hospitable environment for bacteria and other microbes than in heat-based humidifiers. Finally, it is even further an object of the present invention to produce less condensation by operating at temperatures much closer to ambient room temperatures, and through the use of new condensation-removal features in the CPAP device. 
     SUMMARY OF THE INVENTION 
     The present invention encompasses the inclusion of non-heat-based, active-force humidifiers into CPAP devices. These humidifier modules use techniques such as for example ultrasonics, atomization, and nebulization to increase the relative humidity of the surrounding air. Humidity is important in CPAP devices because it is vital to patient comfort and optimum health. All of these various, non-heat-based humidifier modules are components of a CPAP device, and all may employ various procedures and devices for dealing with excess condensation. Most importantly, these humidification modules avoid the main problems associated with heat-based humidifiers, such as the added cost and time needed to operate these humidifiers, the excess condensation produced, and the increased likelihood of microbial growth. 
     Non-heat, active-force humidifiers do not require heat, as distinguished from heat-based (vaporization) humidifiers, and work by applying substantial mechanical force onto a body of water to produce particles small enough for humidification, as distinguished from passive humidifiers. These humidifiers accomplish this active application of mechanical force through various methods, causing the liquid to break up into fine particles, which are then absorbed into the air. In some instances these particles are as small as those in steam. Producing humidification this way produces lower rates of microbial growth and significantly lower energy consumption than, for example, steam humidification, as well as lower maintenance hassles and costs. This process also gives a greater ability to control humidification levels and allows the CPAP device to create a smaller footprint than would be possible using passive humidifiers. 
     The present invention describes the humidification module device as well as methods for delivering air humidified by that device to the patient. A non-heat-based, active-force humidification module is an integrated component of a CPAP device. The airflow traveling through the CPAP device picks up humidified air from the humidification module before it travels to the subject. Condensation can be eliminated before reaching the mask of the subject through a condensation coil or membrane integrated into the humidification module or through any other method, including adding a reservoir to the CPAP device separate from the humidification module. 
     Examples of various embodiments of the present invention are as follows. In one embodiment, the present invention includes a continuous positive airway pressure apparatus for treating sleep apneas comprising a device for delivering a pressurized gas to a subject; and a device for actively humidifying a gas and for delivering the humidified gas to the pressurized gas without substantially heating the humidified gas prior to delivery to the subject. 
     In another embodiment, the present invention includes a method of treating a subject for sleep apneas comprising the steps of actively humidifying a gas without substantially heating a liquid used to humidify the gas; and delivering the humidified gas to a pressurized gas stream prior to delivery of the pressurized gas to a subject. 
     In yet another embodiment, the present invention includes a continuous positive airway pressure apparatus for treating sleep apneas comprising a device for delivering a pressurized gas to a subject; an ultrasonic humidifier for atomizing a liquid into a gas for creating a humidified gas; and a delivery device for delivering the humidified gas to the pressurized gas prior to delivery to the subject. 
     Additional features and advantages of the invention will be set forth in the detailed description which follows, and in part will be readily apparent to those skilled in the art from that description or recognized by practicing the invention as described herein, including the detailed description which follows, the claims, as well as the appended drawings. 
     It is to be understood that both the foregoing general description and the following detailed description are merely exemplary of the invention, and are intended to provide an overview or framework for understanding the nature and character of the invention as it is claimed. The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification. The drawings illustrate various embodiments of the invention, and together with the description serve to explain the principles and operation of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic drawing of a preferred embodiment for complete CPAP system, including the attached humidifier and an optional attached condensation reservoir. 
         FIG. 2  is a diagram showing a preferred embodiment for an ultrasonic humidifier. 
         FIG. 3  is a schematic drawing of a generic liquid delivery system for an atomization humidifier. 
         FIG. 4  is a detailed view of a preferred embodiment for an atomization humidifier. 
         FIG. 5  is a diagram showing the exterior of a preferred embodiment for a nebulizer humidifier. 
         FIG. 6  is a diagram showing a cross-section of the same preferred embodiment for a nebulizer humidifier. 
         FIG. 7  is a diagram detailing the preferred device for removing condensation from the humidified air, which includes the condensation coil or membrane and surrounding components. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIG. 1  describes a preferred embodiment for a complete CPAP system with active humidification. This system includes the attached non-heat, active humidifier further comprised of a condenser coil for collecting and disposing of condensation before the humidified air reaches the subject. Optionally, the CPAP system may include condensation reservoir separate from the humidifier instead of an attached condensation coil. 
     In  FIG. 1 , the subject  2  is wearing a mask  4 , preferably the nose mask  4  and/or face mask  4 , sealed to his or her face. Breathable gas in the form of fresh air, or oxygen enriched air, enters the mask  4  by flexible tubing  12  which, in turn, is connected to a motor driven blower  14  to which there is provided an air inlet  16 . The motor  18  for the blower is controlled by a motor-servo unit  20  to commence, increase or decrease the air pressure supplied to the mask  4  as CPAP treatment. The mask  4  also includes an exhaust port  8  that is close to the junction of the tubing  12  with the mask  4 . Exhaust port  8  includes a pressure release valve which releases excess air pressure that exceeds a preset amount. This amount can be adjusted depending on the air pressure needs of the patient. 
     Interposed between the mask  4  and the exhaust  8  is preferably a linear flow-resistive element  6 . In practice, the distance between mask  4  and exhaust  8  is very short so as to minimize deadspace volume. The mask side of the linear flow-resistive element  6  is connected by a small bore tube  40  to a mask pressure transducer  36  and to an input of a differential pressure transducer  34 . Pressure at the other side of the flow-resistive element  6  is conveyed to the other input of the differential pressure transducer  34  by another small bore tube  38 . 
     The mask pressure transducer  36  generates an electrical signal in proportion to the mask pressure, which is amplified by amplifier  42  and passed both to a multiplexer/ADC unit  26  and to the motor-servo unit  20 . The function of the signal provided to the motor-servo unit  20  is as a form of feedback to ensure that the actual mask static pressure is controlled to be closely approximate to the set point pressure. 
     The differential pressure sensed across the linear flow-resistive element  6  outputs as an electrical signal from the differential pressure transducer  34 , and is amplified by another amplifier  32 . The output signal from the amplifier  32  therefore represents a measure of the mask airflow. The linear flow-resistive element  6  can be constructed using a flexible-veined iris. Alternatively, a fixed orifice can be used, in which case a linearization circuit is included in amplifier  42 , or a linearization step such as table lookup is included in the operation of controller  24 . 
     The output signal from the amplifier  32  is low-pass filtered by the low-pass filter  28 , typically with an upper limit of 10 Hz in order to remove non-respiratory noise. The amplifier  32  output signal is also bandpassed by the bandpass filter  30 , typically in the range of 30 to 100 Hz to yield a snoring signal. The outputs from both the low-pass filter  28  and the bandpass filter  30  are provided to the multiplexer/ADC unit  26 . The digitized respiratory airflow (FLOW), snore, and mask pressure (P mask ) signals from multiplexer/ADC  26  are passed to a controller  24 , typically constituting a microprocessor based device provided with program memory and data processing storage memory. 
     The controller  24  outputs a pressure request signal which is converted to a voltage by DAC  22 , and passed to the motor-servo unit  20 . This signal therefore represents the set point pressure P set(t)  to be supplied by the blower  14  to the mask  4  in the administration of CPAP treatment. The controller  24  is programmed to perform a number of processing functions. 
     This CPAP system is only one of many embodiments of this system, and a number of different variations may be employed to improve efficiency and/or convenience. 
     Also in  FIG. 1  a humidifier  10  is included in the CPAP system by means of the flexible tubing  12  preferably between the linear flow-resistive element  6  and the motor driven turbine  14 . The humidifier  10  should be upstream of the linear flow-resistive element  6  for accurate flow measurements. This active humidification module can take one of many forms. Examples of these forms include ultrasonic humidification, atomization, nebulization humidification, and the like. As described above, these techniques work through active, non-heat humidification, which all utilize a means of applying substantial mechanical force to a body or stream of liquid to cause that liquid to disperse into droplets fine enough to humidify the surrounding air. 
     The humidification devices covered by the present invention are preferably adjustable as to the level of humidification they impart. Further preferably, the relative humidity level of the gas to be humidified can be increased by 10% with respect to the humidity of the ambient air. More preferably, the relative humidity of the gas to be humidified can be increased by 20% with respect to the humidity of the ambient air. Most preferably, the relative humidity of the gas to be humidified can be increased by 30% with respect to the humidity of the ambient air. In a preferred embodiment of the present invention, sensors can be placed to measure the humidification levels of both the humidified gas and the ambient gas in order to determine the humidity difference between these two gases. 
     Because the humidification devices of the present invention do not require a substantial amount of heat for humidification, they usually produce less condensation. This is due to the larger temperature difference between the heated-water humidified air and the surrounding ambient air, when compared to the air humidified by the present invention. It is more likely that liquid droplets will condense out of the hotter humidified air. Thus, preferably, the temperature of the gas humidified by the present invention is no more than 10° C. warmer than the ambient air temperature. More preferably, the temperature of the gas humidified by the present invention is no more than 5° C. warmer than the ambient air temperature. 
     Microbial growth is also deterred by the humidification devices of the present invention, since they do not rely on the application of a substantial amount of heat for the humidification process. By keeping the internal temperature of the CPAP apparatus lower, microorganisms such as bacteria, fungi, and molds will not grow as rapidly. Preferably, the CPAP apparatus of the present invention will show 10% less microbial growth over a period of a month than the best devices requiring a substantial amount of heat, or than what is reported in the literature, at the time this application is filed. More preferably, the apparatus will show 20% less microbial growth over a period of a month than the best devices requiring a substantial amount of heat, or than what is reported in the literature, at the time this application is filed. Finally, most preferably, the apparatus will show 30% less microbial growth over a period of a month than the best devices requiring a substantial amount of heat, or than what is reported in the literature, at the time this application is filed. 
     An ultrasonic humidifier is the preferred humidification device for the present invention. Ultrasonic humidifiers use of high-intensity acoustic energy to alter the properties of liquids, and can turn water into a fine mist through ultrasonic vibrations. Ultrasonic sound is sound with a frequency greater than the upper limit of human hearing (generally above 20 KHz, or 20,000 cycles per second). Ultrasonic humidification, which is an adiabatic type of system, is known for using very little energy (about 7% of the electric usage of electric steam generators). It also provides high-quality moisture and allows close control of the humidification level while requiring little maintenance. Ultrasonic humidification is the preferred way to make a steam size droplet (approximately 1 micron) without having to boil water. An ultrasonic humidifier&#39;s initial costs are often much higher than other types of systems, particularly steam systems. Also, it requires very pure water, although smaller systems can use deionized water canisters, which clean the water to approximately 2.5 ppm. While heat vaporization systems may have much lower initial costs, the money spent on replacement parts can be considerable as steam canisters need to be replaced every so often and can usually only be purchased from the original manufacturer. In addition, ultrasonic humidifiers begin humidifying immediately, while heat vaporization systems first require appreciably heating the water. 
       FIG. 2  shows a cross-section of an ultrasonic humidifier module which is the preferred embodiment for the present invention and can be incorporated or attached to the CPAP. Referring to  FIG. 2 , the ultrasonic humidifier has an upper cabinet  46  and a lower cabinet  52  which is arranged beneath upper cabinet  46 . The bottom portion of upper cabinet  46  is open and lower cabinet  52  has a water vessel  72  which is integrally formed in the central portion of lower cabinet  52 . Upper cabinet  46  and lower cabinet  52  are connected to each other through a chassis board  78 . 
     A power transformer  92 , a high frequency generator  90 , and a motor-blower  88  are fixed on chassis board  78 . Motor blower  88  supplies a space  74  in water vessel  72  with air from outside. The motor blower  88  can be replaced also by using the blower from the CPAP device. A low water detector  76  is suspended below the chassis board  78  so that the low water detector  76  protrudes into the water in water vessel  72 . The low water detector  76  is magnetically operated. The low water detector  76  detects whether the level of water in water vessel  72  has fallen to below a predetermined value. The low water detector  76  comprises a float guide  64  which is perpendicularly fixed to chassis board  78  and extended in the downward direction, a magnetically operated switch  66  installed in float guide  64 , and a float  70  having two bar magnets  68  inserted in float  70  therein. Float  70  is combined with float guide  64 , to move upward and downward. When float  70  drops below the predetermined level of water according as the level of water in water vessel  72  has fallen, switch  66  is opened so high frequency generator  90  is stopped. When float  70  is in a position above the predetermined level, switch  66  is closed so high frequency generator  90  is operated. 
     A mist conduit pipe  60  which is comprised of an ultrasonic wave isolating material such as a plastic material is fixed to chassis board  78 . The upper portion of mist conduit pipe  60  projects through upper cabinet  46  above upper cabinet  46 , and the lower portion of mist conduit pipe  60  extends to near the bottom of water vessel  72  in lower cabinet  52 . An outlet  86  is installed on the upper end of mist conduit pipe  60 . An ultrasonic vibrator assembly  58  is fixed onto the lower end of mist conduit pipe  60 . An ultrasonic vibrator (not shown) is installed in ultrasonic vibrator assembly  58 . A plurality of holes  56  are formed in the lower peripheral portion of mist conduit pipe  60 . Preferably, holes  56  are formed at the position just above the predetermined level of water in water vessel  72 . A coaxial cable  62  for supplying the ultrasonic vibrator with high frequency energy is connected between high frequency generator  90  and ultrasonic vibrator assembly  58 . A water supply tank  48  is removably placed in upper cabinet  46 . The water supply tank  48  has an outlet pipe  50  projecting into water vessel  72 , and a handle  94  for easily removing water supply tank  48  from upper cabinet  46 . 
     A cap  54  having a valve mechanism is installed on the lower end of outlet pipe  50 . The valve mechanism automatically supplies water vessel  72  with water to maintain the standard level determined by the lower end of cap  54 . The upper cabinet  46  is covered with a top plate  80  except at the portion for mounting and removing water supply tank  48 . A power switch  84  for keeping power transformer  92  or high frequency generator  90  operative or inoperative, and a lamp  82  kept lighted while power switch  84  is closed, keeping power transformer  92  and high frequency generator  90  operative, are provided on top plate  80 . 
     When the water in water vessel  72  is positioned at the standard level, if power switch  84  is closed on, power transformer  92 , high frequency generator  90 , and motor blower  88  are in an operating state so a high frequency electric power will be fed to the ultrasonic vibrator through coaxial cable  62  from high frequency generator  90 . Therefore, a high frequency energy generated from the ultrasonic vibrator is applied to the water in mist conduit pipe  60  to produce mist or water droplets smaller than 5 microns in diameter from the water in mist conduit pipe  60 . 
     As shown by an arrow in  FIG. 2 , the air current fed into the space  74  of water vessel  72  by motor blower  88  flows into a mist conduit pipe  60  through holes  56  and is sprayed with the mist through outlet  86  into the flexible tubing  12  (see  FIG. 1 ). When the water level in water vessel  72  lowers due to generating the mist, the pressure of the water vessel  72  is lowered. Thereby, the water in water supply tank  48  flows into water vessel  72  through outlet pipe  50  by the atmospheric pressure, so the water level recovers to the predetermined water level. If water supply tank  48  is removed, float  70  falls below the predetermined water level accordingly as the water level in water vessel  72  has fallen. In that case switch  66  is opened to stop the operation of high frequency generator  90  and motor blower  88 . At the same time, a user is automatically alerted to the shortage of water in water vessel  72  by the lighting of a warning lamp. 
     When the water supply tank  48  is installed in upper cabinet  46  after the water supply tank  48  is filled with water, the water in water supply tank  48  flows into water vessel  72 , so the water level in water vessel  72  recovers to the predetermined water level and switch  66  is closed to operate the humidifier. 
     Atomization can also be used to humidify the gas delivered to the subject. Atomization is a technique which produces droplets of liquid at a specific size and surface area. The most commonly utilized atomization techniques are pressure nozzle atomization, two-fluid nozzle atomization, and centrifugal atomization. In pressure nozzle atomization, a spray is created by forcing the fluid through an orifice. The energy required to overcome the pressure drop is supplied by a feed pump. This technique produces the narrowest particle size distribution possible. Droplet size can be controlled by altering the flow rate of the fluid through the atomizer. This is the most energy efficient atomization technique. Two-fluid nozzle atomization works by combining two fluids which are forced through a nozzle using a compressed gas. The atomization energy is provided by the compressed gas, usually air. The fluid contact can be internal or external to the nozzle. This technique produces a broad particle size distribution, and is the least energy efficient of the atomization techniques. This technique is useful for making extremely fine particles (10-30 micron) because of relatively high wear resistance. This technique is also useful for small flow rates typically found in pilot scale dryers. The initial cost can be lower due to the absence of a pressure pump, as found in pressure nozzle atomization, or a rotary atomizer, as found in centrifugal atomization. Centrifugal atomization creates a spray by passing the fluid across or through a rotary atomizer (a rotating wheel or disk). The energy required for atomization is supplied by the atomizer motor. A broad particle size distribution is generated. The average particle size for most products is no greater than 100 microns. Centrifugal atomizers are usually the most resistant to wear. This technique requires relatively high gas inlet velocity to prevent wall buildup. However, control of wall buildup is otherwise minimal, due to direction of spray (horizontal) and broad particle size distribution, forcing the dryer to be relatively large in diameter. The initial cost of a centrifugal atomizer is typically high. The comparatively larger diameter of the spray dryer can increase the initial cost. As with any high speed rotating machine, maintenance costs are also high. A problem with the centrifugal atomizer will shut down spray drying operations, unlike pressure nozzle atomization with multiple nozzle spray dryers, where a problem with one nozzle will not affect the operation of the other nozzles. 
       FIGS. 3 and 4  show an embodiment of an atomizer module or attachment of the present invention. In  FIG. 3  a generic liquid delivery system is indicated generally as  111 . The delivery system  111  includes a liquid source  112  that contains the liquid to be delivered. A liquid supply line  98  supplies the liquid to the input of a pump  108  via a pre-pump filter  110 . The pump  108  directs the liquid through a post-pump filter  106 , a regulating valve  104 , a flow meter  96 , and finally to the input of the atomizer  100 . An electronic control unit  102  receives input signals from the flow meter  96 . Based on these feedback signals, the control unit  102  determines the appropriate power to deliver to the pump  108  to control the liquid flow rate. In addition, regulating valve  104  may be electronically adjustable so that the control unit  102  may control the liquid pressure “on-the-fly” should this be desired. 
       FIG. 4  shows a preferred embodiment of an atomization humidifier. This embodiment shows a pressure nozzle atomizer. This embodiment is basically a hollow tube  116  (shown here with a circular cross-section, although other shapes can be used), having a length L, an internal diameter D, a wall thickness T, an inlet end  120  and an outlet end  122 . The material used in tube  116  is dependent on the overall size of the atomizer, liquid type, and other factors, although stainless steel has proved satisfactory. The physical mounting of the tube  116  can be provided by internal or external threaded portions of the tube  116 , press fitting the tube or any other method that provides adequate strength while allowing liquid to freely flow therethrough. 
     In operation, liquid enters the inlet end  120  of the atomizer  114  from supply line  98 . Upon exiting the outlet end of the tube  116 , the pressure of the liquid drops rapidly, resulting in atomization of the liquid. The atomized liquid thereby produced is comprised of extremely small droplets (on the order of a few microns). A sleeve  118  of additional material may be installed over the entire length of tube  116  or only along a portion of the tube  116 . The sleeve  118  can simply add structural strength to the atomizer  114 , or may provide electrical and/or thermal insulation between the atomizer  114  and other apparatus components. 
     Nebulization can also be used to deliver humidified air in the CPAP of the present invention. A nebulizer changes liquids into fine droplets (in aerosol or mist form) that are inhaled through a mouthpiece or mask. Nebulizers can be used to deliver bronchodilator (airway-opening) medicines such as albuterol (Ventolin, Proventil or Airet) or ipratropium bromide (Atrovent). A nebulizer may be used instead of a metered dose inhaler. It is powered by a compressed air machine and plugs into an electrical outlet. Portable nebulizers, powered by an internal battery or cigarette lighter, are available for individuals requiring treatments away from home. Nebulizers come in 2 types: jet (or pneumatic) small-volume nebulizers, and ultrasonic nebulizers. Jet nebulizers pump air or oxygen, by means of an air compressor, through a liquid to turn it into a vapor, which is then inhaled through a tube-like mouthpiece similar to that of an inhaler. Ultrasonic nebulizers do not use air compressors but instead use sound vibrations to create the aerosol. The ultrasonic nebulizer humidifier is just another name for the ultrasonic humidifier, previously discussed. Both systems avoid contamination of the environment by the use of filters. 
       FIGS. 5 and 6  show an embodiment of a nebulizer humidifier module or attachment of the present invention. In  FIGS. 5 and 6 , the nebulizer humidifier module or attachment includes a housing  142  consisting of a chamber  146  that is suited to receive and hold a fluid. The chamber is preferably substantially cylindrical; however, any of a number of shapes may be used. The chamber  146  includes an angled bottom portion  148  so that any fluid in the chamber will be directed toward one region of the bottom of the chamber to facilitate removal of all the fluid. In one embodiment, the bottom portion  148  is set at an approximate 45 degree angle in order to reduce wastage by maximizing the amount of fluid that is evacuated from the chamber for nebulization. An air outlet  126  extends away from the housing  142  and communicates with the chamber  146 . A bather  144  on the housing forces any aerosol generated in the chamber to flow up and over the barrier  144  before passing through the air outlet  126 . The indirect path formed by the barrier and the air outlet preferably helps to limit the particle size of the aerosol that escapes the chamber  146 . 
     Preferably, the housing is integrally formed with a lid portion  134  via a hinge  138  such that the lid portion  134  may be sealed and unsealed against the top of the housing to allow someone to fill the chamber  146  with a fluid. The lid portion  134  of the housing  142  is preferably molded as one part with the chamber  146 . 
     The lid  134  preferably includes a group of openings suited to receive an air inlet valve  130 , an exhalation valve  128  and a fluid channel air inlet valve  136 , respectively. A first opening  165  is sized to accommodate the exhalation valve  128 , a second opening  168  is sized to accommodate the air inlet valve  130 , and the third opening  170  is sized to accommodate the fluid channel air inlet valve  136 . The housing and lid may be constructed of a single piece of material formed by an injection molding process. Suitable materials include a plastic material, such as polypropylene, polycarbonate or a polycarbonate blend, or a metal material. 
     In a preferred embodiment, each of the air inlet valve  130 , exhalation valve  128  and fluid channel air inlet valve  136  is integrally formed into a valve system  132  from a single piece of flexible material. The exhalation valve  128  preferably is mounted into the first opening  165  by a center anchor  164  so that the assembled valve and opening form a butterfly configuration allowing air to escape upon exhalation and sealing upon inhalation to prevent inhalation of air through the opening. The air inlet valve  130  preferably has a duck bill valve configuration. The duck bill valve configuration is oriented with the tapered portion directed into the chamber  146  so that ambient air may be drawn in upon inhalation and so that the parallel sealing members, or lips, of the valve prevent any flow of air out of the chamber upon exhalation. An ambient air guide  166  is preferably integrally formed in, or attached to, the lid portion  134 . The ambient air guide  166  is disposed under the second opening  168  and the air inlet valve  130  so that distal opening  172  directs ambient air over the aerosol generating structure. 
     The fluid channel air inlet valve  136  preferably mounts into the third opening  170  and completely seals the third opening. Preferably, the fluid channel air inlet valve is a flexible membrane having a thickness that is sensitive to, and flexibly movable in response to, air pressure changes within the chamber  146  corresponding to inhalation and exhalation through the air outlet  126 . The fluid channel air inlet  171  positioned inside the chamber and directly adjacent to the fluid channel air inlet valve may be sealed and unsealed synchronously with a patient&#39;s breathing or may be manually actuated by physical contact against the outside of the valve  30 . In one embodiment, the material is flexible rubber material. Although individual valves may be fabricated separately on separate pieces of flexible material, or the valves may each be constructed from numerous individual components, the valve system  38  is preferably a one-piece, integrated construction reducing the part count and cost of manufacturing (including the cost of assembly). 
     A passageway  158  may be formed by a spacing between the gas nozzle  140  and nozzle cover  156 , a groove in the inner circumference of the nozzle cover, a groove in the outside of the nozzle, or a combination of grooves on the outside of the nozzle and inside of the nozzle cover. The fluid orifice  160  is positioned adjacent the pressurized gas orifice  174 . The fluid orifice is an annular orifice defined by a gap between the inner diameter of the tip of the nozzle cover and the outer diameter of the tip of the nozzle. In one preferred embodiment, the outer diameter of the tip of the nozzle is 2 mm and the inner diameter of the nozzle cover tip is 2.46 mm. Other diameters may also be used. Although a single annular orifice is shown, embodiments where the fluid outlet has other shapes, or comprises more than one discrete orifice positioned adjacent the pressurized gas orifice, are also contemplated. 
     In this embodiment, the fluid channel air inlet  171  is located near the top of the chamber  146  and is substantially parallel to the longitudinal axis of the chamber  146 . The distal end of the nozzle cover forms a fluid orifice such that the fluid and gas orifices  160 ,  158  are substantially parallel to each other. The space between the nozzle cover  156  and the pressurized gas nozzle  140  forms the fluid passageway  158  at the distal end which leads to the fluid orifice  160 . A non-moveable diverter  162  is located adjacent the distal end. The diverter directs the gas across the fluid orifice  160  to create a venturi effect, thereby causing the fluid to be entrained into the gas stream to create an aerosol. Preferably, the diverter  162  is attached to, or integrally molded with, the nozzle cover  156 . Alternatively, the diverter may be connected to the inside of the nebulizer  124 . 
     The fluid channel stem  152  extends substantially vertically along the longitudinal axis of the chamber  146 . The stem has a carved out portion  150  which forms an enclosed lumen once it is assembled and mated with the recessed channel  154  in the chamber wall. The resulting fluid channel shape is substantially rectangular. In other embodiments, the recessed channel  154  and carved-out portion  150  of the fluid channel stem  152  may be constructed to cooperate and form any of a number of continuous or varying cross-sections along their lengths. In another embodiment, the recessed channel  154  and fluid channel stem  152  may combine to form a plurality of separate fluid channels. In one preferred embodiment, the chamber has a volume of approximately 50 milliliters (ml), with a maximum fluid fill volume of 5 ml. In this embodiment, the fluid channel length is approximately 22.8 mm. 
     The fluid channel air inlet valve  136  is a flexible membrane that on inhalation substantially seals the fluid channel air inlet  171  communicating with the fluid inlet tube. Once substantially sealed, the necessary pressure is created inside the housing in order to entrain the fluid up the fluid channel into the path of the pressurized gas causing the fluid and gas to mix resulting in an aerosol with the desired particle size characteristics. The flexible membrane is preferably very sensitive to flow and, therefore, can be triggered at low flows making the apparatus suitable for children and the elderly who typically have lower rates of inhalation. Further, the membrane can also be manually depressed. Accordingly, the patient or the caregiver can manually actuate the apparatus. 
     A nebulizer capable of both breath actuation and manual actuation has been disclosed where a diverter, gas orifice, and liquid orifice are maintained in a fixed position with one another at all times. Nebulization is initiated by movement of a valve over the fluid channel air inlet that is in communication with the fluid channel linking the liquid orifice with the reservoir in the chamber. By using a flexible membrane as the fluid channel air inlet valve, a very fast and reliable response to both increased and decreased pressures within the chamber of the nebulizer may be realized. 
     The present invention also contemplates devices such as impellers and other non-heat active-force humidifiers for use as the humidification module for the CPAP device. 
     Optionally, for any humidifier covered by the present invention, we can include a condensation coil (condensation membrane) droplet filter within the humidification device. This device can be used to remove larger droplets of water to ensure reduced condensation between the humidifier and subject interface. In a preferred embodiment, shown in  FIG. 7 , patient circuit  201  is mounted detachably to the humidification unit  192  that is provided with a short connection tube  190  as a support member, a mounting flange  194 , and a humidifying element  186 . Connection tube  190  may be a straight tube with both end portions engaged (connected) in an airtight fashion to connection end portions  180  of patient circuit  201 . The outer diameter of connection tube  190  is set so as to be somewhat larger than the inner diameter of patient circuit  201 , in order to ensure the airtight engagement with patient circuit  192  to be connected thereto, and it may be set appropriately in accordance with the patient circuit to be employed. Further, in this case, the use of a packing, a fastening band or the like may be employed in order to enhance airtightness. 
     The peripheral wall on one end of connection tube  190  (e.g., on the left side in  FIG. 7 ) is formed with a mounting opening  210  for mounting flange  194 . Mounting opening  210  is located at a position outside of connection end portion  180  of patient circuit  201  upon connection with connection end portion  180  and disposed so as to allow the inside of connection tube  190  to communicate with the outside thereof. 
     In the illustrated exemplary embodiment, mounting flange  194  consists of a flange portion  182  in a square-plate shape or the like and a cylindrical holding portion  183 . Flange portion  182  of mounting flange  194  is shaped so as to be disposed along an outer peripheral wall of connection tube  190  and it is fixed to connection tube  190  by a screw  196  so as to cover the mounting opening  210  of connection tube  190  in a tight manner. Flange portion  182  is further provided with a communicating opening  206  that allows mounting opening  210  of connection tube  190  to open to the outside in the center of flange portion  182 . 
     Holding portion  183  of mounting flange  194  is disposed so as to stand upright with respect to the plate surface of flange portion  182 , such that opening  206  of flange portion  182  faces an opening  212  at the base end thereof. Holding portion  183  is arranged so as to insert through mounting opening  210  of connection tube  190  over the entire length of mounting opening  210  of connection tube  190 , extending up to the center of connection tube  190  in the radial direction, and then curved on the other end side of connection tube  190  at a generally right angle (on the right end side in  FIG. 7 ). An opening  184  is defined in holding portion  183  so as to face an open end of connection tube  190 . Opening  184  at one end of holding portion  183  is large enough to engage and hold humidifying element  186 , and opening  184  is arranged so as to communicate to the outside through communicating opening  206  of flange portion  6   a  in holding portion  183 . 
     In a preferred embodiment, the humidifying element  186  consists of a cylindrical bundle of tubes through which the humidified air stream passes. Each tube in the bundle is comprised of pores large enough to allow certain size vapor particles to pass through but small enough to keep in larger size particles. These larger liquid particles collect as condensation, which are collected in reservoir  188 . Preferably, the pores are small enough to trap liquid particles in the air larger than 10 microns in diameter. However, the pore size can be adjusted to best suit the needs of the patient. Preferably, the water in the reservoir  188  may be recycled back to the corresponding humidifier holding tank (depending on which non-heat, active-force humidifier is used) or may be disposed of in any other feasible manner. 
     An alternative to the condensation coil or membrane could be a condensation reservoir  44 , which would be attached to flexible tubing  12  between flow-resistive element  6  and the mask  4 , all shown in  FIG. 1 . This reservoir would collect any condensation forming present in the flexible tubing  12  before it could reach the humidifier and subject interface. The collected water could then be recycled back to the humidification module or disposed of by any other manner. A preferred embodiment for the reservoir may include a wall extending from the bottom of the flexible tubing  12  on the subject  2  side of the reservoir to partially obstruct the tube and to block any liquid from progressing further down the tube and thus forcing it to fall into the reservoir. In this embodiment, the reservoir would be lower than the flexible tubing  12  to allow gravity to pull the condensation into the reservoir after hitting the wall. The reservoir may be attached to the flexible tubing  12  by means of another tube or by any other means, including a spout or funnel. 
     It will be apparent to those skilled in the art that various modifications and variations can be made to the present invention without departing from the spirit and scope of the invention. Thus, it is intended that the present invention cover the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.