Abstract:
A portable method and apparatus for allowing an individual to pre-adjust at sea level for future high altitudes is taught. The invention teaches the use of a small portable breathing gas control system to adjust the gas concentrations going to a subject&#39;s face mask.

Description:
[0001]    This application is a continuation of U.S. Ser. No. 09/447,323 soon to issue as U.S. Pat. No. 6,561,185 which was a continuation-in-part of U.S. Ser. No. 08/927,242 issued as U.S. Pat. No. 5,988,161 which is included, by reference, in its entirety. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    Altitude sickness strikes thousands of individuals every year resulting in problems from sleep disorders to pulmonary edemas to death. These individuals are skiers, mountain climbers, or merely business travelers to high altitude regions. The key to dealing with the altitude sickness is taking advantage of the body&#39;s ability to gradually acclimatize through a transition through progressively higher altitudes.  
           [0003]    Unfortunately, most individuals do not have the time to acclimatize. For example, and individual flying to a high ski hill will typically spend a few hours of flying and driving to be at the ski hill thus depriving the body of the opportunity to acclimatize.  
           [0004]    The physiology of altitude sickness and the adjustment to altitude is covered in numerous textbooks. An excellent one is “Medicine For Mountaineering” by James Wilkerson, M.D. (copyright 1992, published by The Mountaineers of Seattle, Wash.) from which the immediately following discussion is liberally taken.  
           [0005]    The body adjusts to altitude by increasing respiratory volume, increasing the pulmonary artery pressure, increasing the cardiac output, increasing the number of red blood cells, increasing the oxygen carrying capability of the red blood cells, and even changing body tissues to promote normal function at lower oxygen levels.  
           [0006]    At an altitude level of 3,000 feet the body already begins increasing the depth and rate of respiration. As a result of this more oxygen is delivered to the lungs.  
           [0007]    In addition, the pulmonary artery pressure is increased which opens up portions of the lung which are normally not used, thus increasing the capacity of the lungs to absorb oxygen. For the first week or so, the cardiac output increases to increase the level of oxygen delivered to the tissues. However, that particular adjustment fades after the first week.  
           [0008]    The body also begins to increase the production of red blood cells. Other changes include the increase of an enzyme (DPG) which facilitates the release of oxygen from the blood and increase the numbers of capillaries within the muscle to better facilitate the exchange of blood with the muscle.  
           [0009]    About 80% of the adaptation is finished by 10 days.  
           [0010]    Slowly increasing the altitude from sea level to the target altitude appears to be the best solution.  
           [0011]    The most difficult time for altitude sickness sufferers is evening when the primary function is sleeping. This is most likely due to the fact that the breathing rate decreases during sleep and thus the coping mechanism of increased respiratory rate is somewhat thwarted.  
           [0012]    Gamow (U.S. Pat. No. 5,398,678) teaches a portable chamber to facilitate the function of an individual at higher altitudes by increasing the pressure within the chamber above that of the ambient. Lane (U.S. Pat. No. 5,101,819) teaches a method of introducing nitrogen into a flight training hypobaric chamber to simulate the lower oxygen concentrations at higher altitudes for fighter pilots.  
           [0013]    The inventor is not aware of any other art that discusses the use of a portable device for helping an individual to adjust to altitudes. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]    [0014]FIG. 1 shows a subject at rest using the device.  
         [0015]    [0015]FIG. 2 shows a simple embodiment of the device.  
         [0016]    [0016]FIG. 3 shows a more complex embodiment of the device.  
         [0017]    [0017]FIG. 4 shows a method of a simple embodiment.  
         [0018]    [0018]FIG. 5 shows a method for a more complex embodiment of the invention.            
     
    
     DETAILED DESCRIPTION  
       [0019]    [0019]FIG. 1 shows a subject  10  using the device with mask  12  over the nose ad mouth secured around the head by strap 14 . The mask communicates with the main exchange unit  20  through hose  16 . For convenience, hose  16  should be long enough so that the exchange unit  20  can be far enough away from the patients so that it does not interfere with their sleep. However, for optimal performance in air mixing, the hose could be made shorter to allow for more shallow breaths for the appropriate gas levels. Alternatively, the exchange unit could be made very small and built into the mask thus obviating the hose 16 .  
         [0020]    [0020]FIG. 2 shows the details of the exchange unit  20  beginning with the hose  16  going to the mask. Flexible sides  22  allow for the chamber to expand and contract. Alternatively, flexibility could be gained by the use of elastic polymers or other materials for the unit surfaces.  
         [0021]    Oxygen sensor  24  sits inside the chamber and feeds its signal to a control unit  28 . The control unit  28  has a setting for an altitude and time. The control unit then controls the room air solenoid  26  to allow the passage of room air into the exchange unit when necessary.  
         [0022]    The basic operation is rather straightforward. The oxygen sensor monitors the oxygen and controls the room air solenoid. The solenoid would be open or closed depending upon whether the internal oxygen level is a that appropriate level desired for the altitude simulation.  
         [0023]    More details of this are given in the discussion of the methods which are following.  
         [0024]    [0024]FIG. 3 shows a more complex embodiment of the invention which adds a pressure sensor  40  and Co2 (carbon dioxide) sensor  42  which again feed into the control unit  28 . This allows for the adjustment of not only the oxygen level but the Co2 level. It maybe important, for some individuals, to minimize the level of Co2 as high levels of Co2 can interfere with breathing reflex.  
         [0025]    A second solenoid  44  is used to allow the passage of nitrogen from a tank  46  into the chamber. This allows the reduction of oxygen levels in the chamber without merely increasing the levels of Co2 as occurs with the simpler embodiment shown in FIG. 2. This further discussion of the use of this is covered in the following method discussions of FIGS. 4 and 5.  
         [0026]    [0026]FIG. 4 shows the method for a simple embodiment of this invention. The first step is to read the altitude setting on the control unit and to convert that to a desired oxygen level. The peak oxygen concentration is red by the O2 sensor. This should occur just before inspiration as the expired air has significantly lower levels of oxygen. If the peak oxygen concentration (OC) is greater than the desired oxygen concentration (DOC) then the solenoid remains shut. This will increase the level of carbon dioxide in the gas chamber and decrease the level oxygen.  
         [0027]    If, in the alternative, the peak oxygen level is less than the desired oxygen concentration then the room air solenoid is open for two seconds to allow fresh air into the chamber to increase the oxygen concentration.  
         [0028]    [0028]FIG. 5 shows a more complex embodiment of the invention. The pressure sensor is continually monitored to track inspiration and expiration. This is due to the fact that the inspiration will reduce the pressure in the tank while the expiration will increase it. Thus the control unit is continuously “aware” of the stage of breathing.  
         [0029]    As before, the desired altitude setting is converted to a desired oxygen concentration (DOC). At the beginning of every breathing cycle (or the start of inspiration) the oxygen level is peak in the exchange box. This is referred to as the “O2I”. If the O2I is greater than the desired oxygen concentration then the method examines the pressure in the box. If the pressure is close to 15 PSI (pounds per square inch—or normal atmospheric pressure) then this means the box has normal pressure and there is plenty of oxygen so the unit just goes back to monitoring. Eventually, breathing will lower the level of oxygen in the box. If, however, the pressure is not near normal sea level pressure then the nitrogen solenoid is opened for two seconds to increase the gas pressure. (There is no risk of great overpressure as the mask will simply allow the excess gas to leak out around the subject&#39;s mouth and nose.) After the nitrogen solenoid has been opened for two seconds then the Co2 concentration is examined. If this is less than 3% then the method returns back to monitoring at the top of FIG. 5.  
         [0030]    If, however, the Co2 concentration is greater than 3% then the method opens a room air solenoid for two seconds. This allows in fresh air and will decrease the Co2 concentration. The step of opening the room air solenoid for two seconds can also be reached from a negative answer to the first question. This was, “is the O2I greater than the desired oxygen concentration?” Of the answer was no then it clearly needs to open the room air solenoid to let in oxygen rich air. After this step then the timer is examined. If the preset timer has expired then the room air solenoid is opened permanently to allow the subject to have comfortable normal breathing. Otherwise the system returns to its normal steps of monitoring, etc.  
         [0031]    An alternative preferred embodiment is shown in FIG. 6. Here flap valve  60  allows the exhaled air to go directly outside of the system. During inhalation the flap valve  60  closes forcing the breathing to take place through the exchange unit  20 . Exchange unit  20  has a disposable screw-in canister  62  of an oxygen absorbent which reduces the level of oxygen in the air supplied to the user. Typical oxygen absorbents include: