Abstract:
A supply of gas such as oxygen is provided to a person in need of such gas supply. The delivery system includes an alarm to alert the recipient of the gas or another when and if the gas supply is disrupted. The alarm system preferably includes a reset and on-off switch that is recessed sufficiently to prevent accidental disabling of the alarm system.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The purpose of this invention is to employ a gas flow alarm in a personal gas supply delivery system.  
         [0003]     2. Description of the Art Practices  
         [0004]     Hospitals, nursing homes, dental offices, clinics and a number of other health care institutions utilize medical gasses in rendering care to patients. It is well known to administer oxygen, air, and nitrous oxide to patients for treatment of a variety of different conditions or during surgical operations.  
         [0005]     A number of medical institutions now employ medical gas systems which use a central gas supply source for providing a positive flow of medical gasses. These systems often utilize a network of conduits or supply lines to deliver the medical gas remote from the central source of the medical gas. The networks often include main and branch shut-off valves to enable isolation of a portion of the network in the event of damage or fire, or to effect needed repairs.  
         [0006]     The lives of patients may depend on receiving a reliable source of the medical gas, a real need has developed to ensure that the medical gas system is functioning properly, and to annunciate an alarm in the event a malfunction or alarm condition is detected. Such conditions may occur, for example, when the shut-off valve is either partially or fully closed. In such circumstances, the necessary supply of gas may be insufficient or non-existent.  
         [0007]     A further inadvertent interruption of the medical gas supply may occur when the medical gas is humidified. Commonly employed humidifying systems utilize a threaded plastic vessel that is screwed into a threaded plastic cap. If the threads of the threaded plastic vessel or threaded plastic cap are damaged or misaligned the medical gas may be lost to the surrounding environment with the consequent non-delivery of the medical gas to the patient.  
         [0008]     There is a further need to detect other defects in the system that may impair the medical gas system effectiveness. For example, usage of the system may eventually result in low pressure conditions in the supply tank when the supply of gas is nearly exhausted. There is a further need for early detection of these problems so that replacement sources of medical gas may be provided to the patient before the medical gas delivery system becomes completely inoperative.  
         [0009]     Finally, due to the escalating costs associated with medical care and the shortage of trained nurses and technicians, monitoring of the medical gas delivery systems should be easy and capable of instant recognition of system faults. In particular, the recipient of the medical gas or a visitor of the patient should be able to recognize system faults.  
         [0010]     Several methods using various apparatus have been employed to determine if a supply of a gas is within operating parameters. Such methods and aparrati are disclosed below.  
         [0011]     U.S. Pat. No. 6,067,022 granted to Laswick, et al., on May 23, 2000 describes an in-line low supply pressure alarm device powered solely by supply flow of pressurized gas from a gas supply for providing an alarm signal when supply gas pressure is below a selected minimum pressure. The alarm device includes a manifold having an input port for communicating with the supply gas supply, an output port for conducting the gas downstream and a manifold chamber disposed therebetween.  
         [0012]     The Laswick, et al., patent utilizes gas powered alarms such as an audible reed alarm or a visual pneumatic alarm are connected to the manifold chamber via an alarm supply conduit, and produce an alarm signal when pressurized gas passes to the alarms. According to the Laswick, et al., patent a supply gas pressure sensor, in communication with the manifold chamber, produces an actuating flow of pressurized gas by activating a pressure switch, in response to sensing of an supply gas pressure below the selected minimum pressure.  
         [0013]     U.S. Pat. No. 6,067,022 to Laswick, et al., further provides a pneumatic alarm output switch, in the alarm supply conduit and in communication with the pressure sensor and pressure switch via an actuation conduit, controls gas flow to the alarms in response to the actuating flow. The Laswick, et al., patent preferably includes an alarm oscillation system is included for alternating the direction of the actuating flow to and from the alarm output switch, to open and close the alarm output switch thereby turning the alarm on and off in a cyclical fashion.  
         [0014]     U.S. Pat. No. 4,674,321 issued to Joshi on Jun. 23, 1987 describes a leak detector employing an ion-conducting membrane is disclosed. The Joshi patent describes an oxygen-ion conducting membrane which employs a high vacuum on one side is used to detect very small quantities of oxygen flowing through a minute fissure in a part to be tested for leaks. The Joshi patent further describes an oxygen-ion conducting membrane which is biased with direct current voltage to drive oxygen-ions through the membrane away from the high vacuum side.  
         [0015]     U.S. Pat. No. 3,133,997 to Greene issued May 19, 1964 describes a fluid-pressure activated switch Pressure activated switches are described in the MPL publication available at mpl@pressureswitch.com 555 SW 12th Avenue Pompano Beach, Fla. 33069. Further disclosures of pressure activated switches are found at World Magnetics 810 Hastings Street Traverse City, Mich. 49686, telephone: 231-946-3800 and fax: 231-946-0274 and located on the web at http://www.worldmagnetics.com.  
         [0016]     U.S. Pat. No. 5,057,822 to Hoffinan issued Oct. 15, 1991 describes a medical gas alarm system is provided which includes a sensor unit pneumatically connected to a medical gas supply line and a switch connected to a valve in the supply line for detecting the open condition of the valve.  
         [0017]     In the Hoffinan patent, in the event either the sensor detects a high pressure or low pressure condition in the supply line or closing of the valve activates the switch, an alarm signal is received by an alarm module and an alarm is activated. The alarm of the Hoffman patent may be visual, audible or both. During normal operations, the alarm module of the Hoffman patent displays both a system on condition and a digital display indicating the pressure in the supply line.  
         [0018]     The Hoffinan patent also includes a method of monitoring the condition of a medical gas delivery system which includes sensing the pressure in the gas supply line, detecting the open condition of the valve, transmitting an alarm signal to an alarm module in response to alarm conditions detected either as a result of improper pressure or valve closure, and generating a humanly perceptible alarm warning in response to receipt of an alarm signal.  
         [0019]     Fukui in U.S. Pat. No. 5,457,333 issued Oct. 10, 1995 describes a gas sensor comprises a precious metal electrode, a semiconductor layer entirely or partly covering the precious metal electrode, a barrier layer having a high potential formed at an interface between the precious metal electrode and the semiconductor layer. The Fukui patent recites a gas sensor for use in a leak detector for detecting a fuel gas such as town gas, the sensor comprising a precious metal electrode; and a semiconductor layer at least partly covering said precious metal electrode, wherein the semiconductor layer includes, as a main component, at least one substance selected from the group consisting of tin oxide, zinc oxide and indium oxide. The Fukui patent precious metal electrode is formed of a substance selected from the group consisting of platinum, gold, ruthenium, lead, silver, iridium, and alloys thereof and has a barrier layer having a high potential formed between said precious metal electrode and said semiconductor layer and on a surface of said precious metal electrode. The barrier layer described in the Fukui patent comprises either a substance formed by electrodeposition and selected from the group consisting of platinum, palladium, gold and rhodium, or a substance formed by thermal decomposition and selected from the group consisting of platinum, palladium and gold, said barrier layer being capable of enhancing sensitivity to isobutane gas relative to other gases.  
         [0020]     U.S. Pat. No. 5,293,866 issued to Padula Mar. 15, 1994 provides a description of an indicator device which can be attached to a standard oxygen flow meter is disclosed. The indicator device described in the Padula patent has a rod along which a pointer can be moved and locked into position. The pointer in the Padula patent can be set at the oxygen flow level prescribed by the physician as indicated by the scale on the oxygen flow meter. If the oxygen flow level, as described in the Padula patent, is changed or if oxygen is discontinued for any period of time, the attendant can then set the oxygen flow to the prescribed level by controlling the valve on the oxygen flow meter so that the float, which indicates oxygen flowing liters per minute is positioned opposite the position of the pointer. The foregoing mechanism recited in the Padula patent prevents erroneous or improper setting of oxygen flow levels to patients after interruption or change of oxygen flow level, which can be dangerous, and life threatening.  
         [0021]     To the extent that the foregoing references are relevant to the present invention, they are herein specifically incorporated by reference. Where temperatures are given, they are in degrees C. unless otherwise indicated. Pressure measurements are reported in KPa. Percentages and ratios given herein are by weight unless otherwise indicated. Measurments herein are stated in degrees of approximation and where appropriate the word “about” may be inserted before any measurement.  
       SUMMARY OF THE INVENTION  
       [0022]     The present invention describes a personal gas supply delivery system comprising: 
        a first conduit, for when in use receiving a supply of a gas at a first pressure from a first gas supply line,     said first conduit connected with a gas flow alarm, said gas flow alarm for when in use for determining an instantaneous difference in the pressure or volume of the gas per unit of time and the volume of the effluent gas per unit of time,     a second conduit connected with said gas flow alarm, for when in use receiving the supply of gas through said gas flow alarm,     said first conduit having a first connector, for when in use providing a detachable airtight seal with a compatible connector on the gas supply line, said first connector located distally from said gas flow alarm, and     said second conduit having a second connector, for when in use providing a detachable airtight seal with a compatible connector on a second gas supply line, 
 
 said second connector located distally from said gas flow alarm 
       
 
         [0028]     The present invention further describes a personal gas supply delivery system comprising: 
        a moisturizing vessel, for when in use, having the capability to contain a liquid to provide a source of moisture to increase the amount of moisture in a gas passing through the liquid,     said moisturizing vessel having a first opening for receiving an influent gas,     said moisturizing vessel having a second opening for an effluent gas,     a first conduit connected with said second opening, said first conduit for when in use, for receiving the effluent gas,     a gas flow alarm connected with said first conduit, and     a second conduit connected with said gas flow alarm said second conduit in fluid communication with said first conduit, 
 
 said gas flow alarm for determining the instantaneous pressure differential of the influent gas and the effluent gas. 
       
 
         [0035]     Yet a further embodiment of the invention is a personal gas supply delivery system comprising: 
        a moisturizing vessel, for when in use, having the capability to contain a liquid to provide a source of moisture to increase the amount of moisture in a gas passing through the liquid,     said moisturizing vessel having a first opening for receiving an influent gas,     said moisturizing vessel having a second opening for an effluent gas,     a first conduit connected with said second opening, said fist conduit for when in use, for receiving the effluent gas,     a gas flow alarm connected with said first conduit, and     a second conduit connected with said gas flow alarm, said second conduit in fluid communication with said first conduit,     said gas flow alarm for determining an instantaneous difference in the volume of the influent 
 
 gas per unit of time and the volume of the effluent gas per unit of time. 
       
 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0043]     The foregoing and other features of the present invention will become apparent to one skilled in the art to which the present invention relates upon consideration of the following description of the invention with reference to the accompanying drawings, wherein:  
         [0044]      FIG. 1  is a frontal perspective of a finished product embodiment according to the invention;  
         [0045]      FIG. 2  is a frontal perspective of a part of the finished product embodiment according to the invention;  
         [0046]      FIG. 3  is a sectional view of a part of the finished product embodiment according to the invention taken along line  3 - 3 ;  
         [0047]      FIG. 4  is a partial sectional view of the alarm according to the invention;  
         [0048]      FIG. 5  is a frontal perspective of a part of the finished product embodiment according to the invention; and  
         [0049]      FIG. 6  is an anterior view of a part of the finished product embodiment according to the invention.  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0050]     As best seen in  FIG. 1  there is a finished product embodiment according to the present invention. A personal gas delivery system  10  includes a hollow flexible tubing  14 . The hollow flexible tubing  14  is conveniently any sufficiently flexible tubing to permit movement without undue risk of crimping, cracking or other damage, which may interrupt the flow of a medical gas.  
         [0051]     A suggested hollow flexible tubing  14  is Tygon tubing available from Saint-Gobain Performance Plastics Corporation PO Box 3660, Akron, Ohio 44309. Saint-Gobain may be reached toll free at 800-798-1544 and direct at 330-798-9240 or at http://www.tygoncom/.  
         [0052]     The hollow flexible tubing  14  is permanently terminated by a hollow tubing connector  18 . The hollow tubing connector  18  is conveniently forced into a nipple connector  24  extending from the gas flow alarm  20 . The hollow tubing connector  18  is conveniently detachable from the nipple connector  24  through moderate hand pressure with a twisting motion. The hollow flexible tubing  14  is in fluid communication with the hollow tubing connector  18 , and the nipple connector  24 .  
         [0053]     In a typical usage, it is not necessary to employ any lubricant to ensure an airtight fit of the hollow flexible tubing connector  18  to the nipple connector  24 . Similarly, there is no need for caulking or adhesive to ensure an airtight fit of the hollow tubing connector  18  to the nipple connector  24 .  
         [0054]     The nipple connector  24  is made of a rigid plastic such as polyvinylchloride, polycarbonate. The nipple connector  24  may also be made of other suitable rigid plastic materials.  
         [0055]     The nipple connector  24  is affixed at the opposite end thereof with a gas flow alarm  20 . The point of attachment of the gas flow alarm  20  to the hollow tubing connector  18  is by a nipple connector  24  extending from the gas flow alarm  20 . The nipple connector  24  is more particularly shown in  FIG. 2 . The hollow tubing connector  18  is in fluid communication with the first nipple connector  24 .  
         [0056]     The gas flow alarm  20  is one, which is suitable for low flow rates and relatively low pressures. Typically, the gas flow alarm  20  is capable of determining the instantaneous pressure differential of a supply of a medical gas in the range of about 0.005 KPa to about 200 Kpa preferably 0.013 KPa to about 150 Kpa, (the equivalent of 0.05 in/H 2 O as a low end and 550 in/H 2 O), above the ambient atmospheric pressure. That is, the supply of a medical gas will be determined by a flow rate approximately equal to the ambient pressure with ambient at see level being 101 KPa (14.7 pounds per square inch).  
         [0057]     The low flow rates and relatively low pressures are utilized because the system is designed to provide a supplement of a medical gas to a patient rather than forcing the gas into the lungs of the patient. The system will work to provide accurate data at elevations from slightly below sea level to above about three thousand meters (minus 200 feet mean sea level to about ten thousand feet).  
         [0058]     As best seen in  FIG. 4 , a switch  30  suitable for use in the gas flow alarm  20  has a flexible metallic reed  32 . The flexible metallic reed  32  is connected at an end  34  to an electrical terminal  36 . The electrical terminal  36  is connected to a low voltage current source. The flexible metallic reed  32  has second end  40 . The second end  40  of the flexible-metallic reed  32  contacts a second electrical terminal  44  to complete an electrical circuit. The flexible metallic reed  32  is sufficiently flexible enough to permit a relatively low flow (consequently low pressure) of a medical gas to displace (break) the second end  40  of the flexible metallic reed  32  away from the second electrical terminal  44  thereby interrupting the electrical circuit. The direction of the flow of the medical gas according to the present invention is shown in  FIG. 4  by the double-headed arrows. A set screw  46  permits the switch  30  to be variably set to accommodate different sensitivities for the gas flow alarm  20 . The set screw  46  impinges on the second electrical terminal  44  to place the second electrical terminal  44  in closer proximity to the second end  40  thereby making the switch  30  more sensitive to gas flow.  
         [0059]     Suitable gas flow alarms  20  are described in U.S. Pat. No. 3,133,997 to Greene issued May 19, 1964 that describes a fluid-pressure activated switch. Pressure activated switches are described in the MPL publication available at mpl@pressureswitch.com from Micro Pneumatic Logic Inc., 555 SW 12th Avenue Pompano Beach, Fla. 33069. Further disclosures of pressure activated switches are found at World Magnetics 810 Hastings Street Traverse City, Mich. 49686, telephone: 231-946-3800 and fax: 231-946-0274 and located on the web at http://www.worldmagnetics.com. The gas flow alarms described in U.S. Pat. No. 3,133,997 to Greene, the MPL publication from Micro Pneumatic Logic Inc., and the World Magnetics are specifically incorporated herein by reference.  
         [0060]     As best seen in  FIG. 2 , the gas flow alarm  20  has protruding from it a second nipple connector  52 . The second nipple connector  52  is similar in construction and design to the first nipple connector  24 . The second nipple connector  52  is in fluid communication with the gas flow alarm  20 .  
         [0061]     A second hollow tubing connector  58  plastic such as PVC or polycarbonate. The design and construction of the second hollow tubing connector  58  is similar to that of the hollow tubing connector  18 . The second hollow tubing connector  58  is in fluid communication with the second nipple connector  52  and accordingly is in fluid communication with the gas flow alarm  20 .  
         [0062]     The second hollow tubing connector  58  is connected with a second hollow flexible tubing  64 . The second tubing connector  58  is conveniently forced into the second nipple connector  52 . The hollow flexible tubing  64  is in fluid communication with the hollow tubing connector  58 . The second hollow tubing connector  58  is conveniently detachable from the second nipple connector  52  through moderate hand pressure with a twisting motion.  
         [0063]     The suggested hollow flexible tubing  64  is Tygon tubing available form the same source as the hollow flexible tubing  14 . As with the hollow connector tubing  18 , the hollow tubing connector  58  it is not necessary to employ any lubricant to ensure an airtight fit of the hollow tubing connector  58  to the nipple connector  52 . Similarly, there is no need for caulking or adhesive to ensure an airtight fit of the hollow connector tubing  58  to the nipple connector  52 .  
         [0064]     The second hollow flexible tubing  64  is connected with a gas distributive device  70 . The point of the connection of the hollow flexible tubing  64  is connected with a gas distributive device  70  is with a unitary to binary connector  74 . The unitary to binary connector  74  connects at the unitary opening  76  to the hollow flexible tubing  64 . The unitary to binary connector  74  is in fluid communication with the hollow flexible tubing  64 . The second hollow flexible tubing  64  is permanently connected to the unitary to binary connector  74 .  
         [0065]     The unitary to binary connector  74  has a binary opening  78  at the end distal from the unitary opening  76 . The binary opening  78  is in fluid communication with the unitary opening  76  and accordingly with the second hollow flexible tubing  64 .  
         [0066]     The unitary to binary connector  74  is formed of a hollow tube  82  and a second hollow tube  84 . The first hollow tube  82  and the second hollow tube  84  are conveniently obtained as a co-extruded material. The first hollow tube  82  and the second hollow tube  84  are typically formed from a flexible material such as the previously discussed Tygon tubing. The first hollow tube  82  and the second hollow tube  84  are each separately in fluid communication with the binary opening  78 .  
         [0067]     A clip  88  is conveniently utilized to maintain the first hollow tube  82  and the second hollow tube  84  in close proximity. The clip  88  is a “C” shaped hard plastic into which the first hollow tube  82  and the second hollow tube  84  are inserted and held in place in the interior curvature of the “C” by pressure fitting. The clip  88  is with moderate effort slideably engaged on the outer surface of the first hollow tube  82  and the second hollow tube  84 .  
         [0068]     The first hollow tube  82  connects with nasal cannula  90  via a first nasal cannula fitting  92 . The second hollow tube  84  with a second nasal cannula fitting  96 . The first nasal cannula fitting  92  is in fluid communication with first hollow tube  82 . The nasal cannula  90  is connected with a second nasal cannula fitting  96 . The second nasal cannula fitting  96  is in fluid communication with second hollow tube  84 .  
         [0069]     The first nasal cannula fitting  92  and the second nasal cannula fitting  96  are a part of the hollow nasal cannula tube  98 . The first nasal cannula fitting  92  and the second nasal cannula fitting  96  are both in fluid communication with the hollow nasal cannula tube  98 .  
         [0070]     The nasal cannula tube  98  has protruding from it a pair of spaced apart nasal fittings  102  and  104 . The spaced apart nasal fittings  102  and  104  are in fluid communication with the hollow nasal cannula tube  98 .  
         [0071]     The spaced apart nasal fittings  102  and  104  have nasal orifices  108  and  110 . The nasal orifices  108  and  110  permit the flow of a medical gas out of the nasal cannula tube  98  to the nostrils of a patient in need of the medical gas.  
         [0072]     A retaining strap (not shown) is conveniently connected with the nasal cannula tube  98 . The retaining strap  118  permits the gas distributive device  70  to be retained around the neck of the patient while the patient is receiving the medical gas. To avoid accidental disconnection and the resultant false alarms, it is suggested that each of the hollow flexible tubing  14  and the hollow flexible tubing  64  be from 25 centimeters to 2 meters, preferably 30 centimeters to one meter in length.  
         [0073]     The personal gas delivery system  10  permits the hollow flexible tubing  14  to receive a medical gas, such as oxygen, from a medical gas supply source (not shown). The hollow flexible tubing  14  receives the medical gas allowing the flow of a medical gas to the hollow tubing connector  18 .  
         [0074]     The medical gas passes through the hollow tubing connector  18  in an uninterrupted flow to the gas flow alarm  20 . The medical gas passes through the gas flow alarm  20 . If the flow rate of the medical gas is below a predetermined point then the alarm is activated.  
         [0075]     The activation of the alarm may be by an audible signal to alert at least the patient that the flow rate of the medical gas is below a predetermined point. As the patient may be suffering from a hearing impairment it is also possible to utilize a visible light to alert the patient that the flow rate of the medical gas is below a predetermined point.  
         [0076]     As the patient may be patient may be suffering from a hearing impairment and a lack of visual acuity it is also possible to utilize a vibratory mechanism to alert the patient that the flow rate of the medical gas has fallen below a predetermined point. The vibratory mechanism is least favored, as it requires an external power source to avoid premature discharge of the batteries.  
         [0077]     Each of the alarms, audible, visual and vibratory has disadvantages. As noted the audible alarm is of limited value with a hearing impaired patient. The light activated alarm requires a sighted patient and is of little use when the patient is sleeping or when the alarm light is hidden beneath a blanket or other covering. Similarly, the vibratory mechanism as an alarm is of limited value when the patient is sleeping and may be covered with a blanket which may absorb the vibrations which are intended to alert the patient that the flow rate of the medical gas has fallen below a predetermined point.  
         [0078]     If the system is otherwise operating properly the medical gas flows through the gas flow alarm  20 , through the second nipple connector  52  and into the second hollow tubing connector  58 . The medical gas then flows from the second hollow tubing connector  58 , into hollow flexible tubing  64 , and from there into the gas distributive device  70 .  
         [0079]     The purpose of having the flow of medical gas divided into two flow paths is important in the present invention. As the gas flow alarm  20  is upstream from the nasal cannula tube  90  it possible for any of the components from the gas flow alarm  20  downstream to become non-functional, e.g. blocked. For example, one of the pair of spaced apart nasal fittings  102  and  104  may become blocked because of mucous in the opening the affected nasal fitting.  
         [0080]     Similarly, one of the first hollow tube  82  and a second hollow tube  84  may be crushed or otherwise blocked. As the present invention permits having the flow of medical gas divided into two flow paths at least some of the medical gas passing through one of the hollow tubes will likely reach the patient. In any other case, the alarm  20  may be fully functional and the patient would still not receive an adequate supply of the medical gas.  
         [0081]     Thus, as an additional feature to the alarm aspect of the present invention is a transmitter  200 . The transmitter  200  is shown in  FIG. 6 . The transmitter  200 , when connected with the gas flow alarm  20 , transmits the fact that the flow rate of the medical gas has fallen below a predetermined point to a remote receiving location such as a nursing station. The transmitter  200  is any conventional low power device that does not interfere with the operation of the overall system. The transmitter  200  transmits through an antenna  202 .  
         [0082]     A second embodiment of the present invention employs the feature of moisturizing a medical gas to be supplied to the patient. As best seen in  FIG. 5 , is a medical gas supply line  210 . The medical gas supply line  210  is connected with a humidifying vessel  220 . The humidifying vessel  220  comprises a humidify container  222  and a humming container cap  224 .  
         [0083]     The humidifying container  222  has a screw sealing mechanism at its upper opening. The humidifying container cap  224  has a screw sealing mechanism. The humidifying container cap  224  has a screw sealing mechanism is mated to the screw sealing mechanism of the humidifying container  222 . The humidifying container cap  224  has extending there through a first opening  228 . The humidifying container cap  224  has extending there through a second opening  232 .  
         [0084]     A gas delivery conduit  236  extends through the first opening  228  in the humidifying container cap  224 . The gas delivery conduit  236  extends into the humidifying container  222 , when the humidifying container cap  224  is screwed onto the humidifying container  222 , to a point just above the humidifying container lower surface  238 . In practice, the gas delivery conduit  236  will be below the level of the humidifying liquid in the humidifying container  222 .  
         [0085]     A gas receiving conduit  242  extends through the second opening  232  in the humidifying container cap  224 . The gas receiving conduit  242 , extends into the humidifying container  222 , when the humidifying container cap  224  is screwed onto the humidifying container  222 , to a point just below the bottom  244  of the humidifying container cap  224 . When the personal gas delivery system  10  is in operation the gas receiving conduit  242  will not extend below the level of the humidifying liquid in the humidifying container  222 .  
         [0086]     A medical gas is introduced to the delivery conduit  236  and into the humidifying container  222 . The humidifying container  222  is filed to a point about 2 centimeters below its top with distilled water. The gas delivery conduit  236  is below the level of the humidifying liquid in the humidify container  222 . The medical gas from the gas delivery conduit  236  is humidified in the humidifying container  222 .  
         [0087]     The gas receiving conduit  242  takes up the humidified medical gas. The double-headed arrows in  FIG. 5  show the direction of gas flow. The medical gas then passes through the gas flow alarm  20  as previously described.  
         [0088]     A third embodiment of the invention is shown in  FIG. 6 . In the last embodiment of he invention there is disclosed a switch  300  for the gas flow alarm  20 . The gas flow alarm  20  has an anterior surface  302 . Located on the anterior surface  302  is a light  304  for alerting the patient that the gas flow alarm  20  has detected a low pressure or low flow rate of the medical gas.  
         [0089]     To allow the patient to be confident that the gas flow alarm  20  is operating properly there is an alarm test switch  306 . A second switch on the anterior surface of the gas flow alarm  20  is a reset switch  306 . The reset switch  306  is located on the anterior surface  302  of the gas flow alarm  20 . The gas flow alarm  20 , when activated will provide a continuous signal until the alarm is reset, or the alarm is inactivated, or the batteries are depleted.  
         [0090]     Accordingly, there is a need to manually reset the alarm when the alarm is activated. When the medical gas supply is intentionally interrupted such as to replace the gas supply, to provide services to the patient such as bathing the patient, or to replenish the humidifying liquid  242  in the humidifying container  222 , it is desirable to turn off the gas flow alarm  20 . Accordingly, the gas flow alarm  20  may also provide an on off switch (or a test feature)  310 .  
         [0091]     Although the above description and accompanying drawings relate to a specific preferred embodiment as presently contemplated by the inventors, it will be understood that the invention in its broad aspect includes mechanical and functional equivalents of the elements described and illustrated.