Abstract:
A system and method to prevent the improper installation of the inlet fittings for a ventilation system is disclosed. The ventilator has two inlet openings configured to accept two different inlet fittings (also called inlet fixtures). The inlet openings are different such that each inlet opening will only accept its corresponding inlet fitting. The difference between the two inlet openings can be a difference in size, shape, the inclusion of a key feature, or a combination of the above.

Description:
RELATED APPLICATIONS  
       [0001]     This application is related to applications “A PNEUMATIC SHUTTLE VALVE FOR A VENTILATOR SYSTEM,” A VENTILATOR SYSTEM,” “AN INTEGRATED MANIFOLD FOR A VENTILATOR SYSTEM,” “A MANIFOLD ASSEMBLY FOR A REGULATOR SYSTEM” and “AN INTEGRATED REGULATOR MOUNT FOR A VENTILATOR SYSTEM” filed on the same day as this application and included by reference into this application.  
       BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The invention is related to the field of heath care products, and in particular, to a portable ventilator system.  
         [0004]     2. Description of the Prior Art  
         [0005]     Ventilator systems typically combine a high pressure oxygen flow with a compressed air flow to form a controlled ratio low pressure flow suitable for delivery into a patient&#39;s lungs. A regulator is used to reduce the pressure of a high pressure oxygen source to a controlled output pressure. The regulator is configured to accept a wide range of input pressures from the oxygen source and produce a constant low pressure, variable flow, output source. Typically the high pressure oxygen is passed through a filtering system before being introduced into the regulator. A second regulator is used to reduce the pressure of a compressed air source to the same controlled output pressure as the oxygen regulator. Typically the compressed air is passed through a separate filtering system before being introduced into the second regulator. Once the pressures of the oxygen and air have been reduced, the two flows are mixed together in a controlled ratio and delivered to a patient. The ratio of oxygen to air is typically a programmable ratio and can be set anywhere between 100% oxygen 0% air, to 0% oxygen 100% air.  
         [0006]     The high pressure oxygen source may be bottled oxygen or may come from a hospital wall supply. Both types of oxygen sources typically connect to the same fitting on the ventilator system. The compressed air source may be a built in air compressor or may use a hospital compressed air wall supply. The two types of compressed air typically  5  connect to different fittings on the ventilator system. There is typically a system of check valves or switching valves that allow the compressed air supply to be changed from the hospital wall source to the air compressor during use by a patient. Currently, ventilator systems connect the filters, regulators, and check valves through a number of different pipes and fittings. Unfortunately, each joint in the series of pipes and fittings is a potential place for a leak. Because oxygen is highly combustible, any leak can be a danger to the patient or the heath care provider. The complex gas passageways may be costly to produce and may produce pressure drops due to the many flow restrictions.  
         [0007]     Today&#39;s ventilator systems may also have a number of usability problems. Many of the ventilator systems used today have the oxygen and compressed air connections in difficult to use locations, for example underneath the unit and partially enclosed. This makes it difficult for the heath care provider to connect the oxygen and air supply to the ventilator. The air and oxygen filters typically have replaceable components. In many of today&#39;s ventilators, the two filters are located in different areas on the unit and may be difficult to access.  
         [0008]     Therefore there is a need for an improved ventilator system.  
       SUMMARY OF THE INVENTION  
       [0009]     A system and method to prevent the improper installation of the inlet fittings for a ventilation system is disclosed. The ventilator has two inlet openings configured to accept two different inlet fittings (also called inlet fixtures). The inlet openings are different such that each inlet opening will only accept its corresponding inlet fitting. The difference between the two inlet openings can be a difference in size, shape, the inclusion of a key feature, or a combination of the above.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]      FIG. 1  is an isometric view of the back side of an integrated manifold assembly  100  in one example embodiment of the invention.  
         [0011]      FIG. 2  is an isometric view of the front of an integrated manifold assembly  200  in one example embodiment of the invention.  
         [0012]      FIG. 3   a  is a cutaway view of a pneumatic shuttle valve in one example embodiment of the invention.  
         [0013]      FIG. 3   b  is a cutaway view of a pneumatic shuttle valve with a straight shouldered shape in one example embodiment of the invention.  
         [0014]      FIG. 3   c  is a cutaway view of a shuttle valve in another example embodiment of the invention.  
         [0015]      FIG. 4  is an isometric top view of manifold  402  in one example embodiment of the invention.  
         [0016]      FIG. 5  is an isometric bottom view of manifold  502  in one example embodiment of the invention.  
         [0017]      FIG. 6  is a bottom view of a drawing of manifold  602  in one example embodiment of the invention.  
         [0018]      FIG. 7  is a sectional view of the oxygen flow path through manifold  702  in one example embodiment of the invention.  
         [0019]      FIG. 8  is a sectional view of the oxygen flow pathway in a manifold assembly in one example embodiment of the invention.  
         [0020]      FIG. 9  is a sectional view of the air flow pathway through manifold  902  in one example embodiment of the invention.  
         [0021]      FIG. 10  is a sectional view of the compressed air pathway in a manifold assembly in one example embodiment of the invention.  
         [0022]      FIG. 11  is a drawing of a compressed air filter adapter in one example embodiment of the invention.  
         [0023]      FIG. 12  is a drawing of a compressed air filter bowl in one example embodiment of the invention.  
         [0024]      FIG. 13  is an exploded view of a manifold assembly in one example embodiment of the invention.  
         [0025]      FIG. 14  is a drawing of an air fitting in one example embodiment of the invention.  
         [0026]      FIG. 15  is a drawing of an oxygen fitting in one example embodiment of the invention.  
         [0027]      FIG. 16  is a drawing of a horse shoe clip in one example embodiment of the invention.  
         [0028]      FIG. 17  is an isometric front view of a ventilator system in an example embodiment of the invention.  
         [0029]      FIG. 18  is an isometric back view of a ventilator system in an example embodiment of the invention.  
         [0030]      FIG. 19  is a drawing of shuttle plug cap  1932  in an example embodiment of the invention.  
         [0031]      FIG. 20  is a drawing of Pneufit self sealing connector  2055  in one example embodiment of the invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0032]      FIGS. 1-20  and the following description depict specific examples to teach those skilled in the art how to make and use the best mode of the invention. For the purpose of teaching inventive principles, some conventional aspects have been simplified or omitted. Those skilled in the art will appreciate variations from these examples that fall within the scope of the invention. Those skilled in the art will appreciate that the features described below can be combined in various ways to form multiple variations of the invention. As a result, the invention is not limited to the specific examples described below, but only by the claims and their equivalents.  
         [0033]      FIG. 1  is an isometric view of the back side of a manifold assembly  100  in one example embodiment of the invention. Manifold assembly  100  comprises manifold  102 , oxygen filter  104 , compressed air filter  106 , compressed air regulator  108 , oxygen regulator  110 , compressed air outlet fixture  112 , oxygen outlet fixture  114 , horse shoe clips  116  and  120 , and plug  122 .  
         [0034]     In operation a high pressure oxygen source (not shown) is connected to an oxygen inlet fixture (not shown) mounted on the front side of the manifold  102 . The high pressure oxygen typically comes from either an in wall oxygen source or an oxygen tank. The high pressure oxygen passes through oxygen filter  104  and then is directed to oxygen regulator  110 . Oxygen filter  104  is mounted on the bottom face of manifold  102 . Oxygen regulator  110  is configured to accept a wide range of input pressures from the oxygen source and produce a constant low pressure, variable flow, oxygen output. Oxygen regulator  110  is mounted on the top side of manifold  102 . The low pressure flow from oxygen regulator  110  exits the integrated manifold assembly  100  through oxygen outlet connector  114  mounted on the back side of manifold  102 . A compressed air source (not shown) is connected to a compressed air inlet fixture (not shown) mounted on the front side of the manifold  102 . The compressed air typically comes from an in wall compressed air source. The compressed air passes through compressed air filter  106  and then is directed to compressed air regulator  108 . Compressed air filter  106  is mounted on the bottom face of manifold  102  and is a different diameter than oxygen filter  104 . Compressed air regulator  108  is configured to accept a wide range of input pressures from the compressed air source and produce a constant low pressure, variable flow, air output. Compressed air regulator  108  is mounted on the top side of manifold  102 . The low pressure flow from compressed air regulator  108  exits the integrated manifold assembly  100  through compressed air outlet connector  112  mounted on the back side of manifold  102 . In one example embodiment of the invention, compressed air regulator  108  and oxygen regulator  110  are essentially identical.  
         [0035]      FIG. 2  is an isometric view of the front of a manifold assembly  200  in one example embodiment of the invention. Manifold assembly  200  comprises manifold  202 , oxygen filter  204 , compressed air filter  206 , compressed air regulator  208 , oxygen regulator  210 , compressed air inlet opening  226 , oxygen inlet opening  224 , compressor inlet opening  274 , and shuttle plug cap  228 .  
         [0036]     In operation, a compressed air source (not shown) is connected to compressed air inlet opening  226  on the front side of the manifold  202 . The compressed air passes through compressed air filter  206  and then is directed to compressed air regulator  208 . A compressor (not shown) can also be used as the compressed air source. When using a compressor as the compressed air source, the compressor is connected to the manifold using compressor inlet opening  274 . A pneumatic shuttle valve is configured to switch between the compressed air inlet fixture and the compressor inlet fixture, dependent on which fixture is being used as the air source.  
         [0037]      FIG. 3   a  is a cutaway view of a pneumatic shuttle valve in one example embodiment of the invention. In one example embodiment of the invention, pneumatic shuttle valve  300  may be formed into manifold  302 . Pneumatic shuttle valve  300  comprises manifold  302 , shuttle plug cap  332 , and shuttle plug  336 . Manifold  302  forms a shuttle valve passageway  351 , a first inlet opening  334  and first sealing surface  340 . Shuttle plug cap  332 , threaded into manifold  302 , forms a second inlet opening  312  and a second sealing surface  342 . Manifold  302  also forms outlet opening  338 . In one example embodiment of the invention, there may be an o-ring or gasket used to form a seal between shuttle plug cap  332  and manifold  302 .  
         [0038]     In operation, when a compressed air source or other high pressure gas is attached to inlet opening  334  and there is nothing attached to inlet opening  312 , the high pressure air entering inlet opening  334  forces shuttle plug  336  against sealing surface  342  in shuttle plug cap  332  preventing flow through inlet opening  312 . With shuttle plug  336  forced against sealing surface  342  the high pressure air from inlet opening  334  is forced into outlet opening  338 . When a compressed air source is attached to inlet opening  312  and there is nothing attached to inlet opening  334 , the high pressure air entering inlet opening  312  forces shuttle plug  336  against sealing surface  340  formed in manifold  302 , preventing flow through inlet opening  334 . With shuttle plug  336  forced against sealing surface  340  the high pressure air from inlet opening  312  is forced into outlet opening  338 . When both inlet openings have an air supply attached to them, the pneumatic shuttle valve will seal the inlet opening to the source having the lowest amount of pressure.  FIG. 3   a  and  3   c  shows the sealing surfaces  340  and  342  as conical surfaces. Other shapes may be use, for example a spherical shape, a straight shouldered shape, or the like.  FIG. 3   b  is a cutaway view of a pneumatic shuttle valve with a straight shouldered shape in one example embodiment of the invention.  
         [0039]      FIG. 3   c  is a sectional view of a shuttle valve in another example embodiment of the invention.  FIG. 3   c  comprises manifold  302 , shuttle plug cap  332 , and shuttle plug  336 . In the example embodiment shown in  FIG. 3c , both inlet openings ( 312  and  334 ) are formed into manifold  302 . Inlet opening  312  passes through the shuttle plug cap. Inlet opening  312  enters the side of shuttle plug cap  332  and exits from the end of shuttle plug cap. The shuttle plug cap shown in  FIG. 3   c  performs a number of different functions, the shuttle plug cap forms sealing surface  342 , allows access for shuttle plug  336  to be inserted into the shuttle valve passageway  351 , forms part of one of the inlet opening  312 , and seals the shuttle valve passageway  351 .  FIG. 19  is a drawing of shuttle plug cap  1932  in an example embodiment of the invention.  
         [0040]      FIGS. 3a, 3   b  and  3   c  show shuttle plug  336  as a spherical shape, but shuttle plug may be formed into other shapes, for example a cylindrical shape with conical ends. Any combination of shapes can be used between sealing surfaces  340  and  342  and the corresponding shuttle plug shape, as long as the shuttle plug forms a seal against the sealing surface when the shuttle plug is forced against the sealing surface by the high pressure gas.  
         [0041]      FIG. 4  is an isometric top view of manifold  402  in one example embodiment of the invention. Manifold  402  has integrated compressed air regulator mount  450  and integrated oxygen regulator mount  452  formed into the top surface of manifold  402 . Four bolt holes  460  are used to attach each regulator to their respective integrated regulator mounts. Compressed air inlet opening  426  and oxygen inlet opening  424  are formed into the front face of manifold  402 . Optional air pressure sensor mount  454  is formed into the top surface of manifold  402  and intersects with compressed air inlet opening  426 . Optional oxygen pressure sensor mount  456  is formed into the top surface of manifold  402  and intersects with oxygen inlet opening  424 . Shuttle plug access port  458  is formed into the side of manifold  402  and is used to insert a shuttle plug into a pneumatic shuttle valve formed inside manifold  402 . Screw holes  462  are used to attach horse shoe clips (not shown) that hold a compressed air connector (not shown) and an oxygen connector (not shown) into compressed air inlet opening  426  and oxygen inlet opening  424 . In one example embodiment of the invention, manifold  402  is fabricated from metal, for example Aluminum, stainless steal or the like. Other materials may also be used to form manifold  402 , for example plastic, or a ceramic material.  
         [0042]      FIG. 5  is an isometric bottom view of manifold  502  in one example embodiment of the invention. Air outlet opening  564  and oxygen outlet opening  566  are formed into the back face of manifold  502 . Integrated air filter mount  570  and integrated oxygen filter mount  568  are formed into the bottom side of manifold  502 . Compressor inlet opening  574  is also formed into the bottom side of manifold  502 . Oxygen regulator access port  572  is also formed into the bottom of manifold  502 .  
         [0043]      FIG. 6  is a bottom view of a drawing of manifold  602  in one example embodiment of the invention. Integrated air filter mount  670  and integrated oxygen filter mount  668  are formed into the bottom side of manifold  602 . Compressor inlet opening  674  and oxygen regulator access port  672  are also formed into the bottom side of manifold  602 . Oxygen filter inlet port  676  and oxygen filter outlet port  678  can be seen in integrated oxygen filter mount  668  formed in the bottom surface of manifold  602 . Oxygen regulator inlet port  686  can be seen in oxygen regulator access port  672 . Air filter inlet port  680 , air filter outlet ports  682  and air regulator inlet port  684  can be seen in integrated air filter mount  670  formed into the bottom of manifold  602 .  
         [0044]     There may be two main flow paths in the manifold, one for oxygen and one for air. The oxygen flow path is shown in sectional view BB from  FIG. 6 . The air flow path is partially shown in sectional view AA from  FIG. 6 . The air flow path can not be fully shown in sectional view AA because the air flow path is more complex. The air flow path is more complex for a number of reasons. The first reason is that the compressed air source can be connected to the manifold in two different locations, at the compressed air inlet opening (not shown) on the front face of the manifold or at the compressor inlet opening  674  on the bottom side of the manifold. A pneumatic shuttle valve is built into the manifold that switches between the two potential connection points for the compressed air source. In addition, the air filter is much larger than the oxygen filter, so some of the gas passageways have been rotated 90 deg. to help limit the manifold to a given width.  
         [0045]      FIG. 7  is a sectional view of the oxygen flow path through manifold  702  in one example embodiment of the invention.  FIG. 7  is from section BB of  FIG. 6 . Oxygen path starts at oxygen inlet opening  724  that forms a passageway connecting to oxygen filter inlet port  776  in integrated oxygen filter mount  768 . Integrated oxygen filter mount  768  is formed into the bottom side of manifold  702 . Oxygen filter outlet port  778  exits from integrated oxygen filter mount  768  and is connected to oxygen regulator inlet port  786  by a passageway formed in the side of oxygen access port  772 . Oxygen then flows into oxygen regulator inlet port  793  and out of oxygen regulator outlet port  794 . Oxygen regulator outlet port  794  is connected to Oxygen outlet port  766 . An optional oxygen pressure sensor mount  756  can be formed into the top surface of manifold  702 . The oxygen pressure sensor mount  756  is directly coupled to the oxygen inlet opening  724 . Because of the direct coupling to the inlet opening, a pressure sensor mounted in this location may be more sensitive to changes in the oxygen inlet pressure.  
         [0046]      FIG. 8  is a sectional view of the oxygen flow pathway in a manifold assembly in one example embodiment of the invention. The manifold assembly comprises manifold  802 , oxygen filter element  890 , oxygen filter bowl  888 , valve spring retaining plug  892 , valve seat  896 , and oxygen regulator  810 . Some parts in the manifold assembly have been removed for clarity, for example the valve assembly and valve spring.  
         [0047]     In operation, oxygen enters the oxygen inlet opening  824  formed in manifold  802 . The oxygen is forced through oxygen filter element  890  that is attached to oxygen filter inlet port  876 . Oxygen filter bowl  888  forces the oxygen into oxygen filter outlet port  878 . The oxygen then exits the oxygen regulator inlet port  886  and is forced by valve spring retaining plug  892  past oxygen valve seat  896  into oxygen outlet opening  866 . Valve seat  896  is configured to mount directly into manifold  802 . The interaction of oxygen regulator and valve spring/valve seat are well known in the art and are not shown to make the oxygen passageways in the manifold more visible. The oxygen filter element  890  that is used is typically a standard oxygen filter element.  
         [0048]     Using this configuration for the oxygen path reduces the number of joints between the oxygen path and the outside air to  3  joints. The first joint is between the oxygen filter bowl and the manifold. The second joint is between the oxygen valve retainer plug and the manifold. The third joint is between the oxygen regulator and the manifold. An additional joint is created when optional oxygen pressure sensor mount is installed. By reducing the number of joints in the oxygen flow path, the potential for leaks has been reduced. The simplified oxygen flow path also reduced the pressure drop through the system.  
         [0049]      FIG. 9  is a sectional view of the air flow path through manifold  902  in one example embodiment of the invention.  FIG. 9  is from section AA of  FIG. 6 . In one example embodiment there may be two possible connections for the compressed air source. The compressed air source can be connected at a compressed air inlet opening or at a compressor inlet opening (not shown). Both inlet openings lead to the exit port  938  of the pneumatic shuttle valve. When there are two sources, opening  953  is used for manufacturing access and is plugged during operation, typically with a ball bearing  5  inserted into opening  953 . When there is only one connection for the compressed air source, opening  953  would be the compressed air inlet opening. A passageway connects the exit port  938  to compressed air filter inlet port  980  in integrated compressed air filter mount  970 . Integrated compressed air filter mount  970  is formed into the bottom side of manifold  902 . The compressed air filter outlet port and the compressed air regulator inlet  10  port have been rotated  90  degrees and are not in the plain cut by view AA, but can be seen in  FIG. 6 . Compressed air filter outlet port  682  exits from integrated compressed air filter mount  670  and is connected to compressed air regulator inlet port  684  by a passageway formed in compressed air filter mount  670 . Compressed air flows into compressed air regulator inlet port  684  and out of compressed air regulator outlet port  15   986 . Compressed air regulator outlet port  986  is connected to compressed air outlet port  982 . Valve seat (not shown) is configured to mount directly into manifold  902 . An optional compressed air pressure sensor mount  954  can be formed into the top surface of manifold  902 . The compressed air pressure sensor mount  982  is directly coupled to the compressed air inlet opening. Because of the direct coupling to the inlet opening, a  20 - pressure sensor mounted in this location may be more sensitive to changes in the compressed air inlet pressure.  
         [0050]      FIG. 10  is a sectional view of the compressed air pathway in a manifold assembly in one example embodiment of the invention. Manifold assembly comprises manifold  1002 , compressed air filter bowl  1021 , compressed air filter element  1023 ,  25  compressed air filter adapter  1025 , valve spring retaining plug  1092 , and compressed air regulator  1008 .  FIG. 11  is a drawing of compressed air filter adapter  1125  in one example embodiment of the invention.  FIG. 12  is a drawing of compressed air filter bowl  1221  in one example embodiment of the invention. Some parts in the manifold assembly have been removed for clarity, for example the air valve assembly, air valve  30  seat and air valve spring.  
         [0051]     In operation, compressed air enters one of the compressed air inlet opening (not shown) formed in manifold  1002 . The pneumatic shuttle valve (not shown) forces the air into shuttle valve exit port  1038  and enters the inlet port of the compressed air filter mount  1080 . The compressed air is forced through compressed air filter element  1023  that is attached to compressed air filter adaptor  1025 . Compressed air filter bowl  1021  forces the compressed air into compressed air filter outlet port  682 . The compressed air then exits the compressed air regulator inlet port  684  and is forced by valve spring retaining plug  1092  into compressed air outlet opening  1086 . The interaction of compressed air regulator and valve spring/valve seat are well known in the art and are not shown to make the compressed air passageways in the manifold more visible. The compressed air filter element  1023  that is used is typically a standard compressed air filter element.  
         [0052]     Using this configuration for the compressed air path reduces the number of joints between the compressed air path and the outside air to 2 joints. The first joint is between the compressed air filter bowl and the manifold. The second joint is between the compressed air regulator and the manifold. An additional joint is created when optional compressed air pressure sensor mount is installed. By reducing the number of joints in the compressed air flow path, the potential for leaks has been reduced. The simplified compressed air flow path also reduced the pressure drop through the system.  
         [0053]      FIG. 13  is an exploded view of a manifold assembly in one example embodiment of the invention. Manifold assembly comprises: manifold  1302 , oxygen regulator case  1310 , compressed air regulator case  1308 , shuttle plug  1332 , shuttle plug cap  1328 , two valve seats  1396 , two valve spring assemblies  1327 , two valve spring retaining plugs  1392 , air filter adaptor  1325 , air filter element  1323 , air filter bowl assembly  1321 , oxygen filter bowl  1388 , and oxygen filter element  1390 . Air filter bowl assembly comprise air filter bowl and a drain valve mounted in the bottom surface of the air filter bowl. The two valve seats mount directly into their respective regulator mounts formed into the manifold  1302 . The two valve spring assemblies are held against, and interact with, the valve seats, by the two valve spring retaining plugs.  
         [0054]     In prior art air filter bowl assemblies, the drain valve was a manual valve. To drain accumulated liquid using a manual drain valve the user would have to hold a cup or bucket underneath the air filter assembly while trying to open the drain valve. This was awkward at best and could cause the liquid to spill or spray onto the user. In one example embodiment of the current invention, a Pneufit self sealing connector is used in the bottom of the air filter assembly, for example the self sealing connector made by Norgren, part number 12 424 0418. With this fixture installed in the filter bowl, to drain accumulated liquid the user just inserts a tube into the end of the fitting. The tube compresses a spring and unseats a plunger, allowing the fluid to drain through the inserted tube. One end of the tube may be already inserted into a bucket or drain. Once the fluid has been removed, the user may remove the tubing, allowing the plunger to reseat and reseal the drain fixture.  FIG. 20  is a drawing of Pneufit self sealing connector  2055  in one example embodiment of the invention. Self-sealing connectors may also be known as quick-action couplers, single-poppet connector, or self-sealing couplers.  
         [0055]     A compressed air inlet fitting and an oxygen inlet fitting are attached to a manifold by two horse shoe clips in one example embodiment of the invention.  FIG. 14  is a drawing of a compressed air inlet fitting in one example embodiment of the invention.  FIG. 14  shows compressed air inlet fitting  1429  with O-ring groove  1433  and horse shoe groove  1435 .  FIG. 15  is a drawing of an oxygen inlet fitting in one example embodiment of the invention.  FIG. 15  shows oxygen inlet fitting  1531  with O-ring groove  1533  and horse shoe groove  1535 . In one example embodiment of the invention, oxygen inlet fitting  1531  and compressed air inlet fitting  1429  are configured to be incompatible such that the oxygen source can not be connected to the compressed air inlet fitting  1429  and the compressed air source can not be connected to the oxygen inlet fitting  1531 . In addition, the outer diameter of the fittings and the inlet openings in the manifold that the fittings mates with, may be sized differently for the two fittings. In one example embodiment of the invention the air inlet fitting may have an outer diameter of 0.816 inches and the air inlet opening in the manifold may be 0.820 inches in diameter, where the oxygen inlet fitting may have a diameter of 0.881 inches and the oxygen inlet opening in the manifold may be 0.866 inches in diameter. This prevents the oxygen inlet fitting from being installed in the compressed air inlet opening of the manifold. By making the outer diameter and mating holes different sizes for the two fittings and making the fittings incompatible, the oxygen source and the air source are more likely to be connected to the correct place in the ventilator system. Other design choices can be made to prevent the oxygen inlet fixture from being installed in the incorrect inlet opening. For example, the size or shape may be different between the two inlet openings and their corresponding inlet fittings, or a key feature may be added to one of the inlet fittings and the corresponding inlet opening. A key feature is typically one or more features that prevent the insertion of a mating part that does not contain the corresponding features, for example a slot with a matching protrusion.  
         [0056]     A filter disk, for example a filter disk having openings  40  microns in size, may be inserted into the oxygen inlet opening. The filter disk would be held inside the oxygen inlet opening by the oxygen inlet fitting. In one example embodiment of the invention, a spring may be inserted with the filter disk to force the filter disk against the manifold. The filter disk may prevent contamination from entering the manifold when an oxygen source is not coupled to the oxygen inlet fitting.  
         [0057]      FIG. 16  is a drawing of a horse shoe clip in one example embodiment of the invention. Horse shoe clip  1642  has two screw holes  1637  and retaining feature  1639 . In operation, O-rings are installed into the two O-ring grooves on the oxygen and air fittings. The retaining feature  1639  of two horse shoe clips mates with the horse shoe groove ( 1535  and  1435 ) in air fitting  1429  and in oxygen fitting  1531 . Screws inserted through screw holes  1637  hold horse shoe clip onto manifold, thereby securing the air and oxygen fittings into their respective inlet ports in the manifold.  
         [0058]      FIG. 17  is an isometric front view of a ventilator system in an example embodiment of the invention. Ventilator system  1743  has display  1747  and gas outlet port  1745 .  FIG. 18  is an isometric back view of a ventilator system in an example embodiment of the invention. Ventilator system  1842  has a cutout region  1849 . Oxygen filter  1804  and air filter  1806  extend down into cutout region  1849 , allowing easy access to the two filters. Cutout region allows the oxygen and compressed air filters to be exposed for easy access by a user. This allows a user to change the filter elements in the filters, or drain any accumulated liquid in the air filter, without having to open a panel in the ventilator system. Oxygen inlet fitting  1814  and air inlet fitting  1812  are located on the back face of ventilator system  1842 , allowing easy access to the two inlet fittings. In one example embodiment of the invention, a manifold assembly is hidden inside the ventilator system just above cutout region  1849  and includes oxygen inlet fitting  1814 , air inlet fitting  1812 , oxygen filter  1804  and air filter  1806 .