Abstract:
A disposable manometer includes a chamber connectable to a source of respiratory gases via a patient breathing valve and a passageway. A pointer is rotatably disposed with respect to a dial to indicate pressure within the chamber. The pointer has an actuator stem with a spiral-shaped protrusion coupled to a groove within an opening of a stem coupling attached at the center of a diaphragm forming one wall of the chamber. Responsive to pressure entering the chamber, the diaphragm reciprocates against the force of a biasing non-magnetic resilient member moving the stem coupling with respect to the actuator stem of the pointer so that the interaction between the spiral-shaped protrusion and the groove causes rotation of the pointer to indicate the pressure within the chamber. The disposable manometer is useful with any source of respiratory gasses and in the vicinity of any strong magnetic field.

Description:
FIELD 
     This invention relates to the field of medicine and more particularly to a device for measuring air pressure that is useful in the vicinity of strong magnetic fields as experienced near an operating Magnetic Resonance Imaging (MRI) system. 
     BACKGROUND 
     The present invention relates to a disposable manometer for use with a source of respiratory gases such as a cardio-pulmonary resuscitator (CPR) bag or other ventilation devices. In the prior art, manometers are known, however, such devices do not include all of the features and aspects of the present invention. For example, U.S. Pat. No. 3,975,959 to Larkin which discloses a pressure gauge including a dial with an indicator pointer connected to a cylindrical follower having projections coupled with grooves formed in a stem portion connected to a movable wall. The movable wall is exposed to a source of air pressure and reciprocates the stem portion directly responsive to changes in air pressure to cause rotation of the follower and the pointer. Devices of the prior art will not provide accurate readings when exposed to the strong electromagnetic radiation of various clinical devices such as a Magnetic Resonance Imaging (MRI) system. 
     Another example is shown in U.S. Pat. No. 5,557,049 to Jeffrey B. Ratner which discloses a disposable manometer. The disclosed manometer has a typical metal spring that operates correctly in most situations but the use of such a manometer in the vicinity of an operational Magnetic Resonance Imaging (MRI) system often results in either a false pressure reading due to the extreme magnetic fields produced by the Magnetic Resonance Imaging system or, in extreme cases, such a manometer is often moved, possibly quickly, creating the possibility of inflicting injuries or damaging equipment. 
     Applicant is not aware of any helix-style manometer device that, prior to this invention, provides accurate readings in the presence of magnetic fields of devices such as a Magnetic Resonance Imaging (MRI) system. 
     What is needed is a helix style manometer device that will provide accurate readings in the presence of magnetic fields of a Magnetic Resonance Imaging (MRI) system. 
     SUMMARY 
     This application relates to a disposable manometer for use with a source of respiratory gases such as a cardio-pulmonary resuscitator (CPR) bag or other ventilation devices. The disposable manometer includes the following interrelated objects, aspects and features: 
     The disposable manometer is intended for use in conjunction with a source of respiratory gases such as a cardio-pulmonary resuscitation bag and performs in the presence of magnetic fields encountered in or near devices such as a Magnetic Resonance Imaging (MRI) system. As an example of respiratory gases, the CPR bag includes a bulb squeezable to dispense air through a duckbill check valve to an outlet coupled to a face mask placeable over the patient&#39;s nose and mouth. When the patient exhales, the exhaled air is prevented from flowing in the reverse direction by a duckbill check valve and instead lifts the peripheral edges of the duckbill check valve to expose an exhaust port exhausting the air to atmosphere. 
     The disposable manometer is coupled to air expelled by the source of respiratory gases such as the CPR bag. The operator of the source of respiratory gases (CPR bag) monitors the pressure of gases being supplied to and from the patient. 
     The disposable manometer includes a housing having a first chamber and a second chamber separated by a movable wall, for example, a diaphragm. The first chamber is connected to the source of air pressure (e.g. the CPR bulb) and the second chamber is exhausted to atmosphere by a suitable vent. A non-ferromagnetic resilient member contained within the second chamber biases the diaphragm. 
     A stem coupling is attached at approximately the center of the diaphragm and has an opening there through including a generally circular portion and a groove extending radially outwardly from the circular portion. In the preferred embodiment, the stem coupling is elongated into the second chamber and has a surface that engages the non-ferromagnetic resilient member. 
     A circular dial is provided with indicia thereon indicating a range of pressures. A pointer is rotatably disposed with respect to the dial and includes an actuator stem received within the generally circular portion of the opening through the stem coupling. The actuator stem also has a peripheral outwardly extending spiral-shaped protrusion received within the stem coupling groove. In this way, reciprocations of the stem coupling translate to rotations of the actuator stem as the stem coupling moves upwardly and downwardly acting upon the captured spiral-shaped protrusion of the actuator stem. The non-ferromagnetic resilient member is so sized and configured that when the pressure within the first chamber of the manometer housing is at atmospheric pressure, the pointer is at a rest position. As pressure increases within the first chamber causing the diaphragm and the stem coupling to move downwardly, the pointer moves along the indicia reading the pressure in the first chamber. When the pressure is released, the non-ferromagnetic resilient member restores the position of the diaphragm and stem coupling and thus the position of the pointer to the rest position (e.g. zero). 
     These and other objects, aspects and features of the disposable manometer will be better understood from the following detailed description of the preferred embodiment when read in conjunction with the appended drawing figures. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention can be best understood by those having ordinary skill in the art by reference to the following detailed description when considered in conjunction with the accompanying drawings in which: 
         FIG. 1  shows a perspective view of a CPR bag having the inventive disposable manometer attached thereto. 
         FIG. 2  shows a top view of the disposable manometer. 
         FIG. 3  shows an exploded perspective view of the disposable manometer. 
         FIG. 4  shows a perspective view of the disposable manometer. 
         FIG. 5  shows a cross-sectional view through the disposable manometer and a portion of the CPR bag housing with the manometer and diaphragm at an upper position thereof so that the dial pointer reads zero pressure. 
         FIG. 6  shows a cross-sectional view through the disposable manometer and a portion of the CPR bag housing showing the effect of air pressure within the first chamber of the manometer housing on the position of the diaphragm and pointer and other associated structure. 
         FIG. 6B  shows a cross-sectional view through the disposable manometer and a portion of the CPR bag housing showing the effect of air pressure from the patient. 
         FIG. 7  shows a perspective view of the inventive disposable manometer fluidly coupled to a patient breathing tube. 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made in detail to the presently preferred embodiments of the invention, examples of which are illustrated in the accompanying drawings. Throughout the following detailed description, the same reference numerals refer to the same elements in all figures. 
     With reference, first, to  FIG. 1 , a typical source of respiratory gases such as a cardio-pulmonary resuscitator (CPR) bag or other ventilation devices is generally designated by the reference numeral  1  and, for example, is shown as a squeeze bulb  2  connected between an inlet  3  and an outlet  4 . As is known to those skilled in the art, the inlet  3  customarily includes a flexible inlet check valve (not shown) allowing the bulb  2  to fill with air when it is released from a compressed position. The check valve  8  (See  FIGS. 5 ,  6  and  6 B) allows flow of air from the bulb  2  but not into the bulb  2  from the patient. Thus, when the bulb  2  is squeezed, the inlet check valve within the inlet  2  closes and the outlet check valve  8  opens to allow air to flow there past. When the bulb  2  is released, the outlet check valve  8  closes and the inlet check valve within the inlet  3  opens allowing the bulb to be filled with a fresh supply of air. This operation is known to those skilled in the art. Any source of respiratory gases is anticipated. 
     The outlet fitting  4  leads to a patient breathing valve  50  through passageway  5  ( FIGS. 5 and 6 ) leading to an internal chamber  6  having an outlet  7  controlled by a duckbill-type check valve  8 . The check valve  8  has an outlet orifice  9  opened when pressure above a threshold level is within the chamber  6 . When pressure in the outlet  7  is greater than pressure in the chamber  6 , the opening  9  of the duckbill check valve  8  is closed as shown in  FIG. 6B  to prevent reverse flow into chamber  6 . When reverse flow occurs, with reference to  FIG. 6B , the duckbill check valve  8  has a surface  10  resting on a seat  11  forming a portion of the outlet  7 . In response to reverse flow of air into the outlet  7 , the portion  10  of the duckbill check valve lifts off the seat  11  while the opening  9  of the duckbill check valve  8  remains closed thereby exposing return air flow to the chamber  12  connected to atmosphere via a series of vent ports  13 . Thus, the duckbill check valve  8  actually operates as a supply and exhaust valve, supplying the patient by the outlet  7  and the mask  14  (see  FIG. 1 ) and exhausting the exhalations of the patient via the mask  14 , outlet  7 , chamber  12  and vent ports  13 . 
     The disposable manometer is generally designated by the reference numeral  20  and, with particular reference, first, to  FIGS. 5 ,  6  and  6 B, includes a housing  21  defining a first chamber  23  and a second chamber  25  which contains a non-ferromagnetic resilient member  27  for a purpose to be described in greater detail hereinafter. The non-ferromagnetic resilient member  27  is made of a non-ferromagnetic material so that it is not pulled, deformed or moved by the strong magnetic forces encountered in or near a device such as a Magnetic Resonance Imaging System (MRI). Other equipment such as stethoscopes made with non-ferromagnetic materials are available for use in the vicinity of Magnetic Resonance Imaging Systems, but, to date, the industry lacks a disposable manometer that meets such requirements with the disclosed helix and dial. 
     An elongated passageway  29  interconnects the first chamber  23  of the disposable manometer housing  21  with the chamber  6  of the CPR bag via an orifice  31 . Other arrangements of the orifice  31  and passageway  29  are anticipated performing similar functionality. 
     The passageway  29  includes a portion  33  incorporated into a patient breathing valve extension  50  of the CPR bag  1 , a further passageway  35  incorporated into the disposable manometer housing  21  and an entry orifice  37  connecting the passageway  35  to the chamber  23 . 
     With further reference to  FIGS. 5 and 6  in particular, the first chamber  23  and second chamber  25  are separated by a movable wall such as, for example, the diaphragm  39  which includes a peripheral enlarged area  41  captured between a shoulder  43  of the housing  21  and an annular protrusion  47  of a cap  45  of the housing. The diaphragm has a central opening  49  carrying a stem coupling  51  having an internal chamber and a first closure  55  having a surface  57  which rests on the top of the non-ferromagnetic resilient member  27 . 
     The cap  45  overlies the housing  21  and closes the first chamber  23  as best seen in  FIGS. 5 and 6 . As also seen in these Figures, the cap  45  has an upwardly extending annulus  61  which receives an upper portion of a pointer mechanism  65 . A sleeve  63  is interposed between the annulus  61  and an upper protrusion  64  of the pointer mechanism  65  to maintain alignment of the pointer mechanism  65  therein. 
     The pointer mechanism  65  includes a pointer  67  attached to an elongated stem  69  having an elongated spiral-shaped protrusion  71  extending there around. As best seen in  FIG. 3 , the stem coupling  51  has a central opening  73  including a circular portion  79  and a radially outwardly extending groove  78  which receives the protrusion  71  therein while the rest of the stem  69  of the pointer mechanism  65  is slidably received within the circular portion  79  thereof. As should now be understood, when the diaphragm  39  is reciprocated within the chambers  23  and  25 , such reciprocations, with the protrusion  71  riding within the groove  78 , cause corresponding rotations of the pointer  67 . With reference to  FIGS. 2 ,  4  and  5 , when the non-ferromagnetic resilient member  27  is in the maximum extended position shown in  FIG. 5 , the pointer  67  is in the appropriate position to read zero pressure. As air pressure enters the first chamber  23  and causes displacement of the diaphragm  39  downwardly in the view of  FIGS. 5 and 6  toward the position shown in  FIG. 6 , the pointer  67  rotates due to the reciprocation of the stem coupling  51  and the interaction between the groove  78  thereof and the protrusion  71  of the pointer mechanism  65  to cause the pointer  67  to rotate to align with the appropriate indicia indicating the pressure within the chamber  23 . As the diaphragm  39  reciprocates either downwardly or upwardly, the pressure within the chamber  25  is always exposed to atmosphere via the vents  26  so that the pressure within the second chamber  25  has no bearing on pressure indications which are indicative of pressure within the CPR bag chamber  6 . As shown in  FIGS. 3 and 4 , the cap  45  has a top surface  46  having indicia  48  indicative of the pressure within the chamber  6  of the CPR bag  1  as indicated by the particular position of the arrow  67 . In the preferred embodiment of the present invention, the cap  45  is transparent or translucent with the pointer  67  situated below the cap  45  within the chamber  23  so that the position of the pointer  67  is visible through the cap  45 . 
     All components of the disposable manometer  20  are made from non-ferromagnetic materials including the non-ferromagnetic resilient member  27 . The resilient member  27  is non-ferromagnetic so that it is not pulled, deformed or moved by the magnetic forces encountered in or near a Magnetic Resonance Imaging System (MRI). The non-ferromagnetic resilient member  27  is preferably a plastic, brass or phosphor bronze spring, but any non-ferromagnetic resilient member  27  is anticipated including, but not limited to, a gas-filled bladder spring, a gas piston spring or any other known formation of a resilient member that is made of a non-ferromagnetic material so that it is not substantially affected by magnetic forces. It should be noted that some non-ferromagnetic materials are slightly pulled or pushed by magnetic forces, but ferromagnetic materials are a class of materials that are more susceptible to magnetic forces. Examples of ferromagnetic materials are iron and steel. Examples of non-ferromagnetic materials are plastic, bronze, brass and rubber. These examples are not meant to be limiting in any way. Some materials, called Paramagnetic materials, are weakly attracted to a magnet. Examples are platinum and aluminum. Some materials, called Diamagnetic materials, are weakly repelled by both poles. Examples of Diamagnetic materials include carbon, copper, and plastic. Such weekly attracted or weekly repelled materials are generally accepted for use in strong magnetic fields such as in an MRI system, but strongly attracted or repelled materials are not acceptable for use in such systems due to the potential relocation of such devices by the magnetic field and/or potential inaccurate readings from such devices. 
     As best seen in  FIGS. 5 and 6 , the patient breathing valve  50  can conveniently include a recess  16  sized to receive a protruding portion  75  of the manometer housing  21  in an interference fit as shown. An O-ring seal  77  may be suitably employed on the protrusion  75  to facilitate the interconnection between the housing  21  and the patient breathing valve  50 . 
     With reference to  FIG. 7 , a patient breathing tube is generally designated by the reference numeral  100  and includes a mouthpiece  101 , an elongated housing  103  having an internal passageway  105 , a distal end  107  includes a one-way check valve and an outlet  109  that optionally includes a second one-way check valve and is comprised of orifices  111  formed on a rotatable valve fitting  113  rotatable in a manner well known to those skilled in the art to adjust which of the differing sized orifices  111  fluidly connected to the mouthpiece  101  to thereby facilitate adjustments of the resistance that is provided to the user. A sensing port  115  is provided which interconnects with the passageway  35  of the inventive disposable manometer  20  via a flexible tube  117 . The patient breathing tube  100  is a device well known to those skilled in the art and is used to allow a patient to exercise their breathing function by blowing into the mouthpiece  101  and through the variable resistance outlet  109 . In this environment of contemplated use, the inventive disposable manometer  20  is employed to display the pressure at which the patient may blow through the breathing tube  100 . Of course, the sensing port  115  is directly fluidly connected to the passageway  105  therein. 
     In the preferred embodiment of the inventive disposable manometer  20 , the non-ferromagnetic resilient member  27  is made of a non-ferromagnetic material and the diaphragm  39  is made of a flexible, non-ferromagnetic material such as rubber. The other components thereof are made of non-ferromagnetic materials such as plastic, preferably in an injection molding process. Of course, any other suitable non-ferromagnetic materials are anticipated to be employed for the various components and structures of the inventive manometer  20 . 
     Equivalent elements can be substituted for the ones set forth above such that they perform in substantially the same manner in substantially the same way for achieving substantially the same result. 
     It is believed that the system and method as described and many of its attendant advantages will be understood by the foregoing description. It is also believed that it will be apparent that various changes may be made in the form, construction and arrangement of the components thereof without departing from the scope and spirit of the invention or without sacrificing all of its material advantages. The form herein before described being merely exemplary and explanatory embodiment thereof. It is the intention of the following claims to encompass and include such changes.