Abstract:
An inflatable air cell pressure transducer. The air cell has a concavity formed therein. The concavity has two edges, wherein increased pressure within the air cell causes contraction of the concavity moving the two edges closer.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This application is a continuation of U.S. patent application Ser. No. 10/769,946, filed Feb. 2, 2004, now U.S. Pat. No. 7,000,483 the entire contents of which are incorporated herein by reference, which claims the benefit of U.S. provisional patent application 60/444,545 filed Feb. 3, 2003, the entire contents of which are incorporated herein by reference, and claims the benefit of U.S. provisional patent application 60/468,728 filed May 7, 2003, the entire contents of which are incorporated herein by reference. 

   BACKGROUND 
   The invention relates to inflatable manometers. Manometers are often used in medical procedures to monitor pressures in apparatus such as inflatable cuffs or manual resuscitators for a patient. For example, it is desirable to maintain the internal pressure of a tracheal tube cuff below 30 cmH 2 O. Existing manometers are typically costly and can be a vehicle for disease transmission, rendering widespread use of such manometers prohibitive. Accordingly, there is a need in the art for a low cost, accurate manometer for medical applications (e.g., single-patient use disposable) and other applications. 
   BRIEF SUMMARY OF THE INVENTION 
   Embodiments of the invention include an inflatable manometer having an air cell. The air cell has a concavity formed therein. The concavity has two edges, or other geometric features, wherein increased pressure within the air cell causes contraction of the concavity moving the two edges closer. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIGS. 1A and 1B  depict inflatable manometers in embodiments of the invention. 
       FIG. 2  depicts the manometer of  FIG. 1A  as pressure increases. 
       FIG. 3  depicts an inflatable manometer in an alternate embodiment of the invention. 
       FIG. 4  depicts the manometer of  FIG. 3  as pressure increases. 
       FIG. 5  depicts an inflatable manometer in an alternate embodiment of the invention. 
       FIG. 6  depicts the manometer of  FIG. 5  as pressure increases. 
       FIGS. 7A and 7B  depict inflatable manometers in alternate embodiments of the invention. 
       FIG. 8  depicts an inflatable manometer in an alternate embodiment of the invention. 
       FIG. 9  depicts the manometer of  FIG. 8  as pressure increases. 
       FIG. 10  depicts an inflatable manometer in an alternate embodiment of the invention. 
   

   DETAILED DESCRIPTION 
     FIG. 1A  depicts an inflatable manometer  10  in an embodiment of the invention. Manometer  10  includes an air cell  12  coupled to a fluid inlet  14 . The manometer serves as an air cell pressure transducer that indicates pressure of the fluid which may be gas, liquid, etc. The air cell  12  is formed by two sheets of material sealed along seal  16 . In one embodiment, the sheets of material are thermoplastic material and are sealed using known techniques such as heat sealing, ultrasonic welding, etc. The sheets of material are not limited to thermoplastic materials and may be implemented using any flexible material such as rubber, glued paper, etc. The air cell  12  is generally circular and includes a concavity  18  in the shape of a triangular wedge. It is understood that the air cell  12  and concavity  18  may have shapes other than those depicted in  FIG. 1A .  FIG. 1B  depicts an alternate manometer similar to that shown in  FIG. 1A , but having differently shaped concavity  18 . 
   A scale  20  is also formed from the same sheets defining the air cell  12  and includes indicia  22  representative of pressure. The scale  20  and indicia  22  may be formed by molding the indicia  22  into thermoplastic sheets (e.g., heat stamping) or printing the indicia  22 . The scale  20  is positioned proximate to edge  24  of concavity  18 . The scale  20  can be designed for different real units of measure, e.g., PSI. In alternate embodiments, scale  20  is affixed to air cell  12  and moves relative to a stationary indicator. 
     FIG. 2  depicts manometer  10  of  FIG. 1A  as pressure in air cell  12  increases. As the air cell  12  is inflated, the two edges that define the concavity  18  will contract towards each other in response to increasing internal fluid pressure. The pressure within the air cell  12  is represented by the position of edge  24  relative to scale  20 . Thus, the size and shape of the air cell  12 , concavity  18  and scale  20  are designed to provide an accurate indication of pressure. 
   Inlet  14  may be coupled to a tube in fluid communication with a chamber for which pressure monitoring is desired. Alternatively, manometer  10  may be secured on a sidewall of a chamber with inlet  14  in fluid communication with the chamber. The seal  16  around inlet  14  may be secured to the chamber wall (e.g., heat sealed to thermoplastic chamber) to provide an integrated manometer. 
     FIG. 3  depicts an alternate manometer  30 . Manometer  30  includes an air cell  32  and a fluid inlet  34 . The manometer  30  indicates pressure of the fluid which may be gas, liquid, etc. The air cell  32  is formed by two sheets of material sealed along edges  36 . Interior seals  38  define a number of rectangular sub-cells  40 , each having a concavity  42  at each end defined by seals  36 . In one embodiment, the sheets of material defining air cell  32  are thermoplastic material and are sealed using known techniques such as heat sealing, ultrasonic welding, etc. The sheets of material are not limited to thermoplastic materials and may be implemented using any flexible material such as rubber, glued paper, etc. 
   Air cell  32  and inlet  34  are positioned within a housing  50  having a first and second sheet sealed along the periphery encasing the air cell  32  and inlet  34 . The first and second housing sheets may be thermoplastic material and are sealed using known techniques such as heat sealing, ultrasonic welding, etc. A scale  52  is also formed on the housing  50  and includes indicia  54  representative of pressure. The scale  52  and indicia  54  may be formed by molding the indicia  54  into thermoplastic sheets (e.g., heat stamping) or printing the indicia  54 . The scale  52  is positioned proximate to a distal end  56  of air cell  32 . The scale  52  can be designed for different real units of measure, e.g., PSI. 
     FIG. 4  depicts manometer  30  as pressure in air cell  32  increases. As the air cell  32  is inflated, rectangular sub-cells  40  expand into cylindrically shaped cells, thereby reducing the length of the air cell  32  in a linear direction. The pressure within the air cell  32  is represented by the position of distal end  56  relative to scale  52 . The distal end  56  of the air cell  32  may be colored to more easily determine the position of the end of the air cell  32  relative to the scale  52 . Thus, the size and shape of the air cell  32  and scale  52  are designed to provide an accurate indication of pressure. 
   Inlet  34  may be coupled to a tube in fluid communication with a chamber for which pressure monitoring is desired. Alternatively, manometer  30  may be secured on a sidewall of a chamber with inlet  34  in fluid communication with the chamber. The seal around inlet  34  may be secured to the chamber wall (e.g., heated sealed to thermoplastic chamber) to provide an integrated manometer. 
     FIG. 5  depicts another manometer  60  in an alternate embodiment. Manometer  60  includes an air cell  62  and a fluid inlet  64 . The manometer  60  indicates pressure of the fluid which may be gas, liquid, etc. The air cell  62  is formed by two sheets of material sealed along edges  66 . The shape of seal  66  defines a number of sub-cells  68 , each having a concavity  70 . The sub-cells are in fluid communication with each other, and inlet  64 . The concavity  70  in  FIG. 5  is a triangular wedge, but it is understood that other geometries may be used. In one embodiment, the sheets of material defining air cell  62  are thermoplastic material and are sealed using known techniques such as heat sealing, ultrasonic welding, etc. The sheets of material are not limited to thermoplastic materials and may be implemented using any flexible material such as rubber, glued paper, etc. 
   Air cell  62  and inlet  64  may be positioned within a housing  72  having a first and second sheet sealed along the periphery encasing the air cell  62  and inlet  64 . The first and second housing sheets may be thermoplastic material and are sealed using known techniques such as heat sealing, ultrasonic welding, etc. A scale  74  is also formed on the housing  72  and includes indicia  76  representative of pressure. The scale  74  and indicia  76  may be formed by molding the indicia  76  into thermoplastic sheets (e.g., heat stamping) or printing the indicia  76 . The scale  74  is positioned proximate to a distal end  78  of air cell  62 . The scale  74  can be designed for different real units of measure, e.g., PSI. 
     FIG. 6  depicts manometer  60  as pressure in air cell  62  increases. As the air cell  62  is inflated, sub-cells  68  contract at concavity  70 , as described above with reference to  FIG. 2 , thereby reducing the length of the air cell  62  in a linear direction. The pressure within the air cell  62  is represented by the position of distal end  78  relative to scale  74 . The distal end  78  of the air cell  62  may be colored to more easily determine the position of the end of the air cell  62  relative to the scale  74 . Thus, the size and shape of the air cell  62  and scale  74  are designed to provide an accurate indication of pressure. 
     FIG. 7A  depicts a manometer  80  in an alternate embodiment of the invention. Manometer  80  is similar to manometer  10  in  FIG. 1A  and similar components are labeled with the same reference numerals. Manometer  80  includes an indicator  82  extending from edge  24  of concavity  18 . Rather than scale  20  formed in the sheet defining the air cell  12 , manometer  80  includes a scale  84  printed on a separate card  86 . The manometer  80  and the printed scale  84  may be encased within a transparent housing  88 . The housing  88  includes an opening to access the fluid inlet  14  to the manometer  80 .  FIG. 7B  depicts an alternate manometer similar to that shown in  FIG. 7A , but having differently shaped concavity  18 . 
     FIG. 8  depicts a manometer  90  in an alternate embodiment of the invention. The manometer  90  is formed from two sheets sealed together (e.g., thermoplastic sheets sealed together) to define an air cell  91  and an inlet  96  for fluid. The sheets of material are not limited to thermoplastic materials and may be implemented using any flexible material such as rubber, glued paper, etc. Inlet  96  is in fluid communication with a chamber for which pressure monitoring is desired. Manometer  90  includes two concavities  92  and  94 , having differing characteristics. The concavities  92  and  94  have different widths so that each notch will close at different pressures. It is understood that other characteristics of concavities  92  and  94  may be varied including length, width and shape. The manometer  90  may also include a single concavity rather than two concavities. The single concavity may correspond to a minimum pressure that should be maintained or a maximum pressure that should be avoided. The distal end  98  of the manometer  90  may serve as a fluid outlet so that manometer  90  may be positioned inline in a pressure system to indicate pressure of a chamber connected to outlet  98 . 
     FIG. 9  shows manometer  90  as pressure increases in air cell  91 . As shown in  FIG. 9 , the opening of concavity  92  with the smaller width closes at a first predetermined pressure while concavity  94  has started to contract. Concavity  94  with the larger width has started to contract and closes at a second pressure. This allows an operator to determine that air cell  91  has been inflated to a pressure between two limits without requiring a scale indicating a numerical pressure value. Manometer  90  may be used in a variety of applications including indicating pressure of pilot balloons associated with tracheal devices. 
   The inlet in the manometers of  FIGS. 1-9  may be eliminated and the air cell pressurized with a fluid and sealed. In this embodiment, the manometer indicates ambient pressure in response to a difference between ambient pressure and pressure in the air cell. 
     FIG. 10  depicts an inflatable manometer in an alternate embodiment of the invention. The manometer  10  is similar to that shown in  FIG. 1  and includes an outlet  15  in air cell  12 . In this embodiment, the manometer  10  serves as a flowmeter to indicate a pressure differential between inlet  14  and outlet  15 . In this configuration, the manometer may be used to indicate positive pressure, negative pressure or fluid flow. As long as the pressure within the manometer chamber  12  is positive to inflate the chamber  12  and cause edge  24  to move relative to scale  20 . 
   While the invention has been described with reference to exemplary embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiments disclosed for carrying out the invention, but that the invention will include all embodiments falling within the scope of the appended claims.