Method and apparatus for measuring blood pressure

Claim 3

A method as recited in claim 1 wherein said positioning comprises: inserting a positioning balloon through the pharynx, down the esophagus, and into the stomach, wherein said positioning balloon is connected to a tethering catheter which extends upwardly from the stomach and exits the nose, wherein said balloon-containing catheter is tied to said tethering catheter at a predetermined distance from the positioning balloon, said predetermined distance corresponding approximately to the relatively constant distance in man between the esophago-gastric junction and the left atrium; inflating said positioning balloon to a sufficient size such that it will not pass through the esophago-gastric junction; and applying gentle traction at the nose to said tethering catheter to keep said balloon-containing catheter in position in the esophagus proximate the left atrium.

Claim 4

A method as recited in claim 1 wherein said balloon-containing catheter comprises a first catheter and a counter-pressure balloon connected to said first catheter and a second catheter and an isovolumetric balloon connected to said second catheter and said positioning further comprises arranging said counter-pressure balloon and said isovolumetric balloon to be in substantial contact with one another and said determining further comprises determining the effect of atrial pressure upon both said counter-pressure and isovolumetric balloons.

Claim 5

A method as recited in claim 3 wherein said inflating comprises regulating compressed gas in said first and second catheters and maintaining approximately equal pressures in said balloons.

Claim 6

A method as recited in claim 4 wherein the pressure of the gas in said first and second catheters is gradually increased to a maximum pressure of approximately 50 cm H 2 O.

Claim 7

A method as recited in claim 4 wherein said determining comprises converting measured pressures in said catheters to electrical signals by means of pressure transducers and displaying said signals as representative of left atrial pressure.

Claim 8

A method as recited in claim 1 wherein said balloon-containing catheter comprises a first catheter and a counter-pressure connected to said first catheter and a second catheter and a flutter-valve balloon connected to said second catheter and said positioning further comprises arranging said counter-pressure balloon and said flutter-valve balloon to be in substantial contact with one another and said determining further comprises determining the effect of atrial pressure upon said flutter-valve balloon.

Claim 9

A method as recited in claim 7 wherein said inflating comprises gradually and uniformly increasing the flow rate of gas into said first and second catheters from a low rate of approximately 0.2 mL/min. to a maximum flow rate of approximately 4.0 mL/min.

Claim 14

Apparatus for measuring left atrial pressure, comprising: a balloon-containing catheter adapted to be insertable into an esophagus; means for positioning said balloon-containing catheter in the esophagus such that when the balloon is inflated, pressure from the left atrium affects said balloon; means for inflating said balloon; and means for determining mean left atrial pressure by the effect of the atrial pressure upon said balloon.

Claim 15

Apparatus for measuring left atrial pressure, comprising: a balloon-containing catheter adapted to be insertable into an esophagus; means for positioning said balloon-containing catheter in the esophagus such that when the balloon is inflated, pressure from the left atrium affects said balloon; means for inflating said balloon; and means for determining mean left atrial pressure by the effect of the atrial pressure upon said balloon.

Claim 16

Apparatus as recited in claim 11 wherein said means for positioning comprises: a positioning balloon adapted to be insertable through the nose, down the esophagus and into the stomach; and a tethering catheter attached to said positioning balloon at a distal end of said catheter and adapted to be insertable into the nose, down the esophagus and into the stomach,-said tethering catheter tied to said balloon-containing catheter so the balloon of the balloon-containing catheter is at a predetermined distance from said positioning balloon, said distance corresponding approximately to the relatively constant distance in man between the esophago-gastric junction and the left atrium, wherein said tethering catheter positions the balloon of said balloon-containing catheter proximate the left atrium when said positioning balloon is inflated in the stomach and gentle traction is applied to said tethering catheter at the nose so as to raise said positioning balloon to the esophago-gastric junction.

Claim 17

Apparatus as recited in claim 11 wherein said balloon-containing catheter comprises: a counter-pressure balloon connected to a first catheter; and an isovolumetric balloon connected to a second catheter, wherein said counter-pressure balloon and said isovolumetric balloon are arranged to be in substantial contact with one another, and wherein left atrial pressure is determined by the effect of atrial pressure upon both said counter-pressure and isovolumetric balloons.

Claim 18

Apparatus as recited in claim 13 wherein said means for inflating comprises: a source of compressed gas; and means for regulating the flow and pressure of said gas in each of said first and second catheters and for maintaining approximately equal pressures in said counter-pressure and isovolumetric balloons.

Claim 19

Apparatus as recited in claim 11 wherein said balloon-containing catheter comprises: a first catheter; a counter-pressure balloon connected to said first catheter; a second catheter; and an isovolumetric balloon connected to said second catheter; wherein said counter-pressure balloon and said isovolumetric balloon are arranged to be in substantial contact with one another, and wherein left atrial pressure is determined by the effect of atrial pressure upon both said counter-pressure and isovolumetric balloons.

Claim 20

An esophageal balloon-containing catheter for sensing and measuring left atrial pressure, comprising: a first catheter, a counter-pressure balloon connected to said first catheter; a second catheter having an inlet section and an exhaust section; and a flutter-valve balloon connected to said second catheter, wherein said counter-pressure balloon and said flutter-valve balloon are arranged to be in substantial contact with one another, and wherein mean left atrial pressure is determined by the effect of atrial pressure upon said flutter-valve balloons.

Claim 21

An esophageal balloon-containing catheter for sensing and measuring left atrial pressure, comprising: a first catheter, a counter-pressure balloon connected to said first catheter; a second catheter having an inlet section and an exhaust section; and a flutter-valve balloon connected to said second catheter, wherein said counter-pressure balloon and said flutter-valve balloon are arranged to be in substantial contact with one another, and wherein mean left atrial pressure is determined by the effect of atrial pressure upon said flutter-valve balloons.

Claim 22

Apparatus as recited in claim 16 wherein said flutter-valve balloon comprises a balloon membrane formed of low density polyethylene film which is secured to said second catheter between said inlet and exhaust sections.

Claim 23

Apparatus as recited in claim 16 wherein said polyethylene film has a thickness of 0.0005 inches.

Claim 24

Apparatus as recited in claim 18 wherein said balloon has a length of approximately 35 millimeters between said inlet and exhaust sections and a width of approximately 4 millimeters.

Claim 25

Apparatus for measuring left atrial pressure, comprising: means for inserting a sensing probe into the esophagus; and means for positioning said probe so that mean pressure from the left atrium is determined by said probe.

Claim 26

Apparatus for measuring left atrial pressure, comprising: means for inserting a sensing probe into the esophagus; and means for positioning said probe so that mean pressure from the left atrium is determined by said probe.

Claim 27

Apparatus as recited in claim 20 wherein said sensing probe comprises a catheter-mounted miniature pressure transducer.

Claim 28

Apparatus for correcting mean left atrial pressure measurements while a person is connected to a breathing machine for the effect of positive end expiratory pressure, comprising: means for measuring esophageal pressure using a nearly collapsed balloon while a person is connected to said breathing machine; means for measuring mean left atrial pressure by inserting a sensing probe into the esophagus and positioning said probe so that pressure from the left atrium is sensed by said probe; and means for calculating corrected mean left atrial pressure from the equation: MLAP.sub.corrected =MLAP.sub.measured -P.sub.E where, MLAP corrected is the corrected mean left atrial pressure; MLAP measured is the measured mean left atrial pressure; and, P E is the measured esophageal pressure.

Claim 29

Apparatus for correcting mean left atrial pressure measurements while a person is connected to a breathing machine for the effect of positive end expiratory pressure, comprising: means for measuring esophageal pressure using a nearly collapsed balloon while a person is connected to said breathing machine; means for measuring mean left atrial pressure by inserting a sensing probe into the esophagus and positioning said probe so that pressure from the left atrium is sensed by said probe; and means for calculating corrected mean left atrial pressure from the equation: MLAP.sub.corrected =MLAP.sub.measured -P.sub.E where, MLAP corrected is the corrected mean left atrial pressure; MLAP measured is the measured mean left atrial pressure; and, P E is the measured esophageal pressure.

Claim 30

Apparatus as recited in claim 20 wherein said sensing probe comprises a balloon.