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Cardiac Output Determination

IP.com Disclosure Number: IPCOM000092387D
Original Publication Date: 1967-Dec-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Lambert, JW: AUTHOR

Abstract

Cardiac output volume is measured by utilization of small perturbations of air pressure within the chest cavity. During a cardiac cycle, a small volume of blood is forced out of the chest cavity. This volume can be related thermodynamically to a decrease in pressure within the cavity.

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Cardiac Output Determination

Cardiac output volume is measured by utilization of small perturbations of air pressure within the chest cavity. During a cardiac cycle, a small volume of blood is forced out of the chest cavity. This volume can be related thermodynamically to a decrease in pressure within the cavity.

The net volume of blood leaving the chest cavity in one pulse Delta v is related to a sharp decrease in air pressure Delta p by Delta v = -VO Delta p/P gamma. VO is the nominal volume of the chest cavity, including airways to instruments. P is the nominal pressure of the air throughout the system, and gamma is the ratio of specific heats of air. VO can be estimated by making physiometric measurements on a particular patient.

An alternative, and probably more accurate approach, is to make a Delta p measurement at each of two different chest cavity volumes, which differ by the volume Delta V of air exhaled, or inhaled, between the times of making the two Delta p measurements Delta p1 and Delta p2. Assuming that the Delta p1 and Delta p2 are made at the same nominal pressure P1 = P2 = P, the above expression becomes Delta v = Delta p1 Delta V/>1 - (Delta p1/Delta p2)P gamma|.

In order to determine the above variables, an air chamber is placed in communication with the chest cavity. As the patient exhales, or inhales, through the chamber, air pressure in the chamber is monitored by a sensitive transducer to detect the decrease in pressure caused by the hea...