### Computerized System for Determination of Cardiac OutputComputerized System for Determination of Cardiac Output

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 Author Katsuura, Tetsuo Source J-STAGE Content type Text Publisher Japan Society of Physiological Anthropology Language English
 Abstract The $CO_{2}$ rebreathing method for the determination of cardiac output has been $computerized.CO_{2}$ concentration of expired air is analyzed by a infrared $CO_{2}$ analyzer.The output voltageof the $CO_{2}$ analyzer is sampled by a micro computer through a 12-bit analog-to-digitalconverter.The values of end-tidal $CO_{2}$ percentages $(FET_{C}O_{2})$ during nomal respiration and thepeak values of $CO_{2}$ percentages in the lung-bag system $(Fb_{C}O_{2})$ during rebreathing are detectedby the computer automatically.The detemination of the partial pressure of $CO_{2}$ in mixed venous blood $(Pv_{C}O_{2})$ is perfomedby computer analysis.The rise in the partial pressure of $CO_{2}$ in the lung-bag system $(Pb_{C}O_{2})with$ time (T) is expressed by the equation [chemical formula] This equation can be transfomed logerithmically to [chemical formula] At first, $Pvco_{2}$ is assumed to be a slightly large value than the last value of $Pb_{C}O_{2}$ and theregression equation of ln $(1-Pb_{C}O_{2}/Pv_{C}O_{2})$ on T is calculated by means of the least-squaresanalysis.Then $Pv_{C}O_{2}$ is successively changed positively, and the regression equations arecalculated on each time.The value of $Pv_{C}O_{2}$ which maximize the value of coefficient ofdetermination $(r^{2})$ is adopted as the very value of $Pv_{C}O_{2}.The$ partial pressure of $CO_{2}$ in arterialblood $(Pa_{C}O_{2})$ is a ssumed to be the same as in end-tidal air.A comparison was made between the cardiac output determined by this computerized andthe conventional $CO_{2}$ rebreathing methods as described by Jernerus et al.(1963).The valuesobtained by the two methods were almost identical, all of 9 paired deteminations of cardiacoutput obtained during exercise were within 10% of one another and 33 of 36 values during restand recovery were within 20% of one another.The correlation coefficient between the valuesobtained by the two methods was 0.992.The computerized method is a more precise and moreconvenient technique for deteming cardiac output. ISSN 02878429 Learning Resource Type Article Publisher Date 1984-01-01 Journal The Annals of physiological anthropology(ahs1983) Volume Number 3 Issue Number 1 Page Count 6 Starting Page 63 Ending Page 68