Springer Online Journal Archives 1860-2000
Chemistry and Pharmacology
Abstract A microcomputer-based system for the breath-by-breath assessment of respiratory and metabolic function during exercise was developed. To minimise the load for subjects ventilation was measured by use of an impedance plethysmograph instead of a pneumotachograph. The computer calculated respiratory frequency, tidal volume, minute ventilation, end-tidal pO2 and pCO2, O2 input and CO2 output, and gas exchange ratio of each breath from the impedance pneumogram and the gas composition of the expired air. To avoid the error due to the cardiogenic oscillations appearing to overlap the impedance pneumogram, discrimination of the inspiratory and expiratory phases was achieved by detecting the temperature difference between ambient and expired air. The impedance pneumogram could follow tidal volume variations during a moderate bicycle exercise (120 W) with satisfactory accuracy, but its sensitivity is apt to fall at the severe exercise (180 W). Possible factors causing errors such as the distribution of regional ventilation and perfusion during exercise are discussed.
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