Cardiopulmonary Readjustments during Prolonged Accelerations.
STATE UNIV OF NEW YORK BUFFALO DEPT OF PHYSIOLOGY
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The researchers developed a new non-invasive technique for measurement of cardiac output that can be applied in the presence of ventilation-perfusion maldistribution, and determined the extent to which the time required for diffusion of inspired gas in the air spaces limits gas exchange and contributes to unequal distribution of ventilation. Cardiac output is measured on the basis of the rise of alveolar carbon dioxide during rebreathing. To use this method it is necessary to measure only the volume of the rebreathing bag before the maneuver and monitor the carbon dioxide fraction at the mouth during 10 seconds of rebreathing. The technique does not postulate equality of alveolar and arterial carbon dioxide tensions, takes into account carbon dioxide storage in lung tissue, and can be applied at any inspired oxygen tension with or without addition of an inert tracer gas. It has been validated on human subjects exercising at different speeds and grades on a treadmill. Modified author abstract
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