Dead Space Ventilation in Old Age

Abstract

Eighteen normal men between the ages of 68 and 89 years have been studied from the standpoint of respiratory function. In all instances basal oxygen consumption was low, but the mean minute volume of ventilation and respiratory frequency were high. Large anatomic dead space volumes were measured, but alveolar ventilation was normal since alveolar gas values did not vary significantly from young adult standards. All subjects showed an arterial oxygen saturation of about 90% with a wide alveolar-arterial oxygen tension difference, and a significant arterial-alveolar CO2 tension difference was measured in some subjects. The shape of the expired CO2 curve and marked fall in the respiratory exchange ratio throughout expiration provided evidence for a maldistribution of alveolar ventilation-blood flow ratios throughout the lung in some individuals. An explanation for the arterial-alveolar CO2 gradient (alveolar dead space) has been sought in the distribution anomaly. Submitted on March 19, 1956