Abstract
Changes in pulmonary diffusing capacity for carbon monoxide (DL), the diffusing capacity of the pulmonary capillary membrane (DM) and pulmonary capillary blood volume (VC) at rest were examined in eight adult subjects of both sexes by the breath-holding method under different posture and temperature conditions; i. e., in a supine position and a head-up position (45°) by the use of a tilting bed at three ambient temperatures of 15, 25 and 35°C. Under all these conditions, DL was closely related to changes in VC. Posture significantly affected DL and VC in both males and females, the degree of difference due to each posture in males being similar to that in females. Although the influence of temperature on DL and VC was significant in males, it was somewhat vague in females. The following causes of this phenomenon were suggested: the range of variation in the pulmonary arterial pressure due to thermal stimulation is narrow and the size of the lung is smaller in females than in males. The relation of DL to wide-spread changes in VC in both sexes showed the form of a curve, probably because the increase in VC mainly reflects the process of transformation of the pulmonary capillary from recruitment to dilation.
