1984 Volume 22 Issue 4 Pages 227-234
Change in pulmonary diffusing capacity for carbon monoxide (DL) with ambient temperature was investigated to compare the relation between DL and pulmonary capillary blood volume (Vc) with that occurring during exercise in the previous study and to examine the possibility of evaluating the potential capacity for increase in Vc. Five subjects were exposed to ambient temperatures of 12, 20, 28 and 36°C for about 100 min. The average DL increased by about 30% from 27.2 at 36°C to 34.9 ml/min/Torr at 12°C. DL was primarily determined by acute change in Vc which might be well related to determinants of change in stroke volume rather than cardiac output. It was implied that the mechanism of change in DL at rest might be different that during exercise. The best parameter matching for change in DL was mean skin temperature, which was considered to make possible the detection of changes in Vc. Comparison with the previous study revealed that the magnitude and pattern of change in DL with Vc was uniform whether Vc was altered either by change in ambient temperature or by performing exercise. This means that it is not always necessary to have a patient perform exercise in order to examine the potential increase in Vc. On the other hand, change in DL in this study seemed to depend mainly on the characteristics of the pulmonary arterial system while change in DL during exercise seemed to depend on the total number of the pulmonary capillaries in the previous study. Therefore, it was implied that selection of stimulation, which could either be change in thermal condition at rest or an exercise regime, could assist in the differentiation of various characteristics of pulmonary diseases.
