A change in the pulmonary diffusing capacity (DL/Va) at rest and during exercise for two different postures

Abstract

1073 The purpose of the present study was to compare the pulmonary diffusing capacity (DL/Va) at rest and during exercise for upright and supine postures. Six healthy male subjects (age: 23.7 ± 1.1 yr; height: 174.5±2.0 cm; body weight: 73.0 ± 5.4 kg) were studied. All subjects were nonsmokers who did not usually exercise. DL/Va was measured at rest and during intermittent incremental maximum exercise on a bicycle ergometer in both postures using the Breath-holding method (Forster et al., 1954). The resting values of DL/Va (6.29 ± 0.70 ml/min/mmHg/l) in the supine posture were higher than the values (5.60 ± 0.52 ml/min/mmHg/l) in the upright posture (p<0.05). Maximum oxygen uptake, maximum ventilation, maximum work load, and exercise time in the upright posture were higher than in the supine posture (p<0.05). DL/Va during submaximum exercise increased with heart rate, oxygen uptake, ventilation, oxygen pulse, and DL/Va in the supine posture were higher than in the upright posture for the same work (p<0.05). However, there was no significant difference in the maximum DL/Va for the upright (8.93±0.61 ml/min/mmHg/l) and supine postures (8.82±0.29 ml/min/mmHg/l). From these results, it was suggested that influences on the blood flow are greatly reflected in the DL/Va at rest and during exercise, and the diffusion in the supine posture is more effective than in the upright posture.