Pulmonary function after exercise with special emphasis on diffusion capacity

The present work focuses on pulmonary gas exchange during repeated rowing to exhaustion and the recovery of pulmonary diffusion capacity for carbon monoxide (DL) after exercise in healthy young subjects. The components of DL are examined at rest using the single breath method at two different alveolar O2 tensions. Electrical impedance and 99mTechnetium labelled erythrocytes were used to evaluate the recovery of blood distribution. Special attention has been given to the role of the inspiratory muscles as a limiting factor for VO2max and performance. The documentation in this study of a reduced DL several hours after exercise conflicts with the prerequisites of optimal conditions for high metabolic rates in elite athletes. Even low intensity exercise induces a reduction in DL, and together with the fact that a diuretic does not attenuate this decrease, emphasises that the reduction in DM is not due to an interstitial pulmonary edema. The major part of the reduction is due to a decreased CBV reflected in a reduction of VC and a minor part is caused by an injury to the membrane component carried over from exercise. The ability in athletes to repeat exhaustive exercise within 2 h indicates that the slow recovery of DL is not combined with either impaired pulmonary gas exchange or performance. Thus, an acute diffusion limitation and a low pH cause the desaturation in some athletes during exhaustive exercise. Despite the inspiratory muscles having a slower response to endurance training compared with the cardiovascular system, selective training of the inspiratory muscles does not improve either VO2max or performance. This indicates that maximal inspiratory pressure is not a limiting factor for maximal exercise and that the stimuli to increase VA depends on an increased metabolic rate; stressing the role of the peripheral chemoreceptors. Together with the post-exercise decrease in ANP, the reduction in DL may be involved in the mechanism increasing the total blood volume in endurance trained athletes.