Pulmonary gas exchange in athletes with exercise-induced hypoxaemia

Hypoxaemia that is induced by physical exercise (EIH) in some athletes, who are however capable of enduring intense muscolar work, is a phenomenon that has been known for some time. However, assumptions such as alveolar hypoventilation, veno-arterial shunt, limitation of diffusion, or mismarch of the VA/Q ratio, have not to date been able to exhaustively explain this phenomenon. In this study five athletes displaying exercise-induced hypoxaemia were evaluated by increasing-load exercise tests, as proposed by other authors, and by means of intermittent tests with supermaximal exercise steps (130% VO2 max) with breaks for incomplete recovery (3 min). The fundamental fact arising from our study is that the intermittent tests did not bring about hypoxaemia in the tests subjects. Analysis of the ventilator and metabolic parameters, of the alveolar pressure of the O2, and of the partial pressures of the CO2 in the arterial blood, all measured during the two different types of muscular exercise, lead to the belief that the different distribution of the pulmonary blood flow, which has been documented in highly trained athletes, plays a very important role in inducing EIH.