Prolonged expiration down to residual volume leads to severe arterial hypoxemia in athletes during submaximal exercise

The goal of this study was to assess the effects of a prolonged expiration (PE) carried out down to the residual volume (RV) during a submaximal exercise and consider whether it would be worth including this respiratory technique in a training programme to evaluate its effects on performance. Ten male triathletes performed a 5-min exercise at 70% of maximal oxygen consumption in normal breathing (NB70) and in PE (PE70) down to RV. Cardiorespiratory parameters were measured continuously and an arterialized blood sampling at the earlobe was performed in the last 15 s of exercise. Oxygen consumption, cardiac frequency, end-tidal and arterial carbon dioxide pressure, alveolar–arterial difference for O2 (PAO2−PaO2PAO2−PaO2) and P50 were significantly higher, and arterial oxygen saturation (87.4 ± 3.4% versus 95.0 ± 0.9%, p < 0.001), alveolar (PAO2PAO2) or arterial oxygen pressure, pH and ventilatory equivalent were significantly lower in PE70 than NB70. There was no difference in blood lactate between exercise modalities. These results demonstrate that during submaximal exercise, a prolonged expiration down to RV can lead to a severe hypoxemia caused by a PAO2PAO2 decrement (r = 0.56; p < 0.05), a widened PAO2−PaO2PAO2−PaO2 (r = −0.85; p < 0.001) and a right shift of the oxygen dissociation curve (r = −0.73; p < 0.001).