The effect of repeat exercise on pulmonary diffusing capacity and EIH in trained athletes

Purpose: The purpose of this study was to determine the effects of repeated heavy exercise on postexercise pulmonary diffusing capacity (DL) and the d evelopment of exercise induced arterial hypoxemia (EIH). Methods: 13 endura nce-trained, male athletes (age = 27 +/- 3 yr, height = 179.6 +/- 5.0 cm, w eight = 71.8 +/- 6.9 kg, (V) over dot O-2max = 67.0 +/- 3.6 mL.kg(-1).min(- 1)) performed two consecutive, continuous exercise tests on a cycle ergomet er to (V) over dot O-2max, separated by 60 min of recovery. Arterial oxygen saturation (%SaO(2)) was measured via ear oximetry, and resting DL was mea sured and partitioned by the single-breath method, before exercise and 60 m in after each exercise bout. Results: No significant differences resulted i n (V) over dot O-2max, (V) over dot E, peak heart rate (HR), or breathing f requency between exercise bouts (P > 0.05). There was a small but significa nt decrease (454-446 W; P < 0.05) in peak power output in the second test. %SaO(2) decreased from resting values during both exercise tasks. but there was no difference between the minimum saturation achieved in test 1 (91.4) or test 2 (91.6; P > 0.05). After the initial exercise bout, significant d ecreases (P < 0.05) occurred in DL (11%), membrane diffusing capacity (DM) (11%) and pulmonary capillary volume (VC) (10%). Further decreases occurred in DL (6%; P < 0.05), DM (2%; P > 0.05), and VC (10%; P < 0.05) after the second exercise bout. Conclusions: These observations question the meaning of post exercise measurements of pulmonary diffusion capacity, and its comp onents, relative to pulmonary gas exchange and pulmonary fluid accumulation during exercise. The fact that there was no further change in %SaO(2) afte r the second test suggests that if any interstitial edema developed, it was of no clinical significance; alternatively, the changes in DLCO may be rel ated more to redistribution of blood than the development of pulmonary edem a.