Exercise-induced oxyhemoglobin desaturation and pulmonary diffusing capacity during high-intensity exercise

The purpose of this investigation was to examine if exercise-induced arterial oxyhemoglobin desaturation selectively observed in highly trained endurance athletes could be related to differences in the pulmonary diffusing capacity (D _L) measured during exercise. The D _L of 24 male endurance athletes was measured using a 3-s breath-hold carbon monoxide procedure (to give D _LCO) at rest as well as during cycling at 60% and 90% of these previously determined O_2max. Oxyhemoglobin saturation (S _aO₂%) was monitored throughout both exercise protocols using an Ohmeda Biox II oximeter. Exercise-induced oxyhemoglobin desaturation (DS) (S _aO₂% < 91% at O_2max) was observed in 13 subjects [88.2 (0.6)%] but not in the other 11 nondesaturation subjects [NDS: 92.9 (0.4)%] (P ≤ 0.05), although O_2max was not significantly different between the groups [DS: 4.34 (0.65) l / min vs NDS: 4.1 (0.49) l / min]. At rest, no differences in either D _LCO [m1 CO · mmHg⁻¹ · min⁻¹: 41.7 (1.7) (DS) vs 41.1 (1.8) (NDS)], D _LCO / _A [8.2 (0.4) (DS) vs 7.3 (0.9) (NDS)], MVV [l / min: 196.0 (10.4) (DS) vs 182.0 (9.9) (NDS)] or FEV₁/FVC [86.3 (2.2) (DS) vs 82.9 (4.7) (NDS)] were found between groups (P ≥ 0.05). However, _E /O₂ at O_2max was lower in the DS group [33.0 (1.1)] compared to the NDS group [36.8 (1.5)] (P ≤ 0.05). Exercise D _LCO (m1 CO · mmHg⁻¹ · min⁻¹) was not different between groups at either 60% O_2max [DS: 55.1 (1.4) vs NDS: 57.2 (2.1)] or at 90% O_2max [DS: 61.0 (1.8) vs NDS: 61.4 (2.9)]. A significant relationship (r = 0.698) was calculated to occur between S _aO₂% and _E /O₂ during maximal exercise. The present findings indicate that the exercise-induced oxyhemoglobin desaturation seen during submaximal and near-maximal exercise is not related to differences in D _L, although during maximal exercise S _aO₂ may be limited by a relatively lower exercise ventilation. Accepted: 25 September 1996