Breathing pattern during and after maximal exercise testing in young untrained subjects and in obese patients

More rapid and more shallow breathing (RSB) than usual, manifested by a lower tidal volume and greater breathing frequency at a given level of ventilation, may be caused by inspiratory muscle fatigue and pulmonary congestion. It has been observed during recovery in young trained adults after very high exercise levels and in middle-aged patients with cardiac disease, after their maximal work load. We studied the breathing pattern during and after exercise testing up to the maximal work capacity in a group of normal untrained, young people and in a group of young obese subjects. RSB was present in normal subjects after a work load which required a maximal O2 consumption near the theoretical value (93% in our cases) and was not present in obese patients probably because neither inspiratory muscle fatigue, nor pulmonary congestion occurs in these subjects. Maximal heart rate at peak of exercise was significantly higher in normal subjects and a direct correlation between delta Vt and maximal heart rate was found in all normal subjects. This is compatible with the hypothesis that RSB is mainly due to an initial interstitial pulmonary edema, as supposed by other authors.