RESUMO
While exercise training appears to have no effect on resting respiratory function, and its effect on ventilation/perfusion relationships is uncertain, it can significantly reduce the rate of lactic acid production, carbon dioxide generated from buffering of acid and the hydrogen ion stimulus to breathe during exercise. We had two objectives in this study: 1) to determine if patients who might benefit from exercise training could be selected based on resting respiratory function measurements; 2) to determine if the work rate at which the metabolic acidosis starts to develop could be reliably determined, non-invasively, by a simple modification of the recently described V-slope method of Beaver et al. Patients with severe obstructive lung disease, all of whom experienced exertional dyspnoea, underwent incremental exercise testing to determine if they could exercise to a level causing metabolic acidosis. About two thirds of the patients with severe airflow obstruction developed a significant metabolic acidosis (arterial standard HCO3- decrease of more than 2 mEq.l-1 after two minutes recovery following an incremental exercise test to maximum). The oxygen uptake (VO2) at which the metabolic acidosis (directly measured) and that of which the increase in CO2 in the expired air attributable to buffering (V-slope method), were in close agreement. There was no significant correlation between the magnitude of the exercise metabolic acidosis and the forced expiratory volume in one second (FEV1) or the diffusing capacity for carbon monoxide (DLCO). Thus, it is necessary to perform exercise testing in order to select patients for exercise training, based on the benefits accrued from reducing the exercise metabolic acidosis.(ABSTRACT TRUNCATED AT 250 WORDS)