SELECTION CRITERIA FOR EXERCISE TRAINING IN PATIENTS WITH COPD

The physical performance of patients with chronic obstructive pulmonar y disease (COPD) is limited mainly by pathophysiological derangements of the ventilatory system. Thus, the exercise performance can be ameli orated by increasing the level of ventilation that they can sustain, o r by reducing the ventilatory requirement for a given level of activit y. Almost all studies have yielded negative results in COPD patients, in terms of exercise training having the ability to improve VEmax. The only way to reduce the ventilatory requirement is to reduce CO2 outpu t. Lower levels of lactate result in less non-metabolic CO2 produced b y bicarbonate buffering. This is the likely mechanism responsible for a lower ventilatory requirement for work rates above the pre-training anaerobic threshold. We specifically wished to determine, whether a pr ogram of intensity, frequency and duration known capable of producing a physiologic training effect in healthy subjects, would do so in COPD patients. Further, we sought to whether exercise training at a work r ate with lactic acidosis is more effective in inducing a training effe ct in COPD patients than a work rate not associated with lactic acidos is. Nineteen COPD patients were selected and performed an incremental test as well as two square wave tests at a low and a high work rate. I dentical tests were performed after an 8-week program of cycle ergomet er training either for 45 min/day at a high work rate or for a proport ionally longer time at a low work rate. For the high work rate trainin g group, identical work rates engendered less lactate (4.5 versus 7.2 mEq/L) and less VE (48 versus 55 L/min) after training; the low work r ate training group had significantly less lactate and VE decrease (p < 0.01). There was a good correlation (r = 0.73, p < 0.005) between the decrease in blood lactate and the decrease in ventilation. The major findings of this study are that COPD patients who experience lactic ac idosis during exercise can achieve physiologic training responses from a program of endurance training and that training work rates engender ing high levels of blood lactate are more effective then work rates el iciting low lactate levels.