Isr Med Assoc J. 2005;7(3):196-197.
Background
One mechanism that may limit training effect in chronic obstructive pulmonary disease (COPD) is the ventilatory limitation and associated dyspnea.
Objectives
To minimize ventilatory limitation during the training of patients with severe COPD by applying bilevel positive pressure ventilation during training in order to augment training intensity (and effect).
Methods
The study group comprised 19 patients (18 men and 1 woman) with a mean age of 64 +/- 9 years. Mean forced expiratory volume in 1 second was 32 +/- 4% of predicted, and all were ventilatory-limited (exercise breathing reserve 3 +/- 9 L/min, normal > 15 L/min). The patients were randomized: 9 were assigned to training with BiPAP and 10 to standard training. All were trained on a treadmill for 2 months, twice a week, 45 minutes each time, at maximal tolerated load. Incremental maximal unsupported exercise test was performed before and at the end of the training period.
Results
BiPAP resulted in an increment of 94 +/- 53% in training speed during these 2 months, as compared to 41 +/- 19% increment in the control group (P < .005). Training with BiPAP yielded an average increase in maximal oxygen uptake of 23 +/- 16% (P < .005), anaerobic threshold of 11 +/- 12% (P < .05), and peak O2 pulse of 20 +/- 19% (P < .05), while peak exercise lactate concentration was not higher after training. Interestingly, in the BiPAP group, peak exercise ventilation was also 17 +/- 20% higher after training (P < .05). Furthermore, contrary to our expectation, at any given work rate, ventilation (and tidal volume) in the BiPAP group was higher in the post-training test as compared to the pre-training test, and the end tidal partial pressure of CO2 at 55 W was lower, 40 +/- 4 and 38 +/- 4 mm Hg, respectively (P < .05). No improvement in exercise capacity was observed after this short training period in the control group.
Conclusion
Pressure-supported ventilation during training is feasible in patients with severe COPD and it augments the training effect. The improved exercise tolerance was associated with higher ventilatory response and therefore lower P(ET)co2 at equal work rates after training.
Comment
The factors that determine which patients with COPD have the greatest likelihood of achieving gains in exercise tolerance following exercise training and pulmonary rehabilitation are incompletely understood. Studies conducted to date do suggest that persons whose exercise impairment relates predominantly to skeletal muscle dysfunction may benefit more from exercise training than persons whose exercise impairment results predominantly from severe ventilatory limitation. Moreover, high-intensity training is generally needed to achieve gains in aerobic fitness following training, yet persons with the most severe ventilatory limitation often are unable to perform training at high-intensity targets. The use of noninvasive ventilation (eg, BiPAP) during exercise has the potential to enable patients with severe ventilatory limitation to undertake levels of exercise that they might otherwise not be able to perform, and in turn may lead to the ability to make greater gains following exercise training. The findings of the present study by Reuveny and colleagues support this concept. Patients with severe COPD and severe ventilatory limitation documented in pre-training exercise testing were randomized to receive BiPAP plus training or exercise training alone over a 2-month study period. The training consisted of twice-weekly (45 min/session) treadmill exercise at maximal tolerated workload. Patients trained with BiPAP achieved greater gains in tolerated walking speed than controls. Persons trained with BiPAP (but not controls) also had significant increases in Vo2 max, anaerobic threshold, and peak O2 pulse. This study confirms the findings of previous studies that the use of assisted ventilation during exercise training is feasible, and shows that patients with severe COPD who have severe ventilatory limitation to exercise can indeed make gains in aerobic fitness during training with this assisted ventilatory support, that might otherwise not be feasible for these persons. The practical aspects of delivering noninvasive ventilation in the context of pulmonary rehabilitation programs to persons who do not otherwise have this equipment for routine use merit further consideration.-CR