Comparison of breathing patterns during exercise in patients with obstructive and restrictive ventilatory abnormalities.

Patients with obstructive and restrictive ventilatory abnormalities suffer from exercise intolerance and dyspnea. Breathing pattern components (volume, flow, and timing) during incremental exercise may provide further insight in the role played by dynamic hyperinflation in the genesis of dyspnea. This study analyzed the breathing patterns of patients with obstructive and restrictive ventilatory abnormalities during incremental exercise. It also explored breathing pattern components with dyspnea at maximum oxygen uptake (VO2 max). Twenty patients, thirteen obstructive patients (forced expiratory volume 38% +/- 13% predicted, forced expiratory volume in 1 s/forced vital capacity ratio 39 +/- 8%), and seven restrictive patients (forced vital capacity 55 +/- 16% predicted, forced expiratory volume in 1 s/forced vital capacity ratio 84% +/- 11%) performed symptom-limited incremental exercise tests on a cycle ergometer with breath-by-breath determination of ventilation and gas exchange parameters. Breathing patterns were analyzed at baseline, 20, 40, 60, 80, and 100 percent of VO2 max. Dyspnea was measured at end-exercise with a 100 mm visual analogue scale. The timing ratio of inspiratory to expiratory time (T(I)/T(E)) and the flow ratio of inspiratory flow to expiratory flow ratio (V(I)/V(E)) were different (p < 0.008) between obstructive and restrictive patients at all exercise intensity levels. The timing components of expiratory time (T(E)) and inspiratory time to total time (T(I)T(TOT)) were significantly different (p < 0.008) at baseline and maximum exercise. Dyspnea scores were not significantly different. For obstructive patients, correlations were noted between T(I)/T(E), V(I)/V(E), T(I)T(TOT) and dyspnea (p < 0.05). Breathing pattern-timing components, specifically T(I)/T(E), in patients with obstructive and restrictive ventilatory abnormalities during exercise provided further insight into the pathophysiology of the two conditions and the contribution of dynamic hyperinflation to dyspnea.