Effects of high-intensity training on indices of ventilatory efficiency in chronic heart failure

Measures of ventilatory inefficiency, such as the slope of the relation between ventilation and carbon dioxide production ((Equation is included in full-text article.)slope) and the oxygen uptake efficiency slope (OUES) have recently been shown to be strong prognostic markers in patients with heart failure. Little is known regarding the effects of exercise training on these indices.

Fifty heart failure patients (mean age = 55 ± 6 years, ejection fraction = 33 ± 6%) referred to a residential cardiac rehabilitation program were randomized to a 2-month high-intensity training program (n = 24) or to a control group (n = 26). Before and after the study period, maximal cardiopulmonary exercise testing was performed, and markers of ventilatory inefficiency were determined.

Training increased peak oxygen uptake ((Equation is included in full-text article.); 23%), exercise time (29%), and peak workload (28%), whereas no changes were observed in controls (all P < .05 between groups). No differences were observed in the (Equation is included in full-text article.)slope in either group. However, the ventilatory equivalent for oxygen ((Equation is included in full-text article.)ratio) was reduced at matched work rates throughout exercise (P < .01). The OUES increased by 12% in the exercise groups (P = .003) and 4% in controls. At baseline, trained patients had an OUES that was 69% of the age-predicted value and this improved to 78% after training (P = .004). The change in OUES was significantly related to the change in peak (Equation is included in full-text article.)with training (r = 0.63, P = .001).

High-intensity training resulted in marked improvements in exercise capacity in patients with heart failure. Training improved the OUES and reduced the (Equation is included in full-text article.)ratio, but the (Equation is included in full-text article.)slope was unchanged. Among measures of ventilatory inefficiency, the OUES may be more sensitive to training than the (Equation is included in full-text article.)slope.