Limited Ventilatory Reserve During Exercise in Heart Failure with Preserved Ejection Fraction

Background

Patients with heart failure with preserved ejection fraction (HFpEF) exhibit a tachypneic breathing strategy during exercise. Patients with HFpEF have pulmonary system alterations that may contribute to the breathing strategy in HFpEF.

Research Question

Do patients with HFpEF have limited ventilatory reserve compared with control patients during exercise? Furthermore, does greater upper body adiposity contribute to the lower ventilatory reserves in HFpEF?

Study Design and Methods

Patients with HFpEF (n = 16; mean age ± SD, 70 ± 8 years) and control patients (n = 19; mean age ± SD, 69 ± 8 years) performed incremental cycling to volitional exhaustion. Trunk percent fat was quantified with dual-energy X-ray absorptiometry. Inspiratory capacity, inspiratory and expiratory reserve volumes, and ventilatory variables were compared between groups at rest and during exercise at 40 W and peak oxygen uptake.

Results

Patients with HFpEF had lower total lung capacity (5.4 ± 1.1 vs 6.4 ± 1.2 L), FVC (3.1 ± 0.7 vs 3.8 ± 0.6 L), and FEV₁ than control patients (all P < .04), respectively. During exercise at 40 W, patients with HFpEF had higher breathing frequency and smaller inspiratory reserve volume (1.2 ± 0.4 vs 1.5 ± 0.3 L) and expiratory reserve volume (0.9 ± 0.4 vs 1.1 ± 0.5 L) than control patients (both P < .05), respectively. At peak oxygen uptake, inspiratory and expiratory reserve volumes were not different between groups (both P > .21), but patients with HFpEF had lower end-inspiratory lung volume (P = .02). Patients with HFpEF had higher trunk percent fat than control patients (49% ± 7% vs 40% ± 8%, respectively; P < .01). Percent trunk fat was related to % predicted FVC (r = –0.57) and tidal volume to FVC ratio during exercise at 40 W (r = 0.53) for patients with HFpEF (both P < .04) but not control patients (both P > .72).

Interpretation

These findings demonstrate that patients with HFpEF have limited ventilatory reserve during exercise, in part due to their smaller lung capacity. Furthermore, our findings suggest that the greater distribution of upper body adiposity in HFpEF is an important contributor to the smaller lung capacity for these patients.