Exercise end-tidal CO2 predicts central sleep apnea in patients with heart failure

Abstract

BACKGROUND: Increased CO2 chemosensitivity and augmented exercise ventilation are characteristic of patients with heart failure (HF) with central sleep apnea (CSA). The aim of this study was to test the hypothesis that decreased end-tidal CO2 by cardiopulmonary exercise testing predicts CSA in patients with HF. METHODS: Consecutive ambulatory patients with New York Heart Association II to III HF were prospectively evaluated by CO2 chemosensitivity by rebreathe, cardiopulmonary exercise testing, and polysomnography (PSG). Subjects were classified as having either CSA (n = 20) or no sleep apnea (n = 13) by PSG; a central apnea-hypopnea index (AHI) ≥ 5 was used to define CSA. Subgroups were compared by t test or Mann-Whitney test and data summarized as mean ± SD. P < .01) and PETCO2 lower (29 ± 6 mm Hg vs 36 ± 5 mm Hg, P < .05). Peak exercise PETCO2 was most strongly associated with CSA (OR, 1.29; 95% CI, 1.08-1.54; P = .01; area under the curve, 0.88). CONCLUSIONS: In patients with HF and CSA, ventilatory drive is increased while awake at rest and during exercise and associated with heightened CO2 chemosensitivity and decreased arterial CO2 set point.