Objectives: Chronic heart failure is closely related to impaired cardiorespiratory reflex control, including decreased ventilatory efficiency during exercise (V̇e/V̇co2-slope) and central sleep apnea (CSA). Continuous positive airway pressure (CPAP) and nocturnal oxygen therapy alleviate CSA. The aim of the present study was to compare the effects of nocturnal CPAP and oxygen therapy on V̇e/V̇co2-slope.
Design and setting: Prospective controlled trial at a university hospital.
Patients: Twenty-six stable patients with chronic heart failure and CSA.
Intervention and measurements: Ten patients received nocturnal oxygen, and 16 patients were assigned to CPAP treatment. At baseline and after 12 weeks of treatment, symptom-limited cardiopulmonary exercise testing was performed on a cycle ergometer. Expiratory gas was analyzed breath by breath for evaluation of ventilation and ventilatory efficiency in combination with arteriocapillary blood gas analysis during rest and exercise.
Results: CPAP treatment significantly reduced the V̇e/V̇co2-slope (31.2 ± 1.6 vs 26.2 ± 1.0, p = 0.005) and improved the left ventricular ejection fraction (LVEF) [31.7 ± 2.6% vs 35.7 ± 2.7%, p = 0.041]. CPAP treatment significantly reduced the apnea-hypopnea index (AHI) [35.9 ± 4.0/h vs 12.2 ± 3.6/h, p = 0.002]. Peak oxygen consumption (V̇o2) [16.2 ± 1.1 L/min/kg vs 16.3 ± 1.2 L/min/kg, p = 0.755] remained similar after CPAP treatment. Oxygen therapy reduced the AHI (28.8 ± 3.2/h vs 8.7 ± 4.1/h, p = 0.019), but did not improve exercise capacity (peak V̇o2, 15.4 ± 1.5 L/min/kg vs 15.6 ± 1.9 L/min/kg, p = 0.760), LVEF (30.9 ± 2.4% vs 32.5 ± 2.3%, p = 0.231), or the V̇e/V̇co2-slope (30.0 ± 1.5 vs 29.8 ± 1.5, p = 0.646).
Conclusion: Nocturnal CPAP and oxygen therapy alleviate CSA to a similar degree. Only CPAP therapy may improve ventilatory efficiency during exercise and may have favorable effects on LVEF. Therefore, our data suggest that CPAP is advantageous compared to oxygen in the treatment of CSA in patients with chronic heart failure.