Introduction: Slow breathing training (SBT) has been proposed as a new nonpharmacologic treatment in patients with chronic heart failure (CHF).

Objectives: The aim of this study was to assess the effects of SBT on exercise capacity, hemodynamic parameters, and sleep respiratory patterns in a relatively large sample of CHF patients.

Patients and methods: A crossover open study was conducted. Patients completed, in a random order, 10- to 12‑week SBT, with 2 15‑minute sessions of device‑guided SBT each day, reaching 6 breaths/ min, and a 10- to 12‑week follow‑up under standard care. Clinical data collection, polysomnography, echocardiography, 6‑minute walk test (6MWT), and laboratory tests were performed.

Results: A total of 96 patients (74 men, 22 women) in New York Heart Association classes I–III, with an average age of 65 years and an ejection fraction (EF) of 31%, completed the study. Home‑based SBT was safe. After training, EF and 6MWT distance improved (EF: 31.3% ±7.3% vs 32.3% ±7.7%; P = 0.030; 6MWT: 449.9 ±122.7 m vs 468.3 ±121.9 m; P <0.001), and the apnea–hypopnea index decreased (5.6 [interquartile range (IQR), 2.1; 12.8] vs. 5.4 [IQR, 2.0; 10.8]; P = 0.043).

Conclusions: SBT improved physical capacity and systolic heart function; it also diminished sleep disturbances. The results support the benefits of SBT as a novel component of cardiorespiratory rehabilitation programs in patients with CHF.