Inclusion Criteria:  New York Heart Association (NYHA) functional classes II and III LVEF either ≤40% or ≥50% V̇E/V̇CO2 slope ≥36, and/or a pattern of exercise oscillatory ventilation defined by established criteria Optimal guideline-directed medical therapy for >3 months Written informed consent  Exclusion Criteria:  Heart failure decompensation within the preceding 3 months LVEF between 41%-49% Non-cardiac conditions and comorbidities associated with hyperventilation like pulmonary diseases Inability or unwillingness to perform apnoea training