Oxygen Therapy in Patients With Chronic Heart Failure With Reduced Ejection Fraction

Inclusion Criteria: * Patients \> 18 years old. * Diagnosis and clinic of chronic heart failure with ventricular dysfunction with left ventricular ejection fraction (LVEF) \<40% under optimal medical treatment regardless of its etiology and having presented at least one episode of decompensation (visits to the emergency room, hospitalizations and/or need for intravenous depletive treatment) during the last year. * Nocturnal desaturation defined as mean SatO2 \<90% and/or Cummulative time (TC) \<90\>22 minutes to nocturnal pulse oximetry done at home. * Signed informed consent Exclusion Criteria: * Chronic lung disease (includes chronic obstructive pulmonary disease with Pulmonary respiratory function (PRF) (forced expiratory volume at one second/forced vital capacity (FEV1/FVC) \<70%), diffuse interstitial diseases, pulmonary hypertension of respiratory). * Obstructive sleep apnea-hypopnea syndrome (OSAHS) with Apnea hypopnea index (AHI) \> 14.9. * Previous treatment with oxygen therapy. * Not agreeing to attend periodic cardiology visits. * Being part of other clinical studies that contraindicate an intervention. * Pregnant or breastfeeding women.