Difficulty in recruitment

The purpose of this study is to assess patients with chronic heart failure and moderate-severe ventricular dysfunction (left ventricular ejection fraction (FEVE) <40%) with nocturnal desaturation (mean Oxygen saturation (SatO2) <90% and/or Cummulative time (TC) <90% > 22 minutes) without underlying respiratory disease, oxygen treatment during hours of night rest will reduce exacerbations, improve the ability to effort, sleep quality and poor prognostic parameters of heart failure, compared to patients not receiving oxygen treatment.

36 patients will attend at baseline, monthly, 3-month and 6-monthly visits.

BASELINE VISIT After being informed about the study and potential risks, all patients giving written informed consent, will be randomized (according to the list) receiving oxygen therapy (treatment group) and those not receiving this treatment (control group).

The following information will be collected:

• Demographics, pathological history, concomitant medication.
• Physical examination, vital signs (pressure, heart rate, weight)
• Doppler echocardiography (an echocardiography performed in the last 6 months will be accepted)
• Analytical determination of biomarkers NT-proBNP and ultrasensitive troponin.
• Assessment of baseline functional class by NYHA classification.
• Respiratory function tests: spirometry and diffusion (will accept tests performed in the last 6 months).
• Arterial blood gases.
• Nocturnal respiratory polygraphy.
• Exercise capacity with the 6-minute walk test (P6MM)
• Evaluation of health-related quality of life with the Minnesota questionnaire
• Assessment of sleep quality using the Pittsburgh questionnaire

If the patient belongs to the treatment group, the intervention will begin with oxygen therapy with a static concentrator and nasal cannula during the night at home, with a minimum compliance of six hours, following the usual clinical practice. Overnight pulse oximetry at home with oxygen will be performed to confirm if the prescribed flow rate is adequate to achieve a mean SatO2 >90% and/or that the correction of the CT90. If this is not achieved, it will be repeated, modifying the oxygen flow until the target is reached.

The control group will not undergo this intervention.

The rest of the medical treatment will be carried out according to the usual protocol of the Heart Failure Unit.

Follow up visits:

Clinical follow-up will be done at one month, three months and six months after the start of the intervention in the Chronic Respiratory Pathology Unit of Pneumology.

At 1 and 3 months

• Analytical determination of biomarkers nt-proBNP and ultrasensitive troponin (TnThs).
• Baseline functional class will be collected by New York Heart Association (NYHA) classification.
• Physical examination, vital signs (blood pressure (BP), Heart rate (HR), weight).
• Adverse effects and concomitant medication.

At 6 months

• Analytical determination of biomarkers nt-proBNP and ultrasensitive troponin (TnThs).
• Baseline functional class by NYHA classification will be collected.
• Physical examination, vital signs (BP, HR, weight).
• Evaluation of exercise capacity will be done by means of the 6-minute walk test (PM6M).
• Nocturnal pulse oximetry of control: treatment group with oxygen to evaluate the response and control group without oxygen to evaluate the evolution.
• Assessment of health-related quality of life with the Minnesota questionnaire.
• Sleep quality will be assessed using the Pittsburgh questionnaire.
• Adverse effects and concomitant medication.

In the follow-up periods (1, 3 and 6 months), the number of decompensations will be recorded:

• Hospitalizations for heart failure.
• Emergency care for heart failure requiring at least one dose of intravenous diuretic treatment.
• Need for outpatient intravenous depletive treatment due to the presence of congestive signs.

The study will be considered completed after 6 months of follow-up.

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.

All individual participant data (IPD) collected data can be shared as long as it is for research collaboration

Once the manuscript is accepted for publication

Study data access will be provided for collaborative purposes