This investigator-initiated, prospective, randomized, blinded, multi-center, controlled trial will investigate the effect of a restrictive vs. liberal oxygenation-strategy in patients hospitalized with acute heart failure with pulmonary congestion.

Patients will be randomized 1:1 in the emergency department to either liberal or restrictive oxygenation after providing informed written consent.

1. Liberal oxygenation group = SpO2 target of 96%.
2. Restrictive oxygenation group = SpO2 target of 90%.

The allocation will be concealed through the use of an oxygen-delivery robot, termed O2MATIC. The study will include 122 patients.

Background:

One million hospitalizations occur each year with a primary diagnosis of acute heart failure in the USA, with comparable numbers in Europe. Most patients with acute heart failure are treated with supplemental oxygen during hospitalization and guidelines recommend initiation of oxygen therapy if SpO2 <90% (class I, level C). However, no clinical trials of oxygen targets in humans with acute heart failure investigating clinically relevant endpoints have been performed.

Primary objective:

To investigate the effect of a restrictive vs. liberal oxygenation-strategy in patients hospitalized with acute heart failure.

Hypothesis:

Restrictive oxygenation is associated with improved clinical outcome compared to liberal oxygenation.

Design: Investigator-initiated, prospective, randomized, blinded, multi-center, controlled trial.

Intervention:

Patients will be randomized 1:1 in the emergency department to either liberal or restrictive oxygenation after providing informed written consent.

1. Liberal oxygenation group = SpO2 target of 96%.
2. Restrictive oxygenation group = SpO2 target of 90%.

Patients will have nasal cannula or oxygen mask placed as the usual care, and oxygen is titrated to the prespecified target range.

Consented patients will be randomly allocated to study groups via the automated web-based system within REDCap. The allocation will be concealed. Time at randomization will be considered as study time zero (T0). All patients will receive usual standard of care except for their oxygen-administration.

The intervention-phase will be 24 h, and hereafter oxygen therapy will be at the discretion of the treating physician.

Inclusion Criteria:

1. Age ≥ 18 years
2. Acute (within minutes to days) onset or worsening of subjective dyspnea
3. Oxygen saturation <92% (on arterial blood gas) or need of oxygen
4. At least one of the following clinical or radiological signs of congestion:

1. Pulmonary rales 2. Chest X-ray or CT with pulmonary congestion 3. Lung ultrasound with multiple B-lines

Exclusion Criteria:

1. More than 4 hours from hospital admission to randomization
2. Suspected infection or sepsis
3. Known severe pulmonary disease
4. Systolic blood pressure <90 mmHg

Oxygen-delivery will be given through a robot, which adjusts oxygen-flow towards a given oxygen-saturation target. The robots monitor will be turned of during the intervention and will only alarm in case of clinically relevant hypoxemia.