Spontaneous vs Controlled Mechanical Ventilation in Acute Hypoxemic Respiratory Failure

Inclusion Criteria: We will include patients who fulfil all the following criteria: * Acutely admitted to the ICU * AND age ≥ 18 years * AND invasive mechanical ventilation via endotracheal tube or tracheostomy for less than 24 hours * AND moderate acute hypoxemic respiratory failure, defined as a PaO₂-FiO₂ ratio between 13.3-26.6 kPa (100-200 mmHg) with PEEP ≥ 5 cm H2O, based on arterial blood gas analysis obtained within 2 hours before randomisation. * AND new pulmonary infiltrate (uni- or bilateral) on chest x-ray or CT-scan obtained no more than 24 hours before randomisation. Exclusion Criteria: * Previously randomised into the SVALBARD trial. * Informed consent following inclusion expected to be unobtainable * Patient under coercive measures * Withdrawal from active therapy or brain death deemed imminent. * Chronic hypercapnic respiratory failure defined as PaCO2 \> 8 kPa (60 mm Hg) in the outpatient setting. * Listed for lung transplant. * Acute heart failure / acute myocardial infarction / cardiac arrest during or causing index ICU admission. * Use of home oxygen. * Chronic mechanical ventilation for any reason except for non-invasive mechanical ventilation (CPAP/BIPAP) used solely for sleep apnoea disorder. * Currently receiving ECMO therapy. * Burns \>70 % total body surface. * Acute brain injury or stroke (any, including subarachnoid haemorrhage, SAH). * Intracranial hypertension. * Patients with planned repeat surgical interventions during current stay in ICU.