The goal of this prospective multi-centre randomised controlled trial is to determine if addition of awake prone positioning to standard oxygen, high flow oxygen therapy and non-invasive ventilation may reduce the rates of endotracheal intubation and mechanical ventilation.

Effectiveness of prone position in mechanically ventilated patients was investigated extensively. During the Covid-19 pandemic a sudden increase in cases of acute respiratory failure, resulted in renewed interest and numerous studies on applying this concept in spontaneously breathing patients and using this in conjunction with less invasive respiratory support. However, evidence form the Covid-19 trials may not be directly extrapolated to other acute respiratory distress causes (for example bacterial pneumonia) as pathology of lung injury is distinctly different. Even though first reports of awake prone positioning were published nearly 30 years ago, but to date there are no prospective randomised trials in adult population treated for acute lung injury unrelated to Covid-19. Existing publications range from case reports (lung transplantation and drowning cases) to small feasibility trials involving 15-20 patients and also neonatal and paediatric populations. Considering that patients with acute lung injury constitute a significant proportion of routine intensive care unit population, results of this study would be highly relevant for the daily practice in intensive care medicine.We are aiming to conduct a prospective multi-centre randomised controlled trial comparing standard care alone with awake prone positioning and standard care in spontaneously breathing patients admitted to Intensive or Intermediate Care Units for acute non-Covid-19 hypoxemic respiratory failure.

Inclusion Criteria:

• Adult patients admitted to intensive care unit for acute hypoxemic respiratory failure.
• Acute hypoxemic respiratory failure is defined by respiratory rate ≥25 breaths/min, and partial pressure of oxygen in the arterial blood (PaO2)/fraction of inspired oxygen (FiO2) ≤300 mm Hg or oxygen saturation (SpO2)/fraction of inspired oxygen (FiO2) ratio <235 while spontaneously breathing under standard oxygen with oxygen flow rate of at least 10 L/min, high flow oxygen therapy or non-invasive ventilation. For patients under standard oxygen, FiO2 is calculated according to the following formula: FiO2=0.21 + 0.03 per litre of supplemental oxygen.
• Informed consent

Exclusion Criteria:

• impaired consciousness - Glasgow coma score <14;
• inability to cooperate or prone position intolerance;
• immediate indications for endotracheal intubation;
• patients with do-not-intubate order at time of inclusion;
• patients with contraindication to high flow oxygen therapy (HFOT) or non-invasive ventilation (NIV);
• Partial pressure of carbon dioxide (PaCO2) above 50 mm Hg and quantitative measure of the acidity (pH) <7,3;
• vasopressor dose >0.3 µg/kg/min of norepinephrine-equivalent to maintain systolic blood pressure >90 mmHg;
• Covid-19 positive

By the nature of the awake prone intervention, it will not be possible to blind clinicians; however, interventions will be blinded to data analysts and outcome assessors.