Acute Hypoxemic Respiratory Failure (AHRF) is one of the prevalent causes of admission around the world and is associated with high mortality in resource-limited settings. Limited access to invasive mechanical ventilation is among the contributing factors to poor outcomes. The Bag CPAP may be useful in reducing the need for intubation and therefore mortality in patients with AHRF but data are lacking. This study aims to determine whether the Bag CPAP compared to standard oxygen care, could reduce the percentage of patients with criteria for intubation in patients with AHRF.

This is a prospective randomized, open-label, controlled trial in which patients presenting at the emergency room in Rwanda will be randomly assigned to receive standard oxygen therapy or Bag CPAP. The primary endpoint is the percentage of patients with criteria for intubation at day 7. Secondary endpoints include the tolerance of the Bag CPAP, overall 28-day mortality rate, mortality rate of intubated patients on mechanical ventilation at day 28, percentage of patients intubated at 28 days, ventilator-free days at day 28, interval between the initiation of treatment and the onset of intubation criteria, the interval between the time when criteria for intubation are met and intubation, organ failure-free days at day 7 and length of hospital stay.

1. Inclusion criteria

   All patients aged 18 years or older will be included in the study if they meet the following criteria:

   • De novo acute respiratory distress, characterized by the presence of dyspnea at rest, the use of accessory muscles for breathing, or a respiratory rate of 25 cycles per minute or more.
   • Hypoxemia, defined as a SpO2/FiO2 ratio less than 315 or a PaO2/FiO2 ratio less than 300 mmHg (if arterial blood gas is available) despite an oxygen therapy of 6 L/min. FiO2 will be estimated by the rule of 3% (Coudroy formula)(18,22). SpO2 should be less than 98% when assessing the SpO2/FiO2 ratio.

2. Exclusion criteria

Patients with one of the following criteria will be excluded from the study:

• Absolute contraindications to CPAP: patient's refusal, uncontrollable vomiting, upper gastrointestinal bleeding, open or sucking chest wound, pneumothorax not drained, craniofacial trauma, severe burns to the face, severe upper airway obstruction, traumatic tetraplegia at the initial stage, tracheostomy.
• Moderate to massive pleural effusion not drained
• Cardiac arrest, severe ventricular arrhythmias, and shock defined as the need for vasopressor support (adrenaline, noradrenaline, or dopamine)
• Altered level of consciousness (GCS below 12), repetitive convulsions, or status epilepticus
• Do not intubate or resuscitate order before the inclusion in the study
• Refusal to participate, already included in the study, enrollment in another interventional trial on acute respiratory failure