Oxygen therapy and noninvasive respiratory supports in acute hypoxemic respiratory failure: a narrative review.

Background: This narrative review was written by an expert panel to the members of the jury to help in the development of clinical practice guidelines on oxygen therapy.

Results: According to the expert panel, acute hypoxemic respiratory failure was defined as PaO₂ < 60 mm Hg or SpO₂ < 90% on room air, or PaO₂/FiO₂ ≤ 300 mm Hg. Supplemental oxygen should be administered according to the monitoring of SpO₂, with the aim at maintaining SpO₂ above 92% and below 98%. Noninvasive respiratory supports are generally reserved for the most hypoxemic patients with the aim of relieving dyspnea. High-flow nasal cannula oxygen (HFNC) seems superior to conventional oxygen therapy (COT) as a means of avoiding intubation and may therefore be should probably be used as a first-line noninvasive respiratory support in patients requiring more than 6 L/min of oxygen or PaO₂/FiO₂ ≤ 200 mm Hg and a respiratory rate above 25 breaths/minute or clinical signs of respiratory distress, but with no benefits on mortality. Continuous positive airway pressure (CPAP) cannot currently be recommended as a first-line noninvasive respiratory support, since its beneficial effects on intubation remain uncertain. Despite older studies favoring noninvasive ventilation (NIV) over COT, recent clinical trials fail to show beneficial effects with NIV compared to HFNC. Therefore, there is no evidence to support the use of NIV or CPAP as first-line treatment if HFNC is available. Clinical trials do not support the hypothesis that noninvasive respiratory supports may lead to late intubation. The potential benefits of awake prone positioning on the risk of intubation in patients with COVID-19 cannot be extrapolated to patients with another etiology.

Conclusions: Whereas oxygen supplementation should be initiated for patients with acute hypoxemic respiratory failure defined as PaO₂ below 60 mm Hg or SpO₂ < 90% on room air, HFNC should be the first-line noninvasive respiratory support in patients with PaO₂/FiO₂ ≤ 200 mm Hg with increased respiratory rate. Further studies are needed to assess the potential benefits of CPAP, NIV through a helmet and awake prone position in patients with acute hypoxemic respiratory failure not related to COVID-19.