In non-intubated patients, symptomatic treatment of hypoxaemic respiratory failure is still debated, with different options: (1) standard oxygen therapy (SOT), (2) high-flow nasal cannula oxygen therapy (HFNC) and (3) non-invasive ventilation (NIV). The objective of this study is to compare the effects of HFNC and NIV on lung volumes assessed by CT scan to allow a better understanding of their effectiveness.

The HONIVAH study (High-flow Oxygen therapy and Non-Invasive ventilation on lung Volumes and on upper Airway in Hypoxemic critically ill patients) is an investigator-initiated, prospective, single-centre, physiological, randomised, parallel-group, unblinded trial with an electronic system-based randomisation. Patients with hypoxaemic respiratory failure, defined as the need for SOT flow ≥3 L/min to maintain a pulsed oxygen saturation ≥95%, and a CT scan prescribed by the physician in charge of the patient, will be randomly assigned to the HFNC group or the NIV group. Two inspiratory thoracic CT scans will be performed, one with SOT as part of the routine patient management and a second thoracic CT scan with HFNC or NIV, depending on the allocation group. The primary outcome is the comparison of the relative variation in ‘poorly aerated’ and ‘non-aerated’ lung volumes before and after the intervention between the HFNC group and NIV group, assessed by thoracic CT scan. Secondary outcomes included the variation in tracheal cross-sectional upper airway area, lung volumes, gas exchange and patient comfort.

The study project has been approved by the appropriate ethics committee (Comité de Protection des Personnes Sud-Ouest et Outre-mer 1, France, 2022-A02458-35). Informed consent is required. The results will be submitted for publication in a peer-reviewed journal and presented at one or more scientific conferences.

ClinicalTrials.gov identifier: NCT05643911.