Trial NCT04477954
Publication Cannellotto M, Emerg Med J, 2021
Primary outcome on the report: Proportion of patients that recovered from hypoxaemia and at 3, 5 and 10 days (to assess if patient recovered after two and five sessions) and median time to recovery within 30 days. Normalisation of oxygen requirement (oxygen independence) was defined as pulse oximetry value in ambient air ≥93% and/or arterial blood gas with a partial pressure of oxygen (PaO2) value of ≥60 mm Hg in ambient air.

Note: The risk of bias by domain corresponds to the highest risk of bias among outcomes by domain.
The overall risk of bias corresponds to the overall highest risk of bias assessed among outcomes.

Bias Author's judgement Support for judgement
Randomization
Some concerns 		Quote: “Participants were randomly assigned to receive either HBO2 treatment in addition to the standard treatment (treatment group) or the standard treatment alone (control group) for respiratory symptoms. We used simple randomisation with number assignment by a random number generator (UX App) from 1 to 10 and entered into tables assigning odd or even number to treatment or control.”
Comment: Allocation sequence random. No information on allocation concealment.
Deviations from intervention
Some concerns 		Quote: “Open-label”
Comment: Unblinded study (participants and personnel/carers)
Deviations from intended intervention arising because of the study context:
No participant cross-over.
No information on the administration of co-interventions of interest: biologics, antivirals. Corticosteroids were administered as per standard care.
Hence, no information on whether deviations arose because of the trial context.
Our analysis for the binary outcome is an intention-to-treat analysis. This method was considered appropriate to estimate the effect of assignment to intervention.
Risk assessed to be some concerns for the outcome: Mortality (D28). WHO score 7 and above (D28).
Missing outcome data
Low 		Comment: 40 participants randomized; 40 participants analyzed.
Data available for all participants randomized.
Risk assessed to be low for the outcome: Mortality (D28). WHO score 7 and above (D28)
Measurement of the outcome
Low 		Comment: Method of measuring the outcome probably appropriate.
Measurement or ascertainment of outcome probably does not differ between groups.
Unblinded study (outcome assessor)

MORTALITY
Mortality is an observer-reported outcomes not involving judgement.
Risk assessed to be low for the outcomes: Mortality (D28).

WHO SCORE 7 AND ABOVE
For this outcome, we consider that the assessment cannot possibly be influenced by knowledge of intervention assignment.
Risk assessed to be low for the outcome: WHO score 7 and above (D28)
Selection of the reported results
Low 		Comment: The registry was available (dated 20 July 2020).
Outcome pre-specified.
Results were not selected from multiple outcome measurements or analyses of the data.
Trial analyzed as pre-specified.
Risk assessed to be low for the outcome: Mortality (D28). WHO score 7 and above (D28).
Overall risk of bias
Some concerns