Table 1

Schedule of enrolment, interventions and assessments

	Study period
	Enrolment	Allocation	Postallocation	Close-out
Timepoint (days)	0	0	0 to 28 maximum	28 maximum
Enrolment
Eligibility screen	X
Express consent	X
Allocation		X
Interventions
HFHO			X
Standard O₂			X
Assessments
Baseline variables
Demographics	X
Medical history	X
Clinical examination	X
Paraclinical examination (pH, SOFA score) SAPS II score ECG–chest X-ray) ACRF aetiology	X
Outcomes variables
NIV duration			X
HFHO or standard O₂ duration according to group allocation			X
Intubation/reintubation			X
Vital status			X	X
VAS comfort after 1 hour of NIV resumption			X
VAS dyspnoea after 1 hour of NIV resumption			X
Likert scale for comfort after 1 hour of NIV resumption			X
Likert scale for dyspnoea after 1 hour of NIV resumption			X
VAS comfort after 2 hours of SB resumption*			X
VAS dyspnoea after 2 hours of SB resumption*			X
Likert scale for comfort after 2 hours of SB resumption*			X
Likert scale for dyspnoea after 2 hours of SB resumption*			X
Respiratory rate after 1 hour of NIV resumption			X
Respiratory rate after 2 hours of SB resumption*			X
Daily ABG			X
Adverse events			X
Hospital length of stay				X
Other variables
Criteria for switching between NIV and SB			X
Criteria to definitely stop NIV			X
Criteria for intubation			X
Discharge conditions			X

*Two hours of SB in the first 48 hours postrandomisation, and 4 hours thereafter.
ABG, arterial blood gas; ACRF, acute-on-chronic respiratory failure; HFHO, high flow heated and humidified nasal oxygen; NIV, non-invasive ventilation; SAPS II, simplified acute physiology score II; SB, spontaneous breathing; SOFA, sequential organ failure assessment; VAS, Visual Analogue Scale.