Vargas 2015.

Study characteristics
Methods	RCT, cross‐over design. Single‐centre study
Participants	Total number of randomized participants: 12 Setting: ICU; France Inclusion criteria: people with AHRF Exclusion criteria: people with tracheostomies; < 18 years of age; chronic retention of CO2; respiratory acidosis; factors related to insertion of an oesophageal catheter; excessive amounts of respiratory secretions; SBP < 90 mmHg; ventricular arrhythmia; encephalopathy or coma; life‐threatening hypoxaemia; decision to limit life‐support treatments in the ICU Baseline characteristics (overall): Age, median (IQR): 63 (59 to 73) years Gender, M/F: 10/2 BMI, mean (SD): not reported SAPS II, median (IQR): 48 (35 to 56) PaCO2: not reported PaO2/FiO2, median (IQR): 178 (157 to 199) mmHg
Interventions	Cross‐over study with each period lasting approximately 20 minutes. All participants were first given conventional oxygen therapy using a non‐rebreather face mask; participants were not randomized to this group. Intervention group (HFNC): Randomized, n = 12; losses, n = 0; analysed, n = 12 Details: HFNC via Optiflow, with largest cannula tolerated by the individual participants, gas flow set at 60 L/min, temperature set at 37 °C Control group (NIV: BiPAP): Randomized, n = 12; losses, n = 0; analysed, n = 12 Details: BiPAP fitted to a face mask. CPAP set at 5 cm H2O
Outcomes	Oesophageal pressure; blood gas analysis and haemodynamic variables; comfort and dyspnoea Note: we did not include outcome data in the review because the study authors did not report outcome data from the first study period.
Notes	Funding/declarations of interest: supported by a research grant from Fisher & Paykel Healthcare Ltd Study dates: January 2011 to January 2012