Gao 2002.

Methods	Randomization procedure: concealed randomization Allocation: not reported Blinding: not reported Design: randomized, controlled Duration: not reported Multicentre: no Analysis (ITT): not reported Informed consent: not reported
Participants	Number of participants: 60 Setting: ICU Age (mean ± SD): O: 64 ± 8.1 years; NPPV: 65 ± 10.4 years Gender (M/W): O: 21/9; NPPV: 23/7 Diagnostic criteria: elderly participants with respiratory rate over 30 breaths/minute after upper abdominal surgery in an ICU Exclusion criteria: indication of endotracheal intubation PaO2 ≤ 60 mm Hg or PaCO2 ≥ 50 mm Hg under oxygen mask or NPPV with oxygen flow rate of 5 L/min Number excluded: not reported
Interventions	Control: routine oxygen mask with oxygen flow rate of 5 L/min Intervention: NPPV. Assisted mechanical ventilation using an oxygen mask. The ventilator was Evita 4, PSV pattern was used, with the flow trigger 3 L/min and FiO2 40%. The PSV levels were adjusted from 10 cm H2O until VT > 7 mL/kg or respiratory rate < 25 breaths/min. PEEP was set at 3‐5 cm H2O Number of participants per group: O: 30; NPPV: 30 Mask: appropriate facial mask was adopted that allowed the stomach tube to pass through
Outcomes	Primary outcome: endotracheal intubation Secondary outcome: ICU and hospital length of stay; incidence of pneumonia, infection, and sepsis within the first month after surgery; and hospital mortality. Pneumonia, infection, and sepsis were identified using standard definitions Mortality: not reported Tracheal intubation rate: O: 8 NPPV: 3 ICU length of stay: O: 7 ± 5 days; NPPV: 4 ± 3 days Hospital length of stay: not reported Treatment failure: not reported Adverse effects: not reported Participant compliance: not reported Drop‐outs/withdrawals: not reported
Notes	Declarations of interest: none reported Funding sources for the study: none reported
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	The method used was not reported. We wrote to the contact author asking about this procedure but did not receive an answer
Allocation concealment (selection bias)	Unclear risk	The method used was not reported. We wrote to the contact author asking about this procedure but did not receive an answer
Blinding of participants and personnel (performance bias) All outcomes	Unclear risk	Not reported. We contacted the authors of this study to ask about blinding of study participants and personnel but did not obtain an answer
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Not reported. We contacted the authors of this study to ask about blinding of study outcome assessors but did not obtain an answer
Incomplete outcome data (attrition bias) All outcomes	Low risk	No missing outcome data
Selective reporting (reporting bias)	Low risk	The study protocol was available and all of the study's pre‐specified (primary and secondary) outcomes that are of interest in the review were reported in the pre‐specified way
Other bias	Low risk	This study was not a cluster randomized or a cross‐over trial. This study was a randomized controlled trial. The participants were randomized. The distribution of the participants was balanced between the control and intervention groups. The authors did not deviate from the study protocol