Shah 2004.

Methods	Single‐centre RCT in the United Kingdom
Participants	33 adults (mean age 49) with ARDS
Interventions	3100B high‐frequency oscillatory ventilator (SensorMedics). Initial settings of frequency of 5 Hz, mPaw of CV+5, pressure amplitude of oscillation set for “vibration down to level of mid‐thigh”. No specific criteria for transitioning to CV were reported but HFO was continued until "resolution of ARDS" Controls were ventilated with time‐cycled pressure‐controlled mechanical ventilation with mean tidal volume of 7 ‐ 8 mL/kg ideal body weight (calculated from mean tidal volume per kg of ideal body weight on day 1, 2, 3). Tidal volume and PEEP were adjusted according to the ARDS Network low tidal volume protocol
Outcomes	Changes in ventilatory parameters (PaO₂/FiO₂ and FiO₂) over the first 72 hours of HFO or CV. Data for 30‐day mortality and other outcomes, including adverse events, were also available after author contact
Notes	No specific use of lung‐volume recruitment manoeuvres Protocols for sedation and paralysis were applied equally to HFO and CV groups. No use of rescue therapies or co‐interventions for ARDS
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Random draw ("sealed opaque envelopes which were drawn in a random manner by physician independent of the research team") (email correspondence, S Shah, 30 Nov 2007)
Allocation concealment (selection bias)	Low risk	Sealed opaque envelopes (email correspondence, S Shah, 30 Nov 2007)
Blinding (performance bias and detection bias) All outcomes	Low risk	Although blinding of caregivers and family members was not possible due to the nature of the intervention, the use of protocols reduces the risk of performance bias due to lack of blinding. The primary outcomes which were included in this review, were measured in a standardized manner in both groups (e.g. PaO₂/FiO₂), or were not likely to be susceptible to detection bias (death). The risk of detection bias is therefore low
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	5 (3 HFO and 2 conventional ventilation)/33 participants were withdrawn after randomization because they died within 48 hours; baseline data, physiologic and other clinical outcomes were not available for these participants even after author contact (email correspondence, S Shah, Nov 14 2014)
Selective reporting (reporting bias)	Low risk	All primary and secondary outcomes were reported; authors provided additional clinical and physiologic outcome data for this review after being contacted
Other bias	Low risk	No other source of bias identified