Bollen 2005.

Methods	Multi‐centre RCT in 5 ICUs in 4 European cities from October 1997 to March 2001
Participants	61 adults (mean age 53) with ARDS Excluded: Patients with a non‐pulmonary terminal disease, severe chronic obstructive pulmonary disease or asthma and grade 3 or 4 air leak
Interventions	3100B high‐frequency oscillatory ventilator (SensorMedics). Frequency of 5 Hz with inspiratory time of 33%, mPaw of CV+ 5 cm H₂O, pressure amplitude of oscillation set according to PaCO₂ and to achieve chest wall vibration Controls were ventilated with time‐cycled pressure‐controlled mechanical ventilation with mean tidal volume of 8 ‐ 9 mL/kg ideal body weight (calculated from mean tidal volume per kg of ideal body weight on day 1, 2, 3). General physiological targets were provided, including limitation of peak inspiratory pressure to 40 cm H₂O, but more detailed ventilation procedures and methods of weaning were according to standard protocols of the investigating centres. Cross‐over to the alternate ventilator was required if the participant met treatment failure criteria
Outcomes	Cumulative survival without mechanical ventilation or oxygen dependency at 30 days; mortality at 30 days; therapy failure; cross‐over rate; and persisting pulmonary problems defined as oxygen dependency or still being on a ventilator at 30 days. Data for ventilator settings and arterial blood gases were available for the first 3 days. Other clinical and adverse outcomes including barotrauma, hypotension, and treatment failure were also reported.
Notes	Lung‐protective ventilation was not mandated in the control group receiving conventional mechanical ventilation 7/61 participants (5 HFO and 2 control) were reported lost to follow‐up at 30 days; ICU mortality, but not 30‐day mortality, was available for all participants lost to follow‐up except 3/61 (2 HFO and 1 control) participants after author contact Trial was terminated early for slow recruitment No specific use of lung‐volume recruitment manoeuvres Use of sedation and paralysis was not reported Use of rescue therapies or co‐interventions for ARDS was not reported Partial industry support (SensorMedics)
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Computerized randomization
Allocation concealment (selection bias)	Low risk	Sealed opaque envelopes(email correspondence, C. Bollen, June 26, 2009)
Blinding (performance bias and detection bias) All outcomes	Unclear risk	Blinding of caregivers and family members was not possible due to the nature of the intervention, which increases the risk of performance bias The primary outcome was death, which is less susceptible to detection bias
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	30‐day mortality available for 54/61 participants; ICU mortality, but not 30‐day mortality, was available for 4/61 after author contact; vital status remains unknown for 3/61 participants
Selective reporting (reporting bias)	Low risk	All primary and secondary outcomes were reported
Other bias	Unclear risk	> 10% of participants (11/61) crossed over from assigned ventilator strategy