Mentzelopoulos 2012.

Methods	Single‐centre RCT in Greece from July 2006 to May 2009
Participants	125 adults (mean age 52) with ARDS; PaO₂/FiO₂ <150, PEEP ≥ 8 cm H₂O
Interventions	3100B high‐frequency oscillatory ventilator (SensorMedics). Initial settings of frequency of 4 Hz, mPaw of 3 above mean tracheal pressure measured distal to the endotracheal tube, pressure amplitude of oscillation set 30 above baseline PaCO₂  during CV. Participants received 6 ‐ 24 hours of HFO each day until PaO₂/FiO₂ ≥ 150 for > 12 hours on CV. All participants received tracheal gas insufflation with HFO Controls were ventilated using volume assist control according to a prespecified protocol with a target tidal volume of 5.5 to 7.5 ml/kg predicted body weight and target plateau pressure of ≤ 35 cm H₂0
Outcomes	Hospital mortality. Additional physiologic and clinical outcomes, including adverse events, were obtained after author contact.
Notes	Protocols for lung volume recruitment manoeuvres were used for both the HFO and CV group Steroids for ARDS were used in 40/61 and 39/64 of the HFO and CV groups respectively Paralysis was administered to 50/61 and 54/64 of the HFO and CV groups respectively In the CV group, 4 participants received HFO (without tracheal gas insufflation) and 2 participants received prone ventilation as rescue therapy
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Computer‐generated list of random numbers (email correspondence, SD Mentzelopoulus, 9 April 2009)
Allocation concealment (selection bias)	Low risk	Telephone (email correspondence, SD Mentzelopoulus, 9 April 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 Study investigators (with expertise in HFO and mechanical ventilation) were available to assist in the ventilatory management of participants randomized to HFO, but not those randomized to conventional ventilation (personal correspondence, S Mentzelopoulos, HFO investigators meeting London, UK, Feb 21 2013). This might introduce potential performance bias Because the primary outcome was death, detection bias was unlikely
Incomplete outcome data (attrition bias) All outcomes	Low risk	Vital status of 1/61 participants randomized to HFO was not known because this participant was transferred to another hospital on day 31 post‐randomization. (However, this participant was assumed to have died in the primary analysis, which would slightly bias the overall results against HFO)
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