Memtsoudis 2012.

Methods	RCT with parallel groups Approved by the Hospital for Special Surgery Institutional Review Board (Protocol no. 28117) and written, informed consents obtained Site: Hospital for Special Surgery, New York, NY, USA Setting: hospital Dates of data collection: February 2009 to September 2010
Participants	26 participants scheduled for elective, primary lumbar decompression and fusion of ≤ 4 spinal levels Exclusion criteria: known previous lung pathology, use of immunosuppressants, renal failure with creatinine > 1.5 mg/dL, recent exposure to a ventilator or surgery during general anaesthesia (< 1 year), and ASA physical status ≥ III
Interventions	Treatment group: tidal volume 6 mL/kg (IBW) and PEEP 8 cmH2O (n = 13) Control group: tidal volume 12 mL/kg (IBW) and no PEEP (n = 13)
Outcomes	Relevant to this review Invasive ventilatory support Others Plasma levels of interleukin‐6 and ‐8 Urinary levels of desmosine
Notes	Funding: Department of Anesthesiology, Hospital for Special Surgery (Stavros G. Memtsoudis), and Clinical Translational Science Center (CTSC) grant: NIH UL1‐RR024996 (Yan Ma) Declaration of interest: none mentioned Volume per body weight: IBW: men: 50 + 0.91 (height in cm – 152.4); women 45.5 + 0.91 (height in cm – 152.4)
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Quote: "patients were randomly assigned by a computer generated list of random numbers."
Allocation concealment (selection bias)	Low risk	Quote: "the allocation sequence was concealed from the research assistant in sequentially numbered, opaque, sealed, and stapled envelopes."
Blinding of participants and personnel (performance bias) All outcomes	Unclear risk	Not mentioned
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Quote: "patients, surgeons, and research assistants who were responsible for subsequent data collection were blinded to the randomization."
Incomplete outcome data (attrition bias) All outcomes	Low risk	Quote: "one patient in the low tidal volume group withdrew consent for blood draws after randomization and surgery."
Selective reporting (reporting bias)	Low risk	All results reported
Other bias	Low risk	Quote: "despite randomization, patients in the low volume group were older (P value = 0.01)."