Koivusalo 1997a.

Methods	Randomised clinical trial.
Participants	Country: Finland. Number randomised: 29. Mean age: 46 years. Females: not stated. Inclusion criteria: Elective cholecystectomy ASA I or II Exclusion criteria: Bronchial asthma Chronic pulmonary disease
Interventions	Participants were randomly assigned to two groups: Group 1: abdominal wall lift (n = 14). Group 2: pneumoperitoneum with 12 to 13 mm Hg pressure (n = 15). Device used for abdominal lift: intra‐peritoneal device.
Outcomes	The main outcome measures were conversion to open cholecystectomy and operating time.
Notes	Withdrawal, one because of malpositioning of nasogastric tube (in this trial, gastric mucosal pH was measured). Attempts were made to contact the author in February 2007 and July 2013.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Comment: This information was not available.
Allocation concealment (selection bias)	Unclear risk	Comment: This information was not available.
Blinding of participants and personnel (performance bias) All outcomes	Unclear risk	Comment: This information was not available.
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Comment: This information was not available.
Incomplete outcome data (attrition bias) All outcomes	High risk	Comment: There were postrandomisation drop‐outs.
Selective reporting (reporting bias)	High risk	Comment: Important outcomes were not reported.
Vested interest bias	Unclear risk	Comment: This information was not available.