Celli 1984.

Methods	Design: randomized controlled trial Multicentre or single‐centre: not reported Period: not reported Sample size: not reported. Generation of allocation: not reported. Allocation concealment: not reported. Blinding of assessment of treatment effect: not reported. Withdrawals: reported (less than 20%). Intention‐to‐treat analysis: not used. Follow up: until the fourth postoperative day
Participants	172 participants. Sex (male/female): 59/113. Age (mean): 46.95 years. Setting: private hospital in Maracaibo, Venezuela. Inclusion criteria: patients undergoing abdominal surgery. Exclusion criteria: not reported
Interventions	Control group (no respiratory treatment): n = 44 patients. IPPB group (intermittent positive pressure breathing therapy for 15 minutes, four times daily): n = 45 patients). IS group (incentive spirometry four times daily): n = 42 patients). DBE group (deep breathing exercises under supervision for 15 min, four times daily): n = 41 patients)
Outcomes	Patients' body temperature, heart rate, forced vital capacity, forced expiratory volume in one second, forced expiratory flow from 25% to 75% of vital capacity, postoperative pulmonary complications, and length of stay
Notes
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Drawing of a number to either the control or treatment groups
Allocation concealment (selection bias)	Unclear risk	Not reported
Blinding of participants and personnel (performance bias) All outcomes	Unclear risk	Not reported
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Not reported
Incomplete outcome data (attrition bias) All outcomes	Low risk	Less than 20% of the total of the participants
Selective reporting (reporting bias)	Low risk	No evidence
Other bias	Unclear risk	Conflict of interest: not reported