Study	Reason for exclusion
Anderes 1979	Participants in one group were intubated for 3 hours, whereas participants in the other group were extubated soon after surgery. Unequal treatment of groups
Celli 1984	Intervention is not CPAP, but positive‐pressure breathing
Conti 2007	Study is a case‐controlled study, not an RCT
Drummond 2002	Even though this is an RCT (stratified), study was done mainly to observe effects of CPAP on sleep pattern and hypoxaemia. Study lasted only 1 day; no relevant data available from this publication for the purpose of the review
Ebeo 2002	This RCT deals with BiPAP ventilation, which is different from CPAP; hence excluded from this review
Huerta 2002	This is not an RCT
Jaber 2005	This study of participants who already have established respiratory failure is not an RCT; it also falls into the exclusion criteria for the review
Joris 1997	This RCT uses BiPAP (bilevel positive airway pressure) during the postoperative period. This is an exclusion criterion
Kindgen‐Milles 2005	This RCT is dealing with thoraco‐abdominal aortic surgery and does not conform with inclusion criteria
Neligan 2009	A randomized trial, but the intervention group receives the same treatment as the control group, except that onset of treatment is delayed by 30 minutes. Therefore, this study was excluded
Olsen 2002	This RCT is dealing with thoraco‐abdominal operations, an exclusion criterion for the review
Rieg 2012	This is not an RCT; participants were allocated into 2 groups on 2 different timelines
Roeseler 1982	Study population is a mixture of randomized and non‐randomized cases, allocated into 2 groups. Therefore, excluded from review
Vartanov 2007	Intervention group received BiPAP ventilation during the postoperative period, even though the study was an RCT
Wong 2011	Used PEEP during surgery; follow‐up with CPAP in the recovery ward, but only for 1 hour

BiPAP = bilevel positive airway pressure

CPAP = continuous positive airway pressure

PEEP = positive end expiratory pressure

RCT = randomised controlled trial