Abstract: Of 785 identified citations, 20 trials from 1990 to 2011 enrolling 1652 participants fulfilled the inclusion criteria. We judged most of the trials to be at low or unclear risk of bias across the six domains, and we judged four studies to have elements of high risk of bias; we did not classify any studies at overall low risk of bias. The quality of evidence was low for five of the seven outcomes (very low N = 1, moderate N = 1) and there was heterogeneity among the studies. There was a variety of adult participants and the procedures were performed by a wide range of differently experienced operators in different situations. There was no evidence of a difference in the rate of the primary outcomes: mortality directly related to the procedure (Peto odds ratio (POR) 0.52, 95% confidence interval (CI) 0.10 to 2.60, I² = 44%, P = 0.42, 4 studies, 257 participants, low quality evidence); and serious, life-threatening adverse events - intraoperatively: risk ratio (RR) 0.93, 95% CI 0.57 to 1.53, I² = 27%, P = 0.78, 12 studies, 1211 participants, low quality evidence,and direct postoperatively: RR 0.72, 95% CI 0.41 to 1.25, I² = 24%, P = 0.24, 10 studies, 984 participants, low quality evidence. PTs significantly reduce the rate of the secondary outcome, wound infection/stomatitis by 76% (RR 0.24, 95% CI 0.15 to 0.37, I² = 0%, P < 0.00001, 12 studies, 936 participants, moderate quality evidence) and the rate of unfavourable scarring by 75% (RR 0.25, 95% CI 0.07 to 0.91, I² = 86%, P = 0.04, 6 studies, 789 participants, low quality evidence). There was no evidence of a difference in the rate of the secondary outcomes, major bleeding (RR 0.70, 95% CI 0.45 to 1.09, I² = 47%, P = 0.12, 10 studies, 984 participants, very low quality evidence) and tracheostomy tube occlusion/obstruction, accidental decannulation, difficult tube change (RR 1.36, 95% CI 0.65 to 2.82, I² = 22%, P = 0.42, 6 studies, 538 participants, low quality evidence). When compared to STs, PTs significantly reduce the rate of wound infection/stomatitis (moderate quality evidence) and the rate of unfavourable scarring (low quality evidence due to imprecision and heterogeneity). In terms of mortality and the rate of serious adverse events, there was low quality evidence that non-significant positive effects exist for PTs. In terms of the rate of major bleeding, there was very low quality evidence that non-significant positive effects exist for PTs. However, because several groups of participants were excluded from the included studies, the number of participants in the included studies was limited, long-term outcomes were not evaluated, and data on participant-relevant outcomes were either sparse or not available for each study, the results of this meta-analysis are limited and cannot be applied to all critically ill adults.

Plain-language summary: The evidence is current to May 2015. We included 20 studies from 1990 to 2011, enrolling 1652 adult participants hospitalized in the ICU, who were scheduled for planned tracheotomy. None of the studies were funded. The application of percutaneous techniques, does not reduce the rate of death, of serious, life-threatening complications (e.g. injuries to the windpipe or the oesophagus), major bleeding or problems with the tracheostomy tube (blockage, accidental loss, difficult tube change). There was some evidence that using percutaneous techniques results in fewer cases of wound infections (- 76%) and unfavourable scarring (- 75%). The quality of the evidence varied by outcome from moderate (wound infection) to low (death, serious complications, unfavourable scarring, problems with the tracheostomy tube) and to very low (major bleeding). Reasons for the limitations are: great differences among the studies, results not similar across the studies, and not enough data. Based on the available data, we conclude that percutaneous tracheostomies offer benefits for some of the outcomes when compared with surgical tracheostomies. However, because several groups of participants were excluded from the included studies (i.e. people with unfavourable neck structure, bleeding disorders or emergency situations), the number of participants in the included studies was limited, long-term outcomes were not evaluated, and data on participant-relevant outcomes were either sparse or not available for each study, the results of this meta-analysis are limited and cannot be applied to all critically ill adults.