BACKGROUND Percutaneous dilatational tracheostomy (PDT) is one of the most common bedside surgical procedures performed in critically ill adult patients on intensive care units (ICUs) who require long-term ventilation. PDT is generally associated with relevant life-threatening complications (e.g. cuff rupture leading to possible hypoxia or aspiration, puncture of the oesophagus, accidental extubation, mediastinitis, pneumothorax, emphysema). The patient's airway can be secured with an endotracheal tube (ETT) or a laryngeal mask airway (LMA). OBJECTIVE To assess the safety and effectiveness of ETT versus LMA in critically ill adult patients undergoing PDT on the ICU.This review addresses the following research questions.1. Is an LMA more effective than an ETT in terms of procedure-related or all-cause mortality?2. Is an LMA safer than an ETT in terms of procedure-related life-threatening complications during a PDT procedure?3. Does use of an LMA influence the conditions for performing a tracheostomy (e.g. duration of procedure)? METHODS We searched the Cochrane Database of Systematic Reviews (CDSR); the Cochrane Central Register of Controlled Trials (CENTRAL) 2013, Issue 6 (part ofThe Cochrane Library); MEDLINE (from 1984 to 27 June 2013) and EMBASE (from 1984 to 27 June 2013). We searched for reports of ongoing trials in the metaRegister of Controlled Trials (mRCT). We handsearched for relevant studies in conference proceedings of the International Symposium on Intensive Care and Emergency Medicine (ISICEM), the Annual Congress of the European Society of Intensive Care Medicine (ESICM), the Annual Congress of the Society of Critical Care Medicine (SCCM), the American Thoracic Society (ATS) and the Annual Meeting of the American College of Chest Physicians (ACCP). We contacted study authors and experts concerning unpublished data and ongoing trials. We searched for further relevant studies in the reference lists of all included trials and of relevant systematic reviews identified in theCDSR. METHODS We included randomized controlled trials (RCTs) that compared use of endotracheal tubes versus laryngeal mask airways in critically ill adult patients undergoing PDT on the ICU. We imposed no restrictions with regard to language, timing or technique of PDT performed. METHODS Two review authors independently assessed the eligibility and methodological quality of each study and carried out data extraction. We resolved disagreements by discussion. Our primary outcomes were all-cause mortality, procedure-related mortality and tally of participants with one or more serious adverse events. When available, we reported on our secondary outcomes, which included duration of the procedure, failure of the procedure requiring conversion to any other procedure, time to extubation after tracheostomy, length of ICU stay after tracheostomy, length of hospital stay after tracheostomy and any other serious adverse events. When possible, we combined homogeneous studies for meta-analysis. We used the risk of bias tool of The Cochrane Collaboration to assess the internal validity of all included studies in six different domains. RESULTS We included in this review eight RCTs involving 467 participants. The included trials exclusively assessed critically ill participants (e.g. with head injury, neurological disease, multi-trauma, sepsis, acute respiratory failure (ARF) and/or chronic obstructive pulmonary disease (COPD)). Internal validity was considerably low in studies with a high or unclear risk of bias. The main reason for this was low methodological quality or missing data, even after study authors were contacted. Study size was generally small, with a minimum of 40 and a maximum of 73 participants. Only one study (40 participants) reported on overall mortality, showing no clear evidence of a difference between treatment groups (risk ratio (RR) 1.5, 95% confidence interval (CI) 0.28 to 8.04, Fisher test P value 1.0, low-quality evidence). Four studies (231 participants) reported that no procedure-related deaths occurred with any intervention. Seven studies reported the numbers of participants with adverse events, showing no clear evidence of benefit of either LMA or ETT during PDT (RR 0.73, 95% CI 0.35 to 1.52, P value 0.41, low-quality evidence). The tally of participants in included studies with adverse events ranged from 0% to 33% in the LMA group and from 0% to 50% in the ETT group. However, the duration of the procedure was significantly shorter in the LMA group (mean difference (MD) -1.46 minutes, 95% CI -1.92 to -1.01 minutes, 324 participants, P value ≤ 0.00001, low-quality evidence). No clear evidence of a difference between ETT and LMA groups was found for all other outcomes. Only one study provided follow-up data for late complications related to the intervention, showing no clear evidence of benefit for any treatment group. CONCLUSIONS Evidence on the safety of LMA for PDT is too limited to allow conclusions to be drawn on its efficacy or safety compared with ETT. Although the LMA procedure is shorter because of optimal visual conditions, its effect on especially late complications has not been investigated sufficiently. Studies focusing on late complications and relevant patient-related outcomes are necessary for definitive conclusions on safety issues related to this procedure.