Abstract: We identified two eligible studies, both comparing the use of one model of SAD, the ProSeal laryngeal mask airway (PLMA) with a TT, with a total study population of 232. One study population underwent laparoscopic surgery. The included studies were generally of high quality, but there was an unavoidable high risk of bias in the main airway variables, such as change of device or laryngospasm, as the intubator could not be blinded. Many outcomes included data from one study only. A total of 5/118 (4.2%) participants randomly assigned to PLMA across both studies were changed to TT insertion because of failed or unsatisfactory placement of the device. Postoperative episodes of hypoxaemia (oxygen saturation < 92% whilst breathing air) were less common in the PLMA groups (RR 0.27, 95% CI 0.10 to 0.72). We found a significant postoperative difference in mean oxygen saturation, with saturation 2.54% higher in the PLMA group (95% CI 1.09% to 4.00%). This analysis showed high levels of heterogeneity between results (I2 = 71%). The leak fraction was significantly higher in the PLMA group, with the largest difference seen during abdominal insufflation－a 6.4% increase in the PLMA group (95% CI 3.07% to 9.73%). No cases of pulmonary aspiration of gastric contents, mortality or serious respiratory complications were reported in either study. We are therefore unable to present effect estimates for these outcomes. In all, 2/118 participants with a PLMA suffered laryngospam or bronchospasm compared with 4/114 participants with a TT. The pooled estimate shows a non-significant reduction in laryngospasm in the PLMA group (RR 0.48, 95% CI 0.09 to 2.59). Postoperative coughing was less common in the PLMA group (RR 0.10, 95% CI 0.03 to 0.31), and there was no significant difference in the risk of sore throat or dysphonia (RR 0.25, 95% CI 0.03 to 2.13). On average, PLMA placement took 5.9 seconds longer than TT placement (95% CI 3 seconds to 8.8 seconds). There was no significant difference in the proportion of successful first placements of a device, with 33/35 (94.2%) first-time successes in the PLMA group and 32/35 (91.4%) in the TT group. We have inadequate information to draw conclusions about safety, and we can only comment on one design of SAD (the PLMA) in obese patients. We conclude that during routine and laparoscopic surgery, PLMAs may take a few seconds longer to insert, but this is unlikely to be a matter of clinical importance. A failure rate of 3% to 5% can be anticipated in obese patients. However, once fitted, PLMAs provide at least as good oxygenation, with the caveat that the leak fraction may increase, although in the included studies, this did not affect ventilation. We found significant improvement in oxygenation during and after surgery, indicating better pulmonary performance of the PLMA, and reduced postoperative coughing, suggesting better recovery for patients.

Plain-language summary: We searched the databases to September 2012, to find controlled trials that had randomly assigned obese participants (with body mass index (BMI) greater than 30 kg/m2) undergoing general anaesthesia to TT or SAD for airway management. We wanted to investigate the effect of airway type on risk of failed placement; serious complications and death; oxygenation of the blood during and after surgery; coughing, sore throat or hoarseness during or after placement; and time taken and number of attempts needed to fit the airway. We found two randomized studies with a total of 232 obese participants, both of which studied one model of SAD－the ProSeal laryngeal mask airway (PLMA). No relevant outcomes for death or other serious complications occurred in these studies.We found that in 3% to 5% of obese participants, it was not possible to fit a PLMA, and a change of device to a TT was required. The proportion of successful first attempts at airway placement did not differ between PLMA and TT, although it took approximately six seconds longer to place an SAD than a TT. We found significant postoperative reduction of almost 75% in episodes of low oxygen saturation and an improvement in mean oxygen saturation of 2.5% during recovery in the PLMA group. Postoperative cough was less common among participants in the PLMA group. Our findings are consistent with both increased and decreased risks of both sore throat and hoarseness in the PLMA group. Identifying optimal anaesthetic techniques for obese patients is a priority for research. We could not establish the safety of SAD use in obese patients. Large databases created from medical records may be needed to clarify this issue.