To determine whether the laryngeal mask airway (LMA) offered any advantages over the tracheal tube (TT) or facemask (FM).

MEDLINE, indexes of anaesthetic journals in Index Medicus and a bibliography supplied by Intavent Research Ltd. were searched, although the search dates were unclear and no search terms were given. 'Reference Manager Update' was also searched for references, though it is unclear whether this is just a database of references compiled by the researchers.

Study designs of evaluations included in the review

Randomised controlled trials (RCTs) comparing LMA with other forms of airway management were included.

Specific interventions included in the review

The LMA, the TT and the FM.

Participants included in the review

The included studies involved adults (78.8%), children (19.2%) and mixed populations (1.9%); 46.6% used intermittent positive pressure ventilation (IPPV), 44.2% spontaneous ventilation (SV) and 7.7% mixed. The majority of users were anaesthetists (86.6%).

Outcomes assessed in the review

The outcomes were all related to the advantages of one system over another. These included: speed and ease of placement, haemodynamic stability at induction and during emergence, rise in intraocular pressure during insertion, anaesthetic requirements for airway tolerance, frequency of coughing during emergence, oxygen saturation during emergence, incidence of sore throat in adults, hand fatigue, improved operating conditions in minor paediatric otological surgery, lower seal pressures, frequency of gastric insufflation and incidence of oesophageal reflux.

How were decisions on the relevance of primary studies made?

The articles were independently assessed by two observers (non-blinded), with any disagreements resolved by a third reviewer.

Deficiencies in the methodology of the included studies were summarised narratively; these related mainly to lack of blinding and lack of information about insertion techniques used. However, differences in quality were not used to weight individual trials in the meta-analysis. The author does not state how the papers were assessed for quality, or how many of the reviewers performed the quality assessment.

The author does not state how the data were extracted for the review, or how many of the reviewers performed the data extraction.

How were the studies combined?

The p-values for homogeneous studies were pooled. Null hypotheses were tested using Fisher's method. The hypotheses were that LMA offered no advantage over TT or FM in 6 areas: (1) placement, (2) physiology, (3) airway mechanics, (4) airway problems/complications, (5)post-operative aspects, and (6)miscellaneous.

How were differences between studies investigated?

Only studies homogeneous in terms of study issue addressed and anaesthesia phase were pooled; no statistical test for homogeneity was carried out.

Fifty-two studies involving a total of 2,440 patients: 35 compared LMA with TT; 14 compared LMA with FM; 1 study compared LMA with TT and FM; and 2 studies compared LMA with a combined TT/FM technique, where TT was replaced with FM in an emergency.

1. Placement, LMA versus TT: LMA advantageous in ease and speed of placement for non-anaesthetists (p<0.001); no significant difference in ease of placement for anaesthetists, although LMA provided increased speed (p<0.025). LMA versus FM: LMA advantageous in ease but not speed of placement for non-anaesthetists (p<.001); no significant difference in speed of placement for anaesthetists.

2. Physiology, LMA versus TT: LMA advantageous in terms of pulse rate and blood-pressure changes during insertion and emergence (all p values <0.001), and in intra-ocular pressure rises (p<0.001); no significant difference in frequency of oesophageal reflux, tolerance or catecholamine release. LMA versus FM: no significant difference in pulse rate or blood-pressure changes; lower frequency of oesophageal reflux with FM (p<0.001).

3. Mechanical LMA versus TT: no significant difference in the breathing process; TT advantageous in terms of air leak and gastric insufflation (both p<0.005).

4. Airway problems/complications, LMA versus TT: reduced coughing observed with LMA (p<0.001); no significant differences in frequency of laryngospasm and oxygen saturation. LMA versus FM: LMA confers advantage in oxygen saturation (p<0.025).

5. Post-operative, LMA versus TT: lower occurrence of sore throat observed in adults with LMA (p<0.05), but not children; voice analysis better with LMA (p<0.001); no significant difference in post-operative pain, vomiting or nausea.

6. Miscellaneous: LMA versus FM: LMA advantageous in terms of surgical conditions for minor otological surgery in children and in hand fatigue (both p<0.025)

There is substantial evidence that the LMA offers advantages and disadvantages over the TT. Benefits include: increased speed and reliability of placement by inexperienced personnel, thus suggesting a potential role in resuscitation; haemodynamic stability in induction and emergence; minimal changes in intra-ocular pressure; reduced coughing, sore throat and voice alteration during emergence; and advantages in oxygen saturation. Its main disadvantage is an increased likelihood of leak and gastric insufflation.

LMA also offers advantages over the FM (oxygen saturation, hand fatigue, operating conditions in minor paediatric otological surgery and suitability for IPPV) and some disadvantages (e. g. reflux). The authors note that the importance of differences between airways could not be determined in terms of patient outcome.

A clearly presented and thorough meta-analysis, which also highlights some of the methodological problems with trials and makes useful recommendations for the design and reporting of further trials. It uses its findings to make practical suggestions for the use of the LMA in specific settings and patient groups. However, detailed results from the meta-analysis would have been helpful, rather than simply reporting individual P values.

Practice: More meticulously designed RCTs, than are currently available, are required to compare LMA with TT and FM.

Research: Further research is required to determine how the advantages of the LMA are reflected in patient outcome.

This is a critical abstract of a systematic review that meets the criteria for inclusion on DARE. Each critical abstract contains a brief summary of the review methods, results and conclusions followed by a detailed critical assessment on the reliability of the review and the conclusions drawn.