Comparison of the flexible and standard laryngeal mask airways

To determine mucosal pressures, ease of insertion, mask position and oropharyngeal leak pressures for the flexible (FLMA) and standard laryngeal mask airway (LMA).

Forty anesthetized, paralysed adult patients were randomly allocated to receive either the FLMA or LMA. Microchip sensors were attached to the LMA or FLMA at identical locations corresponding to the base of tongue, hypopharynx, lateral pharynx, oropharynx, posterior pharynx and pyriform fossa. Mucosal pressure, oropharyngeal leak pressure (OLP) and mask position (assessed fibreoptically) were recorded during inflation of the cuff from 0-40 ml in 10 ml increments.

Ease of insertion and mask position were similar between devices. Mean OLP was higher for the LMA (22 vs 19 cm H2O), but the maximum OLP was similar (25 vs 24 cm H2O). Mean mucosal pressures were generally low (< 12 cm H2O) for both devices, but were higher for the LMA in the lateral pharynx (4 vs 1 cm H2O) and oropharynx (13 vs 3 cm H2O) and higher in the posterior pharynx for the FLMA (4 vs 2 cm H2O). The OLP for both devices increased with increasing intracuff volume from 0-10 ml and 10-20 ml, and from 20-30 ml for the FLMA.

We conclude that the LMA and FLMA perform similarly in terms of ease of insertion and mask position, but OLP and mucosal pressures are slightly higher for the LMA. Pharyngeal mucosal pressures for both devices are lower than those considered safe for the tracheal mucosa. The overall clinical performance between the two devices is similar.