Supplementary oxygenation with the laryngeal mask airway: a comparison of four devices

The provision of supplementary oxygen via the laryngeal mask airway used in the recovery room is important for patient safety. Several devices have be en described for this purpose, but these studies have not included an accur ate measurement of the most clinically important variable, the end-tidal ox ygen concentration. We constructed an artificial model of spontaneous venti lation to compare the efficacy and safety of four devices, a circuit filter , a Hudson mask, the 'T-bag' device and a T-piece. We combined the use of o ximetry with a pneumotachograph to provide a continuous picture of the (-1) . The performances oxygen delivery characteristics of the devices at flow r ates of 2, 4 and 8 l.min(-1). of the T-bag and the T-piece were superior to those of the filter and Hudson mask, with end-tidal oxygen concentrations of 46.1%, 45.8% and 35.4%, 34.8%, respectively, at 8 l.min(-1). Single pain t assessments of oxygen delivery, such as peak inspired oxygen concentratio n, may overestimate the efficacy of test devices.