Gas leakage and the laryngeal mask airway - A comparison with the tracheal tube and facemask during spontaneous ventilation using a circle breathing system

The ability of the laryngeal mask airway, tracheal tube and facemask to provide a leak free seal in a clinical setting was assessed by measuring the minimal fresh gas flows needed in a closed circle system during spontaneous ventilation on 60 subjects. The fresh gasflow was reduced until no spillage occurred from rite pop-off valve. This fresh gas flow was taken to represent the sum of gas uptake by the subject and gas leakage fi on? the circuit. The median fresh gas flow after 20 minutes was 350 ml.min(-1) in the laryngeal mask airway group, 350 ml.min(-1) in the tracheal tube group and 450 ml.min(-1) in the facemask group. The fresh gas flow required for facemask group was significantly higher than that for the laryngeal mask airway ol tracheal tribe groups (p < 0.01). There was no significant difference between the flesh gas flows required for the tracheal tube and laryngeal mask airway groups. We conclude that the laryngeal mask airway provides as good a gas tight seal as a tracheal tribe in this context and would be of benefit in I educing anaesthetic gas pollution.