A high flow semi-open system for preoxygenation: an evaluation.

We have compared an alternative breathing system for preoxygenation comprising a Hudson face mask with high oxygen inflow (48 litre min-1) and a Mapleson A breathing system (100 ml kg-1 min-1). The study consisted of two parts: the first involved adult volunteers (10 male, seven female) and the second part used a lung model for spontaneous ventilation with a sinusoidal ventilatory wave pattern. In the volunteers, preoxygenation was achieved at mean times of 138 (SD 31.3) s and 164 (SD 36.7) s with the high flow semi-open and Mapleson A systems, respectively. In the lung model, at peak inspiratory flow rates of 30 and 40 litre min-1, the preoxygenation times were 139 and 120 s, respectively, with the semi-open system and 167 and 156 s with the Mapleson A system. The high flow semi-open system may be an alternative for current techniques, provided peak inspiratory flows are not excessive.