Pre-oxygenation: a comparison of two techniques using a Bain system.

Pre-oxygenation using a standard technique of tidal breathing for 3 min through a Bain system with a fresh gas flow of 8 l.min-1 was compared with up to six vital capacity breaths from the same system. The technique of vital capacity breaths involved initial expiration to residual volume and use of the oxygen flush throughout controlled full inspirations, ensuring that the reservoir bag remained full. No significant problems were encountered using this method. Although three vital capacity breaths produced significantly inferior pre-oxygenation compared to 3 min of normal breathing, four and five vital capacity breaths were equally effective. With six vital capacity breaths, superior pre-oxygenation was produced. The use of four or more vital capacity breaths with this technique is a reliable and rapid alternative to 3 min of tidal breathing.