Abstract:
Purpose: This study investigates the efficacy of preoxygenation with Mapleson A and Mapleson D breathing systems vs the circle system with CO2 absorber. Methods: Thirteen healthy volunteers underwent tidal volume breathing for three minutes via facemask using Mapleson A, Mapleson D breathing systems or the circle system with CO2 absorber while breathing 100percent O2 at flow rates of 5 L·min-1 and 10·Lmin-1. Each volunteer acted as his-her own control by going through each of six preoxygenation protocols in random order. Fractional end-tidal O2 concentration (FETO2) was measured at 30-sec intervals. The results were compared among the three anesthesia systems at the two fresh gas flow rates. Results: At a fresh gas flow rate of 5 L·min-1, the Mapleson A and circle systems achieved FETO2 values of 90.8 ± 1.4percent and 90.0 ± 1.1percent, respectively, compared with the lower (81.5 ± 6.3percent, P andlt; 0.05), achieved with the Mapleson D system. When breathing O2 at 10 L·min-1, the FETO2 values after three minutes were similar with the Mapleson A, circle, and Mapleson D breathing systems (91.8 ± 2.3percent, 91.2 ± 1.7percent, 90.6 ± 2.7percent, respectively). Conclusion: When using the Mapleson A and the circle systems for preoxygenation, an oxygen flow rate of 5 L·min-1 can adequately preoxygenate the patient within three minutes, while an oxygen flow of 10 L·min-1 is required to achieve a similar fractional end-tidal O2 with the Mapleson D system.