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Preoxygenation with the Mapleson D system requires higher oxygen flows than Mapleson A or circle systems

[La préoxygénation avec le système Mapleson D requiert un débit d’oxygène plus élevé que les systèmes Mapleson A ou en cercle]

From the Department of Anesthesiology, American University of Beirut Medical Center, Beirut, Lebanon.

Address correspondence to: Dr. Anis Baraka, Professor and Chairman, Department of Anesthesiology, American University of Beirut Medical Center, P.O. Box 11 0236 Beirut, Beirut, Lebanon. Phone: 961 1 350000, ext. 6380; E-mail: abaraka{at}aub.edu.lb

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 100% O₂ at flow rates of 5 L·min^–1 and 10 L·min^–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 (F_ETO2) 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 F_ETO2 values of 90.8 ± 1.4% and 90.0 ± 1.1%, respectively, compared with the lower F_ETO2 (81.5 ± 6.3%, P < 0.05), achieved with the Mapleson D system. When breathing O₂ at 10 L·min^–1, the F_ETO2 values after three minutes were similar with the Mapleson A, circle, and Mapleson D breathing systems (91.8 ± 2.3%, 91.2 ± 1.7%, 90.6 ± 2.7%, 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 concentration with the Mapleson D system.