title: Preoxygenation with the Mapleson D system requires higher oxygen flows than Mapleson A or circle systems.
abstract: OBJECTIVE
  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 (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 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).
  
  
  CONCLUSIONS
  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.
authors.affiliation: Department of Anesthesiology, American University of Beirut Medical Center, P.O. Box 11 0236 Beirut, Beirut, Lebanon.
authors.forename: Samar
authors.initials: S
authors.lastname: Taha
authors.forename: Mohamad
authors.initials: M
authors.lastname: El-Khatib
authors.forename: Sahar
authors.initials: S
authors.lastname: Siddik-Sayyid
authors.forename: Carla
authors.initials: C
authors.lastname: Dagher
authors.forename: Jules-Marie
authors.initials: JM
authors.lastname: Chehade
authors.forename: Anis
authors.initials: A
authors.lastname: Baraka
mesh_terms: D000328:Adult; D000764:Anesthesia, Closed-Circuit / Q000379:methods; D000769:Anesthesia, Inhalation; D005260:Female; D006801:Humans; D017214:Laryngeal Masks / Q000145:classification*; D008297:Male; D010100:Oxygen / Q000008:administration & dosage* / Q000502:physiology; D012119:Respiration; D012121:Respiration, Artificial; D013990:Tidal Volume
chemical_list: D010100:Oxygen