Efficiency of the Carden 'Ventmasta' in A and D modes during controlled ventilation in children

J. R. Barrie, G. Meakin, I. T. Campbell, P. C W Beatty, T. E J Healy

    Research output: Contribution to journalArticlepeer-review


    We have determined the efficiencies of the enclosed Mapleson A and Mapleson D modes of the Carden 'Ventmasta' ventilator during controlled ventilation in 19 anaesthetized children. In addition, we determined the suitability for the A mode of the fresh gas formula, V̇F = 0.6 x weight 0.5. Efficiency was assessed in terms of the fraction of fresh gas delivered to the alveoli. When the minute volume to fresh gas flow ratio exceeded 1.5, fractional delivery of fresh gas was 23% greater in the A mode than in the D mode (0.74 vs 0.60) (P <0.0001). Under the same conditions, mean end-tidal carbon dioxide concentration in 27 children undergoing ventilation in the A mode with V̇F = 0.6 x weight 0.5 was 4.6% (range 3.5-5.4%). We conclude that the Carden system is up to 23% more efficient in the A mode than in the D mode, and that under the conditions of this study, normocapnia or mild hypocapnia was produced accurately using the formula V̇F = 0.6 x weight 0.5.
    Original languageEnglish
    Pages (from-to)453-457
    Number of pages4
    JournalBritish Journal of Anaesthesia
    Issue number4
    Publication statusPublished - 1994


    • Breathing systems equipment
    • Mechanical ventilation
    • Paediatric anaesthesia


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