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A new hybrid anaesthetic circuit for a low–flow rebreathing technique
Author(s) -
MENTELL O.,
REVENÄS B.,
JONSSON L.
Publication year - 1994
Publication title -
acta anaesthesiologica scandinavica
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.738
H-Index - 107
eISSN - 1399-6576
pISSN - 0001-5172
DOI - 10.1111/j.1399-6576.1994.tb04015.x
Subject(s) - coaxial , fresh gas flow , medicine , tidal volume , closed circuit , anesthesia , dead space , physics , electrical engineering , respiratory system , mechanical ventilation , sevoflurane , engineering
The coaxial Mapleson D (Bain) circuit is close to an ideal anaesthetic breathing circuit but it requires a high fresh gas flow (V F ). The CO 2 absorber circuit can be used with a low V F but the patient end is clumsy and hyperventilation is common unless a small tidal volume (V T ) and a low respiratory frequency (f) is used. To overcome these problems a new hybrid anaesthetic circuit has been constructed. The new system has a slender coaxial patient end, connected to a Y–piece and a CO 2 absorber circuit with unidirectional valves. The V F supply runs inside the coaxial tube to the patient end, similar to the Bain circuit. The new circuit was tested with simulated controlled ventilation in a lung model and compared to an absorber circuit, an absorber circuit with an added 300 ml dead space (V D ) and a Bain circuit. The fraction of end tidal CO 2 (F E CO 2 ) was measured as a function of V F With V F 1 1 min ‐1 , V T 10 ml kg ‐1 and f 12 breaths min ‐1 a simulated 70 kg patient had an F E CO 2 of 4.8% and a 40 kg patient 5.5% with V F 2 1–min ‐1 . At zero V F the the new system was equal to an absorber circuit with 300 ml V D . With increasing V F the F E CO 2 in the new circuit decrease towards the absorber circuit values. The new system combines the benefits of the Bain circuit with those of a low flow CO 2 absorber circuit and offers flexibility in the choice of combinations of V D , f and V F .