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Calculation of the Fresh Gas Flow Requirements of the Hafnia A and D Anaesthetic Circuits
Author(s) -
Thomsen A.
Publication year - 1980
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.1399-6576.1980.tb01502.x
Subject(s) - hafnia , medicine , fresh gas flow , anesthesia , waveform , electronic circuit , electrical engineering , materials science , voltage , sevoflurane , cubic zirconia , ceramic , composite material , engineering
Semi‐closed anaesthetic circuits are converted into the corresponding Hafnia circuits by replacing the expiratory valve by a side tube connected to an ejector flowmeter. Theoretical analysis of the Hafnia A and D circuits revealed that the fresh gas flow requirements are dependent on the inspiration/expiration time ratio. Using a ratio of 1/1.2 and a sine‐wave respiratory waveform, the minimal fresh gas requirements were calculated as 2.1 (Hafnia A) and 2.5 (Hafnia D) times the respiratory minute volume. The fresh gas requirements are identical with spontaneous or controlled ventilation.