• T Yamada, H Kakoi, T Hirokawa, K Koyama, H Miyao, J Kawasaki, and T Kawazoe.
• Department of Anesthesiology, Saitama Medical Center, Saitama Medical School.
• Masui. 1994 Jan 1; 43 (1): 55-8.

AbstractTo evaluate the effects of fresh gas flow rate on the work of breathing during semi-closed circuit anesthesia, we measured respiratory frequency, tidal volume, inspiratory work of breathing, peak inspiratory and expiratory flow rate and fluctuations in airway pressure during breathing with fresh gas flow of 6 l.min-1, 3 l.min-1 and 1.5 l.min-1. There was no significant difference among three flow rates in terms of tidal volume, respiratory frequency, inspiratory work of breathing, peak inspiratory flow rate and fluctuation in airway pressure at inspiration. On the other hand, in the expiratory phase, peak expiratory flow rate was lower and fluctuation in airway pressure at expiration was higher at 6 l.min-1 than those at 3 l.min-1 and 1.5 l.min-1, which may be indicative of increased expiratory work of breathing. The present study shows that low fresh gas flow rate does not increase the inspiratory work of breathing and high fresh gas flow rate may increase the expiratory work of breathing, implying that lowering the fresh gas flow is profitable for the work of breathing during semi-closed circuit anesthesia.

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