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Rebreathing and ventilatory response to different fresh gas flows in the Bain and Lack systems. A clinical study
Author(s) -
Jonsson L. O.,
Johansson S. L. G.,
Zetterström H.
Publication year - 1987
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.1399-6576.1987.tb02545.x
Subject(s) - medicine , anesthesia , ventilation (architecture) , zoology , halothane , respiratory system , body weight , carbon dioxide , fresh gas flow , mechanical engineering , ecology , sevoflurane , engineering , biology
Thirty‐four adults were studied during halothane anaesthesia with spontaneous breathing, while undergoing orthopaedic surgery. They were randomly divided into two groups according to whether the Bain (n = 18) or the Lack (n = 16) system was used. Respiratory flows were recorded and arterial blood gases drawn at different fresh gas flows (· F ). The values obtained were compared with those recorded under non‐rebreathing conditions (NRC). In the Bain system the proportion of rebreathers was 0.22, 0.25. 0.55 and 0.83 when the · F was 175, 150, 125 and 100 ml · min ‐1 · kg ‐1 body weight (b.w.), respectively. In the Lack system these proportions were 0.43. 0.55 and 0.92 at · F of 85, 70 and 55 ml · min ‐1 kg ‐1 b.w., respectively. The ventilatory response to rebreathing was an increase in minute ventilation (· E ), keeping the partial pressure of arterial carbon dioxide (Paco 2 ) almost unaltered. In the Bain system the · E · kg ‐1 · b.w. thus increased by 18% and 38% at · F of 125 and 100 ml · min ‐1 kg ‐1 b.w., respectively, when compared to NRC (P < 0.05). The corresponding increases in the Lack system were 15% and 37% at · F of 70 and 55 ml · min ‐1 · kg ‐1 b.w., respectively (P < 0.01). In the Lack group also the Paco 2 increased by 6% when a · F of 55 ml ·min ‐1 · kg ‐1 b.w. was used compared to the value obtained under NRC (P<0.05). The respiratory flow pattern was similar in both groups and at all studied · F levels, despite a small, insignificant, decrease in expiratory flows when high · F was given in the Bain system. The conclusion is that · F of 150 ml · min·kg ‐1 b.w. in the Bain system and 85 ml·min ‐1 · kg ‐1 b.w. in the Lack system should be used.