Abstract
Back ground
Measurements with various flowmeters are affected by changes in gas mixture density. The Avance Carestation incorporates ventilator feedback controlled by a built-in flowmeter with a variable orifice sensor. We hypothesised that changes in the composition of delivered gas may cause changes in the delivered tidal volume by affecting the flow measurement unless appropriate corrections are made.
Methods
We used 100 % O2, 40 % O2 in N2 and 40 % O2 in N2O as carrier gases with/without sevoflurane and desflurane. We measured delivered tidal volume using the FlowAnalyzer™ PF 300 calibrated with the corresponding gas mixtures during volume control ventilation with 500-ml tidal volume using the Avance Carestation connected to a test lung.
Results
Change of carrier gas and addition of sevoflurane and desflurane significantly altered delivered tidal volume. Desflurane 6 % reduced delivered tidal volume by 7.6, 3.6 and 16 % of the pre-set volume at 100 % O2, 40 % O2 in N2 and 40 % O2 in N2O, respectively. Importantly, the Carestation panel indicator did not register these changes in measured expired tidal volume. Ratios of delivered tidal volume to 500 ml correlated inversely with the square root of the delivered gas density.
Conclusions
These results support our hypothesis and suggest that changing gas composition may alter delivered tidal volume of anesthesia machines with built-in ventilators that are feedback-controlled by uncorrected flowmeters due to changes in gas mixture density.
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Acknowledgments
This work was presented, in part, at the Annual Meeting of the Japanese Society of Anesthesiologists, Sapporo, May 2013. This work was financially supported by the department fund.
Conflict of interest
The authors have no conflict of interests to declare.
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Miyaji, T., Fukakura, Y., Usuda, Y. et al. Effects of gas composition on the delivered tidal volume of the Avance Carestation . J Anesth 29, 690–695 (2015). https://doi.org/10.1007/s00540-015-2018-8
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DOI: https://doi.org/10.1007/s00540-015-2018-8