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Real-Time Measurement of Xenon Concentration in a Binary Gas Mixture Using a Modified Ultrasonic Time-of-Flight Anesthesia Gas Flowmeter

David J. Williams, Gregory D. Hallewell, Ela Chakkarapani, John Dingley

Anesthesia & Analgesia, Start page: 1

Swansea University Author: John Dingley

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DOI (Published version): 10.1213/ANE.0000000000003806

Abstract

Background: Xenon (Xe) is an anesthetic gas which may have potential as a neuroprotectant. To measure each gas in a xenon/oxygen mixture one would typically use a thermal conductivity meter and a fuel cell respectively. The speed of sound in a binary gas mixture like this is related to fractional co...

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Published in: Anesthesia & Analgesia
ISSN: 0003-2999
Published: Pennsylvania, United States Lippincott Williams and Wilkins
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URI: https://cronfa.swan.ac.uk/Record/cronfa43534
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Abstract: Background: Xenon (Xe) is an anesthetic gas which may have potential as a neuroprotectant. To measure each gas in a xenon/oxygen mixture one would typically use a thermal conductivity meter and a fuel cell respectively. The speed of sound in a binary gas mixture like this is related to fractional concentration, temperature, pressure, and masses of the gases present. We assessed the feasibility of developing a novel single sterilizable device which used the time of flight of ultrasound through the gas to measure both real-time gas flow and also the concentration of Xe in O2.Method: We adapted an ultrasonic time-of-flight flow meter from a conventional anesthetic machine to also measure the real time fractional concentration of Xe in O2. A total of 5 095 readings of were taken in the range 5 % to 95 % xenon, and compared with simultaneous measurements from a commercially available thermal conductivity xenon analyser.Results: Ultrasonic measurements of Xe (%) showed agreement with thermal conductivity meter measurements but there was marked discontinuity in the central region of the measurement range. Bland-Altman analysis (95% CI): Mean Difference (Bias) 3.1 (2.9 % to 3.2 %); lower 95 % Limit of Agreement -4.6 % (-4.8 % to -4.4 %); upper 95 % Limit of Agreement 10.8 % (10.5 % to 11.0 %).Conclusions: The modified ultrasonic flow meter estimated the Xe (%) however at present the accuracy is not sufficient for clinical use. With further work it may be possible to improve the accuracy sufficiently for potential clinical use.
Keywords: Xenon, Anaesthesia, concentration, measurement, ultrasound, time of flight,
College: Faculty of Medicine, Health and Life Sciences
Start Page: 1

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