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Original Research ARTICLE Provisionally accepted The full-text will be published soon. Notify me

Front. Vet. Sci. | doi: 10.3389/fvets.2019.00160

Do the manual or computer-controlled flowmeters generate similar isoflurane concentrations in Tafonius?

  • 1Vetsuisse-Fakultät (Veterinärmedizin), Universität Bern, Switzerland
  • 2Bristol Veterinary School, Faculty of Health Sciences, University of Bristol, United Kingdom

Introduction: Tafonius is an anaesthesia machine with computer-controlled monitor and ventilator. We compared the isoflurane fluctuations in the circuit with manual (MF) or computer-driven (CF) flowmeters, investigated the origin of the differences and assessed whether isoflurane concentration time course followed a one-compartment model.
Material and Methods: A calibrated TEC-3 isoflurane vaporiser was used. Gas composition and flows were measured using a multiparametric monitor and a digital flowmeter. Measurements included: 1) Effects of various FiO2 with MF/CF on the isoflurane fraction changes in the breathing system during mechanical ventilation of a lung model; wash-in kinetic was fitted to a compartmental model; 2) Gas outflow at the common gas outlet (CGO) with MF/CF at different FiO2; 3) Isoflurane output of the vaporiser at various dial settings with MF/CF set at different flows without and with reduction of the CGO diameter.
Results: 1) The 3% targeted isoflurane concentration was not reached; additional time was required to reach specific concentrations with CF (lowest FiO2, longer time). The exponential course fitted a two-compartment model; 2) Set and measured flows were identical with MF. With CF at 0.21 FiO2, flow was intermittently 7.6 L minute-1 or zero (mean total: 38% of the set flow); with CF at 1.00 FiO2, flow was 10.6 L minute-1 or zero (mean: 4-5.3 L minute-1); with 0.21Conclusions and clinical relevance: Using MF or CF led to different isoflurane fraction time course in Tafonius. Flows were lower than set with CF; the TEC-3 did not compensate for high/intermittent flows and pressures; the CGO diameter influenced isoflurane output.

Keywords: Anesthesia, Flowmeter, Horses, TEC 3, Vaporiser, Ventilator, Veterinary

Received: 24 Dec 2018; Accepted: 10 May 2019.

Edited by:

Karine Portier, Université de Lyon, France

Reviewed by:

Rene Doerfelt, Klinik für Kleintierinnenmedizin, Veterinärmedizinische Fakultät, Ludwig-Maximilians Universität München, Germany
Francesco Staffieri, University of Bari Aldo Moro, Italy  

Copyright: © 2019 Raillard, Levionnois and MacFarlane. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

* Correspondence: Dr. Mathieu Raillard, Vetsuisse-Fakultät (Veterinärmedizin), Universität Bern, Bern, Switzerland, mathieu_raillard@yahoo.it