Citation
Inadvertent Hypoxic Gas Mixtures During Low Flow Anesthesia, Including High Fire Risk Cases

Material Information

Title:
Inadvertent Hypoxic Gas Mixtures During Low Flow Anesthesia, Including High Fire Risk Cases
Series Title:
19th Annual Undergraduate Research Symposium
Creator:
Bursian Ortiz, Monica
Wakim, Jonathan
Language:
English
Physical Description:
Undetermined

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Subjects / Keywords:
Center for Undergraduate Research
Center for Undergraduate Research
Genre:
Conference papers and proceedings
Poster

Notes

Abstract:
Anesthesia providers set fresh gas flow (FGF) and fraction of delivered oxygen (FDO2) on anesthesia machines based on patients' particular conditions, phase of the case, procedure type, surgical fire risk and preference. Surgical fires constrain FiO2 to ≤ 0.3 (30% O2); thus air (0.21) is sometimes used. Low FGF is attractive for its economic and ecological benefits. We explored whether low flow anesthesia at FDO2 0.3 or air (FDO2 0.21) results in inadvertent delivery of hypoxic inspired mixtures (FiO2 < 0.21) in the Aestiva (GE Healthcare, Madison, WI) anesthesia machine, and performed experiments to evaluate the FGF ≥ MV (minute ventilation) heuristic to prevent rebreathing as a secondary outcome. With FDO2 at 0.3 instead of air, significant dips in FiO2 also resulted in hypoxic inspired mixtures. Our results confirm (a) that the minimum FGF administered to a patient must be equal to or greater than MV to avoid rebreathing and (b) that FGF ≥ MV prevents delivering a hypoxic inspired gas mixture when the FGF is air. ( en )
General Note:
Research authors: Monica Bursian Ortiz, Jonathan Wakim, Derek O’Hara BS, David E. Lizdas BS, Nikolaus Gravenstein, MD, Samsun Lampotang, Ph.D. - University of Florida
General Note:
Faculty Mentor: Samsun Lampotang - Anesthesiology, University of Florida

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Source Institution:
University of Florida
Rights Management:
Copyright Monica Bursian Ortiz. Permission granted to University of Florida to digitize and display this item for non-profit research and educational purposes. Any reuse of this item in excess of fair use or other copyright exemptions requires permission of the copyright holder.

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Conclusion References Inadvertent Hypoxic Inspired Gas Mixtures during Low Flow Anesthesia, Including High Fire Risk Cases Monica Bursian Lizdas BS, Anthony DeStephens MS, Nikolaus Gravenstein MD, Samsun Lampotang Ph.D. Department of Anesthesiology, University of Florida College of Medicine and Center for Safety, Simulation & Advanced Learning Technologies, Gainesville Introduction Results and Discussion Materials and Methods Fresh gas flow (FGF) and the fraction of delivered oxygen (F D O 2 ) set on an anesthesia machine are operator particular conditions, phase of the case, type of procedure, surgical fire risk, and operator preference. The Joint Commission recommends FiO 2 surgical fire risk which may lead some to use air (FiO 2 = 0.21) to further reduce fire risk. 1 Low flow anesthesia is recommended for multiple reasons, including preservation of costly inhaled agents and the environment. 2,3 There is no consensus agreement on minimum FGF requirements for anesthesia breathing circuits that include a carbon dioxide absorber beyond supplying sufficient oxygen to meet the patient's basic metabolic requirements. We explore whether low flow anesthesia at a FGF of 0.3 F D O 2 or air (F D O 2 = 0.21) results in inadvertent delivery of hypoxic inspired mixtures (FiO 2 < 0.21). recommendation as a secondary outcome of our study. We used a human patient simulator (HPS; version B, CAE Healthcare/Medical Education Technologies Inc., Sarasota, FL) to model a 70 kg male. We used an anesthesia machine ( Aestiva S/5 with 7900 Ventilator, GE Healthcare, Madison, WI) to mechanically ventilate the intubated HPS during each trial. We set the HPS CO 2 production factor to 1.0, respiratory quotient to 0.8, and minute ventilation to 6 L/min. We integrated an Arduino R3 microcontroller with a 0.1% resolution oxygen analyzer (PSR 11 39 MD, Analytical Industries, Inc., Pomona, CA) calibrated with laboratory calibration gases to record F D O 2 at the anesthesia machine inspiratory port. Each of the 3 repeated trials lasted for 5 min. We automatically recorded data points every 0.5 sec. We set O 2 consumption to 225 mL/min and we began with FGF of air (F D O 2 = 0.21) equal to the MV. In subsequent trials, we decreased FGF by 0.5 L/min increments until we began to see a hypoxic inspired mixture (FiO 2 < 0.21). As an additional element of the study, we delivered FGF values of 2 L/min and 5 L/min with F D O 2 of 0.3 by using a 7:1 ratio of air to oxygen. Figure 1. MV 6 L/min. F D O 2 : 0.21. O 2 Consumption: 225 mL/min Using air FGF at a MV of 6 L/min, was the most appropriate setting to prevent rebreathing over 5 minutes. FGF settings MV fell under the FiO 2 value of 0.21 (corresponding to a hypoxic inspired mixture) during a timeframe of 5 minutes. With F D O 2 at 0.3 oxygen instead of air, significant dips in FiO 2 were also observed; at 2 and 5 L/min FGF, FiO 2 readings after 5 minutes were around ~0.19 and ~0.27 respectively. Our results confirm that the minimum FGF must be equal to or greater than the MV to avoid rebreathing and therefore to prevent delivering a hypoxic inspired gas mixture when FGF is air. It is counterintuitive that oxygen inflows > 200 mL/min 2 consumption) are not sufficient to prevent hypoxic inspired mixtures from developing. [1] The Joint Commission. Sentinel Event Alert, Issue 29: Preventing surgical fires | Joint Commission. [2] Hnemann C, Hagemann O, Doll D. Inhalational anaesthesia with low fresh gas flow. Indian Journal of Anaesthesia 2013;57(4):345 350. doi:10.4103/0019 5049.118569. [3] Brattwall M, Warrn Stomberg M, Hesselvik F, Jakobsson J. Brief review: Theory and practice of minimal fresh gas flow anesthesia. Canadian Journal of Anesthesia/Journal canadien 2012;59(8):785 797. doi:10.1007/s12630 012 9736 2. Figure 2. MV 10 L/min. F D O 2 : 0.3 O 2 O 2 Consumption: 450 mL/min