J.H. Philip British Journal of Anaesthesia

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Using screen-based simulation of inhaled anaesthetic delivery to improve patient care J.H. Philip British Journal of Anaesthesia Volume 115, Pages ii89-ii94 (December 2015) DOI: 10.1093/bja/aev370 Copyright © 2015 The Author(s) Terms and Conditions

Fig 1 Path of anaesthetic from vaporizer to brain. Inhaled anaesthetics traverse the path from vaporizer to breathing circuit, lungs, arterial blood, and to tissues, most notably the brain and spinal cord, which are important members of the vessel-rich tissue group. Anaesthetic returns to the lungs (alveoli) in mixed venous blood that returns from all tissue groups. British Journal of Anaesthesia 2015 115, ii89-ii94DOI: (10.1093/bja/aev370) Copyright © 2015 The Author(s) Terms and Conditions

Fig 2 Connecting flows and measurements along the path of anaesthetic. Flows are fresh gas flow (FGF), alveolar ventilation (VA), and cardiac output (CO). Measurements are delivered (Set) concentration, inhaled concentration, alveolar concentration, and tissue concentration expressed as partial pressure, tension, or fraction so that tissue concentration equals arterial concentration at equilibrium. British Journal of Anaesthesia 2015 115, ii89-ii94DOI: (10.1093/bja/aev370) Copyright © 2015 The Author(s) Terms and Conditions

Fig 3 Annotated Gas Man® picture. The containers and connections depict the structure of the model. The level of filling depicts the anaesthetic tension in the respective compartments. This filling state is the model behaviour in response to all changes made in the input variables up to the present time. Possible input changes are vaporizer setting, fresh gas flow, alveolar ventilation, and cardiac output. British Journal of Anaesthesia 2015 115, ii89-ii94DOI: (10.1093/bja/aev370) Copyright © 2015 The Author(s) Terms and Conditions

Fig 4 Annotated Gas Man® graph showing time course of aneasthesia. Fresh gas flow (FGF) and delivered anaesthetic tension are shown in the top two graphs. Below, anaesthetic tension in inspired gas, expired gas, vessel-rich tissue group, muscle, fat, and venous blood are shown in the bottom graph. British Journal of Anaesthesia 2015 115, ii89-ii94DOI: (10.1093/bja/aev370) Copyright © 2015 The Author(s) Terms and Conditions

Fig 5 Gas Man® picture, graph, and overlay showing the alveolar tension curve in response to a step change in inspired concentration. The alveolar tension curve features are depicted in a clockwise direction. Panel 1 is the Gas Man® picture at the beginning of the simulation. Panel 2 is the graph of the initial increase in alveolar tension when cardiac output is zero. Panel 3 shows the alveolar tension plateau created by disabling the return of venous blood. Panel 4 shows the normal alveolar tension curve. Panel 5 shows the overlay of panels 1, 2, and 3. British Journal of Anaesthesia 2015 115, ii89-ii94DOI: (10.1093/bja/aev370) Copyright © 2015 The Author(s) Terms and Conditions