For example, the underlying perfusion-limited model may be false, the values of the perfusion and solubility parameters may be wrong, the relationship assumed between anaesthetic partial pressures in end-expired gas samples and arterial blood may not hold at the very low concentrations present days after anaesthesia. There are many possible explanations for this failure. The output from this generic algorithm is determined by the derivatives of the variables and their calculation is described in the Appendix. All the differential equations were solved simultaneously using a fourth-order Runge–Kutta numerical routine. Anaesthetic partial pressure in mixed venous blood was calculated by a weighted average of the compartmental perfusions. Similarly, minute ventilation was constant at 7.5 litre min −1 throughout. The perfusion of each compartment was constant, an unrealistic point but sound data upon which to base changes in compartmental perfusion during anaesthesia are lacking. Each compartment was assumed to follow perfusion-limited kinetics, so that the partial pressure of anaesthetic in the venous blood was in equilibrium with that in the compartment. A right-to-left shunt equal to 10% of the cardiac output (6 litre min −1) was assumed when calculating arterial anaesthetic partial pressures. The rate of change of anaesthetic alveolar concentration was calculated from the difference between the rate at which anaesthetics entered (from inspired gas and mixed venous blood) and left (in expired gas and pulmonary capillary blood) the alveoli. Deadspace ventilation was assumed to be 35% of the minute ventilation, and end-expired gas was assumed to be a mixture of 90% alveolar gas and 10% inspired gas: this mixture was used for comparison with earlier publications of ‘alveolar’ gas samples, except when explicitly stated otherwise. non-tidal) ventilation and did not include a time lag for circulation, making it unrealistic for investigations of a few minutes but simpler and much faster for longer simulations. The computer model assumed continuous (i.e. Special Issue on Memory and Awareness in Anesthesia (PDF).Special Issue on Mass Casualty Medicine and Anaesthesia: Science and Clinical Practice (JPG).Special Issue on Thoracic Anaesthesia and Respiratory Physiology (PDF).Hong Kong College of Anaesthesiologists.College of Anaesthesiologists of Ireland.Memory, Awareness and Anaesthesia 2022 Special Collection.
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COVID-19 and the Anaesthetist: A Special Series.
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