Simulation of inhalational anaesthetic uptake using a lung model with charcoal

A physical lung model for simulation of volatile anaesthetic uptake is described. Two communicating water-filled chambers simulate pulmonary mechanics allowing adjustment of functional residual capacity, resistance and compliance. The uptake of the volatile anaesthetics is reproduced by pumping gas from the lung chamber through a charcoal absorber at different rates; using a second pump for a bypass an arterial to end-tidal gradient can be generated. Changes of cardiac output are simulated by adjusting pump speed and of alveolar ventilation by adapting the ventilator setting. The results are reproducible and correspond with patient studies and computer stimulation, not necessitating empirical correction factors as in a previously described oil-based lung model. The model can serve as a teaching instrument, for the comparison and testing of anaesthetic equipment and the development of feedback systems.