A reply

Abstract

We thank Mercer for his letter in response to our article [1]. We have experienced similar difficulties and accept that problems arise from the linear course of events simulated by deductive models. Rather than being a problem of deductive modeling per se, however, we suggest that this requires physiological fidelity on the part of system designers, and deeper ‘architectural’ insight on the part of the controller(s) in order to use the system appropriately and effectively. In our opinion, the conduct of a complex scenario involving a five-member faculty is unaffordable. It is our belief that low-cost, high-fidelity deductive models will derive from high-performance simulators in future, and interface with low-cost manikins. Recently, we have demonstrated this approach successfully using tablet computers for virtual pacemaker teaching [2]. In both ‘deductive’ and ‘on the fly’ (instructor-driven) models the candidate is interacting with a physiological model. In the former, the model is a software program written by an engineering team, and in the latter a mental construct in the head of the manikin controller. Both models have problems with validity. The key advantages of a software model are that it can be based on published evidence, it can be subjected to peer review, and its limitations can be openly described. In contrast, the individual controlling the manikin introduces an unquantifiable risk of negative learning. We accept that further problem inherent to ‘deductive’ simulation is that scenario controllers do not necessarily want realism. For example, in the event of oxygen supply failure, arterial oxygen saturation often declines fairly slowly towards 90% but thereafter decreases rapidly. However, scenario controllers may simulate a gradual and linear saturation decline in order to give candidates time to implement their rescue. Whether or not this practice is a good idea, and indeed improves the learning experience, is an important question. Finally, we contend Mercer’s closing statement. In addition to faculty experience, simulated alterations should be conducted according to a valid evidence base. This is best achieved in a peer-reviewed physiological model.