Proceedings of The Physiological Society

University of Cambridge (2008) Proc Physiol Soc 11, PC47

Poster Communications

Use of a high fidelity Human Patient Simulator to demonstrate the control of ventilation

E. Lloyd1, R. J. Helyer1, P. Dickens1, J. R. Harris1

1. Department of Physiology and Pharmacology, University of Bristol, Bristol, United Kingdom.

The Human Patient Simulator (HPS; METI, Florida) is a high fidelity, life-sized, computer-controlled manikin that includes a mechanical lung and simulated gas exchange mechanisms. It models a range of physiological variables and we have previously described (Lloyd et al, 2006) how it can be used to enhance cardiovascular teaching. The present study describes how the HPS can also be used to good effect in demonstrating the importance of blood gases in controlling ventilation. The scenario we have developed extends and enhances our existing respiratory physiology practical classes in which students use spirometers, vitalographs, Haldane tubes and pulse oximeters to study their own respiratory function. The HPS provides a real-time numerical display of simulated respiratory variables such as arterial and alveolar partial pressures of oxygen and carbon dioxide, arterial oxygen saturation, respiratory rate and tidal volume. The HPS scenario is delivered to groups of ca. 20 students who record the simulated data on worksheets and also observe physical signs such as the manikin’s depth and frequency of breathing. The manikin is intubated and baseline data for breathing room air are recorded. Responses to the following interventions are then recorded: a)breathing 90% nitrogen and 10% oxygen (to provide a hypoxic stimulus); b)breathing 95% oxygen and 5% carbon dioxide (to provide a hyperoxic and hypercapnic stimulus); c)breathing 100% nitrogen; d)increasing dead space by attaching a length of tubing to the endotracheal tube; e)neuromuscular blockade; f)bag-valve-mask external ventilation. The teaching is delivered in a problem-solving format, facilitated by a member of staff. Students are required to identify the composition of each gas mixture (a - c) by observing the simulated respiratory responses, and to predict the outcome of the other interventions. The scenario therefore provides a vivid and memorable illustration of the nature and rapid time course of the ventilatory responses to changes in arterial gases. Student feedback for the scenario is very positive with 83% of a cohort of 250 second year medical students reporting that it was helpful in increasing their understanding of the control of ventilation. During development of the scenario we established that there is good correspondence between the simulated responses to breathing gas mixtures compared to published human data (e.g. Padget, 1928). We conclude that the HPS is an engaging and effective educational tool for teaching respiratory physiology.

Where applicable, experiments conform with Society ethical requirements