Verification and Validation Of The Hybrid Pulmonary Gas Exchange Model Of The Human Patient Simulator

Date(s) - 07/03/2014
3:00 pm

Hillary Wehry, MS student

The Human Patient Simulator (HPS), developed at the University of Florida and manufactured by CAE Healthcare, Montreal, Canada, provides a platform for immersive medical training. Patient responses to typical clinical scenarios are simulated by physiologic models, and trainees interact with the simulator to evaluate clinical signs and monitored signals and provide therapeutic interventions. Such physiology-based simulators are complex, dynamical systems and are challenging to evaluate. The HPS contains two models of pulmonary gas exchange (PGE) based on the same underlying conceptual model: a mathematical model implemented in software only, and a hybrid model implemented with hardware and software components. A reference software implementation based on the same conceptual model and acting as a “gold standard” was developed as part of a previous project and used to evaluate the software implementation of the HPS lung [1]. This report expands the method for verification and validation of simulation models and applies it to the hybrid HPS PGE model. We designed and implemented the control software for a “benchtop” implementation consisting of HPS PGE model hardware. Simulation of the physiological operating point demonstrated a moderate
discrepancy in simulated partial pressures of oxygen and carbon dioxide in the alveolar space between the hybrid model and the reference standard. We formulated hypotheses for the origin of these discrepancies. Simulation of dynamic experiments reflecting extreme physiological situations, such as apnea, demonstrate the physical limitations of the hybrid lung model, which can be attributed to a specific gas flow rate in the lung model. Both observations are expected to lead to optimizations and improvements of the hybrid lung model. The overall verification and validation method was presented in an invited lecture at an international conference.