Proceedings of The Physiological Society
University of Manchester (2010) Proc Physiol Soc 19, PC75
Hypoxic pulmonary vasoconstriction: a comparison of the Human Patient Simulator with human data
B. Healey1, R. Pedley1, D. Brown1, R. Helyer1, E. Lloyd1
1. University of Bristol, Bristol, United Kingdom.
The Human Patient Simulator (HPS; METI, Sarasota, Florida) has a computer driven mechanical lung and gas exchange mechanism, designed to model the human respiratory system. We have previously shown that that the HPS response to hypoxia  can be refined to increase its validity as an educational tool to illustrate high altitude physiology . The aim of this study was to determine whether the HPS demonstrates an appropriate increase in pulmonary vascular resistance (PVR) in response to levels of hypoxia consistent with ascent to high altitude. Humans exhibit an exponential increase in PVR in response to breathing gas mixtures of decreasing fractional concentration of oxygen [3, 4]. Simulated ascent to an altitude of 7620 m is associated with a 3.5 fold increase in PVR above base-line . The HPS was intubated and baseline recordings were made of the mean pulmonary artery pressure (MPAP), pulmonary capillary wedge pressure (PCWP) and cardiac output (CO) using a simulated Swan-Ganz catheter and thermodilution measurement. PVR was calculated by subtracting PCWP from MPAP and dividing by CO. The ascent to altitude was simulated by administering varying mixtures of oxygen and nitrogen for a duration of 10 minutes using Douglas bags. The fractional concentration of oxygen in the mixtures ranged from 0.21 to 0.003. The PVR was determined following administration of each of the gas mixtures. In response to hypoxia the HPS did not exhibit any significant change in PVR over the range tested (P>0.05). We conclude that the HPS does not exhibit an appropriate increase in PVR in response to a simulated ascent to altitude. At altitude, factors such as extreme exhaustion and the harsh environmental conditions present a unique challenge to homeostatic mechanisms. Remodelling of the HPS could provide an invaluable resource for simulating of high-altitude emergency medicine.
Where applicable, experiments conform with Society ethical requirements