Investigating hypoxemia during apnea : Validation of a set of physiological models

The aim of our study was to validate the Nottingham Physiology Simulator (NPS) for examining pulmonary denitrogenation and apnea by reproducing the methodology and results of previous clinical studies. Only four studies provided sufficient detail in their description of their methodology to allow accurate reproduction by using the NPS or provided a sufficiently detailed description of their subjects to allow accurate modelling. The results of the NPS recreation of the studies were within 13% of the values found clinically in all cases and were within 2% in the majority of cases. The four studies included healthy and morbidly obese patients, conscious and anesthetized patients, and included examination of the effect of denitrogenation and apnea on plasma pH and on lung and arterial oxygen and carbon dioxide tensions at various lung volumes. We used mathematical, physiological models to recreate the methods and subjects of four clinical studies investigating oxygenation and low oxygen levels during cessation of breathing. Our aim was to validate the models, allowing theoretical investigations into this area. The blindly recreated results closely matched the clinical studies, validating the models.