A mathematical and physiological evaluation of the different hypoxic response models in normal man

The purpose was: (1) to investigate which hypoxic response (HR) model(s) might be most suitable to measure the HR taking into account 'goodness of fit' to the individual data, clinical applicability and information obtained from each model; and (2) to investigate if the models are mutually exchangeable. The ventilatory (VE) and occlusion pressure (P0.1) HR were measured in 33 healthy volunteers (37+/-12 years). We found that the exponential, linear on oxygen saturation (LINSAT), hyperbolic with either a fixed (HYPV) or a variable position of the vertical asymptote (HYPH) models were comparable with respect to 'goodness of fit' to the individual data, but the correlation between the HR models was poor, except for the correlation between LINSAT and HYPV. Comparing HR data is justified when they are either provided by the same HR model, or by LINSAT or HYPV. Within each model the VE HR can be replaced by the P0.1 HR. LINSAT has the advantage of an easy applicable linear relationship, HYPH provides additional information about the O2-CO2 interaction component of the HR, but the model is more complex because two variables have to be determined by computerized iteration.