title: Modelling the dynamic ventilatory response to hypoxia in normal subjects.
abstract: We have developed a mathematical model to describe the dynamic ventilatory response to hypoxia. The ventilatory response to both transient (two to three breaths nitrogen) and 3 min step change hypoxic stimuli were measured in ten normal subjects during moderate exercise (oxygen consumption 0.96 +/- 0.08 1 min-1). The simplest model relating ventilation to ear oxygen saturation which adequately described the responses in all subjects consisted of two linear differential equations in parallel; both using the fall in oxygen saturation as input, and with the outputs summed to give the rise in ventilation. One equation had a fast time constant (< 3 sec), and the other a slow time constant. Non-linear terms included were (i) a "saturating" effect, similar to that described by the Michaelis-Menten equation, reducing the gain of the equation with the slow time constant as oxygen saturation falls, and (ii) "inhibition" or "potentiation" of the gain of the equation with a slow time constant as the output of the fast time constant equation increased. Repeated measurements in four subjects showed intra- and inter-subject variability for all parameters, with significant between-subject variability for the gain of the fast time constant equation. The final model structure is similar to that describing the peripheral chemoreceptor-mediated hypoxic ventilatory response in anaesthetized cats.
authors.affiliation: Rayne Laboratory, Unit of Respiratory Medicine, University of Edinburgh, Scotland, U.K.
authors.forename: T P
authors.initials: TP
authors.lastname: Kirby
authors.forename: P K
authors.initials: PK
authors.lastname: Wraith
authors.forename: S C
authors.initials: SC
authors.lastname: De Cort
authors.forename: M A
authors.initials: MA
authors.lastname: Airlie
authors.forename: J E
authors.initials: JE
authors.lastname: Hill
authors.forename: E R
authors.initials: ER
authors.lastname: Carson
authors.forename: D C
authors.initials: DC
authors.lastname: Flenley
authors.forename: P M
authors.initials: PM
authors.lastname: Warren
mesh_terms: D000328:Adult; D003198:Computer Simulation; D005260:Female; D006801:Humans; D000860:Hypoxia / Q000503:physiopathology*; D008168:Lung / Q000503:physiopathology*; D008297:Male; D008954:Models, Biological