Figure 1. Technique for determining and modelling the physiological traits using CPAP drops.

To determine the four physiological traits, CPAP is dropped to a subtherapeutic level (A) which causes partial airway obstruction and a reduction in ventilation (B). Using the time course in ventilation, we calculate the pharyngeal anatomy/collapsibility (), upper airway gain (z/x), loop gain (x/y) and arousal threshold (if an arousal occurs); see text for details. C depicts how these four traits can be incorporated into a model to predict the susceptibility towards OSA. In this example, the new steady state (the intersection of the diagonal lines) occurs in the unstable region (i.e. right of the arousal threshold) and thus OSA is predicted to be present.