Physiological phenotypes

OSA is a multifactorial disorder with several physiological phenotypes. Pharyngeal anatomy/collapsibility is the primary abnormality in most OSA patients. However, the extent of UA anatomical compromise varies widely between OSA patients. Many have only a modest degree of anatomical impairment. Accordingly, a number of other non-anatomical contributors also play a role. These include an oversensitive ventilatory control system, a low respiratory arousal threshold, and poor pharyngeal muscle responsiveness or effectiveness during sleep. The contribution of these non-anatomical factors has only recently been recognised. This chapter reviews the data establishing the importance of these variables and describes a graphic, physiological model integrating them to illustrate their relative contribution. Ultimately, such a model could be useful for guiding therapy and advancing the field of OSA management beyond the “one size fits all” approach of CPAP.