 3. is preferentially effective in patients whose OSA phenotype predicts that an increase in the arousal threshold is sufficient to resolve OSA versus those without such favorable physiology. Favorable physiology is defined here as having a low ventilatory drive at which stable breathing is theoretically feasible stable Vdrive is 100 above eupneic ventilatory drive due to any combination of a high upper airway muscle response, good passive anatomy high Vpassive, and low steady-state loop gain see Owens RL et al SLEEP 2014; Wellman A et al J Appl Physiol 2011, 2013; Eckert DJ et al 2013 AJRCCM. 