Fig. 5

a Dynamics of sleep depth (odds-ratio-product; ORP) following arousal in two patients. In both cases ORP increases during the arousal and there is a step decrease in ORP immediately (within ≈ 9 s) after the arousal. In patient Y deep sleep returns very quickly after the arousal (ORP at 9 s (ORP-9) is 0.35). In patient X ORP-9 is high (1.2) and sleep deepens gradually over several minutes but only if there are no subsequent arousals. With a high ORP-9, the patient remains in a highly arousable state for several minutes following an arousal. Adapted from (Younes and Hanly 2016). b Impact of post-arousal sleep dynamics on sleep continuity and average sleep depth. In the presence of random arousal stimuli of various intensities (grey columns) patient X is more likely to develop another arousal soon after each arousal with the result that sleep can be highly fragmented and average ORP remains high. By contrast, Patient Y is relatively immune to further arousals and average ORP is low throughout