Fig. 1

Determinants and physiological consequences of sleep and circadian rhythm disruptions in the intensive care unit (ICU). Interaction between determinants (light blue) and possible consequences (light green) of sleep and circadian rhythm disruptions are shown. Interestingly, most interactions are bidirectional, meaning that the determinants might predispose the patient to such disturbances and be a consequence of them. An intimate relationship between sleep, circadian rhythm disruption and delirium is shown (purple). Main interactions are represented by thicker and continuous arrows. More complex and less proven interactions have dashed arrows. Most of the determinants are modified by factors related to the disease process such as pain, inflammation and end-organ dysfunction. Additionally, many patients admitted to the ICU have previous sleep disturbances, which will probably increase the risk of having them in the ICU