Melissa Knauert, MD, PhD

Dr. Knauert investigates sleep deprivation and circadian disruption in critically ill patients. Sleep deprivation and circadian disruption are likely key factors in the development of ICU delirium. Furthermore, sleep and circadian abnormalities are implicated in broader perturbations of normal physiology including abnormalities of cardiovascular, immune, endocrine and metabolic systems. Over the long-term, this patient-oriented research will improve outcomes in the ICU by investigating questions and developing interventions at the intersection of sleep, circadian biology, and critical illness.

Past and current projects include:

• A feasibility study of ambulatory polysomnography in the medical ICU (MICU) examining sleep architecture. This work demonstrated the feasibility of portable polysomnography in a MICU setting, alterations in normal sleep architecture, and a high percentage of daytime sleep in MICU patients. (Funding R21 NR011066)
• A randomized controlled trial of a nocturnal clustered care intervention in the MICU (“Naptime”). Monitoring of sound levels during the Naptime Study revealed a large burden of low frequency sound which had not been previously reported. During Naptime (midnight to 4:00 AM), the intervention arm had 32% fewer room entries, and fewer minutes per hour of in-room activity. Naptime almost doubled the length of time between room entrances from 26 to 46 minutes. The intervention arm also had lower average and peak sound levels during the intervention period. (Funding P20 NR014126)
• An observational cohort study examining the overlap between delirium, electroencephalographic atypia and atypical sleep as defined by sleep montage electroencephalography. Patients without K-complexes or without sleep spindles had more severe encephalopathy and higher odds of death. The odds ratio (OR) for patients without K-complexes was 18.8 (p=0.046). The odds ratio for patients without sleep spindles was 6.3 (p=0.036). We concluded that loss of stage N2 features is common and associated with more severe encephalopathy and higher odds of death. The absence of either Stage N2 feature, K complexes or sleep spindles, may have important prognostic value. (Pepper Scholar, Funding P30 AG021342)
• An observational cohort study examining circadian rhythms in ICU using continuous heart rate monitoring. Analysis is in progress. (YCCI Scholar, Funding KL2 TR000140)
• An observational cohort study examining the influence of light on circadian rhythms in the ICU. This study will also examine the influence or circadian rhythm abnormalities on the duration of ICU delirium. (K23 HL138229)
• A randomized controlled trial of daytime bright light examining the impact of daytime bright light on circadian alignment and duration of delirium. (AASM Strategic Research Award)