title: Long-term acute care patients weaning from prolonged mechanical ventilation maintain circadian rhythm.
abstract: BACKGROUND
  Circadian rhythm regulates many physiologic and immunologic processes. Disruption of these processes has been demonstrated in acutely ill, mechanically ventilated patients in the ICU setting. Light has not been studied as an entraining stimulus in the chronically mechanically ventilated patient. The purpose of this study was to determine the association of naturally occurring ambient light levels in a long-term acute care (LTAC) hospital with circadian rhythm in patients recovering from critical illness and requiring prolonged mechanical ventilation (PMV).
  
  
  METHODS
  We performed a prospective observational study of 15 adult patients who were recovering from critical illness and receiving PMV and who were admitted to the ventilator weaning unit at an LTAC hospital. Demographic data were obtained from chart review. Light stimuli in each patient room were assessed using a photometer device placed at eye level. Circadian rhythm was assessed by wrist actigraphy. Cumulative data were obtained from each device for a 48-h period, averaged into 4-h intervals, and analyzed.
  
  
  RESULTS
  Patients receiving PMV were obese (mean body mass index of 32.7 ± 10.3 kg/m2) and predominantly female (73%) and had an average age of 63.1 ± 14.3 y. Light exposure to this cohort maintained diurnal variation (P < .001) and was significantly different across time periods. Circadian rhythm, as represented by actigraphy, also maintained diurnal variation (P < .001) and was in phase with light. Linear regression of movement and time demonstrated a moderate relationship between light and actigraphy (R2 = 0.56).
  
  
  CONCLUSIONS
  Despite requiring continued high-level care and a prolonged stay in a medical facility, patients recovering from critical illness and actively weaning from PMV maintain their circadian rhythm in phase with normal diurnal variations of light.
authors.affiliation: Division of Pulmonary and Critical Care Medicine, University of Maryland School of Medicine, Baltimore, Maryland.
authors.forename: Dafna
authors.initials: D
authors.lastname: Koldobskiy
authors.forename: Montserrat
authors.initials: M
authors.lastname: Diaz-Abad
authors.forename: Steven M
authors.initials: SM
authors.lastname: Scharf
authors.forename: John
authors.initials: J
authors.lastname: Brown
authors.forename: Avelino C
authors.initials: AC
authors.lastname: Verceles
mesh_terms: D056044:Actigraphy; D002940:Circadian Rhythm; D016638:Critical Illness; D005260:Female; D006801:Humans; D007362:Intensive Care Units; D008027:Light; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D015300:Ventilator Weaning
keywords: actigraphy; circadian rhythm; light; long-term care; mechanical ventilation; respiratory failure
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