title: Factors affecting sleep in the critically ill: an observational study.
abstract: OBJECTIVE
  The aims of the current study were to describe the extrinsic and intrinsic factors affecting sleep in critically ill patients and to examine potential relationships with sleep quality.
  
  
  METHODS
  Sleep was recorded using polysomnography (PSG) and self-reports collected in adult patients in intensive care. Sound and illuminance levels were recorded during sleep recording. Objective sleep quality was quantified using total sleep time divided by the number of sleep periods (PSG sleep period time ratio). A regression model was specified using the "PSG sleep period time ratio" as a dependent variable.
  
  
  RESULTS
  Sleep was highly fragmented. Patients rated noise and light as the most sleep disruptive. Continuous equivalent sound levels were 56 dB (A). Median daytime illuminance level was 74 lux, and nighttime levels were 1 lux. The regression model explained 25% of the variance in sleep quality (P = .027); the presence of an artificial airway was the only statistically significant predictor in the model (P = .007).
  
  
  CONCLUSIONS
  The presence of an artificial airway during sleep monitoring was the only significant predictor in the regression model and may suggest that although potentially uncomfortable, an artificial airway may actually promote sleep. This requires further investigation.
authors: Faculty of Health, University of Technology Sydney, Broadway 2007, New South Wales, Australia. Electronic address: Rosalind.Elliott@uts.edu.au.
authors: Rosalind
authors: R
authors: Elliott
authors: School of Mathematical Sciences, Faculty of Science, University of Technology Sydney, Broadway 2007, New South Wales, Australia. Electronic address: Tapan.Rai@uts.edu.au.
authors: Tapan
authors: T
authors: Rai
authors: Faculty of Health, University of Technology Sydney, Broadway 2007, New South Wales, Australia; Intensive Care Unit, Royal North Shore Hospital, Northern Sydney Local Health District, St Leonards 2065, New South Wales, Australia. Electronic address: Sharon.McKinley@uts.edu.au.
authors: Sharon
authors: S
authors: McKinley
mesh_terms: D000328:Adult; D000368:Aged; D003422:Critical Care; D016638:Critical Illness; D020920:Dyssomnias / Q000209:etiology*; D005260:Female; D006801:Humans; D007362:Intensive Care Units; D008029:Lighting / Q000009:adverse effects*; D008297:Male; D008875:Middle Aged; D009622:Noise / Q000009:adverse effects*; D017286:Polysomnography; D012044:Regression Analysis; D057566:Self Report; D012890:Sleep / Q000502:physiology; D013997:Time Factors
keywords: Illuminance levels; Intensive care; Sleep disruption; Sound levels