title: The influence of white noise on sleep in subjects exposed to ICU noise.
abstract: OBJECTIVE
  There is disagreement in the literature about the importance of sleep disruption from intensive care unit (ICU) environmental noise. Previous reports have assumed that sleep disruption is produced by high-peak noise. This study aimed to determine whether peak noise or the change in noise level from baseline is more important in inducing sleep disruption. We hypothesized that white noise added to the environment would reduce arousals by reducing the magnitude of changing noise levels.
  
  
  METHODS
  Four subjects underwent polysomnography under three conditions: (1) baseline, (2) exposure to recorded ICU noise and (3) exposure to ICU noise and mixed-frequency white noise, while one additional subject completed the first two conditions. Baseline and peak noise levels were recorded for each arousal from sleep.
  
  
  RESULTS
  A total of 1178 arousals were recorded during these studies. Compared to the baseline night (13.3+/-1.8 arousals/h) the arousal index increased during the noise (48.4+/-7.6) but not the white noise/ICU noise night (15.7+/-4.5) (P<0.004). The change in sound from baseline to peak, rather than the peak sound level, determined whether an arousal occurred and was the same for the ICU noise and white noise/ICU noise condition (17.7+/-0.4 versus 17.5+/-0.3 DB, P=0.65).
  
  
  CONCLUSIONS
  Peak noise was not the main determinant of sleep disruption from ICU noise. Mixed frequency white noise increases arousal thresholds in normal individuals exposed to recorded ICU noise by reducing the difference between background noise and peak noise.
authors.affiliation: Pulmonary/Critical Care and Sleep Medicine Division, Rhode Island Hospital and Brown Medical School, 593 Eddy St. APC 7, Providence, RI 02903, USA. mstanchina@lifespan.org
authors.forename: Michael L
authors.initials: ML
authors.lastname: Stanchina
authors.forename: Muhanned
authors.initials: M
authors.lastname: Abu-Hijleh
authors.forename: Bilal K
authors.initials: BK
authors.lastname: Chaudhry
authors.forename: Carol C
authors.initials: CC
authors.lastname: Carlisle
authors.forename: Richard P
authors.initials: RP
authors.lastname: Millman
mesh_terms: D000328:Adult; D001143:Arousal / Q000502:physiology; D005260:Female; D006801:Humans; D007362:Intensive Care Units; D008297:Male; D009622:Noise / Q000009:adverse effects; D010470:Perceptual Masking / Q000502:physiology; D017286:Polysomnography; D012016:Reference Values; D012892:Sleep Deprivation / Q000209:etiology* / Q000503:physiopathology / Q000517:prevention & control*; D012894:Sleep Stages / Q000502:physiology