Article

The influence of white noise on sleep in subjects exposed to ICU noise

Brown University, Providence, Rhode Island, United States
Sleep Medicine (Impact Factor: 3.15). 10/2005; 6(5):423-8. DOI: 10.1016/j.sleep.2004.12.004
Source: PubMed

ABSTRACT

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.
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.
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).
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.

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    • "The abundant and seemingly increasing noise level and its serious health impacts suggests that it would be useful to try to minimize noise levels in ICUs. Such attempts have been evaluated in a handful of studies where sound levels were slightly reduced by adding ceiling panels [23] or where the impact was modified by introducing white noise [14]. Further studies are needed to determine what sound quality changes are required in ICUs to promote adequate sleep quality and restoration. "
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    ABSTRACT: Uninterrupted sleep is of vital importance for restoration and regaining health. In intensive care units (ICUs) where recovering and healing is crucial, patients' sleep often is fragmented and disturbed due to noise from activities from oneself, other patients, and alarms. The aim of our study was to explore if sleep could be improved by modifying the sound environment in a way that is practically feasible in ICUs. We studied the effects of originally recorded ICU noise and peak reduced ICU noise on sleep in healthy male participants. Sleep was registered with polysomnography (PSG) during four nights: one adaptation night, one reference (REF) night, and the two exposed nights with similar equivalent sound levels (47dB LAeq) but different maximum sound levels (56- vs 64-dB LAFmax). The participants answered questionnaires and saliva cortisol was sampled in the morning. During ICU exposure nights, sleep was more fragmented with less slow-wave sleep (SWS), more arousals, and more time awake. The effects of reduced maximum sound level were minor. The subjective data supported the polysomnographic findings, though cortisol levels were not significantly affected by the exposure conditions. Noise in ICUs impairs sleep and the reduction of maximal A-weighted levels from 64 to 56dB is not enough to have a clear improved effect on sleep quality.
    Full-text · Article · Sep 2013 · Sleep Medicine
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    • "Three previously reported studies [20-22] used continuous polysomnography alongside environmental noise measurements to determine whether noise could be the reason for irregular sleep patterns in ICU patients and reported that environmental noise caused between 11% and 17% of arousals and awakenings. In interviews after ICU discharge, patients regularly reported disturbed sleep, attributing this to noise, light and frequent nursing interventions [23-28]. "
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    ABSTRACT: Patients in intensive care units (ICUs) suffer from sleep deprivation arising from nursing interventions and ambient noise. This may exacerbate confusion and ICU-related delirium. The World Health Organization (WHO) suggests that average hospital sound levels should not exceed 35dB with a maximum of 40dB overnight. We monitored five ICUs to check compliance with these guidelines. Sound levels were recorded in five adult ICUs in the UK. Two sound level monitors recorded concurrently for 24 hours at the ICU central stations and adjacent to patients. Sample values to determine levels generated by equipment and external noise were also recorded in an empty ICU side room. Average sound levels always exceeded 45dBA and for 50% of the time exceeded between 52 and 59dBA in individual ICUs. There was diurnal variation with values decreasing after evening handovers to an overnight average minimum of 51dBA at 4am. Peaks above 85dBA occurred at all sites, up to 16 times per hour overnight and more frequently during the day. WHO guidelines on sound levels could be only achieved in a side room by switching all equipment off. All ICUs had sound levels greater than WHO recommendations, but the WHO recommended levels are so low they are not achievable in an ICU. Levels adjacent to patients are higher than those recorded at central stations. Unit-wide noise reduction programmes or mechanical means of isolating patients from ambient noise, such as earplugs, should be considered.
    Full-text · Article · Sep 2013 · Critical care (London, England)
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    • "The abundant and seemingly increasing noise level and its serious health impacts suggests that it would be useful to try to minimize noise levels in ICUs. Such attempts have been evaluated in a handful of studies where sound levels were slightly reduced by adding ceiling panels [23] or where the impact was modified by introducing white noise [14]. Further studies are needed to determine what sound quality changes are required in ICUs to promote adequate sleep quality and restoration. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Objective: Uninterrupted sleep is of vital importance for restoration and regaining health. In intensive care units (ICU) where recovering and healing is crucial, patients’ sleep is often fragmented and disturbed due to noise from activities from personal, other patients and alarms. The aim of this study was to explore if sleep could be improved by modifying the sound environment in a way that is practically feasible in an ICU. Methods: The effects of originally recorded ICU noise and peak reduced ICU noise on sleep in healthy male subjects was studied. Sleep was registered with polysomnography (PSG) during four nights: one adaptation night, one reference night and the two exposed nights with similar equivalent sound levels (47 dB LAeq) but different maximum sound levels (56 vs 64dB LAFmax). The subjects answered questionnaires and saliva cortisol were sampled in the morning. Results: During ICU exposure nights, sleep was more fragmented with less slow wave sleep, more arousals and more time awake. The effects of reduced maximum sound level were minor. The subjective data supported the polysomnographical findings while cortisol levels were not significantly affected by the exposure conditions. Conclusions: Intensive care noise impairs sleep and the reduction of maximal A-weighted levels from 64 dB to 56 dB is not enough to have a clear improved effect on sleep quality.
    Full-text · Article · Jan 2013
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