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Observational Study
. 2015 Jul-Aug;29(4):1013-21.
doi: 10.1111/jvim.13574. Epub 2015 Jun 26.

Sound Pressure Levels in 2 Veterinary Intensive Care Units

B Fullagar  1   2 , S R Boysen  3 , M Toy  4 , C Makwana  4 , D S J Pang  3   5
Affiliations
Observational Study

Sound Pressure Levels in 2 Veterinary Intensive Care Units

B Fullagar et al. J Vet Intern Med. 2015 Jul-Aug.

Abstract

Background: Intensive care units (ICUs) in human hospitals are consistently noisy environments with sound levels sufficient to substantially decrease sleep quality. Sound levels in veterinary ICUs have not been studied previously, but environmental sound has been shown to alter activity in healthy dogs.

Hypothesis: Veterinary ICUs, like those in human medicine, will exceed international guidelines for hospital noise.

Animals: NA.

Methods: Prospective, observational study performed consecutively and simultaneously over 4 weeks in 2 veterinary ICUs. Conventional A-weighted sound pressure levels (equivalent continuous level [a reflection of average sound], the sound level that is exceeded 90% of the recording period time [reflective of background noise], and maximum sound levels) were continuously recorded and the number of spikes in sound >80 dBA were manually counted.

Results: Noise levels were comparable to ICUs in human hospitals. The equivalent continuous sound level was higher in ICU1 than in ICU2 at every time point compared, with greatest differences observed on week day (ICU1, 60.1 ± 3.7 dBA; ICU2, 55.9 ± 2.5 dBA, P < .001) and weekend nights (ICU1, 59.9 ± 2.4 dBA; ICU2, 53.4 ± 1.7 dBA, P < .0001) reflecting a 50% difference in loudness. Similar patterns were observed for the maximum and background noise levels. The number of sound spikes was up to 4 times higher in ICU1 (162.3 ± 84.9 spikes) than in ICU2 (40.4 ± 12.2 spikes, P = .001).

Conclusions and clinical importance: These findings show that sound in veterinary ICUs is loud enough to potentially disrupt sleep in critically ill veterinary patients.

Keywords: Critical care; Hospital soundscape; Noise; Sleep.

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Figures

Figure 1
Figure 1
Floor plans of intensive care units (ICU)1 and ICU2. Drawing is not to scale. Mic, microphone suspended 2.5 m above floor level.
Figure 2
Figure 2
Sample of sound pressure level data from a 3‐hour week day recording in intensive care unit (ICU)1 illustrating relationships between LA 90 (grey line), LA eq (black line), and LA max (red line). Data are mean ± SD. The shaded horizontal box represents the WHO (30–35 dBA) and US EPA (45 dBA) range for hospital noise.
Figure 3
Figure 3
Intensive care unit (ICU)1 has higher equivalent sound pressure levels (LA eq) than ICU2 during both week days and nights (top panel) and weekend days and nights (bottom panel). Data are mean ± SD. *P < .05, ***P < .001, ****P < .0001.
Figure 4
Figure 4
Intensive care unit (ICU)1 has higher mean peak sound pressure levels (LA max) than ICU2 during both week days and nights (top panel) and weekend days and nights (bottom panel). Data are mean ± SD. *P < .05, ***P < .001, ****P < .0001.
Figure 5
Figure 5
Intensive care unit (ICU)1 has higher background sound pressure levels (LA 90) than ICU2 during both week days and nights (top panel) and weekend days and nights (bottom panel). Data are mean ± SD. **P < .01, ****P < .0001.
Figure 6
Figure 6
The number of sound spikes observed at each intensive care unit (ICU) on week days and nights (top panel) and weekend days and nights (bottom panel). Data are mean ± SD. *P = .03 **P = .003 (week nights) and P = .001 (weekend nights).
Figure 7
Figure 7
Box and whisker plot showing patient occupancy rates in each intensive care unit (ICU) at different times of day. Box shows median value and is delimited by interquartile range. Whiskers are range (minimum, maximum). **P = .003.
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