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. Jul-Aug 2018;20(95):121-130.
doi: 10.4103/nah.NAH_53_17.

Noise in the Neonatal Intensive Care Unit: A New Approach to Examining Acoustic Events

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Free PMC article

Noise in the Neonatal Intensive Care Unit: A New Approach to Examining Acoustic Events

Shaylynn W Smith et al. Noise Health. .
Free PMC article

Abstract

Introduction: Environmental noise is associated with negative developmental outcomes for infants treated in the neonatal intensive care unit (NICU). The existing noise level recommendations are outdated, with current studies showing that these standards are universally unattainable in the modern NICU environment.

Study aim: This study sought to identify the types, rate, and levels of acoustic events that occur in the NICU and their potential effects on infant physiologic state.

Materials and methods: Dosimeters were used to record the acoustic environment in open and private room settings of a large hospital NICU. Heart and respiratory rate data of three infants located near the dosimeters were obtained. Infant physiologic data measured at time points when there was a marked increase in sound levels were compared to data measured at time points when the acoustic levels were steady.

Results: All recorded sound levels exceeded the recommended noise level of 45 decibels, A-weighted (dBA). The 4-h Leq of the open-pod environment was 58.1 dBA, while the private room was 54.7 dBA. The average level of acoustic events was 11-14 dB higher than the background noise. The occurrence of transient events was 600% greater in the open room when compared to the private room. While correlations between acoustic events and infant physiologic state could not be established due to the extreme variability of infant state, a few trends were visible. Increasing the number of data points to overcome the extreme physiologic variability of medically fragile neonates would not be feasible or cost-effective in this environment.

Conclusion: NICU noise level recommendations need to be modified with an emphasis placed on reducing acoustic events that disrupt infant state. The goal of all future standards should be to optimize infant neurodevelopmental outcomes.

Keywords: acoustic environment; hospital noise; infant development; neonatal intensive care unit; physiologic monitoring.

Conflict of interest statement

There are no conflicts of interest

Figures

Figure 1
Figure 1
Panel (A) displays the dosimeter placement in the NICU open pod area. Baby A was located in the isolette to the right of the microphone, while Baby B was located immediately to the left. Panel (B) displays the dosimeter placement for the private room.
Figure 2
Figure 2
The time waveforms of the L eq and peak levels for open (left) and private rooms (right) are shown. For each figure the recorded, 1-s L eq was logarithmically averaged over a 20-s period while the 1-s peak levels were averaged over a 5-s period for greater resolution of the brief transients. These 2-h samples are a good representation of the overall acoustic environment described in Tables 1–3.
Figure 3
Figure 3
The intersubject variability of infant heart and respiratory rate is shown. Each panel displays 1 h of the total recording of the heart rate (black) and respiratory rate (gray) with a 1-s resolution for each infant. Babies A and B (left) were in the open room environment while Baby C (right) was in the private room environment. Note that while Babies A and B were in the same acoustic environment, the heart and respiratory rate were more variable in Baby B. Dashed lines indicate extraction of physiologic data during infant handling.
Figure 4
Figure 4
The mean infant heart rates following acoustic events are shown. For each infant (Baby A = triangle, B = square, and C = circle), the mean heart rate during the acoustic event was calculated and shown at 0 s on the graph. Then, mean heart rate was calculated at delays of 2, 4, 8, and 16 s from the onset of the acoustic event. There was no significant effect of delay on heart rate. The bars indicate one standard deviation.
Figure 5
Figure 5
The time waveform of the L eq in the open room is shown over a 20-min period with corresponding heart rate data for Babies A and B. Multiple acoustic events, which were identified by the observer to be alarms that were unrelated to either infant, took place during this time window. Visual examination reveals that Baby B’s heart rate may be fluctuating with the onset of acoustic events; however, Baby A’s heart rate remains stable. Overall variability of infants precluded measurable correlation between events and physiologic changes.

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