Noise measurement in NICUs and incubators with newborns: a systematic literature review

Systematic review of environmental noise in neonatal intensive care units

AIM

To systematically review the literature on noise exposure within the neonatal intensive care unit/special care nursery settings, specifically to describe: noise characteristics, sources of noise and ways of measuring noise.

METHODS

Systematic searches were conducted through databases Medline, Embase and PubMed. Studies were included if they met the inclusion criteria (1) reported noise characteristics; (2) reported noise exposure measurements; (3) in the neonatal intensive care unit/ special care nursery settings. Methods and key findings were extracted from included studies. Quality analysis was done using a modified version of the Newcastle-Ottawa Scale.

RESULTS

We identified 1651 studies, screened 871, reviewed 112 and included 47. All reported NICU average equivalent sound levels were consistently louder than recommended guidelines (45 dB). The most consistent association with higher sound pressure levels were noise sources grouped under people congregation. Half of the studies did not use measuring devices adhering to international sound level meter (SLM) standards.

CONCLUSION

All NICUs exceeded recommended accumulative sound levels. People were the most consistent source of noise. Sound pressure levels need to be consistently measured with devices adhering to international SLM standards in future studies.

"Every breath you take": evaluating sound levels and acoustic characteristics of various neonatal respiratory support and ventilation modalities

Background

Early sensory experiences have a significant impact on the later life of preterm infants. The NICU soundscape is profoundly influenced by various modalities of respiratory support or ventilation, which are often mandatory early in the care. The incubator, believed to shield from external noise, is less effective against noise originating inside. The objective of this study was to evaluate the sound levels and characteristics of frequently used respiratory support and ventilation modalities, taking into consideration the developing auditory system of premature infants.

Methods

To evaluate sound dynamics inside and outside an incubator during respiratory support/ventilation, experimental recordings were conducted at the Center for Pediatric Simulation Training of the Medical University Vienna. The ventilator used was a FABIAN HFOI®.

Results

Jet CPAP (Continuous positive airway pressure), whether administered via mask or prongs, generates significantly higher sound levels compared to High-flow nasal cannula (HFNC) and to High-frequency oscillatory ventilation (HFOV) delivered through an endotracheal tube. Upon evaluating the sound spectrum of jet CPAP support, a spectral peak is observed within the frequency range of 4 to 8 kHz. Notably, this frequency band aligns with the range where the hearing threshold of preterm infants is at its most sensitive.

Conclusion

Non-invasive HFNC and invasive HFOV generate lower sound levels compared to those produced by jet CPAP systems delivered via masks or prongs. Moreover, HFNC and HFOV show a reduced acoustic presence within the frequency range where the preterm infant's hearing is highly sensitive. Therefore, it is reasonable to speculate that the potential for auditory impairment might be more pronounced in preterm infants who require prolonged use of jet CPAP therapy during their time in the incubator.

Noise level in neonatal incubators: A comparative study of three models

BACKGROUND

Preterm infants usually have to spend a long time in an incubator, excessive noise in which can have adverse physiological and psychological effects on neonates. In fact, incubator noise levels typically range from 45 to 70 dB but differences in this respect depend largely on the noise measuring method used. The primary aim of this work was to assess the extent to which noise in an incubator comes from its own fan and how efficiently the incubator can isolate external noise.

METHODS

Three different incubator models were characterized for acoustic performance by measuring their internal noise levels in an anechoic chamber, and also for noise isolation efficiency by using a pink noise source in combination with an internal and an external microphone that were connected to an SVAN958 noise analyzer.

RESULTS

The incubators studied produced continuous equivalent noise levels of 53.5-58 dB and reduced external noise by 5.2-10.4 dB.

CONCLUSIONS

A preterm infant in an incubator is exposed to noise levels clearly exceeding international recommendations even though such levels usually comply with the limit set in the standard IEC60601-2-19: 2009 (60 dBA) under normal conditions of use.

Effect of peer education on the noise management in Iranian neonatal intensive care unit

Background:

Advancements in neonatal intensive care unit (NICU) science and technology have increased the survival rate of preterm infants. Despite these advances, they are still facing with neurobehavioral problems. Noise level in NICU is a potential source of stress for preterm infants. It should be decreased to the standard level as much as possible. The purpose of this study was to evaluate the effect of peer education on the performance of staff in noise management in the NICU.

Materials and Methods:

A pre-post test quasi-experimental design was used. Fifty-eight staff members (nurses and physicians) participated in this study. Sound pressure levels were measured before and after the intervention. Peer education program formed the intervention. The staff performance in noise management was evaluated before and after the intervention by using a questionnaire. Data analysis was done by using t-test.

Results:

The results of the study showed that the mean sound level in different environments significantly decreased after the intervention. It reached from 86.7 to 74.9 dB in the center of unit and from 68.2 to 48.50 dB in the infants' bedside (P < 0.0001). The mean score of the staff performance in noise management significantly increased after the intervention, compared to the pre-intervention score. It increased from 74.6 to 83.4 (P < 0.0001).

Conclusions:

Peer education was found to be successful in noise management because behavioral changes were done to avoid generating unnecessary noise by the staff.

Are high flow nasal cannulae noisier than bubble CPAP for preterm infants?

BACKGROUND

Noise exposure in the neonatal intensive care unit is believed to be a risk factor for hearing loss in preterm neonates. Continuous positive airway pressure (CPAP) devices exceed recommended noise levels. High flow nasal cannulae (HFNC) are an increasingly popular alternative to CPAP for treating preterm infants, but there are no in vivo studies assessing noise production by HFNC.

OBJECTIVE

To study whether HFNC are noisier than bubble CPAP (BCPAP) for preterm infants.

METHODS

An observational study of preterm infants receiving HFNC or BCPAP. Noise levels within the external auditory meatus (EAM) were measured using a microphone probe tube connected to a calibrated digital dosimeter. Noise was measured across a range of frequencies and reported as decibels A-weighted (dBA).

RESULTS

A total of 21 HFNC and 13 BCPAP noise measurements were performed in 21 infants. HFNC gas flows were 2-5 L/min, and BCPAP gas flows were 6-10 L/min with set pressures of 5-7 cm of water. There was no evidence of a difference in average noise levels measured at the EAM: mean difference (95% CI) of -1.6 (-4.0 to 0.9) dBA for HFNC compared to BCPAP. At low frequency (500 Hz), HFNC was mean (95% CI) 3.0 (0.3 to 5.7) dBA quieter than BCPAP. Noise increased with increasing BCPAP gas flow (p=0.007), but not with increasing set pressure. There was a trend to noise increasing with increasing HFNC gas flows.

CONCLUSIONS

At the gas flows studied, HFNC are not noisier than BCPAP for preterm infants.

Early exposure to maternal voice: effects on preterm infants development

BACKGROUND

Preterm infants complete their development in Neonatal Intensive Care Unit being exposed to environmental stimuli that lead to the early maturation of the sensory systems. It is known that the fetus perceives sounds and reacts to them with movements since the 26th-28th week of gestational age. Maternal voice represents a source of sensory stimulation for the fetus.

AIMS

To investigate the effect of the exposure to maternal voice, administered by bone conduction, on preterm infants autonomic and neurobehavioral development.

STUDY DESIGN

Longitudinal, explorative, case control study.

SUBJECTS

71 preterm infants with birth weight <1500g, born adequate for gestational age

OUTCOME MEASURES

vital and neurobehavioral parameters at term, neurofunctional assessment at 3 and 6months of corrected age.

RESULTS

Infants in the treatment group had lower heart rate values and a higher proportion of stable skin color at each study point as compared to the control group. The scores in the visual attention performance and in the quality of the general movements at term were better in the treatment group than in the control one. Neurofunctional assessment score at 3months of corrected age was higher in the treatment group whereas no difference between the two groups was detected at 6months of corrected age.

CONCLUSIONS

Early exposure to maternal voice exerts a beneficial effect on preterm infants autonomic and neurobehavioral development.

Assessment of Noise Exposure to Children: Considerations for the National Children's Study

Evidence has been accruing to indicate that young children are vulnerable to noise in their physical environment. A literature review identified that, in addition to hearing loss, noise exposure is associated with negative birth outcomes, reduced cognitive function, inability to concentrate, increased psychosocial activation, nervousness, feeling of helplessness, and increased blood pressure in children. While increasing attention has been given to the health effects of noise in children, research about noise exposure is sparse and often the measure of exposure is simply proximity to a noise source. The U.S. National Children's Study (NCS) provides a unique opportunity to investigate noise exposures to pregnant women and children using a number of assessment modalities at different life stages. Measurement of noise levels in homes and other environments, personal dosimetry measurements made over a period of days, and questionnaires addressing sources of noise in the environment, annoyance to noise, perceived noise level, use of head phones and ear buds, noisy activity exposures, and occupational exposures, are planned for evaluation within the NCS Vanguard pilot study. We describe the NCS planned approach to addressing noise exposure assessment in study visits over a child's lifetime.

Assessment of sound levels in a neonatal intensive care unit in tabriz, iran

INTRODUCTION

High levels of sound have several negative effects, such as noise-induced hearing loss and delayed growth and development, on premature infants in neonatal intensive care units (NICUs). In order to reduce sound levels, they should first be measured. This study was performed to assess sound levels and determine sources of noise in the NICU of Alzahra Teaching Hospital (Tabriz, Iran).

METHODS

In a descriptive study, 24 hours in 4 workdays were randomly selected. Equivalent continuous sound level (Leq), sound level that is exceeded only 10% of the time (L10), maximum sound level (Lmax), and peak instantaneous sound pressure level (Lzpeak) were measured by CEL-440 sound level meter (SLM) at 6 fixed locations in the NICU. Data was collected using a questionnaire. SPSS13 was then used for data analysis.

RESULTS

Mean values of Leq, L10, and Lmax were determined as 63.46 dBA, 65.81 dBA, and 71.30 dBA, respectively. They were all higher than standard levels (Leq < 45 dB, L10 ≤50 dB, and Lmax ≤65 dB). The highest Leq was measured at the time of nurse rounds. Leq was directly correlated with the number of staff members present in the ward. Finally, sources of noise were ordered based on their intensity.

CONCLUSION

Considering that sound levels were higher than standard levels in our studied NICU, it is necessary to adopt policies to reduce sound.