How the NICU environment sounds to a preterm infant: update

Noise or sound management in the neonatal intensive care unit for preterm or very low birth weight infants

BACKGROUND

Infants in the neonatal intensive care unit (NICU) are subjected to different types of stress, including sounds of high intensity. The sound levels in NICUs often exceed the maximum acceptable level recommended by the American Academy of Pediatrics, which is 45 decibels (dB). Hearing impairment is diagnosed in 2% to 10% of preterm infants compared to only 0.1% of the general paediatric population. Bringing sound levels under 45 dB can be achieved by lowering the sound levels in an entire unit; by treating the infant in a section of a NICU, in a 'private' room, or in incubators in which the sound levels are controlled; or by reducing sound levels at the individual level using earmuffs or earplugs. By lowering sound levels, the resulting stress can be diminished, thereby promoting growth and reducing adverse neonatal outcomes. This review is an update of one originally published in 2015 and first updated in 2020.

OBJECTIVES

To determine the benefits and harms of sound reduction on the growth and long-term neurodevelopmental outcomes of neonates.

SEARCH METHODS

We used standard, extensive Cochrane search methods. On 21 and 22 August 2023, a Cochrane Information Specialist searched CENTRAL, PubMed, Embase, two other databases, two trials registers, and grey literature via Google Scholar and conference abstracts from Pediatric Academic Societies.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) or quasi-RCTs in preterm infants (less than 32 weeks' postmenstrual age (PMA) or less than 1500 g birth weight) cared for in the resuscitation area, during transport, or once admitted to a NICU or stepdown unit. We specified three types of intervention: 1) intervention at the unit level (i.e. the entire neonatal department), 2) at the section or room level, or 3) at the individual level (e.g. hearing protection).

DATA COLLECTION AND ANALYSIS

We used the standardised review methods of Cochrane Neonatal to assess the risk of bias in the studies. We used the risk ratio (RR) and risk difference (RD), with their 95% confidence intervals (CIs), for dichotomous data. We used the mean difference (MD) for continuous data. Our primary outcome was major neurodevelopmental disability. We used GRADE to assess the certainty of the evidence.

MAIN RESULTS

We included one RCT, which enroled 34 newborn infants randomised to the use of silicone earplugs versus no earplugs for hearing protection. It was a single-centre study conducted at the University of Texas Medical School in Houston, Texas, USA. Earplugs were positioned at the time of randomisation and worn continuously until the infants were 35 weeks' postmenstrual age (PMA) or discharged (whichever came first). Newborns in the control group received standard care. The evidence is very uncertain about the effects of silicone earplugs on the following outcomes. • Cerebral palsy (RR 3.00, 95% CI 0.15 to 61.74)and Mental Developmental Index (MDI) (Bayley II) at 18 to 22 months' corrected age (MD 14.00, 95% CI 3.13 to 24.87); no other indicators of major neurodevelopmental disability were reported. • Normal auditory functioning at discharge (RR 1.65, 95% CI 0.93 to 2.94) • All-cause mortality during hospital stay (RR 2.07, 95% CI 0.64 to 6.70; RD 0.20, 95% CI -0.09 to 0.50) • Weight (kg) at 18 to 22 months' corrected age (MD 0.31, 95% CI -1.53 to 2.16) • Height (cm) at 18 to 22 months' corrected age (MD 2.70, 95% CI -3.13 to 8.53) • Days of assisted ventilation (MD -1.44, 95% CI -23.29 to 20.41) • Days of initial hospitalisation (MD 1.36, 95% CI -31.03 to 33.75) For all outcomes, we judged the certainty of evidence as very low. We identified one ongoing RCT that will compare the effects of reduced noise levels and cycled light on visual and neural development in preterm infants.

AUTHORS' CONCLUSIONS

No studies evaluated interventions to reduce sound levels below 45 dB across the whole neonatal unit or in a room within it. We found only one study that evaluated the benefits of sound reduction in the neonatal intensive care unit for hearing protection in preterm infants. The study compared the use of silicone earplugs versus no earplugs in newborns of very low birth weight (less than 1500 g). Considering the very small sample size, imprecise results, and high risk of attrition bias, the evidence based on this research is very uncertain and no conclusions can be drawn. As there is a lack of evidence to inform healthcare or policy decisions, large, well designed, well conducted, and fully reported RCTs that analyse different aspects of noise reduction in NICUs are needed. They should report both short- and long-term outcomes.

Preventing Excessive Noise Exposure in Infants, Children, and Adolescents

Noise exposure is a major cause of hearing loss in adults. Yet, noise affects people of all ages, and noise-induced hearing loss is also a problem for young people. Sensorineural hearing loss caused by noise and other toxic exposures is usually irreversible. Environmental noise, such as traffic noise, can affect learning, physiologic parameters, and quality of life. Children and adolescents have unique vulnerabilities to noise. Children may be exposed beginning in NICUs and well-baby nurseries, at home, at school, in their neighborhoods, and in recreational settings. Personal listening devices are increasingly used, even by small children. Infants and young children cannot remove themselves from noisy situations and must rely on adults to do so, children may not recognize hazardous noise exposures, and teenagers generally do not understand the consequences of high exposure to music from personal listening devices or attending concerts and dances. Environmental noise exposure has disproportionate effects on underserved communities. In this report and the accompanying policy statement, common sources of noise and effects on hearing at different life stages are reviewed. Noise-abatement interventions in various settings are discussed. Because noise exposure often starts in infancy and its effects result mainly from cumulative exposure to loud noise over long periods of time, more attention is needed to its presence in everyday activities starting early in life. Listening to music and attending dances, concerts, and celebratory and other events are sources of joy, pleasure, and relaxation for many people. These situations, however, often result in potentially harmful noise exposures. Pediatricians can potentially lessen exposures, including promotion of safer listening, by raising awareness in parents, children, and teenagers. Noise exposure is underrecognized as a serious public health issue in the United States, with exposure limits enforceable only in workplaces and not for the general public, including children and adolescents. Greater awareness of noise hazards is needed at a societal level.

Noise survey of neonatal intensive care unit at a government tertiary-care centre

BACKGROUND

With technological advancement, Neonatal Intensive Care Units (NICU) have become noisier than ever. Studies have shown the detrimental effects of increasing noise in NICU on growing pre-term and sick neonates. The present study aimed to survey the amount of noise in one of the NICU blocks of a government tertiary care centre and explore ways to control it when dealing with these sick babies.

METHODS

A detailed noise survey was carried out, for February 2023, in one of the two blocks of NICU in a government tertiary-care centre. The noise measurements were performed using two "Sound Ear 3" noise meters. The analyses were done in Leq (equivalent continuous sound levels) A-weighted decibels (dBA).

RESULTS

The extracted data analysis revealed that the NICU block was exposed to a mean Leq of 67.78 dBA noise with a maximum of 89.0 dBA. There was a significant difference between the values noted in devices at different locations and across different periods. There were certain instances (57 and 42 for two devices) when there were sudden spikes in the noise levels beyond 80 dBA. It was also seen that noise was more than 65 dBA most of the time (72% and 66% for the two devices).

CONCLUSION

The noise survey carried out over one month revealed a considerable amount of noise in the NICU of a government tertiary-care centre. The study also explored ways such as environmental modification, human behavior modification, awareness programs, and neonatal-centered modifications to reduce the noise and lower its detrimental effects on the growth of neonates.

Effect of environmental music on autonomic function in infants in intensive and growing care units

BACKGROUND

The aim of this study is (1) to observe the effect of the background music (BGM) in the incubator on heart rate variability (HRV) during the first few weeks of life in preterm infants in the neonatal intensive (NICU) and growing care units (GCU) and (2) to investigate the effect of environmental music on autonomic function in the infants.

METHODS

Thirty infants, including premature (26 3/7 - 38 4/7 weeks) and low-birth weight (LBW) (946-2,440 g) infants, admitted to the NICU or GCU were involved. The heart rate, low- (LF, 0.05-0.15 Hz) and high- (HF, 0.15-0.4 Hz) frequency HRV components, and LF/HF ratio were measured. The BGM, lullabies for a baby, was delivered through a speaker in the incubator, and the HRV components were compared among before, during, and after intervention with BGM.

RESULTS

The mean HR did not change among the experimental conditions. The LF and HF values decreased during the BGM condition, but not LF/HF, compared with the condition before BGM.

CONCLUSIONS

The present results showed that an auditory environment affected the autonomic function of infants with a range of BGM in the NICU/GCU. The present study also suggested that BGM, a non-invasive and non-pharmacological intervention, could be an evaluation tool for autonomic function in infants in NICU/GCU.

Ambient Noise Production by High-Frequency Neonatal Ventilators

OBJECTIVE

To assess sound levels of 4 high-frequency neonatal ventilators to determine whether there is a safety benefit in using modern high-frequency ventilators compared with older models.

STUDY DESIGN

We performed a bench study comparing noise production of the Sensormedics 3100A Oscillator, Bunnell Life Pulse Jet Ventilators Model 203 and Model 204, and Dräger VN500 in high-frequency mode. A wide range of ventilation settings was examined. All measurements were performed in triplicate using a high-fidelity sound meter, with data analyzed using ANOVA and regression analyses.

RESULTS

The Dräger ventilator was quietest overall, with average sound levels of 49.8 ± 0.49 dB across all settings. The average noise from the Sensormedics was 53.6 ± 2.01 dB, for Bunnell Model 203 was 54.1 ± 1.09 dB, and for Bunnell Model 204 was 53.7 ± 1.45 dB. Adjustments made to frequency/rate and mean airway pressure/positive end-expiratory pressure had minimal effect on noise, and increasing amplitude/peak inspiratory pressure resulted in significantly more noise by all ventilators. At all settings, the Sensormedics and Bunnell ventilators were louder than the Dräger, and the difference became greater as amplitude/peak inspiratory pressure was increased.

CONCLUSIONS

The Dräger VN500 in high-frequency mode produces significantly less noise that both the Sensormedics and Bunnell ventilators. These data suggest that using the Dräger VN500 as a high-frequency ventilator may reduce the potential for adverse outcomes created by ventilator noise.

Noise Reduction in the Neonatal Intensive Care Unit: A Quality Improvement Initiative

Exogenous noise has deleterious effects on the developing fetus and infant. The aim of this quality improvement project was to lower the mean ambient noise level within a level IV neonatal intensive care unit (NICU) by 10% from the baseline in one year. Multiple noise reduction strategies were tested through Plan-Do-Study-Act cycles based on the Institute for Healthcare Improvement model for improvement. Strategies targeted environmental and behavioral modifications. Noise levels were recorded continuously; means and peaks were calculated. The mean noise level decreased from 62.4 dB to 56.1 dB, and peak noise level decreased from 115 dB to 76 dB within 12 months. Day shift noise level decreased by 7.7 dB; night shift noise level decreased by 4.9 dB from baseline. Targeted education, behavioral, and environmental modifications decreased the noise level in the NICU as per the study aim. To create a change in culture, constant dialogue between the project champions and the NICU staff is necessary.

Effect of gentamicin and levels of ambient sound on hearing screening outcomes in the neonatal intensive care unit: A pilot study

OBJECTIVE

Hearing loss rates in infants admitted to neonatal intensive care units (NICU) run at 2-15%, compared to 0.3% in full-term births. The etiology of this difference remains poorly understood. We examined whether the level of ambient sound and/or cumulative gentamicin (an aminoglycoside) exposure affect NICU hearing screening results, as either exposure can cause acquired, permanent hearing loss. We hypothesized that higher levels of ambient sound in the NICU, and/or gentamicin dosing, increase the risk of referral on the distortion product otoacoustic emission (DPOAE) assessments and/or automated auditory brainstem response (AABR) screens.

METHODS

This was a prospective pilot outcomes study of 82 infants (<37 weeks gestational age) admitted to the NICU at Oregon Health & Science University. An ER-200D sound pressure level dosimeter was used to collect daily sound exposure in the NICU for each neonate. Gentamicin dosing was also calculated for each infant, including the total daily dose based on body mass (mg/kg/day), as well as the total number of treatment days. DPOAE and AABR assessments were conducted prior to discharge to evaluate hearing status. Exclusion criteria included congenital infections associated with hearing loss, and congenital craniofacial or otologic abnormalities.

RESULTS

The mean level of ambient sound was 62.9 dBA (range 51.8-70.6 dBA), greatly exceeding American Academy of Pediatrics (AAP) recommendation of <45.0 dBA. More than 80% of subjects received gentamicin treatment. The referral rate for (i) AABRs, (frequency range: ∼1000-4000 Hz), was 5%; (ii) DPOAEs with a broad F2 frequency range (2063-10031 Hz) was 39%; (iii) DPOAEs with a low-frequency F2 range (<4172 Hz) was 29%, and (iv) DPOAEs with a high-frequency F2 range (>4172 Hz) was 44%. DPOAE referrals were significantly greater for infants receiving >2 days of gentamicin dosing compared to fewer doses (p = 0.004). The effect of sound exposure and gentamicin treatment on hearing could not be determined due to the low number of NICU infants without gentamicin exposure (for control comparisons).

CONCLUSION

All infants were exposed to higher levels of ambient sound that substantially exceed AAP guidelines. More referrals were generated by DPOAE assessments than with AABR screens, with significantly more DPOAE referrals with a high-frequency F2 range, consistent with sound- and/or gentamicin-induced cochlear dysfunction. Adding higher frequency DPOAE assessments to existing NICU hearing screening protocols could better identify infants at-risk for ototoxicity.

Sound Environments Surrounding Preterm Infants Within an Occupied Closed Incubator

Preterm infants often exhibit functional disorders due to the stressful environment in the neonatal intensive care unit (NICU). The sound pressure level (SPL) in the NICU is often much higher than the levels recommended by the American Academy of Pediatrics. Our study aims to describe the SPL and sound frequency levels surrounding preterm infants within closed incubators that utilize high frequency oscillation (HFO) or nasal directional positive airway pressure (nasal-DPAP) respiratory settings.

DESIGN AND METHODS

This is a descriptive research study of eight preterm infants (corrected age<33 weeks) exposed to the equipment when placed in an incubator. The actual noise levels were observed and the results were compared to the recommendations made by neonatal experts.

RESULTS

Increased noise levels, which have reported to affect neonates' ability to self-regulate, could increase the risk of developing attention deficit disorder, and may result in tachycardia, bradycardia, increased intracranial pressure, and hypoxia.

CONCLUSION AND PRACTICE IMPLICATIONS

The care provider should closely assess for adverse effects of higher sound levels generated by different modes of respiratory support and take measures to ensure that preterm infants are protected from exposure to noise exceeding the optimal safe levels.

The effect of positioning on preterm infants' sleep-wake states and stress behaviours during exposure to environmental stressors

Previous studies separately examined the effects of positioning or environmental stressors on preterm infants' sleep and stress. Since positioning and environmental stressors occur simultaneously during infant hospitalization exploring these variables in the same study may offer new insights. A quasi-experimental study by one-group interrupted time-series design. In the current study, a total of 22 preterm infants were enrolled. Each infant was moved to either the supine or prone position for an hour at a time. Infants were videotaped and the sleep-wake states, stress behaviours and environmental conditions (light, noise and stimulation/handling) were recorded during the observation period. A total of 80 observations from 22 infants were accrued. In the supine position, preterm infants demonstrated more frequent waking states after adjusting for various environmental stressors (p < .01). These infants demonstrated more frequent stress behaviours in the supine position after adjusting for various environmental stressors (p < .01). These results suggest that the prone position is a more favourable position for facilitating sleep and reducing stress for preterm infants exposed to varying environmental stressors. Preterm infants present different stress behaviours in response to varying types of environmental stimuli.

Intervention minimizing preterm infants' exposure to NICU light and noise

Neonatal intensive care unit (NICU) light and noise may be stressful to preterm infants. This research evaluated the physiological stability of 54 infants born at 28- to 32-weeks' gestational age while wearing eye goggles and earmuffs for a 4-hour period in the NICU. Infants were recruited from four NICUs of university-affiliated hospitals and randomized to the intervention-control or control-intervention sequences. Heart rate (HR), heart rate variability (HRV), and oxygen saturation (O2 sat) were collected using the SomtéTM device. Confounding variables such as position and handling were assessed by videotaping infants during the study periods. Results indicated that infants had more stress responses while wearing eye goggles and earmuffs since maximum HR was found to be significantly higher and high-frequency power of HRV significantly lower during the intervention as compared with the control period. Therefore, this intervention is not recommended for the clinical practice.

The effects of environmental noise and infant position on cerebral oxygenation

PURPOSE

To assess how different infant positions and peak sound levels affected cerebral oxygen saturation over time.

SUBJECTS

Twenty-four premature infants who were born less than 32 weeks' gestational age without congenital cardiac, neurologic, and gastrointestinal anomalies.

DESIGN

Repeated-measures design with the first observation between 2 and 48 hours of life; once again between 49 and 96 hours of life; on day of life 7; and every 7 days thereafter until discharge home, transfer to another hospital, or 40 weeks postmenstrual age, whichever came first.

METHODS

Continuous sound levels (decibels) were obtained and 2 infant positions were performed while measuring cerebral oxygen saturation during 40-minute observation periods.

MAIN OUTCOME MEASURES

Effect of peak sound and differences in infant position on cerebral oxygen saturation.

RESULTS

Peak sound levels 5 dB above the average ambient sound level did not significantly change cerebral oxygen saturation values. Differences in cerebral oxygenation were significantly less when infants were changed from a supine, head midline position to a right lateral, 15° head elevation compared with a left lateral, 0° elevation position.

CONCLUSIONS

Aspects of the current neonatal intensive care unit environment do not appear to affect cerebral oxygen saturation.

Gestural development and its relation to language acquisition in very preterm children

This longitudinal study examined the development of communicative gesture in 16 preterm children and two groups of full term children at 12, 18 and 24 months of age. Children's spontaneous communicative gestures were analyzed during mother-child observation sessions. Preterm children's motor, mental and linguistic development were also measured. The development of gestural communication did not significantly differ between the groups except for the use of gesture-plus-word combinations at 18 and 24 months, when full term children produced significantly more combinations than preterm children. For preterm children, the production of pointing at 12 months was positively associated with lexical skills at 24 months as was the use of gestures-plus-word utterances at 18 months with morphosyntactic skills at 24 months. Our analyses also revealed a subgroup of preterm children characterized by a low birth-weight and mental scores who demonstrated an enduring increase in communicative gesture production over time. This profile could be associated with later delays in language acquisition.

In vitro comparison of noise levels produced by different CPAP generators

INTRODUCTION

Minimization of noise exposure is an important aim of modern neonatal intensive care medicine. Binasal continuous positive airway pressure (CPAP) generators are among the most important sources of continuous noise in neonatal wards. The aim of this study was to find out which CPAP generator creates the least noise.

METHOD

In an experimental setup, two jet CPAP generators (Infant Flow® generator and MediJet®) and two conventional CPAP generators (Bubble CPAP® and Baby Flow®) were compared. Noise production was measured in decibels in an A-weighted scale [dB(A)] in a closed incubator at 2 mm lateral distance from the end of the nasal prongs. Reproduction of constant airway pressure and air leak was achieved by closure of the nasal prongs with a type of adhesive tape that is semipermeable to air.

RESULTS

The noise levels produced by the four generators were significantly different (p < 0.001). Values measured at a continuous constant flow rate of 8 l/min averaged 83 dB(A) for the Infant Flow® generator with or without sound absorber, 72 dB(A) for the MediJet®, 62 dB(A) for the Bubble CPAP® and 55 dB(A) for the Baby Flow®.

CONCLUSION

Conventional CPAP generators work more quietly than the currently available jet CPAP generators.

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

This systematic literature review evaluated the methodological quality of studies measuring noise in neonatal intensive care units. A manual and also electronic search in the Medline, Scielo, Lilacs, BDENF, WHOLIS, BDTD, Science Direct, NCBI and Scirus databases resulted in 40 studies that met the criterion "measuring noise in neonatal units and/or incubators". Experts in neonatology and acoustics validated the critical analysis instrument, which obtained a mean = 7.9 (SD=1.3). The inter-observer reliability in 18 articles resulted in an Intra-class correlation coefficient (ICC) of 0.89 (CI 0.75-0.95). The quality indicators were 50% better in those studies that measured noise only in the unit's environment and associated measuring strategies to the physical area. The results showed great methodological variability, which hindered comparability and raised the probability of bias. The conditions required to ensure internal and external validity were observed in few studies.

The infant incubator in the neonatal intensive care unit: unresolved issues and future developments

Since the 19th century, devices termed incubators were developed to maintain thermal stability in low birth weight (LBW) and sick newborns, thus improving their chances of survival. Remarkable progress has been made in the production of infant incubators, which are currently highly technological devices. However, they still need to be improved in many aspects. Regarding the temperature and humidity control, future incubators should minimize heat loss from the neonate and eddies around him/her. An unresolved issue is exposure to high noise levels in the Neonatal Intensive Care Unit (NICU). Strategies aimed at modifying the behavior of NICU personnel, along with structural improvements in incubator design, are required to reduce noise exposure. Light environment should be taken into consideration in designing new models of incubators. In fact, ambient NICU illumination may cause visual pathway sequelae or possibly retinopathy of prematurity (ROP), while premature exposure to continuous lighting may adversely affect the rest-activity patterns of the newborn. Accordingly, both the use of incubator covers and circadian lighting in the NICU might attenuate these effects. The impact of electromagnetic fields (EMFs) on infant health is still unclear. However, future incubators should be designed to minimize the EMF exposure of the newborn.

The influence of neonatal intensive care unit design on sound level

BACKGROUND

Excessive noise in nurseries has been found to cause adverse effects in infants, especially preterm infants in neonatal intensive care units (NICUs). The NICU design may influence the background sound level. We compared the sound level in two differently designed spaces in one NICU. We hypothesized that the sound level in an enclosed space would be quieter than in an open space.

METHODS

Sound levels were measured continuously 24 hours a day in two separate spaces at the same time, one enclosed and one open. Sound-level meters were placed near beds in each room. Sound levels were expressed as decibels, A-weighted (dBA) and presented as hourly L(eq), L(max), L(10), and L(90).

RESULTS

The hourly L(eq) in the open space (50.8-57.2dB) was greater than that of the enclosed space (45.9-51.7dB), with a difference of 0.4-10.4dB, and a mean difference of 4.5dB (p<0.0001). The hourly L(10), L(90), and L(max) in the open space also exceeded that in the enclosed space (p<0.0001).

CONCLUSION

The sound level measured in the enclosed space was quieter than in the open space. The design of bed space should be taken into consideration when building a new NICU. Besides the design of NICU architecture, continuous monitoring of sound level in the NICU is important to maintain a quiet environment.

Music as a nursing intervention for preterm infants in the NICU

Although there is general agreement that noise in the neonatal intensive care unit should be reduced, there is controversy about the use of music as a developmental care strategy with prererm infants. Much literature supports using music with preterm infants, indicating that it enhances physiologic and neurobehavioral functioning, but some experts worry that music is overstimulating. This article presents evidence supporting the use of music with preterm infants as well as criticism of same. Recommendations for music interventions with preterm infants are discussed, although fUrther research is needed before specific guidelines can he established.