Behavioural and autonomic responses to sound in pre-term and full-term babies

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.

Influence of the NICU on the Acoustic Isolation of a Neonatal Incubator

The neonatal intensive care unit (NICU) is a very noisy place as compared to the intrauterine environment. To protect the neonate's health, international guidelines suggest avoiding noise levels above 45 dB in NICUs, but this recommendation is not normally met. The incubator acoustic isolation and the acoustic features of the NICU play important roles in determining the noise measured inside the incubator. In this study, the influence of two types of rooms, one with sound-absorbent covering and the other with reverberant surfaces, on the acoustic isolation of a neonatal incubator was evaluated using three acoustic isolation indexes: the level difference, the apparent sound reduction index, and the standardized level difference. Results show that the acoustic isolation of the incubator is very poor, with a level difference below 11 dBA at all frequencies. At 62.5 Hz, the level difference measured in both rooms exhibits a negative value, indicating that the incubator amplifies the noise coming from the NICU. Isolation of the incubator is poor, and the reverberation time (RT) of the containing room influences RT of the incubator, which is consequently higher when the containing room is reverberant; for example, the incubator RT in the reverberant NICU is 0.72 s higher at 500 Hz than that in a room with sound-absorbent covering.

Effects of Cycled Lighting Versus Continuous Near Darkness on Physiological Stability and Motor Activity Level in Preterm Infants

BACKGROUND

Preterm infants generally spend weeks in the neonatal intensive care unit where light intensity can fluctuate as well as be high, leading to physiological instability and increased motor activity in these infants. To date, 2 lighting control methods have been studied: cycled lighting and continuous near darkness. The most appropriate method of lighting is still unknown due to ambivalent results from the studies that have assessed these 2 interventions.

OBJECTIVE

To compare the effects of cycled lighting versus continuous near darkness on physiological stability and motor activity level in preterm infants born between 28 and 32 weeks of gestation.

METHODS

A randomized clinical trial was conducted to compare physiological stability and motor activity level in preterm infants assigned to cycled lighting or continuous near darkness. Thirty-eight participants were recruited and randomly assigned to one of the lighting conditions for 24 hours. Physiological stability was measured using the Stability of the Cardiorespiratory System in Premature Infants (SCRIP) score, the means, and the coefficient of variation of each physiological parameter measured. The level of motor activity was measured with an accelerometer.

RESULTS

There were no significant differences between the 2 groups with regard to physiological stability measured by the SCRIP score, means, and coefficient of variation as well as motor activity level. Participants in both groups were physiologically stable and their motor activity level was comparable.

IMPLICATIONS FOR PRACTICE AND RESEARCH

Neither cycled lighting nor continuous near darkness negatively impacted infant's physiologic stability and motor activity level. Further research is required to identify the most appropriate lighting control method for preterm infants born between 28 and 32 weeks of gestation.

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.

Sound Interferes with the Early Tactile Manual Abilities of Preterm Infants

Premature birth is a sudden change of the sensory environment of a newborn, while their senses are still in development, especially in the stressful and noisy environment of the NICU. The study aimed to evaluate the effect of noise on the early tactile manual abilities of preterm infants (between 29 and 35 weeks PCA). Infants were randomly assigned to one of the two conditions: Silence and Noise. For each condition, two phases were introduced: a habituation phase (repeated presentation of the same object, prism or cylinder), followed by a test phase (presentation of the familiar or a novel object). In the Silence condition, they received the tactile habituation and test phases: In the Noise condition, they went through the same phases, while an alarm sounded. Sixty-three preterm infants were included. They displayed a strong and effective ability to memorize tactile manual information and to detect the difference between two shape features, but this ability seems to be impaired by the concomitant exposure to an alarm sound. This study is the first to highlight the effect of a negative stimulus on sensory functioning in premature infants. It reinforces the importance of developing environmental measures to lower the sound level in NICUs.

Effect of holding on co-regulation in preterm infants: a randomized controlled trial

OBJECTIVE

To determine whether kangaroo holding of healthy preterm infants over the first eight weeks of an infant's life facilitates co-regulation of salivary cortisol between mother and infant.

STUDY DESIGN

Randomized control trial. Infants were assigned to receive 1h of daily kangaroo (skin-to-skin contact on the chest of mother) or blanket holding (dressed and held in mother's arms). A registered nurse visited mothers weekly for eight weeks to encourage holding and provide information about infant development. A control group had no holding restrictions and received weekly brief social visits.

SUBJECTS

The study included 79 preterm infants, born between 32 and 35weeks gestational age and were a mean of 15days (±5.7) at enrollment.

OUTCOME MEASURES

Co-regulation was conceptualized as progressive reduction in the absolute difference between mother and infant cortisol levels across 60min of holding at each holding session. Mother and infant cortisol levels were measured before holding and at 30 and 60min after holding began during three holding sessions (baseline and at two and eight weeks after study initiation). Primary analyses were conducted using hierarchical linear models.

RESULTS

There was much variability in cortisol levels. Levels of mother and infant cortisol decreased during holding. No significant co-regulation occurred in any group at any holding session or over time.

CONCLUSIONS

Decreasing level of cortisol in both mothers and infants suggests that holding promoted the expected decline in stress hormone levels. However, supported holding methods did not differentially affect co-regulation compared to controls. Holding is pleasurable and stress may need to be present in order for mothers and infants to demonstrate co-regulation in cortisol levels.

Physical therapy intervention in the neonatal intensive care unit

This article presents the elements of the Intervention section of the Infant Care Path for Physical Therapy in the Neonatal Intensive Care Unit (NICU). The types of physical therapy interventions presented in this path are evidence-based and the suggested timing of these interventions is primarily based on practice knowledge from expert therapists, with supporting evidence cited. Physical therapy intervention in the NICU is infant-driven and focuses on providing family-centered care. In this context, interventions to facilitate a calm behavioral state and motor organization in the infant, address positioning and handling of the infant, and provide movement therapy are presented.

Noise levels of neonatal high-flow nasal cannula devices--an in-vitro study

BACKGROUND

Excessive ambient noise levels have been identified as a potential risk factor for adverse outcome in very preterm infants. Noise level measurements for continuous positive airway pressure (CPAP) devices demonstrated that these constantly exceed current recommendations. The use of high-flow nasal cannula (HFNC) as an alternative non-invasive ventilation modality has become more popular in recent years in neonatal care.

OBJECTIVE

To study noise levels of two HFNC devices commonly used in newborns. As a comparison, noise levels of a continuous flow CPAP device were also studied.

METHODS

In-vitro study. The noise levels of two contemporary HFNC devices (Fisher & Paykel NHF™ and Vapotherm Precision Flow®) and one CPAP device (Dräger Babylog® 8000 plus) were measured in the oral cavity of a newborn manikin in an incubator in a quiet environment. HFNC flows of 4-8 l/min and CPAP pressures of 4-8 cm H2O were applied. The CPAP flow was set at 8 l/min as per unit practice.

RESULTS

Vapotherm HFNC generated the highest noise levels, measuring 81.2-91.4 dB(A) with increasing flow. Fisher & Paykel HFNC noise levels were between 78.8 and 81.2 dB(A). The CPAP device generated the lowest noise levels between 73.9 and 77.4 dB(A).

CONCLUSIONS

Both HFNC devices generated higher noise levels than the CPAP device. All noise levels were far above current recommendations of the American Academy of Pediatrics. In light of the long duration of non-invasive respiratory support of very preterm infants, less noisy devices are required to prevent the potentially adverse effects of continuing excessive noise exposure in the neonatal intensive care unit.

The effects of noise reduction by earmuffs on the physiologic and behavioral responses in very low birth weight preterm infants

OBJECTIVE

Preterm infants are exposed to loud noises during their stay in the neonatal intensive care unit which can lead to physiologic and behavioral alterations and even hearing loss. The use of earmuffs can reduce sound level and these changes. The objective of the present study is to evaluate the effectiveness of the earmuffs in preterm infants solely cared for in closed incubators.

METHODS

A comparative prospective study comprising 20 clinically stable preterm infants weighing less than 1500 g cared in closed incubator was conducted. Preterm infants acted as their own controls whereby they were observed without earmuffs (Group 1) for 2 days and with earmuffs (Group 2) on consecutive 2 days. The preterm infants' physiologic responses and Anderson Behavioral State Scoring System (ABSS) scores were assessed over 30s every 2h for 8h during daytime for 4 days.

RESULTS

Out of 20 preterm infants, 6 were male and 14 female with a mean birth weight of 1220 ± 209 g, gestational age of 29.9 ± 2.1 weeks. The total number of measurements was 320. The mean ABSS scores of Group 1 and 2 were 3.07±1.1 and 1.34 ± 0.3, respectively. Statistically significant difference was noted between the means of ABSS scores (p<0.001). Preterm infants with earmuffs (87.5%) were more frequently observed in a quiet sleep state of ABSS compared with those without earmuffs (29.4%).

CONCLUSIONS

Noise level reduction was associated with significant improvement in behavioral states of ABSS. We suggest that noise reduction in preterm infants with earmuffs is helpful by improving sleep efficiency and increasing time of quiet sleep.

Auditory brain development in premature infants: the importance of early experience

Preterm infants in the neonatal intensive care unit (NICU) often close their eyes in response to bright lights, but they cannot close their ears in response to loud sounds. The sudden transition from the womb to the overly noisy world of the NICU increases the vulnerability of these high-risk newborns. There is a growing concern that the excess noise typically experienced by NICU infants disrupts their growth and development, putting them at risk for hearing, language, and cognitive disabilities. Preterm neonates are especially sensitive to noise because their auditory system is at a critical period of neurodevelopment, and they are no longer shielded by maternal tissue. This paper discusses the developmental milestones of the auditory system and suggests ways to enhance the quality control and type of sounds delivered to NICU infants. We argue that positive auditory experience is essential for early brain maturation and may be a contributing factor for healthy neurodevelopment. Further research is needed to optimize the hospital environment for preterm newborns and to increase their potential to develop into healthy children.

Infants born very preterm react to variations of the acoustic environment in their incubator from a minimum signal-to-noise ratio threshold of 5 to 10 dBA

INTRODUCTION

Very early preterm infants (VPIs) are exposed to unpredictable noise in neonatal intensive care units. Their ability to perceive moderate acoustic environmental changes has not been fully investigated.

RESULTS

Physiological values of the 598 isolated sound peaks (SPs) that were 5-10 and 10-15 dB slow-response A (dBA) above background noise levels and that occurred during infants' sleep varied significantly, indicating that VPIs detect them. Exposure to 10-15 dBA SPs during active sleep significantly increased mean heart rate and decreased mean respiratory rate and mean systemic and cerebral oxygen saturations relative to baseline.

DISCUSSION

VPIs are sensitive to changes in their nosocomial acoustic environment, with a minimal signal-to-noise ratio (SNR) threshold of 5-10 dBA. These acoustic changes can alter their well-being.

METHODS

In this observational study, we evaluated their differential auditory sensitivity to sound-pressure level (SPL) increments below 70-75 dBA equivalent continuous level in their incubators. Environmental (SPL and audio recording), physiological, cerebral, and behavioral data were prospectively collected over 10 h in 26 VPIs (GA 28 (26-31) wk). SPs emerging from background noise levels were identified and newborns' arousal states at the time of SPs were determined. Changes in parameters were compared over 5-s periods between baseline and the 40 s following the SPs depending on their SNR thresholds above background noise.

Decreasing noise level in our NICU: The impact of a noise awareness educational program

BACKGROUND

The literature demonstrates that most NICUs exceed the standard recommendations for noise levels and that high noise levels have a negative impact on patients and staff.

OBJECTIVE

The objective of this research was to measure baseline noise level in an NICU, compare it to recommendations of international bodies, and evaluate the impact of a noise awareness educational program (NAEP) as a strategy to decrease it.

DESIGN/METHODS

Means of hourly average noise levels in decibels (dB) were compared with the recommendations and pre- and postintervention (P = .05).

RESULTS

Mean noise-level preintervention was significantly higher than recommended (58.15 vs 45 dB; P < 0.001). The participation rate in NAEP was excellent and most participants thought that the content was relevant and would change their practice. Overall, at first glance, the impact of the NAEP was not as expected: the noise levels increased nonsignificantly postintervention (58.15 vs 58.46 dB; P < .181). However, a significant increase in activity level (number of nurses and patient) was thought to be responsible for the lack of significance postintervention. After controlling for these variables, it was demonstrated that the noise level did significantly decrease postintervention (6.33 vs 5.42 dB per RN & 4.68 vs 4.08 dB per patient, P < .000).

CONCLUSION

Although the efficacy of the program was significantly limited by an increase in general activity, it raised staff awareness and had important effects reflected by the significant decrease in mean noise level after standardization and the participant's comments.

Stabilizing immature breathing patterns of preterm infants using stochastic mechanosensory stimulation

Breathing patterns in preterm infants consist of highly variable interbreath intervals (IBIs) that might originate from nonlinear properties of the respiratory oscillator and its input-output responses to peripheral and central signals. Here, we explore a property of nonlinear control, the potential for large improvement in the stability of breathing using low-level exogenous stochastic stimulation. Stimulation was administered to 10 preterm infants (postconceptional age: mean 33.3 wk, SD 1.7) using a mattress with embedded actuators that delivered small stochastic displacements (0.021 mm root mean square, 0.090 mm maximum, 30-60 Hz); this stimulus was subthreshold for causing arousal from sleep to wakefulness or other detectable changes in the behavioral state evaluated with polysomnography. We used a test-retest protocol with multiple 10-min intervals of stimulation, each paired with 10-min intervals of no stimulation. Stimulation induced an approximately 50% reduction (P = 0.003) in the variance of IBIs and an approximately 50% reduction (P = 0.002) in the incidence of IBIs > 5 s. The improved stability of eupneic breathing was associated with an approximately 65% reduction (P = 0.04) in the duration of O(2) desaturation. Our findings suggest that nonlinear properties of the immature respiratory control system can be harnessed using afferent stimuli to stabilize eupneic breathing, thereby potentially reducing the incidence of apnea and hypoxia.

NICU noise and the preterm infant

Premature infants in the NICU are often exposed to continuous loud noise despite research documenting the presence and damaging effects of noise on the preterm infant's development. Excessive auditory stimulation creates negative physiologic responses such as apnea and fluctuations in heart rate, blood pressure, and oxygen saturation. Preterm infants exposed to prolonged excessive noise are also at increased risk for hearing loss, abnormal brain and sensory development, and speech and language problems. Reducing noise levels in the NICU can improve the physiologic stability of sick neonates and therefore enlarge the potential for infant brain development. Recommendations include covering incubators with blankets, removing noisy equipment from the incubator environment, implementing a quiet hour, educating staff to raise awareness, and encouraging staff to limit conversation near infants.

Coregulation in Salivary Cortisol During Maternal Holding of Premature Infants

Purpose: The purpose of this study was to examine coregulation between mothers and preterm infants in hypothalamic-pituitary-adrenocortical (HPA) system activity, as indicated by salivary cortisol levels, while mothers held their infants. The research questions were (a) does mother—infant coregulation in HPA activity occur during holding? and (b) if mother— infant coregulation in HPA activity exists during holding, do type of holding, antenatal steroids, sound level, and maternal touch influence this coregulation? Sample: The sample consisted of 20 mother— infant dyads with infants at a mean postconceptional age of 34.7 weeks (+0.7) and average postnatal age of 15 days (+9) at the time of cortisol sampling. Design: The design was exploratory using convenience sampling. Maternal and infant cortisol levels were obtained at Time 1 (baseline) and Time 2 (end of holding); at each time, the absolute differences in levels between mother and infant were determined. Coregulation was operationalized as less difference between maternal-infant cortisol levels immediately after holding (Time 2) as compared to before holding (Time 1). Results: The two variables with the highest correlation with the Time 1/Time 2 difference score included antenatal steroids and ambient sound level, which were entered into a linear regression equation as predictor variables. A coregulatory relationship in cortisol levels existed between mothers and infants during holding, which was moderated by sound levels. Nurses in the neonatal intensive care unit (NICU) can facilitate the mother—infant relationship, as reflected in coregulatory measures, by promoting a quiet environment, particularly around mothers who are holding their infants.

Iatrogenic environmental hazards in the neonatal intensive care unit

Premature infants in the neonatal intensive care unit (NICU) face many illnesses and complications. Another potential source of iatrogenic disease is the NICU environment. Research in this area, however, is limited.

The development of potentially better practices to support the neurodevelopment of infants in the NICU

OBJECTIVE

To review the existing evidence used to identify potentially better care practices that support newborn brain development.

STUDY DESIGN

Literature review.

RESULT

Sixteen potentially better practices are identified and grouped into two operational clinical bundles based upon timing for recommended implementation.

CONCLUSION

Existing evidence supports the implementation of selected care practices that potentially may support newborn brain development.

Effect of environmental changes on noise in the NICU

PURPOSE

To evaluate the effect of changes in the NICU environment on sound levels.

DESIGN

A prospective quasi-experimental design evaluated sound levels in a 43-bed NICU. Decibel levels were monitored utilizing a data-logging dosimeter for 24 hours weekly over 12 months. Sound levels were also measured inside four different incubator models.

SAMPLE

Forty-four 24-hour decibel recordings were obtained in one of eight randomly selected four-bed pods. In addition, a single 1-hour recording was obtained in four different models of vacant incubators.

MAIN OUTCOME VARIABLE

Ambient sound levels.

RESULTS

Decibel levels were analyzed to identify changes in noise levels following alterations in the NICU environment. Installation of motion-sensing motorized paper towel holders significantly increased levels at beds closest to the towel dispensers, as did thetrial of a new communication system. Decibel levels in four different incubators revealed varying noise levels. This study suggests that all environmental changes must be monitored to ensure that they reduce rather than increase noise levels.