Preterm infants' sympathetic arousal and associated behavioral responses to sound stimuli in the neonatal intensive care unit

Intermittent hypoxia in neonatal rodents affects facial bone growth

Preterm human infants often show periodic breathing (PB) or apnea of prematurity (AOP), breathing patterns which are accompanied by intermittent hypoxia (IH). We examined cause-effect relationships between transient IH and reduced facial bone growth using a rat model. Neonatal pups from 14 timed pregnant Sprague-Dawley rats were randomly assigned to an IH condition, with oxygen altering between 10% and 21% every 4 min for 1 h immediately after birth, or to a litter-matched control group. The IH pups were compared with their age- and sex-matched control groups in body weight (WT), size of facial bones and nor-epinephrine (NE) levels in blood at 3, 4, and 5-weeks. Markedly increased activity of osteoclasts in sub-condylar regions of 3-week-old IH-treated animals appeared, as well as increased numbers of sympathetic nerve endings in the same region of tissue sections. Male IH-pups showed significantly higher levels of NE levels in sera at 3, 4 as well as 5-week-old time points. NE levels in 4- and-5-week-old female pups did not differ significantly. Intercondylar Width, Mandible Length and Intermolar Width measures consistently declined after IH insults in 3- and 4-week-old male as well as female animals. Three-week-old male IH-pups only showed a significantly reduced (p < 0.05) body weight compared to those of 3-week controls. However, female IH-pups were heavier than age-matched controls at all 3 time-points. Trabecular bone configuration, size of facial bones, and metabolism are disturbed after an IH challenge 1 h immediately after birth. The findings raise the possibility that IH, introduced by breathing patterns such as PB or AOP, induce significantly impaired bone development and metabolic changes in human newborns. The enhanced NE outflow from IH exposure may serve a major role in deficient bone growth, and may affect bone and other tissue influenced by that elevation.

Pain Behavioural Response to Acoustic and Light Environmental Changes in Very Preterm Infants

Noise and high light illumination in the neonatal intensive care unit (NICU) are recognized as stressors that could alter the well-being and development of vulnerable preterm infants. This prospective observational study evaluated the pain behaviours of very preterm infants (VPIs) to sound peaks (SPs) and light levels variations (LLVs) in the NICU. We measured spontaneously occurring SPs and LLVs in the incubators of 26 VPIs over 10 h. Their behavioural responses were analysed through video recordings using the "Douleur Aigue du Nouveau-né" (DAN) scale. We compared the maximum DAN scores before and after environmental stimuli and the percentage of VPIs with a score ≥ 3 according to the type of stimuli. A total of 591 SPs and 278 LLVs were analysed. SPs of 5 to 15 dBA and LLVs significantly increased the maximum DAN scores compared to baseline. The occurrence of DAN scores ≥ 3 increased with both stressors, with a total of 16% of SPs and 8% of LLVs leading to quantifiable pain behaviour. Altogether, this study shows that VPIs are sensitive to SPs and LLVs, with a slighter higher sensitivity to SPs. The mechanisms leading to pain behaviours induced by noise and light changes should be evaluated further in the context of VPIs brain development. Our results provide further arguments to optimize the NICU sensory environment of neonatal units and to adapt it to the expectations and sensory abilities of VPIs.

Available Instruments to Assess Pain in Infants

Pain assessment in newborns and infants is challenging for clinicians. Although behavioral and behavioral-physiological scales are validated pain assessment instruments, their use in this age group has significant limitations. In this review, we summarize the methods currently available for assessing pain in neonates and infants. It is possible that these pain detection methods are also useful for assessing the quality of anesthesia and analgosedation in these populations. Further research should be aimed at confirming the usefulness of these tools in infants and identifying additional pain assessment options for clinical practice.

A pilot study to assess the safety, efficacy and ease of use of a novel hearing protection device for hospitalized neonates

BACKGROUND

Loud noises in the neonatal intensive care unit (NICU) exacerbate patient cardiac and respiratory activity, disrupt sleep, and may contribute to hearing deficits, speech and language disorders, and neurodevelopmental delays among NICU graduates.

AIMS

This study evaluated infant-patient tolerance and nurse ease of use of a novel frequency-selective hearing protection device, DREAMIES (NEATCap Medical, LLC).

STUDY DESIGN AND SUBJECTS

Fifty neonates receiving care in a Level III NICU participated in a 2-phase prospective study. In Phase 1, 25 infants (mean 36.6 wks GA) wore DREAMIES for two consecutive 30-min periods. In Phase 2, 25 infants (mean 34.8 wks GA) wore DREAMIES between care and feeding times during an 8-h Device-On period followed by an 8-h Device-Off period for three consecutive days.

OUTCOME MEASURES

Subject tolerance was defined by device-related skin irritation, vital sign measurements, and behavioral state. Device fit and ease of use were also evaluated by NICU nurses.

RESULTS

No skin breakdown was reported in any infant in either phase. Only transient skin erythema was observed. Periods when infants wore DREAMIES resulted in lower heart and respiratory rates and increased sleep (P < 0.001). Nurses reported little to no difficulty in applying or removing the device.

CONCLUSION

Findings suggest DREAMIES are a safe, easy to use, and effective device that reduces exposure to NICU noise, and may improve cardio-respiratory activity and promote sleep among neonatal patients. Further studies are warranted to examine longer term use and potential benefits of DREAMIES for improving outcomes in infants receiving NICU care. This trial is registered on clinicaltrials.govNCT02744066.

Skin-to-Skin Care Is a Safe and Effective Comfort Measure for Infants Before and After Neonatal Cardiac Surgery

OBJECTIVES

To determine the effect of skin-to-skin care on stress, pain, behavioral organization, and physiologic stability of infants with critical congenital heart disease before and after neonatal cardiac surgery.

DESIGN

A baseline response-paired design was used, with infants acting as their own controls before, during, and after skin-to-skin care at two distinct time points: once in the preoperative period (T1) and once in the postoperative period (T2).

SETTING

Cardiac ICU and step-down unit in a large metropolitan freestanding children's hospital.

SUBJECTS

Convenience sample of 30 infants admitted preoperatively for critical congenital heart disease.

INTERVENTIONS

Eligible infants were placed into skin-to-skin care for 1 hour with their biological mothers once each at T1 and T2.

MEASUREMENTS AND MAIN RESULTS

Measurements of stress (salivary cortisol), pain and behavior state (COMFORT scale), and physiologic stability (vital signs) were assessed immediately before skin-to-skin care, 30 minutes into skin-to-skin care, and 30 minutes after skin-to-skin care ended.At both T1 and T2, infant pain scores were significantly decreased (p < 0.0001) and infants moved into a calmer behavior state (p < 0.0001) during skin-to-skin care as compared to baseline. At T1, infants also had significantly reduced heart rate (p = 0.002) and respiratory rate (p < 0.0001) and increased systolic blood pressure (p = 0.033) during skin-to-skin care. At both T1 and T2, infant cortisol remained stable and unchanged from pre-skin-to-skin care to during skin-to-skin care (p = 0.096 and p = 0.356, respectively), and significantly increased from during skin-to-skin care to post-skin-to-skin care (p = 0.001 and p = 0.023, respectively). Exploratory analysis revealed differences in cortisol reactivity for infants with higher baseline cortisol (> 0.3 μg/dL) versus lower (≤ 0.3 μg/dL) prior to skin-to-skin care. Infants with higher baseline cortisol at T2 experienced significantly reduced cortisol during skin-to-skin care (p = 0.025). No significant differences in demographics or baseline variables were found between infants in either group.

CONCLUSIONS

Skin-to-skin care is a low-cost, low-risk intervention that promotes comfort and supports physiologic stability in infants before and after neonatal cardiac surgery.

Nociception monitoring tools using autonomic tone changes for intraoperative analgesic guidance in pediatric patients

Nociception monitoring devices using changes in autonomic nervous system activity have been developed in numerous ways. Although there have been few studies conducted on children, compared to the relatively higher number of studies on adults, most of the nociception monitors in children, as in adults, appear to be more useful than the standard clinical practice that uses hemodynamic parameters in the evaluation and treatment of intraoperative nociception (pain) during general anesthesia. Particularly, when monitoring the surgical pleth index (SPI) in anesthetized children, the application of a new target range of SPI values (≤ 40) to the SPI monitoring criteria seems to be necessary for providing a more proper intraoperative analgesia. The analgesia nociception index (ANI) shows promising results in anesthetized adults, and recently, positive results along with cardiorespiratory coherence have been reported in pediatric patients. Newborn infant parasympathetic evaluation (NIPE) could be useful for providing adequate analgesia in newborns, infants, and children under 2 years of age in anesthetized or awake states. In cases of skin conductance and pupillometry, further studies are needed. Understanding the pros, cons, and limitations of these nociception monitoring tools will provide more effective and safe intraoperative analgesia to pediatric patients undergoing general anesthesia, and it may also help to plan and conduct promising research on the use of perioperative nociception monitoring in pediatric patients in the future.

Autonomic responses of premature newborns to body position and environmental noise in the neonatal intensive care unit

Objective

Evaluate the physiological and autonomic nervous system responses of premature newborns to body position and noise in the neonatal intensive care unit.

Methods

A quasi-experimental study. The autonomic nervous system of newborns was evaluated based on heart rate variability when the newborns were exposed to environmental noise and placed in different positions: supine without support, supine with manual restraint and prone.

Results

Fifty premature newborns were evaluated (gestational age: 32.6 ± 2.3 weeks; weight: 1816 ± 493g; and Brazelton sleep/awake level: 3 to 4). A positive correlation was found between environmental noise and sympathetic activity (R = 0.27, p = 0.04). The mean environmental noise was 53 ± 14dB. The heart rate was higher in the supine position than in the manual restraint and prone positions (148.7 ± 21.6, 141.9 ± 16 and 144 ± 13, respectively) (p = 0.001). Sympathetic activity, represented by a low frequency index, was higher in the supine position (p < 0.05) than in the other positions, and parasympathetic activity (high frequency, root mean square of the sum of differences between normal adjacent mean R-R interval and percentage of adjacent iRR that differed by more than 50ms) was higher in the prone position (p < 0.05) than in the other positions. The complexity of the autonomic adjustments (approximate entropy and sample entropy) was lower in the supine position than in the other positions.

Conclusion

The prone position and manual restraint position increased both parasympathetic activity and the complexity of autonomic adjustments in comparison to the supine position, even in the presence of higher environmental noise than the recommended level, which tends to increase sympathetic activity.

The biological embedding of neonatal stress exposure: A conceptual model describing the mechanisms of stress-induced neurodevelopmental impairment in preterm infants

The biological embedding of early life stress exposure may result in life-long neurodevelopmental impairment in preterm infants. Infants hospitalized in the neonatal intensive care unit are exposed to significant experiential, environmental, and physiologic stressors over the course of their extended hospitalization. Stress exposure during the sensitive period of brain development may alter biological processes, including functioning of the immune system, the autonomic nervous system, and the hypothalamic-pituitary-adrenal axis as well as gene expression. These alterations may subsequently affect brain structure and function. Changes to these processes may mediate the relationship between neonatal stress exposure and neurodevelopment in preterm infants and represent potential therapeutic targets to improve long-term outcomes. The purpose of this paper is to introduce a conceptual model, based on published research, that describes the mechanisms mediating stress exposure and neurodevelopment impairment in preterm infants and to provide the theoretical foundation on which to base future descriptive research, intervention studies, and clinical care.

A Knowledge-Based Approach to Automatic Detection of Equipment Alarm Sounds in a Neonatal Intensive Care Unit Environment

A large number of alarm sounds triggered by biomedical equipment occur frequently in the noisy environment of a neonatal intensive care unit (NICU) and play a key role in providing healthcare. In this paper, our work on the development of an automatic system for detection of acoustic alarms in that difficult environment is presented. Such automatic detection system is needed for the investigation of how a preterm infant reacts to auditory stimuli of the NICU environment and for an improved real-time patient monitoring. The approach presented in this paper consists of using the available knowledge about each alarm class in the design of the detection system. The information about the frequency structure is used in the feature extraction stage, and the time structure knowledge is incorporated at the post-processing stage. Several alternative methods are compared for feature extraction, modeling, and post-processing. The detection performance is evaluated with real data recorded in the NICU of the hospital, and by using both frame-level and period-level metrics. The experimental results show that the inclusion of both spectral and temporal information allows to improve the baseline detection performance by more than 60%.

Heightened sympathetic arousal is demonstrated by skin conductance responsivity to auditory stimuli in a small cohort of neonates with opiate withdrawal

To determine the effects of auditory stimulus on skin conductance (SC) in infants with severe neonatal abstinence syndrome (NAS) that required morphine treatment (MT) compared with NAS infants that did not require morphine treatment (non-MT). We prospectively enrolled opiate-exposed term infants without polysubstance exposure. Skin conductance responses to an auditory stimulus (ringing a bell for 3s) near the time of discharge were obtained. Skin conductance was measured before, during, and after the stimulus. Non-parametric tests were used to determine between group and within phase differences. Infants were off MT at the time of SC measurement in response to an auditory stimulus. In a 2-group comparison of MT vs. non-MT infants, there was significantly higher SC responsivity to an auditory stimulus (p <0.05) in the MT group as compared with the non-MT group near discharge. The mean +SE peak morphine dose was 0.85+0.20mg/kg/day in the MT group. The mean Length of Stay (LOS) was 32 vs. 7 (p <0.05) days respectively, for the MT vs. the non-MT group. Our preliminary data suggest that in infants with severe NAS symptoms, higher sympathetic arousal in response to an auditory stimulus persists at discharge, underscoring the need for ongoing evaluation and specialized care at home.

Physiological stress responses in infants at 29-32 weeks' postmenstrual age during clustered nursing cares and standardised neurobehavioural assessments

OBJECTIVE

To compare the physiological stress responses of infants born <30 weeks' gestational age when undergoing clustered nursing cares with standardised neurobehavioural assessments in neonatal nurseries.

DESIGN/METHODS

Thirty-four infants born <30 weeks' gestation were recruited from a tertiary neonatal intensive care unit. Heart rate (HR) and oxygen saturation were recorded during clustered nursing cares and during standardised neurobehavioural assessments (including the General Movements Assessment, Hammersmith Neonatal Neurological Examination and Premie-Neuro Assessment). Two assessors extracted HR and oxygen saturations at 5 s intervals, with HR instability defined either as tachycardia (HR >180 beats per minute (bpm)) or bradycardia (HR <100 bpm). Oxygen desaturations were defined as SpO₂<90%. Physiological stability was compared between nursing cares and neurobehavioural assessments using linear (for continuous outcomes) and logistic (HR instability and oxygen desaturation) regression.

RESULTS

Compared with clustered nursing cares HR was lower (mean difference -5.9 bpm; 95% CI -6.5 to 5.3; P<0.001) and oxygen saturation higher (mean difference 2.4%; 95% CI 2.1% to 2.6%; P<0.001) during standardised neurobehavioural assessments. Compared with clustered nursing cares neurobehavioural assessments were also associated with reduced odds of tachycardia (OR 0.44, 95% CI 0.22 to 0.86), HR instability (OR 0.43, 95% CI 0.22 to 0.85) and oxygen desaturation (OR 0.43, 95% CI 0.26 to 0.70).

CONCLUSIONS

Standardised neurobehavioural assessments are associated with less physiological stress than clustered nursing cares in infants aged 29-32 weeks' postmenstrual age, and are therefore possible without causing undue physiological disturbance in medically stable infants.

Skin conductance in neonates suffering from abstinence syndrome and unexposed newborns

The aims of this study were to compare the skin conductance (SC) of newborns with opiate-induced neonatal abstinence syndrome (NAS) to that of unexposed newborns and to evaluate the potential of SC readings to detect distress in the context of NAS objectively. The SC of 12 newborns with NAS and 12 unexposed newborns was measured at nine specific times during their first 6 weeks of life. The number of SC fluctuations per second (NSCF/s), the amplitude of SC fluctuation, and the mean level of SC were recorded and analyzed. The SC of newborns treated for symptoms of NAS differed significantly from the SC of unexposed newborns with regard to the NSCF/s (p = 0.04). With the mean level of SC, we observed an interaction between groups over time (p value for interaction = 0.02). With increasing postnatal age, we observed higher values in all three SC parameters.

CONCLUSION

The NSCF/s and the mean level of SC appear to be suitable to reflect the distress of newborns suffering from NAS. As it is known that the sensitivity of SC increases with the level of stress experienced, its potential to indicate elevated stress levels in infants with NAS should be investigated in future studies evaluating different therapy regimens.

WHAT IS KNOWN

• Skin conductance is a result of the filling of palmar and plantar sweat glands innervated by the sympathetic nervous system • Skin conductance can be used as a measure of stress and pain in newborns What is New: • Skin conductance of newborns with neonatal abstinence syndrome (NAS) differs significantly from the SC of non-substance-exposed newborns during the first 6 weeks of life • Skin conductance appears to reflect the increased distress of infants with NAS.

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.

Skin conductance at baseline and postheel lance reflects sympathetic activation in neonatal opiate withdrawal

AIM

Skin conductance (SC) provides an objective measure of autonomic system regulation through sympathetic-mediated filling of sweat glands. This study aimed to test the utility of SC to detect sympathetic activation in neonatal abstinence syndrome (NAS).

METHODS

Fourteen term (mean, SE: 38.8 ± 0.35 weeks gestational age) neonates with chronic prenatal opiate exposure were enrolled. SC (peaks/seconds and mean of peaks) was measured at baseline, during heel lance/squeeze (HLS) and recovery from HLS at 24-48 (mean 38) hours of life prior to treatment for NAS. Blinded coders with established reliability assessed neonates using the Modified Finnegan Neonatal Scoring System (MFNSS). Nonparametric tests were used to determine group differences, phase differences from baseline to HLS and HLS to recovery, and associations between MFNSS and SC measures.

RESULTS

Neonates that would later require morphine treatment for NAS (n = 6) had higher baseline SC mean of peaks than those that did not require treatment (n = 8) (p < 0.05). Moreover, there were unique phase differences between groups and SC positively correlated with MFNSS (p < 0.05).

CONCLUSION

SC provides early identification of NAS severity. However, a larger sample is needed to determine sensitivity and specificity of SC for early identification of NAS and treatment effectiveness.

Preterm infants' behaviors and skin conductance responses to nurse handling in the NICU

Stress response patterns are indicative of the neonate's unique ability to cope with environmental demands and can be evaluated through autonomic and behavioral response parameters.

OBJECTIVE

To characterize stress responses during tactile stimulation to standard nurse handling in the NICU, and their association with severity of illness in preterm infants.

METHODS

Thirty preterm neonates were studied at postnatal day 4-5 during standard nurse caregiving. Heart rate (HR), respiratory rate (RR), skin conductance responses per second (SCR/s), and NIDCAP® stress behaviors were recorded before and during care. Non-parametric tests were used to assess differences from before to during care. Pearson's correlations were used to determine the association of biological and behavioral variables to the score for neonatal acute physiology (SNAP), a severity of illness index.

RESULTS

HR, RR, SCR/s and NIDCAP® behaviors (motor and attentional cues, and ability to self-console) increased from before to during the care (p < 0.01). NIDCAP® behaviors showed a significant negative association to the SNAP score (R = -0.45, p < 0.05).

CONCLUSIONS

HR, RR, SCR/s and NIDCAP® behaviors significantly increased during care. NIDCAP® stress behaviors were influenced by the severity of illness of the infant, while SCR/s was not influenced by severity of illness.

Does skin-to-skin contact reduce stress during diaper change in preterm infants?

BACKGROUND

Skin-to-skin contact reduces pain response in preterm infants subjected to minor painful procedures, such as heel lance. Diaper change is a procedure performed several times daily in hospitalized preterm infants. Routine care giving tasks such as diaper change may be stressful for the infant.

AIMS

The purpose of this study was to investigate whether diaper change induces stress and if skin-to-skin contact could reduce such stress, measured by changes in skin conductance.

STUDY DESIGN

This was a randomized crossover pilot study in 19 preterm infants with gestational age between 28 and 34 weeks. The diaper change procedure was done twice in each infant, once during skin-to-skin contact, and once in incubator or bed with the mother present.

OUTCOME MEASURES

During diaper change heart rate (HR), peripheral oxygen saturation (SpO2), and changes in skin conductance (SC) peaks per sec, using the Skin Conductance Algesimeter (SCA), were registered.

RESULTS

The mean SC peaks/sec increased/decreased significantly under/after change of diapers which thereby underpins that this is a stressful procedure for the preterm infant. Skin-to-skin contact (SSC) entails significantly lower stress levels (p<0.05) compared to diaper changed in an incubator/bed measured by the SCA.

CONCLUSIONS

Diaper change is a stressful procedure for preterm infants and may be ameliorated by skin-to-skin contact.

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.

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.

Safe sound exposure in the fetus and preterm infant

Exposure to sound can have beneficial and harmful effects on the developing fetus and preterm infant. Although recommendations for safe exposure to sound have existed for more than three decades, reports indicate that these recommendations are not being followed. Recommendations are made to promote attention to the problem of unsafe exposure to sound in early development, and a multidisciplinary team, including representatives from disciplines beyond medicine and nursing, must redress safe exposure.

Sound and vibration: effects on infants' heart rate and heart rate variability during neonatal transport

AIM

To measure the effect of sound and whole-body vibration on infants' heart rate and heart rate variability during ground and air ambulance transport.

METHODS

Sixteen infants were transported by air ambulance with ground ambulance transport to and from the airports. Whole-body vibration and sound levels were recorded and heart parameters were obtained by ECG signal.

RESULTS

Sound and whole-body vibration levels exceeded the recommended limits. Mean whole-body vibration and sound levels were 0.19 m/s(2) and 73 dBA, respectively. Higher whole-body vibration was associated with a lower heart rate (p < 0.05), and higher sound level was linked to a higher heart rate (p = 0.05). The heart rate variability was significantly higher at the end of the transport than at the beginning (p < 0.01). Poorer physiological status was associated with lower heart rate variability (p < 0.001) and a lower heart rate (p < 0.01). Infants wearing earmuffs had a lower heart rate (p < 0.05).

CONCLUSIONS

Sound and whole-body vibration during neonatal transport exceed recommended levels for adults, and sound seem to have a more stressful effect on the infant than vibrations. Infants should wear earmuffs during neonatal transport because of the stress-reducing effect.