Sound spectrographic analysis of pain cry in preterm infants

Noise phenomena in distress cries of term and very preterm infants at term-equivalent age

BACKGROUND AND AIM

To examine whether the noise components in distress cries of term infants differed from very preterm infants whose cries were collected at a comparable "corrected" gestational age.

METHODS

Distress cries were collected from 20 term and 20 preterm infants. The cries were acoustically examined for the occurrence of aperiodic phonatory behavior within and across moments of crying.

RESULTS

The findings indicated no significant differences between term and preterm infants at term age in the occurrence of noise.

CONCLUSIONS

Distress cries of both term and term-equivalent preterm infants appear to contain high instances of phonatory noise. The high arousal associated with distress crying and associated increase in subglottal pressure appeared to influence both term and term-equivalent preterm infants similarly.

Acoustic Correlates and Adult Perceptions of Distress in Infant Speech-Like Vocalizations and Cries

Prior research has not evaluated acoustic features contributing to perception of human infant vocal distress or lack thereof on a continuum. The present research evaluates perception of infant vocalizations along a continuum ranging from the most prototypical intensely distressful cry sounds ("wails") to the most prototypical of infant sounds that typically express no distress (non-distress "vocants"). Wails are deemed little if at all related to speech while vocants are taken to be clear precursors to speech. We selected prototypical exemplars of utterances representing the whole continuum from 0 and 1 month-olds. In this initial study of the continuum, our goals are to determine (1) listener agreement on level of vocal distress across the continuum, (2) acoustic parameters predicting ratings of distress, (3) the extent to which individual listeners maintain or change their acoustic criteria for distress judgments across the study, (4) the extent to which different listeners use similar or different acoustic criteria to make judgments, and (5) the role of short-term experience among the listeners in judgments of infant vocalization distress. Results indicated that (1) both inter-rater and intra-rater listener agreement on degree of vocal distress was high, (2) the best predictors of vocal distress were number of vibratory regimes within utterances, utterance duration, spectral ratio (spectral concentration) in vibratory regimes within utterances, and mean pitch, (3) individual listeners significantly modified their acoustic criteria for distress judgments across the 10 trial blocks, (4) different listeners, while showing overall similarities in ratings of the 42 stimuli, also showed significant differences in acoustic criteria used in assigning the ratings of vocal distress, and (5) listeners who were both experienced and inexperienced in infant vocalizations coding showed high agreement in rating level of distress, but differed in the extent to which they relied on the different acoustic cues in making the ratings. The study provides clearer characterization of vocal distress expression in infants based on acoustic parameters and a new perspective on active adult perception of infant vocalizations. The results also highlight the importance of vibratory regime segmentation and analysis in acoustically based research on infant vocalizations and their perception.

Video and audio processing in paediatrics: a review

OBJECTIVE

Video and sound acquisition and processing technologies have seen great improvements in recent decades, with many applications in the biomedical area. The aim of this paper is to review the overall state of the art of advances within these topics in paediatrics and to evaluate their potential application for monitoring in the neonatal intensive care unit (NICU).

APPROACH

For this purpose, more than 150 papers dealing with video and audio processing were reviewed. For both topics, clinical applications are described according to the considered cohorts-full-term newborns, infants and toddlers or preterm newborns. Then, processing methods are presented, in terms of data acquisition, feature extraction and characterization.

MAIN RESULTS

The paper first focuses on the exploitation of video recordings; these began to be automatically processed in the 2000s and we show that they have mainly been used to characterize infant motion. Other applications, including respiration and heart rate estimation and facial analysis, are also presented. Audio processing is then reviewed, with a focus on the analysis of crying. The first studies in this field focused on induced-pain cries and the newest ones deal with spontaneous cries; the analyses are mainly based on frequency features. Then, some papers dealing with non-cry signals are also discussed.

SIGNIFICANCE

Finally, we show that even if recent improvements in digital video and signal processing allow for increased automation of processing, the context of the NICU makes a fully automated analysis of long recordings problematic. A few proposals for overcoming some of the limitations are given.

Fundamental Frequency Variation of Neonatal Spontaneous Crying Predicts Language Acquisition in Preterm and Term Infants

Spontaneous cries of infants exhibit rich melodic features (i.e., time variation of fundamental frequency [F0 ]) even during the neonatal period, and the development of these characteristics might provide an essential base for later expressive prosody in language. However, little is known about the melodic features of spontaneous cries in preterm infants, who have a higher risk of later language-related problems. Thus, the present study investigated how preterm birth influenced melodic features of spontaneous crying at term-equivalent age as well as how these melodic features related to language outcomes at 18 months of corrected age in preterm and term infants. At term, moderate-to-late preterm (MLP) infants showed spontaneous cries with significantly higher F0 variation and melody complexity than term infants, while there were no significant differences between very preterm (VP) and term infants. Furthermore, larger F0 variation within cry series at term was significantly related to better language and cognitive outcomes, particularly expressive language skills, at 18 months. On the other hand, no other melodic features at term predicted any developmental outcomes at 18 months. The present results suggest that the additional postnatal vocal experience of MLP preterm infants increased F0 variation and the complexity of spontaneous cries at term. Additionally, the increases in F0 variation may partly reflect the development of voluntary vocal control, which, in turn, contributes to expressive language in infancy.

Utilizing Infant Cry Acoustics to Determine Gestational Age

OBJECTIVES/HYPOTHESIS

The date of last menstruation period and ultrasonography are the most commonly used methods to determine gestational age (GA). However, if these data are not clear, some scoring systems performed after birth can be used. New Ballard Score (NBS) is a commonly used method in estimation of GA. Cry sound may reflect the developmental integrity of the infant. The aim of this study was to evaluate the connection between the infants' GA and some acoustic parameters of the infant cry.

STUDY DESIGN

A prospective single-blind study was carried out.

METHODS

In this prospective study, medically stable infants without any congenital craniofacial anomalies were evaluated. During routine blood sampling, cry sounds were recorded and acoustic analysis was performed. Step-by-step multiple linear regression analysis was performed.

RESULTS

The data of 116 infants (57 female, 59 male) with the known GA (34.6 ± 3.8 weeks) were evaluated and with Apgar score of higher than 5. The real GA was significantly and well correlated with the estimated GA according to the NBS, F0, Int, Jitt, and latency parameters. The obtained stepwise linear regression analysis model was formulized as GA=(31.169) - (0.020 × F0)+(0.286 × GA according to NBS) - (0.003 × Latency)+(0.108 × Int) - (0.367 × Jitt). The real GA could be determined with a ratio of 91.7% using this model.

CONCLUSIONS

We have determined that after addition of F0, Int, Jitt, and latency to NBS, the power of GA estimation would be increased. This simple formula can be used to determine GA in clinical practice but validity of such prediction formulas needs to be further tested.

Methylation of the Glucocorticoid Receptor (NR3C1) in Placenta Is Associated with Infant Cry Acoustics

Epigenetic mechanisms regulating expression of the glucocorticoid receptor gene (NR3C1) promoter may influence behavioral and biological aspects of stress response in human infants. Acoustic features of infant crying are an indicator of neurobehavioral and neurological status not yet investigated in relation to epigenetic mechanisms. We examined NR3C1 methylation in placental tissue from a series of 120 healthy newborn infants in relation to a detailed set of acoustic features extracted from newborn infant cries. We identified significant associations of NR3C1 methylation with energy variation in infants' cries as well as with the presence of very high fundamental frequency in cry utterances. The presence of high fundamental frequency in cry (above 1 kHz) has been linked to poor vocal tract control, poor regulation of stress response, and may be an indicator or poor neurobehavioral integrity. Thus, these results add to evidence linking epigenetic alteration of the NR3C1 gene in the placenta to neurodevelopmental features in infants.

Associations between respiratory arrhythmia and fundamental frequency of spontaneous crying in preterm and term infants at term-equivalent age

This study investigated whether lower vagal function in preterm infants is associated with increased fundamental frequency (F₀; frequency of vocal fold vibration) of their spontaneous cries. We assessed respiratory sinus arrhythmia (RSA) during quiet sleep as a measure of vagal function, and its relationship with the F₀ of spontaneous cries in healthy preterm and term infants at term‐equivalent age. The results showed that preterm infants have significantly lower RSA, and higher overall F₀ than term infants. Moreover, lower RSA was associated with higher overall F₀ in preterm infants, whereas higher RSA was positively associated with mean and maximum F₀, and a larger F₀ range in term infants. These results suggest that individual differences in vagal function may be associated with the F₀ of spontaneous cries via modulation of vocal fold tension in infants at an early developmental stage. © 2016 The Authors. Developmental Psychobiology Published by Wiley Periodicals, Inc. Dev Psychobiol 58:724–733, 2016.

Preterm birth is associated with an increased fundamental frequency of spontaneous crying in human infants at term-equivalent age

Human infant crying has been researched as a non-invasive tool for assessing neurophysiological states at an early developmental stage. Little is known about the acoustic features of spontaneous cries in preterm infants, although their pain-induced cries are at a higher fundamental frequency (F₀) before term-equivalent age. In this study, we investigated the effects of gestational age, body size at recording and intrauterine growth retardation (IUGR) on the F₀ of spontaneous cries in healthy preterm and full-term infants at term-equivalent age. We found that shorter gestational age was significantly associated with higher F₀, although neither smaller body size at recording nor IUGR was related to increased F₀ in preterm infants. These findings suggest that the increased F₀ of spontaneous cries is not caused by their smaller body size, but instead might be caused by more complicated neurophysiological states owing to their different intrauterine and extrauterine experiences.

High-resolution cry analysis in preterm newborn infants

Infant monitoring is a common procedure in clinical practice in neonatal critical care units. A number of vital functions are monitored, such as heart beat, breathing, blood flow, etc. Specifically, preterm and/or low-birth-weight infants often present respiratory problems that require monitoring. These may range from insufficient ventilation to apnoea. One of the most common events that may affect the respiratory flow is crying, a physiological action made by the infant to communicate and draw attention, but, for a preterm infant, this action requires great effort, which may cause distress and even may have an adverse impact on blood oxygenation. Acoustic analysis of newborn infant cry is thus of importance, since it is related to other basic neuro-physiological parameters. Being easy to perform, cheap and completely non-invasive, it can be successfully applied in many circumstances. The newborn infant cry is characterised by very high fundamental frequency (F(0)) and resonance frequency (RFs) values, with abrupt changes and voiced/unvoiced features of very short duration in a single utterance. To deal with such signals, a new user-friendly software tool has been developed, that allows robust tracking of main acoustic parameters on very short and time-varying signal frames. The software developed provides the user with a high-resolution picture of the cry signal characteristics.

Analgesic properties of oral sucrose during routine immunizations at 2 and 4 months of age

OBJECTIVE

The purpose of this work was to evaluate the analgesic properties of oral sucrose during routine immunizations in infants at 2 and 4 months of age.

PATIENTS AND METHODS

A prospective, randomized, placebo-controlled clinical trial was conducted at a pediatric ambulatory care clinic. One-hundred healthy term infants scheduled to receive routine immunizations were recruited, randomly stratified into 2- or 4-month study groups, and further randomly assigned to receive 24% oral sucrose and pacifier or the sterile water control solution. The study preparations were administered 2 minutes before the combined diphtheria-tetanus-acellular pertussis, inactivated polio vaccine, and hepatitis B vaccine. Haemophilus influenzae type b vaccine was administered 3 minutes after the combined injection, followed by the pneumococcal conjugate vaccine, 2 minutes after the H. influenzae type b injection. The University of Wisconsin Children's Hospital Pain Scale measured serial acute pain responses for the treatment and control groups at baseline and 2, 5, 7, and 9 minutes after solution administration. Repeated-measures analysis of variance examined between-group differences and within-subject variability of treatment effect on overall pain scores.

RESULTS

Two- and 4-month-old infants receiving oral sucrose (n = 38) displayed reductions in pain scores 2 minutes after solution administration compared with 2- and 4-month-old infants in the placebo group (n = 45). Between-group comparisons for the oral sucrose and placebo groups showed lower pain responses at 5, 7, and 9 minutes after solution administration. The oral sucrose and placebo groups demonstrated their highest mean pain score at 7 minutes, with a mean pain score of 3.8 and 4.8, respectively. At 9 minutes, the placebo group had a mean pain score of 2.91 whereas the mean pain score for the oral sucrose group returned to near baseline, reflecting a 78.5% difference in mean pain score (oral sucrose - placebo) relative to the placebo mean.

CONCLUSIONS

Oral sucrose is an effective, easy-to-administer, short-acting analgesic for use during routine immunizations.

Is the ABC pain scale reliable for premature babies?

AIM

We recently developed the ABC scale to assess pain in term newborns. The aim of the present study was to assess the reliability of the scale in preterm babies.

MATERIAL AND METHODS

The scale consists of three cry parameters: (a) pitch of the first cry, (b) rhythmicity of the bout of crying and (c) cry constancy. Changes in these parameters were previously found to distinguish medium and high levels of pain as evaluated by spectral analysis of crying. We enrolled 72 babies to perform the steps usually requested to validate a scale, namely the study of the concurrent validity, specificity and sensibility. Moreover, we assessed the interjudge reliability and the clinical utility and ease of the scale.

RESULTS

A good correlation (r = 0.68; r(2)= 0.45; p < 0.0001) was found between scores obtained with the ABC scale and the premature infant pain profile (PIPP) scale, demonstrating a good concurrent validity. The scale also showed good sensitivity and specificity (we found statistically significant differences between mean values of scores obtained in babies who underwent pain and babies who underwent non-painful stimulus.) Interobserver reliability was good: Cohen's kappa = 0.7.

CONCLUSION

The good correlation between the two scales shows that the ABC scale is also reliable for premature babies.

Acoustic quality of cry in very-low-birth-weight infants at the age of 1 1/2 years

BACKGROUND

Infant cry characteristics reflect the integrity of the central nervous system. Previous studies have shown that preterm infants and infants with neurological conditions have different cry characteristics such as fundamental frequency compared to healthy full-term infants. Cry characteristics of preterm infants after the first year of life have not been studied.

AIMS

The aim of this study was to assess the quality of cry in 1 1/2-year-old very-low-birth-weight infants (VLBWI, < or =1500 g at birth). STUDY SUBJECTS AND DESIGN: Study groups included 21 VLBWI and 25 healthy full-term controls. Thirty seconds of pain cry after vaccination was recorded at well-baby clinics. The first cry utterance was acoustically analyzed using Praat software. The quality of cry was compared between the groups. In addition, the association of cry quality to patient characteristics, to developmental outcome, and to findings in brain imaging studies of the VLBWI was studied.

RESULTS

The cry response was elicited in 20 of the 21 VLBWI and in 20 out of 25 full-term infants. VLBWI had higher minimum fundamental frequency and fourth formant values. Patient characteristics that were associated with cry quality were 5-min Apgar scores, the occurrence of bronchopulmonary dysplasia, Bayley Psychomotor Index scores at 12 months, and current weight and head circumference.

CONCLUSIONS

Differences found between the study groups were not explained primarily by brain pathology or by patient characteristics, so it seems that prematurity has an impact on cry quality still at the age of 1 1/2 years.

Valor e variações da freqüência fundamental no choro de dor de recém-nascidos

OBJETIVO: estudar o valor da freqüência fundamental e suas variações presentes no choro de dor de recém-nascidos. MÉTODOS: foram gravadas as emissões de 111 recém-nascidos de termo e saudáveis, com idade de 24 a 72 horas durante procedimento da punção venosa periférica. A análise acústica foi realizada por meio dos softwares VOXMETRIA 1.1 com extração do valor da freqüência fundamental e GRAM 5.7 para verificar a ocorrência de variações da freqüência fundamental como quebras, bitonalidade e freqüência hiperaguda. A escala de dor NIPS foi realizada no momento da punção. A análise estatística é descritiva com extração dos valores de média, desvio-padrão e freqüência de ocorrência dos eventos. RESULTADOS: os recém-nascidos apresentaram 100% de suas emissões com variações de freqüência, ou seja, quebras e bitonalidade. A freqüência hiperaguda foi encontrada em 34,2% dos recém-nascidos. CONCLUSÃO: por meio do choro, o recém-nascido comunica sua dor. A emissão de dor do recém-nascido é tensa e estridente, com freqüência fundamental aguda e variações encontradas no traçado espectrográfico, como quebras, bitonalidade e freqüência hiperaguda. Tais características são importantes para chamar a atenção do adulto no pronto atendimento ao recém-nascido e auxiliar na avaliação de dor durante um procedimento.

Determining behavioural and physiological responses to pain in infants at risk for neurological impairment

Multiple researchers have validated indicators and measures of infant pain. However, infants at risk for neurologic impairment (NI) have been under studied. Therefore, whether their pain responses are similar to those of other infants is unknown. Pain responses to heel lance from 149 neonates (GA>25-40 weeks) from 3 Canadian Neonatal Intensive Care units at high (Cohort A, n=54), moderate (Cohort B, n=45) and low (Cohort C, n=50) risk for NI were compared in a prospective observational cohort study. A significant Cohort by Phase interaction for total facial action (F(6,409)=3.50, p=0.0022) and 4 individual facial actions existed; with Cohort C demonstrating the most facial action. A significant Phase effect existed for increased maximum Heart Rate (F(3,431)=58.1, p=0.001), minimum Heart Rate (F(3,431)=78.7, p=0.001), maximum Oxygen saturation (F(3,425)=47.6, p=0.001), and minimum oxygen saturation (F(3,425)=12.2, p=0.001) with no Cohort differences. Cohort B had significantly higher minimum (F(2,79)=3.71, p=0.029), and mean (F(2,79)=4.04, p=0.021) fundamental cry frequencies. A significant Phase effect for low/high frequency Heart Rate Variability (HRV) ratio (F(2,216)=4.97, p=0.008) was found with the greatest decrease in Cohort A. Significant Cohort by Phase interactions existed for low and high frequency HRV. All infants responded to the most painful phase of the heel lance; however, infants at moderate and highest risk for NI exhibited decreased responses in some indicators.

Neonatal pain analyzer: development and validation

We developed a pain analyzer (ABC analyzer) to perform automatic acoustic analysis of neonatal crying and to provide an objective estimate of neonatal pain. The ABC analyzer uses a validated pain scale (ABC scale) based on three acoustic parameters: pitch frequency, normalized RMS amplitude, and presence of a characteristic frequency- and amplitude-modulated crying feature, defined as "siren cry". Here we assessed the reliability of the analyzer. We enrolled 57 healthy neonates. Each baby was recorded with a video camera during heel prick. Pain intensity was evaluated using a validated scale [Douleur Aigue du Nouveau-Né (DAN) scale] and the analyzer and the two scores were compared. We found a statistically significant concordance between the DAN score and ABC analyzer score (p < 0.0001). The ABC analyser is a novel approach to cry analysis that should now have its properties carefully evaluated in a series of studies, just as is necessary in the development of any other pain measurement tool.

Identification of pain indicators for infants at risk for neurological impairment: a Delphi consensus study

BACKGROUND

A number of infant pain measures have been developed over the past 15 years incorporating behavioural and physiologic indicators; however, no reliable or valid measure exists for infants who are at risk for neurological impairments (NI). The objective of this study was to establish consensus about which behavioural, physiologic and contextual indicators best characterize pain in infants at high, moderate and low levels of risk for NI.

METHODS

A 39- item, self-administered electronic survey that included infant physiologic, behavioral and contextual pain indicators was used in a two round Delphi consensus exercise. Fourteen pediatric pain experts were polled individually and anonymously on the importance and usefulness of the pain indicators for the 3 differing levels of risk for NI.

RESULTS

The strength of agreement between expert raters was moderate in Round 1 and fair in Round 2. In general, pain indicators with the highest concordance for all three groups were brow bulge, facial grimace, eye squeeze, and inconsolability. Increased heart rate from baseline in the moderate and severe groups demonstrated high concordance. In the severe risk group, fluctuations in heart rate and reduced oxygen saturation were also highly rated.

CONCLUSION

These data constitute the first step in contributing to the development and validation of a pain measure for infants at risk for NI. In future research, we will integrate these findings with the opinions of (a) health care providers about the importance and usefulness of infant pain indicators and (b) the pain responses of infants at mild, moderate and high risk for NI.

Development and validation of the ABC pain scale for healthy full-term babies

AIM

We developed and validated a pain scale (ABC scale) for term babies based on acoustic features of crying.

METHODS

The scale consisted of three different cry parameters: (a) pitch of the first cry; (b) rhythmicity of the crying bout; (c) constancy of crying intensity. These parameters were previously found to distinguish between medium and high levels of pain measured by spectral analysis of crying. We validated the scale using healthy term babies undergoing routine heel prick. Concurrent validity was assessed comparing pain values obtained with our scale with those obtained with another pain scale; this relationship was also used to assess the sensitivity of the scale. To assess specificity we compared the ABC scores during a painful event (heel prick) with two non-painful events (preliminary phase of prick in the same group of babies, and heel prick with analgesia in another group).

RESULTS

Specificity: (a) analgesic/non-analgesic comparison, p < 0.0001; (b) pain/sham comparison, p < 0.0001). Sensitivity: a high correlation between scores of the ABC scale and the Douleur Aigue du Nouveau-Né scale indicates good sensitivity. Concurrent validity: Spearman rho = 0.91. Internal consistency: Cronbach's alpha = 0.76. Inter-rater reliability: Cohen's kappa for multiple raters = 0.83. Intra-rater reliability: Cohen's kappa = 0.85. Practicality: All nurses who used it scored the scale as "good".

CONCLUSION

The ABC scale proved to be simple and reliable for assessing pain in healthy, non-intubated term newborns.

Can cry in the newborn be used as an assessment of pain?

Pain in the neonate is a complex subject. The assessment of pain should be simple and clinically usable. So far, the scales that have been used to assess pain are too time consuming and complex. The analysis of cry in a simple manner, as described in this issue of Acta Paediatrica by Bellieni et al., could be used in a simple and effective way at the bedside.

CONCLUSION

Since sick and premature newborns are not studied, the scale needs further confirmation.

Assessment of infant cry: acoustic cry analysis and parental perception

Infant crying signals distress to potential caretakers who can alleviate the aversive conditions that gave rise to the cry. The cry signal results from coordination among several brain regions that control respiration and vocal cord vibration from which the cry sounds are produced. Previous work has shown a relationship between acoustic characteristics of the cry and diagnoses related to neurological damage, SIDS, prematurity, medical conditions, and substance exposure during pregnancy. Thus, assessment of infant cry provides a window into the neurological and medical status of the infant. Assessment of infant cry is brief and noninvasive and requires recording equipment and a standardized stimulus to elicit a pain cry. The typical protocol involves 30 seconds of crying from a single application of the stimulus. The recorded cry is submitted to an automated computer analysis system that digitizes the cry and either presents a digital spectrogram of the cry or calculates measures of cry characteristics. The most common interpretation of cry measures is based on deviations from typical cry characteristics. Another approach evaluates the pattern across cry characteristics suggesting arousal or under-arousal or difficult temperament. Infants with abnormal cries should be referred for a full neurological evaluation. The second function of crying--to elicit caretaking--involves parent perception of the infant's needs. Typically, parents are sensitive to deviations in cry characteristics, but their perception can be altered by factors in themselves (e.g., depression) or in the context (e.g., culture). The potential for cry assessment is largely untapped. Infant crying and parental response is the first language of the new dyadic relationship. Deviations in the signal and/or misunderstanding the message can compromise infant care, parental effectiveness, and undermine the budding relationship. (c) 2005 Wiley-Liss, Inc. MRDD Research Reviews 2005;11:83-93.

Foundations of knowledge about neonatal pain

This review appraises trends in the neonatal pain research literature. We searched the literature produced from 1941 to 2001. Information about the model of pain, measures of pain, design, and sample characteristics is included for each citation. Gaps in knowledge are attributed to specific conceptual and methodological problems, including the lack of basic knowledge about pain behavior, over-reliance on an invasive short-term pain model, pain measurement issues, and lack of knowledge about confounders. Ethological research methods could be used to expand basic knowledge about newborn pain.

Cry features reflect pain intensity in term newborns: an alarm threshold

The purpose of this study was to assess differences in sound spectra of crying of term newborns in relation to different pain levels. Fifty-seven consecutively born neonates were evaluated during heel-prick performed with different analgesic techniques. Crying was recorded and frequency spectrograms analyzed. A pain score on the DAN (Douleur Aiguë du Nouveau-né) scale was assigned to each baby after the sampling. Three features were considered and correlated with the corresponding DAN scores: 1) whole spectral form; 2) the fundamental frequency of the first cry emitted (F0); and 3) root mean square sound pressure normalized to its maximum. After emission of the first cry, babies with DAN scores >8, but not with DAN scores < or =8 (p < 0.001), showed a pattern ("siren cry") characterized by a sequence of almost identical cries with a period on the order of 1 s. A statistically significant correlation was found between root mean square (r2 = 89%, p < 0.01), F0 (r2 = 32%, p < 0.05), siren cry (r2 = 68.2%, p = 0.02), and DAN score. F0 did not show significant correlation with DAN score in the subset of neonates with DAN scores < or =8 (r2 = 1.4%, p = 0.94), and babies with a DAN score >8 had a significantly higher F0 than those with lower DAN scores (p = 0.016). An alarm threshold exists between high (>8) and low (< or =8) DAN scores: crying has different features in these two groups. When pain exceeds a DAN score of 8, usually a first cry at a high pitch is emitted, followed by the siren cry, with a sound level maintained near its maximum.

Procedural pain in newborns at risk for neurologic impairment

In the past decade, our knowledge of pain in newborn infants has advanced considerably. However, infants at significant risk for neurologic impairment (NI) have been systematically excluded from almost all research on pain in neonates. The objectives of this study were to compare: (a). the nature, frequency and prevalence of painful procedures, (b). analgesics and sedatives administered, and (c). the relationship between painful procedures and analgesia for neonates at risk for NI. One hundred and ninety-four infants at high (cohort A, n=67), moderate (cohort B, n=59) and low (cohort C, n=68) risk for NI from two tertiary level Neonatal Intensive Care Unit's in Canada were included in a retrospective cohort study on the first 7 days of life. Data were collected from medical records and analyzed using chi-square, ANOVA and regression approaches. All cohorts had a mean of >10 painful procedures per day during the first 2 days of life. There was an interaction effect between cohort group and day of life (F(5,188)=2.13, P<0.06) with cohort A having significantly more painful procedures on day 1 (F(2,191)=4.79, P<0.009). There was no statistical difference in the number of infants who received continuous infusion (F(2,20)=1.9, P=0.13) or bolus (F(2,20)=1.3, P=0.25) opioids or sedatives (F(2,20)=0.45, P=0.84) by cohort over the 7 day period. There was a statistical difference in bolus opioid administration for days 1 (P<0.05) and 2 (P<0.001) with less than 10% of infants in cohort A receiving bolus opioids compared with approximately 22-33% of infants in cohorts B and C. There was a statistically significant correlation between painful procedures and analgesic use (r=0.29, P<0.001), although significant associations existed for cohorts B and C only. The number of painful procedures and study site primarily accounted for the variance (61% in cohort B and 35% in cohort C) in analgesic use, while in cohort A, only study site contributed to the variance (16%). Neonates at the highest risk for NI had the greatest number of painful procedures and the least amount of opioids administered during the first day of life. There was no relationship between painful procedures and analgesic use in this group. As these infants are vulnerable to pain and its consequences, the rational underlying health professional strategies regarding painful procedures and analgesic use for procedural pain in this population urgently awaits exploration.

Phonation in the newborn, infant cry

Sound spectrographic studies have shown that the crying of newborn infants has a fundamental frequency of about 400-600 cycles per second, and mostly a slightly rising-falling melody contour. In sick infants, and especially those with diseases affecting the central nervous system, abnormal cry characteristics occur. The fundamental frequency has been increased, and the melody contour is unstable. Various cry characteristics, which rarely occur in cries of healthy infants, are more often present in cries of the sick ones. Studies of cries in newborn infants have been especially aimed to determine whether cry analysis could be successful in diagnostics and in the early detection of the infant at risk for developmental difficulties.

Multidimensional pain assessment in premature neonates: a pilot study

OBJECTIVE

To describe the physiologic and behavioral responses of premature neonates to a painful stimulus.

DESIGN

Descriptive.

SETTING

Secondary-level neonatal unit in a large metropolitan university teaching hospital.

PARTICIPANTS

Forty neonates between 32 and 34 weeks' postconceptual age and less than 5 days' postnatal age.

MAIN OUTCOME MEASURES

Physiologic (heart rate, oxygen saturation, and intracranial pressure) and behavioral (facial expression and cry) outcomes observed during a routine heel stick.

RESULTS

Physiologic responses were significant, but were not specific to pain. Behavioral responses were more promising and indicated that premature neonates were capable of responding in a manner similar to full-term neonates.

CONCLUSIONS

Premature neonates are capable of expressing their pain in a manner similar to healthy, full-term neonates. Factors that alter this response were not clearly delineated. Further research is needed to determine more precise patterns of response in this age group.

[Acute pain in children and its treatment]

Pain in paediatrics has long been underestimated. The numerous scientific studies carried out during the last decade show that its existence can no longer be doubted: in fact, pain already exists during the neonatal period, and probably throughout the last trimester of gestation as well. Pain pathways mature during the embryonic period and peripheral receptors develop between the 7th and 20th week. A-delta and C fibers, as well as spinal roots and nerves, are completely differentiated before the end of the second month. The development of specific neurotransmitters and thalamic and cortical dendritic branching occurs later on; it is well enough developed to allow perception of painful stimuli (slow or protopathic component) from the beginning of the foetal period onwards. The discriminative rapid component develops in parallel to myelinisation, and the psycho-affective component, which requires a long and complex learning process, will not be fully operative until the end of puberty. Assessing pain, already a difficult task in the adult, is all the more so in children because of lesser verbal communicative capabilities, difficulty in handling abstract concepts, lack of experience of painful stimuli to make comparisons, and ignorance of their body image. In the very young child, diagnosing pain relies on suggestive circumstances, and an altered behaviour, knowing that no one symptom in pathognomonic. As the child grows up, methods for self-assessment of pain become usable, such as coloured scales and simplified verbal scales. However, behavioural tests remain the mainstay until the prepubertal period. The treatment of acute pain requires a reasoned approach which takes into account the state of the child, that of the aetiological investigations, the likely course of the lesions, as well as the patient's analgesic requirements. Therapeutic means do not differ from those for adult patients; however, the differences of distribution of body water, the small possibilities of linking with plasma proteins, and limited conjugation with glucuronate must be taken into account, especially during the first months of life. Local and regional anaesthetic block techniques are of great interest in elective and emergency surgery, as well as in trauma: they can provide complete pain relief, mostly without having any effect on the patient's physiological state (haemodynamics and consciousness). Peripherally acting analgesic agents, which are well supported on the whole, as well as co-analgesics, have a great part to play, although there are less drugs available than for adults. The most useful ones are paracetamol, followed by the salicylates, propionic acid derivatives and non steroid anti-inflammatory drugs.(ABSTRACT TRUNCATED AT 400 WORDS)

Pain in newborns and prematures: current practice and knowledge

No unambiguous answer can be given as to whether newborns are able to feel pain similar to that experienced by older children and adults. However, there are several lines of evidence--anatomical, physiological and behavioral--which substantiate the possible presence of distressing nociceptive activity in the full-term and preterm neonate. Although the efficacy and safety of anesthesia in newborns and prematures has repeatedly been demonstrated, there are still numerous recommendations and current practices, based on antiquated theories, that withhold adequate medications from neonates during surgery. Even if the emotional and cognitive aspects of nociception in the newborn remain a subject of speculation giving rise to philosophical discussions as to the correct terminology, it is the mandate of newborns' physicians to provide the best possible therapy to their patients and to protect them from distress, unease and presumptive pain.

Evaluating a child's pain

Much recent attention has focused on the development and refinement of pain measures, as well as on the use of more effective pain control methods for infants, children, and adolescents. This article reviews the primary categories of pediatric pain measures, with a specific focus on the selection of the most appropriate behavioral, physiologic, or subjective method for assessing a child's pain. The optimum pain measure depends on the age and cognitive level of a child, the type of pain experienced, and the situation in which the pain occurs. While no single measure is adequate for all children for all types of acute, recurrent, and chronic pain, it is possible to choose practical, valid, and reliable methods for evaluating any child's pain experience.

An assessment of children's pain: a review of behavioral, physiological and direct scaling techniques

Research on the assessment and management of pain in infants and children has increased dramatically, with the consequence that a wide variety of behavioral, physiological, and psychological methods are now available for measuring pediatric pain. Although the criteria for a pain measure for children are identical to those required for any measuring instrument, special problems exist in pediatric pain measurement because the influence of developmental factors, previous pain experience, and parental attitudes on children's perceptions and expressions of pain is not known. This article reviews the recent advances in the measurement of pain in children, with special emphasis on the methods that satisfy the criteria for reliability and validity, the methods that can be used to assess multiple dimensions of pain, and the methods that may be appropriate for assessing all types of acute, recurrent, and chronic pediatric pain.

Acute pain response in infants: a multidimensional description

Fourteen infants who were undergoing routine immunization were studied from a multidimensional perspective. The measures used were heart rate, crying, body movement/posturing, and voice spectrographs. There was wide variability between infants on the measures, especially on the cry spectrographs, although facial expression was consistent across infants. The pattern that did emerge was characterized by an initial response: a drop in heart rate, a long, high pitched cry followed by a period of apnea, rigidity of the torso and limbs, and a facial expression of pain. This was followed by a sharp increase in heart rate, lower pitched, but dysphonated cries, less body rigidity, but still facial expression was of pain. Finally, in the second half of the minute's response, heart rate remained elevated, cries were lower pitched, more rhythmic, with a rising-falling pattern, and were mostly phonated, and body posturing returned to normal. Those faces that could be viewed also were returning to the at rest configuration. It was suggested that facial expression may be the most consistent across-infant indicator of pain at this point in time.