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

A Narrative Review on Different Novel Machine Learning Techniques for Detecting Pathologies in Infants From Born Baby Cries

This paper reviews the research work on the analysis and classification of pathological infant cries in the last 50 years. The literature review mainly covers the need and role of early clinical diagnosis, pathologies detected from cry samples, challenges in pathological cry signal data acquisition, signal processing techniques, and signal classifiers. The signal processing techniques include preprocessing, feature extraction from domains, such as time, spectral, time-frequency, prosodic, wavelet, etc, and feature selection for selecting dominant features. Literature covers traditional machine learning classifiers, such as Bayesian networks, decision trees, K-nearest neighbor, support vector machine, Gaussian mixture model, etc, and recently added neural network models, such as convolutional neural networks, regression neural networks, probabilistic neural networks, graph neural networks, etc. Significant experimental results of pathological cry identification and classification are listed for comparison. Finally, it suggests future research in the direction of database preparation, feature analysis and extraction, neural network classifiers to provide a non-invasive and robust automatic infant cry analysis model.

How can cry acoustics associate newborns' distress levels with neurophysiological and behavioral signals?

Introduction

Even though infant crying is a common phenomenon in humans' early life, it is still a challenge for researchers to properly understand it as a reflection of complex neurophysiological functions. Our study aims to determine the association between neonatal cry acoustics with neurophysiological signals and behavioral features according to different cry distress levels of newborns.

Methods

Multimodal data from 25 healthy term newborns were collected simultaneously recording infant cry vocalizations, electroencephalography (EEG), near-infrared spectroscopy (NIRS) and videos of facial expressions and body movements. Statistical analysis was conducted on this dataset to identify correlations among variables during three different infant conditions (i.e., resting, cry, and distress). A Deep Learning (DL) algorithm was used to objectively and automatically evaluate the level of cry distress in infants.

Results

We found correlations between most of the features extracted from the signals depending on the infant's arousal state, among them: fundamental frequency (F0), brain activity (delta, theta, and alpha frequency bands), cerebral and body oxygenation, heart rate, facial tension, and body rigidity. Additionally, these associations reinforce that what is occurring at an acoustic level can be characterized by behavioral and neurophysiological patterns. Finally, the DL audio model developed was able to classify the different levels of distress achieving 93% accuracy.

Conclusion

Our findings strengthen the potential of crying as a biomarker evidencing the physical, emotional and health status of the infant becoming a crucial tool for caregivers and clinicians.

A Scientometric Review of Infant Cry and Caregiver Responsiveness: Literature Trends and Research Gaps over 60 Years of Developmental Study

Infant cry is an adaptive signal of distress that elicits timely and mostly appropriate caring behaviors. Caregivers are typically able to decode the meaning of the cry and respond appropriately, but maladaptive caregiver responses are common and, in the worst cases, can lead to harmful events. To tackle the importance of studying cry patterns and caregivers' responses, this review aims to identify key documents and thematic trends in the literature as well as existing research gaps. To do so, we conducted a scientometric review of 723 documents downloaded from Scopus and performed a document co-citation analysis. The most impactful publication was authored by Barr in 1990, which describes typical developmental patterns of infant cry. Six major research thematic clusters emerged from the analysis of the literature. Clusters were renamed "Neonatal Pain Analyzer" (average year of publication = 2002), "Abusive Head Trauma" (average year of publication = 2007), "Oxytocin" (average year of publication = 2009), "Antecedents of Maternal Sensitivity" (average year of publication = 2010), "Neurobiology of Parental Responses" (average year of publication = 2011), and "Hormonal Changes & Cry Responsiveness" (average year of publication = 2016). Research clusters are discussed on the basis of a qualitative inspection of the manuscripts. Current trends in research focus on the neurobiology of caregiver responses and the identification of factors promoting maternal sensitivity. Recent studies have also developed evidence-based strategies for calming crying babies and preventing caregivers' maladaptive responses. From the clusters, two topics conspicuously call for future research: fathers' responsiveness to infant cry and the impact of caregiver relationship quality on cry responsiveness.

Using CCA-Fused Cepstral Features in a Deep Learning-Based Cry Diagnostic System for Detecting an Ensemble of Pathologies in Newborns

Crying is one of the means of communication for a newborn. Newborn cry signals convey precious information about the newborn's health condition and their emotions. In this study, cry signals of healthy and pathologic newborns were analyzed for the purpose of developing an automatic, non-invasive, and comprehensive Newborn Cry Diagnostic System (NCDS) that identifies pathologic newborns from healthy infants. For this purpose, Mel-frequency Cepstral Coefficients (MFCC) and Gammatone Frequency Cepstral Coefficients (GFCC) were extracted as features. These feature sets were also combined and fused through Canonical Correlation Analysis (CCA), which provides a novel manipulation of the features that have not yet been explored in the literature on NCDS designs, to the best of our knowledge. All the mentioned feature sets were fed to the Support Vector Machine (SVM) and Long Short-term Memory (LSTM). Furthermore, two Hyperparameter optimization methods, Bayesian and grid search, were examined to enhance the system's performance. The performance of our proposed NCDS was evaluated with two different datasets of inspiratory and expiratory cries. The CCA fusion feature set using the LSTM classifier accomplished the best F-score in the study, with 99.86% for the inspiratory cry dataset. The best F-score regarding the expiratory cry dataset, 99.44%, belonged to the GFCC feature set employing the LSTM classifier. These experiments suggest the high potential and value of using the newborn cry signals in the detection of pathologies. The framework proposed in this study can be implemented as an early diagnostic tool for clinical studies and help in the identification of pathologic newborns.

Evaluation and Treatment of Pain in Fetuses, Neonates and Children

The perception of pain is individual and differs between children and adults. The structures required to feel pain are developed at 24 weeks of gestation. However, pain assessment is complicated, especially in neonates, infants and preschool-age children. Clinical scales adapted to age are the most used methods for assessing and monitoring the degree of pain in children. They evaluate several behavioral and/or physiological parameters related to pain. Some monitors detect the physiological changes that occur in association with painful stimuli, but they do not yet have a clear clinical use. Multimodal analgesia is recommended for pain treatment with non-pharmacological and pharmacological interventions. It is necessary to establish pharmacotherapeutic protocols for analgesia adjusted to the acute or chronic, type and intensity of pain, as well as age. The most used analgesics in children are paracetamol, ibuprofen, dipyrone, opioids (morphine and fentanyl) and local anesthetics. Patient-controlled analgesia is an adequate alternative for adolescent and older children in specific situations, such as after surgery. In patients with severe or persistent pain, it is very important to consult with specific pain services.

Investigation of Relation Between Hypoxic-Ischemic Encephalopathy and Spectral Features of Infant Cry Audio

Despite advances in medical technologies, Hypoxic-Ischemic Encephalopathy (HIE) continues to be a problem for neonatal intensive care units. Analysis of crying sounds may be a valuable tool for predicting neonatal disease. However, the characteristics of crying in newborns with HIE are still unclear. One of the factors limiting the ability to focus on that subject is the lack of commercially available infant cry database for research. Also, another reason that complicates the classification is the varying characteristics of infant cry. Accordingly, crying sounds were recorded from 35 infants and demographic characteristics of the study groups are presented as well as the numerical representation of spectral features. Experiments reveal that the existence of HIE causes distinctive variation in energy, energy entropy and spectral centroid features of the utterances; which leads us to conclude that the presented combination of spectral features would function well with any supervised or unsupervised machine learning algorithm.

Can the Vocal Expression of Intellectually Disabled Individuals Be Used as a Pain Indicator? Initial Findings Supporting a Possible Novice Assessment Method

Pain is difficult to assess in non-verbal populations such as individuals with intellectual and developmental disability (IDD). Due to scarce research in this area, pain assessment for individuals with IDD is still lacking, leading to maltreatment. To improve medical care for individuals with IDD, immediate, reliable, easy to use pain detection methods should be developed. The goal of this preliminary study was to examine the sensitivity of acoustic features of vocal expressions in identifying pain for adults with IDD, assessing their feasibility as a pain detection indicator for those individuals. Such unique pain related vocal characteristics may be used to develop objective pain detection means. Adults with severe-profound IDD level (N = 9) were recorded in daily activities associated with pain (during diaper changes), or without pain (at rest). Spontaneous vocal expressions were acoustically analyzed to assess several voice characteristics. Analyzing the data revealed that pain related vocal expressions were characterized by significantly higher number of pulses and higher shimmer values relative to no-pain vocal expressions. Pain related productions were also characterized by longer duration, higher jitter and Cepstral Peak Prominence values, lower Harmonic-Noise Ratio, lower difference between the amplitude of the 1st and 2nd harmonic (corrected for vocal tract influence; H1H2c), and higher mean and standard deviation of voice fundamental frequency relative to no-pain related vocal productions, yet these findings were not statistically significant, possibly due to the small and heterogeneous sample. These initial results may prompt further research to explore the possibility to use pain related vocal output as an objective and easily identifiable indicator of pain in this population.

The emotional canvas of human screams: patterns and acoustic cues in the perceptual categorization of a basic call type

Screams occur across taxonomically widespread species, typically in antipredator situations, and are strikingly similar acoustically, but in nonhuman primates, they have taken on acoustically varied forms in association with more contextually complex functions related to agonistic recruitment. Humans scream in an even broader range of contexts, but the extent to which acoustic variation allows listeners to perceive different emotional meanings remains unknown. We investigated how listeners responded to 30 contextually diverse human screams on six different emotion prompts as well as how selected acoustic cues predicted these responses. We found that acoustic variation in screams was associated with the perception of different emotions from these calls. Emotion ratings generally fell along two dimensions: one contrasting perceived anger, frustration, and pain with surprise and happiness, roughly associated with call duration and roughness, and one related to perceived fear, associated with call fundamental frequency. Listeners were more likely to rate screams highly in emotion prompts matching the source context, suggesting that some screams conveyed information about emotional context, but it is noteworthy that the analysis of screams from happiness contexts (n = 11 screams) revealed that they more often yielded higher ratings of fear. We discuss the implications of these findings for the role and evolution of nonlinguistic vocalizations in human communication, including consideration of how the expanded diversity in calls such as human screams might represent a derived function of language.

The vocal repertoire of preterm infants: Characteristics and possible applications

We investigated infants' capacities to express themselves orally at very early developmental stages. Most reports focus on crying when in pain or hungry. We evaluated young preterm infants' spontaneous vocal production in non-painful contexts. We identified a vocal repertoire composed of nine types of vocalisations. High-pitched sounds were associated with relaxed postures, implying a positive valence, whereas long low-pitched vocalisations, associated more with grimaces and muscle tensions, appeared to have a more negative valence. Infants' vocalisations were useful indicators of their internal state in two situations (when exposed to clothing constraints and environmental noises).

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.

Cry presence and amplitude do not reflect cortical processing of painful stimuli in newborns with distinct responses to touch or cold

OBJECTIVE

Newborns requiring hospitalisation frequently undergo painful procedures. Prevention of pain in infants is of prime concern because of adverse associations with physiological and neurological development. However, pain mitigation is currently guided by behavioural observation assessments that have not been validated against direct evidence of pain processing in the brain. The aim of this study was to determine whether cry presence or amplitude is a valid indicator of pain processing in newborns.

DESIGN

Prospective observational cohort.

SETTING

Newborn nursery.

PATIENTS

Healthy infants born at >37 weeks and <42 weeks gestation.

INTERVENTIONS

We prospectively studied newborn cortical responses to light touch, cold and heel stick, and the amplitude of associated infant vocalisations using our previously published paradigms of time-locked electroencephalogram (EEG) with simultaneous audio recordings.

RESULTS

Latencies of cortical peak responses to each of the three stimuli type were significantly different from each other. Of 54 infants, 13 (24%), 19 (35%) and 35 (65%) had cries in response to light touch, cold and heel stick, respectively. Cry in response to non-painful stimuli did not predict cry in response to heel stick. All infants with EEG data had measurable pain responses to heel stick, whether they cried or not. There was no association between presence or amplitude of cries and cortical nociceptive amplitudes.

CONCLUSIONS

In newborns with distinct brain responses to light touch, cold and pain, cry presence or amplitude characteristics do not provide adequate behavioural markers of pain signalling in the brain. New bedside assessments of newborn pain may need to be developed using brain-based methodologies as benchmarks in order to provide optimal pain mitigation.

[Pain assessment scales in newborns: integrative review]

OBJECTIVE

To analyze studies on methods used to assess pain in newborns.

DATA SOURCES

Integrative review study of articles published from 2001 to 2012, carried out in the following databases: Scopus, PubMed, CINAHL, LILACS and Cochrane. The sample consisted of 13 articles with level of evidence 5.

DATA SYNTHESIS

29 pain assessment scales in newborns, including 13 one-dimensional and 16 multidimensional, that assess acute and prolonged pain in preterm and full-term infants were available in scientific publications.

CONCLUSION

Based on the characteristics of scales, one cannot choose a single one as the most appropriate scale, as this choice will depend on gestational age, type of painful stimulus and the environment in which the infant is inserted. It is suggested the use of multidimensional or one-dimensional scales; however, they must be reliable and validated.

Status of Neonatal Pain Assessment and Management in Jordan

Current pain assessment and management in neonates need to be fully described before neonatal pain care can be optimized. This study's purpose was to report neonatal nurses' knowledge, existing pain assessment practice, and pharmacological pain management of neonates in Jordan. A cross-sectional descriptive study was conducted. Eighteen neonatal intensive care units in Jordan were included in the study. One hundred eighty-four neonatal nurses participated. Questionnaires were distributed by and returned to the neonatal intensive care units' managers between June and August 2014. Descriptive and inferential statistics were used to present study results. Of 240 questionnaires distributed, 184 useable responses were returned. Nurses' knowledge regarding neonates' neurological development, nociception, and need for neonatal pain management was suboptimal. The analgesics most commonly used to treat neonatal pain were acetaminophen (52%) and lidocaine (45%). Benzodiazepines, phenobarbitone, and muscles relaxants were also used. Most nurses (54%-97%) reported that pain emanating from most painful procedures was never or rarely treated. Circumcision, lumbar punctures, and chest tube insertion were assigned the highest pain scores (≥9), but were rarely accompanied by analgesia. Pain assessment scales were more likely to be used, and procedural pain was more likely to be treated, in private hospitals than public hospitals. Neonates who require special care still suffer unnecessary pain that could be avoided and managed by following best practice recommendations. Disparities between developed and developing countries in quality of neonatal pain care appear to exist. Resources for education and routine care are needed to address these discrepancies.

Sex stereotypes influence adults' perception of babies' cries

Background

Despite widespread evidence that gender stereotypes influence human parental behavior, their potential effects on adults’ perception of babies’ cries have been overlooked. In particular, whether adult listeners overgeneralize the sex dimorphism that characterizes the voice of adult speakers (men are lower-pitched than women) to their perception of babies’ cries has not been investigated.

Methods

We used playback experiments combining natural and re-synthesised cries of 3 month-old babies to investigate whether the interindividual variation in the fundamental frequency (pitch) of cries affected adult listeners’ identification of the baby’s sex, their perception the baby’s femininity and masculinity, and whether these biases interacted with their perception of the level of discomfort expressed by the cry.

Results

We show that low-pitched cries are more likely to be attributed to boys and high-pitched cries to girls, despite the absence of sex differences in pitch. Moreover, low-pitched boys are perceived as more masculine and high-pitched girls are perceived as more feminine. Finally, adult men rate relatively low-pitched cries as expressing more discomfort when presented as belonging to boys than to girls.

Conclusion

Such biases in caregivers’ responses to babies’ cries may have implications on children’s immediate welfare and on the development of their gender identity.

Electronic supplementary material

The online version of this article (doi:10.1186/s40359-016-0123-6) contains supplementary material, which is available to authorized users.

Effect of change in sequence of administration of DTwP and Hepatitis B vaccines on perception of pain in infants: A randomized control trial

OBJECTIVE

This study was designed with objective to study pain response of infants to change in sequence of administration of Hepatitis B and DTwP vaccines.

METHODS

This was a randomized parallel control trial. The study was carried out in the immunization clinic of the Department of Pediatrics, LLRM Medical College, Meerut. One hundred and thirty healthy term infants up to 4 months of age were injected either DTwP vaccine first or Hepatitis B vaccine first, followed one minute later by the other vaccine.

RESULT

Baseline characteristics did not differ between the groups. The mean (SD) of AUC of MFCS and NIPS was significantly more in DF group as compared to HF group (for MFCS 25.5 ± 5.4 versus 22.5 ± 5.5, p<0.01; for NIPS 31.77 ± 5.5 versus 27.64 ± 6.9, p < 0.01). Similarly mean (SD) of AUC of Heart rate and saturation of oxygen showed significant variation in DF group as compared to HF group (for heart rate 591.6 ± 55 versus 559.6 ± 49, p< 0.01; for SpO2 326.4 ± 12 versus 335 ± 8, p < 0.01).

CONCLUSION

These results showed that infant experienced lesser pain when Hepatitis B was administered first than when DTwP vaccine was given first.

Bayesian estimation on diagnostic performance of Face, Legs, Activity, Cry, and Consolability and Neonatal Infant Pain Scale for infant pain assessment in the absence of a gold standard

BACKGROUND

Nonverbal pediatric patients such as infants are unable to describe their pain, which leads to the lack of a gold standard scale for their pain assessment. The aim of this study was to estimate the diagnostic performance of Face, Legs, Activity, Cry, and Consolability (FLACC) scale and Neonatal Infant Pain Scale (NIPS) for infants' pain in the absence of a gold standard.

METHODS

This prospective observational study recruited 202 postoperative infants, aged <12 months. Postoperative pain intensity was evaluated using FLACC and NIPS scales. The diagnostic performance of these two scales was to estimate using a Bayesian latent class model with conditional dependence. McNemar's test was applied to test whether NIPS and FLACC tests differ from each other.

RESULTS

Under a combined model with conditional dependence, the median posterior sensitivity and specificity of the FLACC were 89.94% (95% CI: 78.48-96.83%) and 87.82% (95% CI: 78.6-95.23%), respectively. The sensitivity and specificity of the NIPS were 85.94% (95% CI: 72.15-95.6%) and 92.61% (84.05-97.52%), respectively. McNemar's test demonstrated no significant difference between FLACC and NIPS in either sensitivity or specificity.

CONCLUSION

Both the FLACC and NIPS have excellent sensitivity and specificity for pain assessment in infants. The comparison test showed that the FLACC scale was no different to the NIPS scale in sensitivity and specificity.

Pain assessment scales in newborns: integrative review

OBJECTIVE: To analyze studies on methods used to assess pain in newborns.DATA SOURCES: Integrative review study of articles published from 2001 to 2012, carried out in the following databases: Scopus, PubMed, CINAHL, LILACS and Cochrane. The sample consisted of 13 articles with level of evidence 5.DATA SYNTHESIS: 29 pain assessment scales in newborns, including 13 one-dimensional and 16 multidimensional, that assess acute and prolonged pain in preterm and full-term infants were available in scientific publications.CONCLUSION: Based on the characteristics of scales, one cannot choose a single one as the most appropriate scale, as this choice will depend on gestational age, type of painful stimulus and the environment in which the infant is inserted. It is suggested the use of multidimensional or one-dimensional scales; however, they must be reliable and validated.

Oral sucrose administration to reduce pain response during immunization in 16-19-month infants: a randomized, placebo-controlled trial

Although the analgesic effect of sucrose on newborns is well established, little is known about whether these solutions are effective in reducing procedural pain in infants beyond the newborn period. The purpose of this study was to determine the effect of sucrose solution given orally on infant crying times and measure the distress in a 16-19-month age group. A total of 537 healthy, 16-19-month-old infants attending for their immunizations with intramuscular diphtheria, tetanus, and acellular pertussis (DTaP)/Haemophilus influenza type b/IPV (along with oral polio vaccination (OPV)), intramuscular pneumococcus and intramuscular hepatitis A were randomized to receive 2 mL of a 75 % sucrose solution, a 25 % sucrose solution or sterile water 2 min before injections. Infants receiving a 75 % sucrose solution had significantly reduced total crying times and Children's Hospital of Eastern Ontario Pain Scale scores (CHEOPS) compared with infants in the control and 25 % sucrose solution groups (p < 0.001).

CONCLUSION

Sucrose solution reduces infant distress and is safe and clinically useful even for 16-19-month-old infants.

Pain assessment and measurement in neonates: an updated review

Pain assessment and measurement are the cornerstones of pain management. Pain assessment connotes a comprehensive multidimensional description. Conversely, pain measurement provides a numeric quantitative description of each factor illustrating pain qualities. Pain scales provide a composite score used to guide practice and research. The type of infant pain instrument chosen is a significant factor in guiding pain management practice. The purpose of this review was to summarize current infant pain measures by introducing a conceptual framework for pain measurement. Although more than 40 infant pain instruments exist, many were devised solely for research purposes; several of the newly developed instruments largely overlap with existing instruments. Integration of pain management into daily practice remains problematic. Understanding how each instrument measures infant pain allows clinicians to make better decisions about what instrument to use with which infant and in what circumstances. In addition, novel new measurement techniques need further testing.

Spontaneous cries can alter the physiological well-being and cerebral oxygenation of very preterm infants

INTRODUCTION

Infant crying is a major expression of distress and can occur without any exogenous stimulation. Little is known, however, about the effects of crying on physiological homeostasis in very preterm infants (VPIs).

METHODS

Environmental, behavioral (video and audio recording) and physiologic (heart rate [HR], respiratory rate [RR], and systemic [SaO(2)] and regional cerebral oxygenation [rSO(2)]) parameters were prospectively evaluated over 10h in 18 VPIs (median gestational age, 28 [27-31] weeks). Only episodes of "spontaneous" and isolated cries were analyzed. Changes in parameters were compared over 5-second periods between baselines and 40s following the onset of crying. Two periods were distinguished: 0-20s (a) and 20-40s (b). Minimal and/or maximal values in these periods were also compared to the baseline.

RESULTS

Of the 18 VPIs initially studied, 13 (72%) presented crying episodes (CE). They experienced 210 "spontaneous" and isolated CE, with a median of 9 [range, 1-63] CEs per child. Physiological values varied significantly from the baseline with mainly a mean decrease in HR of -4.8±5.3 beats/min (b) after an initial mean increase of +2.6±2.0 beats/min (a); a mean decrease in RR of -3.8±4.8 cycles/min (a), followed by a mean increase of +5.6±7.3 cycles/min (b) and mean unidirectional decreases in SaO(2) and rSO(2) (minimal values) of -1.8±2.3% and -2.5±3.0%, respectively.

CONCLUSION

Spontaneous cries can alter the homeostasis of VPIs. Their possible adverse consequences and high occurrence emphasize the need for better prevention and response to them.

Infant Crying: Pattern of Weeping, Recognition of Emotion and Affective Reactions in Observers

This study has three objectives: a) to describe the main differences in the crying patterns produced by the three affective states most closely related to crying: fear, anger and pain; b) to study the adults' accuracy in the recognition of the affective states related to the infant's crying, and c) to analyze the emotional reaction that infant crying elicits in the observers. Results reveal that the main differences appear in the ocular activity and in the pattern of weeping. The infants maintain their eyes open during the crying produced by fear and anger, but in the case of crying provoked by painful stimuli, the eyes remain closed almost all the time. In regard to the pattern of weeping, the crying gradually increase in the case of anger, but the weeping reaches its maximum intensity practically from the beginning in the case of pain and fear. In spite of these differences, it is not easy to know the cause that produces crying in infants, especially in the case of fear or anger. Although observers can't recognize the cause of crying, the emotional reaction is greater when the baby cries in pain than when the baby cries because of fear or anger.

Vocal signature in wild infant chimpanzees

A large array of communication signals supports the fission/fusion social organization in chimpanzees, and among them the acoustic channel plays a large part because of their forest habitat. Adult vocalizations convey social and ecological information to their recipients allowing them to obtain cues about an ongoing event from calls only. In contrast to adult vocalizations, information encoded in infant calls had been hardly investigated. Studies mainly focused on vocal development. The present article aims at assessing the acoustic cues that support individual identity coding in infant chimpanzees. By analyzing recordings performed in the wild from seven 3-year-old infant chimpanzees, we showed that their calls support a well-defined individual vocal signature relying on spectral cues. To assess the reliability of the signature across the calls of an individual, we defined two subsets of recordings on the basis of the characteristics of the frequency modulation (whimpers and screams) and showed that both call types present a reliable vocal signature. Early vocal signature may allow the mother and other individuals in the group to identify the infant caller when visual contact is broken. Chimpanzee mothers may have developed abilities to cope with changing vocal signatures while their infant, still vulnerable, gains in independence in close habitat.

Pain assessment in human fetus and infants

In humans, painful stimuli can arrive to the brain at 20-22 weeks of gestation. Therefore several researchers have devoted their efforts to study fetal analgesia during prenatal surgery, and during painful procedures in premature babies. Aim of this paper is to gather from scientific literature the available data on the signals that the human fetus and newborns produce, and that can be interpreted as signals of pain. Several signs can be interpreted as signals of pain. We will describe them in the text. In infants, these signs can be combined to create specific and sensible pain assessment tools, called pain scales, used to rate the level of pain.

The effect of a familiar scent on the behavioral and physiological pain responses in neonates

There are adverse physiologic effects of pain in neonates, and effective pain management must be an essential aspect of neonatal care. In this study we assessed the effect of a nonmaternal familiar scent on the neonatal pain responses. This study included 135 neonates randomly assigned to one of three groups. During arterial puncture, one group was exposed to a vanillin scent on a gauze pad held next to their nose. They were familiarized with it the night before blood sampling by a scented gauze pad placed in the incubator next to their head for an average duration of 8.65 hours. The second group was not familiarized with the scent but was exposed to it during the procedure. The third group was neither familiarized nor exposed to the scent. The duration of crying in the familiar scent group was significantly lower than in the two other groups. Comparison of the physiologic parameters showed less variation in oxygen saturation level during arterial puncture in the familiar scent group. In this study, a familiar scent could reduce crying and oxygen consumption during arterial puncture.

Decoupling between fundamental frequency and energy envelope of neonate cries

BACKGROUND

The presence of decoupling, i.e. the absence of coupling between fundamental frequency variation and energy envelope during phonetic crying, and its extent, reflects the degree of maturation of the central nervous system.

AIM

We hereby wanted to assess the existence and extent of decoupling in term neonates (neurodevelopmental relevance) and whether an association between decoupling and clinical pain expression could be unveiled (clinical relevance).

STUDY DESIGN

To assess decoupling in healthy term neonates during procedural pain, newborns were videotaped and crying was recorded during venous blood sampling. Besides acoustic analysis, pain expression was quantified based on the Modified Behavioral Pain Scale (MBPS).

SUBJECTS

47 healthy term neonates underwent venous blood puncture at the 3rd day of life.

OUTCOME MEASURES

Beside the MBPS score, the correlation coefficients were calculated between the fundamental frequency variation and energy envelope of the cries.

RESULTS

Based on data collected in 47 healthy term neonates, correlation coefficients varied between 0.20 and 0.68. The degree of decoupling displayed extensive variability between the neonates and also in different cry bouts in a crying sequence within an individual neonate. A negative association was found between MBPS value and decoupling (r(2)=-0.12), the same as for the intra-subject variability although less extensive (r(2)=-0.02).

CONCLUSION

Decoupling only relates weakly with the amount of distress in 3day old newborns, even though a great intra-subject variability is present. This study suggests that there is no evidence of extensive decoupling as the newborn still has to fully develop the control of larynx and abdominal muscles.

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.

Kangaroo Care (skin contact) reduces crying response to pain in preterm neonates: pilot results

Crying commonly occurs in response to heel stick and adversely affects the infant's physiologic stability. Minimal crying in response to pain is desired. "Kangaroo Care," skin contact between mother and infant, reduces pain and may reduce crying in response to pain. The purpose of this pilot study was to test Kangaroo Care's effect on the preterm infant's audible and inaudible crying response to heel stick. Inaudible crying has not been previously studied. A prospective randomized cross-over study with 10 preterm infants 2-9 days old (30-32 weeks' postmenstrual age) was conducted. Infants were randomly assigned to two sequences (sequence A: day 1 heel stick in Kangaroo Care [after 30 min of prone skin contact upright between maternal breasts] and day 2 heel stick in incubator [inclined, nested and prone]; or sequence B: opposite of sequence A) was conducted. Videotapes of baseline, heel warming, heel stick, and recovery phases were scored for audible and inaudible crying times. Audible and inaudible crying times for each subject in each phase were summed and analyzed by repeated-measures analysis of variance. Subject characteristics did not differ between those in the two sequences. Crying time differed between the study phases on both days (p <or= .001). When in Kangaroo Care compared with the incubator, crying time was less during the heel stick (p = .001) and recovery (p = .01) phases, regardless of sequence. Because Kangaroo Care reduced crying in response to heel stick in medically stable preterm infants, a definitive study is merited before making recommendations.

Affect cues in vocalizations of the bat, Megaderma lyra, during agonistic interactions

Some features of emotional prosody in human speech may be traced back to affect cues in mammalian vocalizations. The present study addresses the question whether affect intensity, as expressed by the intensity of behavioral displays, is encoded in vocal cues, i.e., changes in the structure of associated calls, in bats, a group evolutionarily remote from primates. A frame-by-frame video analysis of 109 dyadic agonistic interactions recorded in approach situations was performed to categorize displays into two intensity levels based on a cost-benefit estimate. M. lyra showed graded visual displays accompanied by specific calls and response calls of the second bat. A sound analysis revealed systematic changes of call sequence parameters with display level. At the high intensity level, total call duration, number of syllables within a call, and the number of calls within a sequence were increased, while intervals between call syllables were decreased for both call types. In addition, the latency of the response call was shorter, and its main syllable-type durations and fundamental frequency were increased. These systematic changes of vocal parameters with affect intensity correspond to prosodic changes in human speech, suggesting that emotion-related acoustic cues are a common feature of vocal communication in mammals.

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.

Neonatal Facial Coding System Scores and Spectral Characteristics of Infant Crying During Newborn Circumcision

OBJECTIVE

To determine the relations between Neonatal Facial Coding System (NFCS) scores and measures of infant crying during newborn circumcision.

METHODS

Video and audio recordings were made of infant facial activity and cry sounds, respectively, during the lysis phase of circumcisions of 44 healthy term males (<3 d of age). All infants received topical analgesia before circumcision. NFCS scores were determined by blinded assistant from video recordings of facial activity. Measures of infant crying were determined via spectrum analysis of audio recordings by a blinded, independent researcher. Pearson product-moment correlations were used to examine relationship between NFCS scores and measures of crying. Principal component factor analysis detected dimensions underlying related measures of crying. Factor scores from a factor analysis were used in stepwise linear regression to predict NFCS scores.

RESULTS

Higher NFCS scores correlated with lower peak fundamental frequency of crying (P<0.01) and with higher amplitudes of crying at peak fundamental frequency and dominant frequency and in overall cry sample (P<0.01). The factor analysis showed 3 significant orthogonal dimensions underlying measures of crying: Power and Velocity (amplitude and rapidity), Pitch of Crying (frequency characteristics), and Infant Arousal (turbulence and intensity) accounting for 42.3%, 17.8%, and 14.6% of variance, respectively. A regression analysis showed all 3 factor scores accounted for significant and separate portions of variance (P<0.001). The best predictor of NFCS score was Power and Velocity (P<0.002), followed by Infant Arousal (P<0.002), and Pitch of Crying (P<0.007).

DISCUSSION

These data provide some of the first known evidence linking specific measures of infant crying with an independent, validated measure of pain.

The newborn pain cry: descriptive acoustic spectrographic analysis

INTRODUCTION

Study the characteristics of pain vocal emission of newborns during venepuncture through acoustic analysis and relate it to NIPS pain scale and some variables of the newborns.

METHODS

Emissions of 111 healthy term newborns were recorded, whose lifetime varied from 24 to 72 h. The acoustic analysis was realized with GRAM 5.7 software verifying the occurrence of tense strangled voice quality, sounds, concentration of acoustic energy, breaks, double harmonic breaks and frequency instability, type of phonation, vocal attack and cough. The NIPS scale was realized during venepuncture and descriptive statistical analysis and correlation through Spearman test.

RESULTS

Hundred percent of the emissions had guttural sounds, vowels, hard vocal attack, frequency, breaks, double harmonic breaks and tense strangled voice quality; 34.2% higher fundamental frequency; 62.2% periods of emission absence and 100% occurrence of tracing instability, concentration of acoustic energy, inspiratory and expiratory phonation. The cough occurred in 14.4%. The signs of vocal tract constriction associated with all the parameters. There was a negative correlation between the higher fundamental frequencies and the weight of newborns and positive correlation between cough and NIPS score.

CONCLUSIONS

The newborn pain emission is tense and strident, the modifications of frequency and spectrographic tracing and the presence of sounds show laryngeal and vocal tract participation. The smaller the newborn weight, the bigger the presence of higher fundamental frequency with tense strangled voice quality and the bigger the NIPS score, the more frequent the cough. Such characteristics make pain crying peculiar, helping in the evaluation of pain during a procedure.

A pilot study of changes in cerebral blood flow velocity, resistance, and vital signs following a painful stimulus in the premature infant

PURPOSE

The purpose of this pilot study was to determine the cerebral blood flow velocity and resistance changes and vital signs following a painful stimulus in the premature infant.

SUBJECTS

A convenience sample of 12 infants was randomly assigned to one of 2 treatment groups. In the final analysis, there were 10 infants younger than 24 hours of age and between 25 and 32 weeks' gestational age.

DESIGN

A randomized 2-period, 2-group, crossover design was used.

METHODS

Cerebral blood flow velocity and resistance were measured via a Doppler head ultrasound transducer placed over the anterior fontanel. Vital signs were measured with a cardiorespiratory monitor. The infant then received the heel stick procedure or the sham procedure (heel preparation with no heel puncture). Each infant served as his or her own control. After each procedure, there was ultrasound and vital sign measurement at 15, 60, 120, 180, 240, and 300 seconds. Thereafter, the alternate treatment was used and 6 more measurements were taken.

MAIN OUTCOME MEASURES

Cerebral values: peak systolic velocity (PSV) and resistive index (RI); vital signs: heart rate, respiratory rate, oxygen saturation (SpO2), and blood pressure.

RESULTS

Treatment groups were similar at baseline except for gestational age. There were no carryover or period effects in the crossover design for the primary outcomes except for SpO2. There was a significant group effect (heel stick compared with sham) (P = .009) for peak systolic velocity; however, there were no significant differences between groups at each time point. Two subjects had a distinctive pattern based on simultaneous changes in flow and resistance: when flow velocity increased, resistance decreased. This may be reflective of risk for intraventricular hemorrhage (IVH). Mean arterial blood pressure (MAP) was not significant. However, heart rate was significantly different between stick and sham at 15 seconds (P = .022); respiratory rate was significant at 180 seconds (P = .029); and SpO2 was significant at 3 different time points. There were no significant correlations between PSV and mean arterial blood pressure and PSV and SpO2 when comparing stick to sham.

CONCLUSIONS

This is a study based on a small sample size. However, the Doppler-measured peak systolic velocity increases significantly after a painful stimulus. The clinical implication of this finding needs to be established.

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.

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.

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.