Spectographic analysis of vocal response to pain stimuli in infants with Down's syndrome

Comparative Spectrographic Analysis of the Newborns' Cry in the Presence of Tight Intrapartum Nuchal Cord vs. Normal using the Neonat App. Preliminary Results

Background and objectives: The objective of this study was to contribute to the evaluation of the newborn (NB) cry as a means of communication and diagnosis. Materials and Methods: The study implied the recording of the spontaneous cry of 101 NBs with no intrapartum events (control sample), and of 72 NBs with nuchal cord (study sample) from the "Bega" University Clinic of Obstetrics-Gynecology and Neonatology of Timisoara, Romania. The sound analysis was based upon: Imagistic highlighting methods, descriptive statistics, and data mining techniques. Results: The differences between the cry of NBs with no intrapartum events and that of NBs affected by nuchal cord are statistically significant regarding the volume unit meter (VUM) (p = 0.0021) and the peak point meter (PPM) (p = 0.041). Conclusions: While clinically there are no differences between the two groups, the cry recorded from the study group (nuchal cord group) shows distinctive characteristics compared to the cry recorded from the control group (eventless intrapartum NBs group).

Auditory-Perceptual Speech Features in Children With Down Syndrome

Speech disorders occur commonly in individuals with Down syndrome (DS), although data regarding the auditory-perceptual speech features are limited. This descriptive study assessed 47 perceptual speech features during connected speech samples in 26 children with DS. The most severely affected speech features were: naturalness, imprecise consonants, hyponasality, speech rate, inappropriate silences, irregular vowels, prolonged intervals, overall loudness level, pitch level, aberrant oropharyngeal resonance, hoarse voice, reduced stress, and prolonged phonemes. These findings suggest that speech disorders in DS are due to distributed impairments involving voice, speech sound production, fluency, resonance, and prosody. These data contribute to the development of a profile of impairments in speakers with DS to guide future research and inform clinical assessment and treatment.

A fully automated approach for baby cry signal segmentation and boundary detection of expiratory and inspiratory episodes

The detection of cry sounds is generally an important pre-processing step for various applications involving cry analysis such as diagnostic systems, electronic monitoring systems, emotion detection, and robotics for baby caregivers. Given its complexity, an automatic cry segmentation system is a rather challenging topic. In this paper, a framework for automatic cry sound segmentation for application in a cry-based diagnostic system has been proposed. The contribution of various additional time- and frequency-domain features to increase the robustness of a Gaussian mixture model/hidden Markov model (GMM/HMM)-based cry segmentation system in noisy environments is studied. A fully automated segmentation algorithm to extract cry sound components, namely, audible expiration and inspiration, is introduced and is grounded on two approaches: statistical analysis based on GMMs or HMMs classifiers and a post-processing method based on intensity, zero crossing rate, and fundamental frequency feature extraction. The main focus of this paper is to extend the systems developed in previous works to include a post-processing stage with a set of corrective and enhancing tools to improve the classification performance. This full approach allows to precisely determine the start and end points of the expiratory and inspiratory components of a cry signal, EXP and INSV, respectively, in any given sound signal. Experimental results have indicated the effectiveness of the proposed solution. EXP and INSV detection rates of approximately 94.29% and 92.16%, respectively, were achieved by applying a tenfold cross-validation technique to avoid over-fitting.

Developmental Organization, Stress, and Illness

The link between behavioral responsiveness to stress and subsequent health has been demonstrated in adults but not in infants and very young children. The ability of infants to suppress responding to acutely painful events was examined both as a function of neonatal status and as a predictor of incidence of illness at 18 to 24 months. Responding to stress in early infancy was predictive of later health but the nature of the relation depended on the maturity of the child.

Pain perception in people with Down syndrome: a synthesis of clinical and experimental research

People with an intellectual disability experience both acute and chronic pain with at least the same frequency as the general population. However, considerably less is known about the pain perception of people with Down syndrome. In this review paper, we evaluated the available clinical and experimental evidence. Some experimental studies of acute pain have indicated that pain threshold was higher than normal but only when using a reaction time method to measure pain sensitivity. However, when reaction time is not part of the calculation of the pain threshold, pain sensitivity in people with Down syndrome is in fact lower than normal (more sensitive to pain). Clinical studies of chronic pain have shown that people with an intellectual disability experience chronic pain and within that population, people with Down syndrome also experience chronic pain, but the precise prevalence of chronic pain in Down syndrome has yet to be established. Taken together, the literature suggests that people with Down syndrome experience pain, both acute and chronic, with at least the same frequency as the rest of the population. Furthermore, the evidence suggests that although acute pain expression appears to be delayed, once pain is registered, there appears to be a magnified pain response. We conclude by proposing an agenda for future research in this area.

Ultrasonic vocalizations during male-female interaction in the mouse model of Down syndrome Ts65Dn

Down syndrome (DS) is the leading cause of genetically defined intellectual disability. Although speech and language impairments are salient features of this disorder, the nature of these phenotypes and the degree to which they are exacerbated by concomitant oromotor dysfunction and/or hearing deficit are poorly understood. Mouse models like Ts65Dn, the most extensively used DS animal model, have been critical to understanding the genetic and developmental mechanisms that contribute to intellectual disability. In the present study, we characterized the properties of the ultrasonic vocalizations (USVs) emitted by Ts65Dn males during courtship episodes with female partners. USVs emitted by mice in this setting have been proposed to have some basic correlation to human speech. Data were collected and analyzed from 22 Ts65Dn mice and 22 of their euploid littermates. We found that both the minimum and maximum peak frequencies of Ts65Dn calls were lower than those produced by euploid mice, whereas the mean individual duration of "down" and "complex" syllable types was significantly longer. Peak, minimal and maximal, and the fundamental frequencies of short syllables generated by Ts65Dn mice were lower compared to those by euploid mice. Finally, Ts65Dn males made fewer multiple jumps calls during courtship and the mean total duration of their "arc", "u", and "complex" syllables was longer. We discuss the human correlates to these findings, their translational potential, and the limitations of this approach. To our knowledge, this is the first characterization of differences between adult Ts65Dn and euploid control mice with respect to USVs.

A flexible analysis tool for the quantitative acoustic assessment of infant cry

PURPOSE

In this article, the authors describe and validate the performance of a modern acoustic analyzer specifically designed for infant cry analysis.

METHOD

Utilizing known algorithms, the authors developed a method to extract acoustic parameters describing infant cries from standard digital audio files. They used a frame rate of 25 ms with a frame advance of 12.5 ms. Cepstral-based acoustic analysis proceeded in 2 phases, computing frame-level data and then organizing and summarizing this information within cry utterances. Using signal detection methods, the authors evaluated the accuracy of the automated system to determine voicing and to detect fundamental frequency (F 0) as compared to voiced segments and pitch periods manually coded from spectrogram displays.

RESULTS

The system detected F 0 with 88% to 95% accuracy, depending on tolerances set at 10 to 20 Hz. Receiver operating characteristic analyses demonstrated very high accuracy at detecting voicing characteristics in the cry samples.

CONCLUSIONS

This article describes an automated infant cry analyzer with high accuracy to detect important acoustic features of cry. A unique and important aspect of this work is the rigorous testing of the system's accuracy as compared to ground-truth manual coding. The resulting system has implications for basic and applied research on infant cry development.

Speech impairment in Down syndrome: a review

PURPOSE

This review summarizes research on disorders of speech production in Down syndrome (DS) for the purposes of informing clinical services and guiding future research.

METHOD

Review of the literature was based on searches using MEDLINE, Google Scholar, PsycINFO, and HighWire Press, as well as consideration of reference lists in retrieved documents (including online sources). Search terms emphasized functions related to voice, articulation, phonology, prosody, fluency, and intelligibility.

CONCLUSIONS

The following conclusions pertain to four major areas of review: voice, speech sounds, fluency and prosody, and intelligibility. The first major area is voice. Although a number of studies have reported on vocal abnormalities in DS, major questions remain about the nature and frequency of the phonatory disorder. Results of perceptual and acoustic studies have been mixed, making it difficult to draw firm conclusions or even to identify sensitive measures for future study. The second major area is speech sounds. Articulatory and phonological studies show that speech patterns in DS are a combination of delayed development and errors not seen in typical development. Delayed (i.e., developmental) and disordered (i.e., nondevelopmental) patterns are evident by the age of about 3 years, although DS-related abnormalities possibly appear earlier, even in infant babbling. The third major area is fluency and prosody. Stuttering and/or cluttering occur in DS at rates of 10%-45%, compared with about 1% in the general population. Research also points to significant disturbances in prosody. The fourth major area is intelligibility. Studies consistently show marked limitations in this area, but only recently has the research gone beyond simple rating scales.

A classification model for infant cries with hearing impairment and unilateral cleft lip and palate

OBJECTIVE

The aim of the study was to examine the acoustic features of infant cries in order to find differences between infants with normal development, hearing impairment (HI) and unilateral cleft lip and palate (UCLP). The study focused on two issues: (1) are differences in acoustic cry parameters specific of a certain pathological development, and (2) do these differences allow for a reliable classification of infant cries?

PATIENTS AND METHODS

In total, 128 spontaneous cries of infants up to 12 months of age were recorded. The mean values of acoustic cry parameters were statistically analyzed by one-way analysis of variance and Sheffé post hoc tests. A C5.0 decision tree was trained to classify infant cries by their acoustic parameters.

RESULTS

Significant differences in cry duration, fundamental frequency, formants 2 and 4, intensity, jitter, shimmer and harmonics-to-noise ratio were found between the groups. The C5.0 decision tree was able to predict an infant's membership to the healthy, UCLP or HI groups with a probability of 89.2%.

CONCLUSION

We conclude that C5.0 decision trees are suited to reliably classify healthy infants as well as infants with HI and UCLP by acoustic parameters.

Anaesthesia and postoperative analgesia in surgical neonates with or without Down's syndrome: is it really different?

BACKGROUND

Reports conflict on optimal postoperative analgesic treatment in children with intellectual disability. We retrospectively compared postoperative analgesics consumption between neonates with and without Down's syndrome in relation to anaesthesia requirements and pain scores.

METHODS

We analysed hypnotic and analgesic drug administration, pain scores [COMFORT-Behaviour (COMFORT-B) scale], and duration of mechanical ventilation during the first 48 h after surgical repair of congenital duodenal obstruction in neonates, between 1999 and 2011. Data of 15 children with Down's syndrome were compared with data of 30 children without Down's syndrome.

RESULTS

General anaesthesia requirements did not differ. The median (inter-quartile range) maintenance dose of morphine during the first 24 h after operation was 9.5 (7.8-10.1) µg kg(-1) h(-1) in the Down's syndrome group vs 7.7 (5.0-10.0) µg kg(-1) h(-1) in the control group (P=0.46). Morphine doses at postoperative day 2 and COMFORT-B scores at day 1 did not significantly differ between the two groups. COMFORT-B scores at day two were lower in children with Down's syndrome (P=0.04). The duration of postoperative mechanical ventilation did not statistically differ between the two groups (P=0.89).

CONCLUSIONS

In this study, neonates with and without Down's syndrome received adequate postoperative analgesia, as judged from comparable analgesic consumption and pain scores. We recommend prospective studies in children of different age groups with Down's syndrome and in other groups of intellectually disabled children to provide further investigation of the hypothesis that intellectual disability predisposes to different analgesic requirements.

Segmentation of expiratory and inspiratory sounds in baby cry audio recordings using hidden Markov models

The paper describes an application of machine learning techniques to identify expiratory and inspiration phases from the audio recording of human baby cries. Crying episodes were recorded from 14 infants, spanning four vocalization contexts in their first 12 months of age; recordings from three individuals were annotated manually to identify expiratory and inspiratory sounds and used as training examples to segment automatically the recordings of the other 11 individuals. The proposed algorithm uses a hidden Markov model architecture, in which state likelihoods are estimated either with Gaussian mixture models or by converting the classification decisions of a support vector machine. The algorithm yields up to 95% classification precision (86% average), and its ability generalizes over different babies, different ages, and vocalization contexts. The technique offers an opportunity to quantify expiration duration, count the crying rate, and other time-related characteristics of baby crying for screening, diagnosis, and research purposes over large populations of infants.

Mode of delivery modulates physiological and behavioral responses to neonatal pain

OBJECTIVE

To study whether the mode of delivery alters pain expression.

STUDY DESIGN

Full-term infants born by vaginal delivery or elective caesarean section were observed following high- and low-intensity pain stimuli, with recording of electrocardiogram, facial expression and vocalization.

RESULT

Graded physiological and behavioral responses occurred, with greater responses to higher than lower intensity pain stimuli. Elevation in heart rate following both stimuli increased with time after vaginal delivery. Infants delivered by elective caesarean section showed stronger facial expressions and briefer time in vocalizations response to both interventions.

CONCLUSION

Diminished responses following vaginal delivery suggest that physiological events associated with a normal delivery reduce the physiologic and sympathoadrenal activation by nociceptive mechanisms. Pain and stress reactivity appear to be inhibited during fetal life and sensory inputs during vaginal delivery may reverse this inhibition. To minimize neonatal pain, we recommend that postnatal invasive procedures to be performed shortly after vaginal birth.

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.

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.

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.

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.

Pain expression and stimulus localisation in individuals with Down's syndrome

BACKGROUND

Individuals with Down's syndrome do not always exhibit signs of distress in reaction to noxious stimuli comparable with the general population. This pilot study was designed to measure the ability of individuals with Down's syndrome to detect and express sensation in comparison with healthy volunteers.

METHODS

In the first test, the latency of pain detection to self-administered cold stimuli on the wrist and on the temple was measured. The second test was designed to assess ability to localise cold stimuli on sites on the hand, on the face, and in the mouth.

FINDINGS

75 control individuals and 26 individuals with Down's syndrome were tested. Individuals with Down's syndrome had significantly longer median latencies than controls: Down's syndrome median (quartiles) 28.7 s (1st 18.0, 3rd 47.6); controls 20.6 s (1st 12.4, 3rd 31.0); p=0.0005. In addition, more individuals with Down's syndrome had difficulties in localising the cold stimulus. The differences in distribution for precise localisation were significant for the hand (Down's syndrome [p<0.0005] 54%; control 99%), the mouth (31%; 84%), and the face (54%; 97%).

INTERPRETATION

Individuals with Down's syndrome are not insensitive to pain. However, they do express pain or discomfort more slowly and less precisely than the general population. This implies that medical teams managing these patients should use pain-control procedures, even in the absence of obvious pain manifestations.

Factors that influence the behavioral pain responses of premature infants

The responses of preterm neonates to acute tissue-damaging stimuli have been described. However, factors which influence these responses have received little attention. In this study, we observed 124 premature infants before, during and after a routine heel lance and determined how two contextual variables (severity of illness and behavioral state) influenced their behavioral responses. Significant changes in facial actions occurred between baseline and the most invasive phase of the heel lance procedure, stick. The fundamental frequency, harmonic structure and peak spectral energy of the infant's cry were also significantly increased during the stick phase. Behavioral state was found to influence the facial action variables and severity of illness modified the acoustic cry variables. Accurate identification of pain in premature infants requires consideration of factors that influence their response.

Computerized cry analysis in infants affected by severe protein energy malnutrition

A new method of computerized cry analysis has been utilized to evaluate the cries of infants affected by severe protein energy malnutrition. We studied 17 Kenian babies affected by severe malnutrition for more than four months (9 cases of marasmus and 8 of kwashiorkor) and a control group of 17 well-nourished babies. The cries of the malnourished children showed lower inter-utterance variability, formants' frequencies and cry score, assigned by the Infant Cry Modulation Assessment Scale. The melodic pattern was more often flat, rising or falling-rising, when compared to the cries of the well-nourished babies. We hypothesize that these differences reflect the state of brain damage associated with protein energy malnutrition. No differences were found between the cries of infants affected by marasmus and those affected by kwashiorkor, between the cries recorded before and after nutritional therapy and between the first cries of malnourished children who subsequently died during hospitalization and those of infants who survived.

Assessment of infant cry variability in high-risk infants

Two studies were conducted to determine the relationship between variability in acoustic features of the infant cry and medical risk factors. In study 1, 3 groups of preterm infants (healthy, sick and CNS pathology) were compared with term infants at 40 weeks gestational age. The cry was analyzed by computer. The coefficient of variability of cry amplitude and the formant features of the cry differed among the groups of preterm infants. In study 2, 3 groups of term infants at low, moderate and high levels of hyperbilirubinemia were compared on the cry measures. More variability in the formant features of the cry was found in infants with higher levels of bilirubin. The correlation between the coefficient of variation in the cry formants and level of bilirubin was statistically significant. These two studies suggest that variability in the acoustic features of the cry relate to the medical status of the infant and may provide a measure of neurophysiological integrity.

Sound spectrographic cry analysis of infants with hydrocephalus

Altogether 248 cries from 62 infants with hydrocephalus were analysed by sound spectrography: 92 cries from infants with congenital hydrocephalus and 52 cries from each of the groups with cerebral malformations, hydrocephalus as sequelae of meningitis, and after closure of a meningomyelocele. The cries were compared with 104 cries of normal healthy infants of corresponding age. The cry analysis showed that the most abnormal cries were seen in infants with congenital hydrocephalus and cerebral malformations. The pitch of the fundamental frequency did not differ from normal crying in cries of infants collected after recovery from meningitis and after closure of a meningomyelocele. The cries in hydrocephalus after meningitis showed more commonly flat melody types and the occurrence of bi-phonation.

Sound spectrographic analysis of pain cry in preterm infants

Sound spectrographic cry analysis was performed on 302 cries of 48 preterm infants born at 30-37 gestational weeks. The cries were recorded during the first week of life and thereafter weekly until the infants were discharged. The control series comprised 54 cries from 27 fullterm healthy infants. The results showed that the cries of the smallest prematures compared with the controls were shorter, more high-pitched, and included bi-phonation and glide more often. The cry characteristics changed with increasing conceptual age and the older the child the more the cry pattern resembled that of the fullterm. The cries of the preterm infants when they had reached 38 conceptual weeks were similar to those of newly born fullterm infants. The results indicate that the gestational age should be taken into consideration in cry analysis.