Cry Features Reflect Pain Intensity in Term Newborns: An Alarm Threshold

Abstract

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 (F 0 ); and 3) root mean square sound pressure normalized to its maximum. After emission of the first cry, babies with DAN scores Ͼ8, but not with DAN scores Յ8 (p Ͻ 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 (r 2 ϭ 89%, p Ͻ 0.01), F 0 (r 2 ϭ 32%, p Ͻ 0.05), siren cry (r 2 ϭ 68.2%, p ϭ 0.02), and DAN score. F 0 did not show significant correlation with DAN score in the subset of neonates with DAN scores Յ8 (r 2 ϭ 1.4%, p ϭ 0.94), and babies with a DAN score Ͼ8 had a significantly higher F 0 than those with lower DAN scores (p ϭ 0.016). An alarm threshold exists between high (Ͼ8) and low (Յ8) 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. Crying is simultaneously a sign, symptom, and signal (1). It is the infant's earliest form of communication, but the significance and meaning of neonatal crying are still unclear (2) because different crying features do not reflect different causes (e.g. hunger, pain, and fussiness) (3), but different degrees of distress (4 -6), so that gradations of crying may help a listener to narrow down the range of possible causes, but only with the help of contextual information (4, 6 -9). In the last few years, pain scales have been developed to discriminate levels of pain suffered by newborns (10 -15), but when analyzing crying, the level of the pain that provoked it is rarely considered (16). The aim of this study was to investigate to what extent crying features vary with the level of pain. To achieve this goal, we studied cry frequency spectrograms at different pain levels expressed by a validated pain scale. METHODS SubjectsThis report is based on analysis of a cohort of 57 newborns extrapolated from a previous study (17) consisting of 120 healthy term infants who underwent heel-prick for neonatal screening. Inclusion criteria were Apgar score at least 9 at 5 min, gestational age 38 -41 wk, age more than 48 h, and more than 2 h since last meal. During heel-prick, different analgesic procedures were used, namely SS, SS without oral sugar, oral sugar, sucking, and oral sugar plus sucking. These analgesic procedures were chosen to assess whether SS, a multisensorial stimulation consisting of m...

Pain Assessment in Human Fetus and Infants

“…Thus, the presence of crying is not a direct sign of pain (27,28). Nevertheless, some crying features are typical of pain, such as the high-pitched cry in response to painful event (29). A pain scale combining several crying features has recently been developed and validated (30)(31)(32).…”

Decoupling between fundamental frequency and energy envelope of neonate cries

“…Bellieni et al were able to document that newborns with a higher DAN (Douleur Aigue du Nouveau-né) score during venous blood sampling (heel lancing) also had a higher fundamental frequency and a correlation was found between the pain intensity (DAN score) and the normalized Root Mean Square value (RMS) [3]. The observation that the normalized RMS value increases with the DAN score indicates that the stationary character of the overall cry intensity increases with increasing pain.…”

“…At early stage, it is believed that a cry is the result of respiratory action and the effect of air going through a pipe, causing the vocal folds to vibrate, resulting in a cry bout [2], this is the vocalization produced during one expiration. The more the neural system matures, the more laryngeal control can be exerted resulting in manipulation and modulation of the cry signal, but observations on maturational aspects of the cry signal are limited and conflicting [3,4]. The development of the central neural system has been linked with the extent of vocalization control [4].…”

“…Such clinical scoring systems are often multimodal and not only include scoring of the body movements, but also acoustic features of the cry signal [6][7][8][9]. Within a predefined context like pain, analysis of crying characteristics might therefore provide additional information [3,10].…”

Application of Pattern Recognition Techniques to the Classification of Full-Term and Preterm Infant Cry

“…Most of the studies investigated possible differences in infant gender, their neurophysiological maturity, and risks of brain damage for preterm infants caused by deoxygenation due to prolonged crying. [10][11][12][13][14][15][16] In general, the automatic infant cry classification process is a pattern recognition problem. From the infant's cry (input pattern), the goal was to classify the kind of cry or pathology detected on the baby.…”