Reflections on measuring pain in infants: dissociation in responsive systems and “honest signalling”

• Published in: Archives of disease in childhood. Fetal and neonatal edition Vol. 79; no. 2; pp. F152 - F156
• Main Author: Barr, Ronald G
• Format: Journal Article
• Language: English
• Published: London BMJ Publishing Group Ltd and Royal College of Paediatrics and Child Health 01.09.1998; BMJ; BMJ Publishing Group LTD; BMJ Group
• Subjects: Babies; Behavior; Biological and medical sciences; Crying; Current Topic; Facial Expression; Heart rate; Humans; Infant Behavior; Infant, Newborn; Infant, Premature; Infants; Intensive care; Medical sciences; Nervous system involvement in other diseases. Miscellaneous; Neurology; Nonverbal Communication; Pain; Pain Measurement; Physiology; Human; Evaluation; Pain; Child
• ISSN: 1359-2998; 1468-2052
• DOI: 10.1136/fn.79.2.F152

[...]they cannot make decisions as to when they could benefit from analgesia and activate their own patient controlled morphine analgesia units. [...]there is a classic concatenation of facial features (mouth open, brow bulge, eyes closed, increased nasal-labial furrow) that is always there when a pain stimulus is applied. 16 19 20 However, it is also often present in many situations when an infant cries, such as when it is hungry. 21 Similarly, a spectrographic analysis of a pain cry often indicates features of a delayed onset, a prolonged expiratory phase, a higher pitch, and increased likelihood of disrupted harmonic structure (or dysphonation) when the stimulus is applied. 22 23 However, very soon after the pain stimulus is removed, the acoustic structure of the cry reverts to what is referred to as the basic, more rhythmical structure of the cry. 24 25 The non-specificity was equally true for the physiological measures, where almost any novel or often only mildly stressful stimulus situation could be reflected in changes in these systems. 26-28 The third observation was perhaps even more problematic-namely, that behavioural indices of pain and stress were very loosely correlated and/or sometimes completely dissociated from physiological indices. 27 This was an interesting finding, because it has not widely been reported and is rarely the main point of the studies in which the dissociation was reported.