Sex differences in parent and child pain ratings during an experimental child pain task.

Research in the field of pediatric pain has largely ignored the role of fathers in their children's pain experiences. The first objective of the present study was to examine the effect of the presence of mothers versus fathers on children's subjective ratings, facial expressions and physiological responses to acute pain. The second objective was to examine whether child and parent sex influence parents' proxy ratings of their children's pain. The final objective was to compare levels of agreement between mothers' and fathers' assessments of their children's pain. Participants included 73 children (37 boys, 36 girls), four to 12 years of age, along with 32 fathers and 41 mothers. Children undertook the cold pressor pain task while observed by one of their parents. During the task, the children's heart rates and facial expressions were recorded. Children provided self-reports and parents provided proxy reports of child pain intensity using the seven-point Faces Pain Scale. Neither child nor parent sex had a significant impact on children's subjective reports, facial expressions or heart rates in response to acute pain. Fathers gave their sons higher pain ratings than their daughters, whereas mothers' ratings of their sons' and daughters' pain did not differ. Kappa statistics and t tests revealed that fathers tended to be more accurate judges of their children's pain than mothers. Overall, this research highlights the importance of examining both parent and child sex differences in pediatric pain research.

Subjective judgments of deception in pain expression: accuracy and errors.

Accuracy and errors in judges' attempts to differentiate facial expressions that displayed genuine pain, no pain or were dissimulated (i.e., masked and exaggerated) were examined. Judges were informed that misrepresentations in the facial expressions were present and were asked to rate their confidence in classifying these expressions. Detailed, objective coding of the patients' facial reactions (e.g., brow lowering, mouth opening) were related to judges' decisions. Judges' classification decisions were better than chance, but there were many errors. Extreme expressions (i.e., no pain, and exaggerated expressions) were identified more accurately than genuine and masked expressions. Judges level of confidence was consistent with their level of accuracy. Judges consistently used rules of thumb based on specific facial cues when making judgments. Certain cues were effectively discriminative. Systematic training in the use of specific cues or the use of articulated decision rules may be helpful in improving judges' accuracy.

The expression of pain in infants and toddlers: developmental changes in facial action.

Age-related changes in the facial expression of pain during the first 18 months of life have important implications for our understanding of pain and pain assessment. We examined facial reactions video recorded during routine immunization injections in 75 infants stratified into 2-, 4-, 6-, 12-, and 18-month age groups. Two facial coding systems differing in the amount of detail extracted were applied to the records. In addition, parents completed a brief questionnaire that assessed child temperament and provided background information. Parents' efforts to soothe the children also were described. While there were consistencies in facial displays over the age groups, there also were differences on both measures of facial activity, indicating systematic variation in the nature and severity of distress. The least pain was expressed by the 4-month age group. Temperament was not related to the degree of pain expressed. Systematic variations in parental soothing behaviour indicated accommodation to the age of the child. Reasons for the differing patterns of facial activity are examined, with attention paid to the development of inhibitory mechanisms and the role of negative emotions such as anger and anxiety.

A comparison of faces scales for the measurement of pediatric pain: children's and parents' ratings.

Faces scales have become the most popular approach to eliciting children's self-reports of pain, although different formats are available. The present study examined: (a) the potential for bias in children's self-reported ratings of clinical pain when using scales with smiling rather than neutral 'no pain' faces; (b) levels of agreement between child and parent reports of pain using different faces scales; and (c) preferences for scales by children and parents. Participants were 75 children between the ages of 5 and 12 years undergoing venepuncture, and their parents. Following venepuncture, children and parents independently rated the child's pain using five different randomly presented faces scales and indicated which of the scales they preferred and why. Children's ratings across scales were very highly correlated; however, they rated significantly more pain when using scales with a smiling rather than a neutral 'no pain' face. Girls reported significantly greater levels of pain than boys, regardless of scale type. There were no age differences in children's pain reports. Parents' ratings across scales were also highly correlated; however, parents also had higher pain ratings using scales with smiling 'no pain' faces. The level of agreement between child and parent reports of pain was low and did not vary as a function of the scale type used; parents overestimated their children's pain using all five scales. Children and parents preferred scales that they perceived to be happy and cartoon-like. The results of this study indicate that subtle variations in the format of faces scales do influence children's and parents' ratings of pain in clinical settings.

Acute and chronic low back pain: cognitive, affective, and behavioral dimensions.

Despite strong suppositions concerning differences between patients suffering acute and chronic low back pain, relatively few data-based comparisons have been made. In this study, affective, cognitive, behavioral, and demographic contrasts were conducted. Chronic patients were divided into those who demonstrated signs and symptoms that were either congruent or incongruent with underlying anatomical and physiological principles. Low socioeconomic status, compensation claims, use of opiate analgesics, greater disability, catastrophizing cognitions, stronger emotionality, and passive coping were more characteristic of both acute and chronic incongruent patients than chronic congruent patients. A relatively stereotyped, spontaneous facial expression of pain was observed in all groups when responding to painful movements during a physical examination. The similarities between acute and chronic incongruent patients have implications for the assessment and treatment of low back pain.

Pain measurement in persons with intellectual disabilities.

OBJECTIVE: The goal was to study the utility of nonverbal facial expressions as a research tool for assessing pain in persons with intellectual disabilities. Biases and stereotypes related to age, gender, physical attractiveness, and intellectual disability that may influence the ability of observers to evaluate pain reactions were also examined. DESIGN: Facial reactions to an intramuscular injection of 40 adults (mean age = 49.6 years) with an intellectual disability were videotaped and objectively examined using the Facial Action Coding System. Self-reported pain ratings were obtained using a Colored Visual Analogue Scale for pain. Pain reactions were also rated by untrained observers. RESULTS: A significant proportion of participants (35%) was unable to provide valid self-report. The intensity of objectively coded facial activity as well as observer-rated pain intensity showed significant increases from baseline to injection segments. Observers' pain ratings were primarily determined by the intensity of facial activity and were not significantly affected by stereotypes based on perceived level of intellectual disability, gender, age, or physical attractiveness. CONCLUSIONS: The findings support the validity of both objectively coded and observer-rated facial expressions of pain as research tools in treatment outcome studies involving persons with intellectual disabilities. Self-report has substantial limitations for the assessment of pain in this population.

Social barriers to optimal pain management in infants and children.

OBJECTIVE: To examine the social barriers that lead to less than optimal management of pain in children. DESIGN: Recognizing the vulnerabilities of infants and children and their dependence on caring adults, a model of pain communication is proposed. The model examines (a) the pain experiences of children, including social determinants; (b) developmental variations in the capacity to encode the severity and qualities of pain as expressive behavior; (c) adult skills and deficiencies in decoding pain; and (d) the actions of adults predicated on the meaning and significance attached to children's actions. Limitations in care were examined. DATA SOURCES: The current research and professional literature were accessed through searches of the Psyclit and Medline databases for relevant investigations on the basis of our working knowledge of the literature. CONCLUSION: Numerous deterrents to optimal care are identified in the domains of commonplace beliefs about the nature of pain in infants and children: failure to recognize the impact of socialization in familial and cultural modes of experience and expression; needs for age-specific assessment instruments; the limited capacity to use available evidence concerning pain; the need to employ clinicians, parents, and other adults more effectively in delivering care; and structural problems in the health care system.

Measuring movement-exacerbated pain in cognitively impaired frail elders.

OBJECTIVE: Prior research examining the utility of nonverbal measures of pain in persons with cognitive impairments has focused on acute procedurally-induced phasic pain (i.e., venipuncture and needle injections). The goal of the current project was to examine the utility of both self-report and nonverbal measures of pain in frail elders experiencing exacerbations of chronic musculoskeletal pain. These were assumed to be more representative of the day-to-day pain experience of elderly patients. DESIGN: Participants were 58 frail elders, 29 of whom had been found to have significant cognitive impairments. All were filmed as they undertook a series of structured activities (e.g., walking and reclining), and pain was assessed using self-report. Trained coders identified the incidence of pain-related behaviors using the videotapes. The various pain measures (i.e., self-report and nonverbal indices) were compared across both patient groups and the several activities. RESULTS: Consistent with our hypotheses, more pain was identified (using both self-report and nonverbal measures) when patients engaged in more physically demanding activities. Facial reactions varied as a function of patient cognitive status, with those participants who were cognitively impaired more responsive. Of the various nonverbal indices that we examined, guarded behavior appeared to be especially sensitive. The various pain indices were only modestly correlated with one another. CONCLUSIONS: This study supports the validity of self-report and behavioral measures of pain in frail elders with and without cognitive impairments. Each of the measures used contributed different information to pain assessment, suggesting that investigations of pain in elders with cognitive impairments should employ varying types of pain assessment tools.

Biobehavioral responses to acute pain in adolescents with a significant neurologic impairment.

OBJECTIVE: To further understand acute pain response in children with a significant neurologic impairment (SNI), we undertook a descriptive hypothesis-generating study of the response to a routine vaccine among adolescents with SNI. DESIGN: Within-subject crossover design. SETTING: Tertiary care facility for children and adolescents with SNI. PATIENTS: Eight adolescents (mean age = 15 years). INTERVENTIONS: Mock and real vaccine injections. OUTCOME MEASURES: Quantitative measures of heart rate, videotaped facial action, Child Facial Coding System (CFCS), and Facial Action Coding System (FACS); observer ratings visual analog scale (VAS) were obtained before, during, and after a mock injection and routine annual influenza vaccine injection presented in a counterbalanced order. RESULTS: VAS scores were significantly higher during the injection phase than during the other time periods; however, there were no significant differences across study time periods when using the other outcome measures. CONCLUSIONS: Although the dampened behavioral and physiologic reactions to an acute noxious stimulus were similar to those of previous work with developmentally delayed children and frail elderly, it remains unclear what underlies the apparent reduced pain response in this setting. These findings have potentially important implications for the daily care of individuals with significant neurologic impairment and illustrate the compelling need tor further study of the unique character of the pain experience in this setting.

Agreement between child and parent reports of pain.

OBJECTIVE: Parents are often the primary source of information regarding their children's pain in both research and clinical practice. However, parent-child agreement on pain ratings has not been well established. The objective of the present study was to examine agreement between child- and parent-rated pain following minor surgery. SETTING: Tertiary care children's hospital. PARTICIPANTS: A total of 110 children (56.4% male) aged 7-12 years undergoing surgery and their parents. OUTCOME MEASURES: Parents and children independently rated pain intensity by using a 7-point Faces Pain Scale on the day of the child's surgery and the following 2 days. RESULTS: Correlations (both Pearson's and intraclass correlation coefficients) indicated a highly significant relationship between child and parent ratings. However, kappa statistics indicated only poor to fair agreement beyond chance. Parents tended to underestimate their children's pain on the day of surgery and the following day, but not on the second day following surgery. When children's and parents' pain ratings for each of the 3 days were collapsed into a no-pain/low-pain group or a clinically significant pain group, kappa statistics indicated fair to good agreement. Parents demonstrated low levels of sensitivity in identifying when their children were experiencing clinically significant pain. CONCLUSIONS: Correlations between parent and child pain reports do not accurately represent the relationship between these ratings and in fact overestimate the strength of the relationship. Parents' underestimation of their child's pain may contribute to inadequate pain control.

Facial expression of children receiving immunizations: a principal components analysis of the child facial coding system.

OBJECTIVE: To identify the structure of facial reaction to procedural pain and to determine the subset of facial actions that best describe the response. DESIGN: Observational. SETTING: Five rural and five urban physicians' offices. PATIENTS: One hundred twenty-three children aged 4 to 5 years undergoing routine diphtheria, pertussis, tetanus, and polio immunization. OUTCOME MEASURES: The Child Facial Coding System, comprising 13 discrete facial actions, was used to code each second of five 10-second phases from videotape: baseline, preneedle, needle, postneedle, and posthandling. Parents and a technician provided visual analog scale ratings of children's pain. Children provided a self-report using a Faces Pain Scale, and parents and nurses rated the children's pain and anxiety using visual analog scales. RESULTS: A "pain face" similar to that reported in adults emerged with the onset of pain. Principal component analyses revealed the frequency and intensity of facial action during the needle phase could be represented by components reflecting pain sensation, a "brave face," and the children's expectations for pain. Children's Faces Pain Scale and adult visual analog scale ratings were best predicted by components reflecting pain sensation and expectations of high pain. CONCLUSIONS: These results provide a preliminary indication that the Child Facial Coding System can be reduced to components that reflect several aspects of children's acute pain experience and predict self-reports and observer reports of children's pain.

Postoperative pain expression in preschool children: validation of the child facial coding system.

OBJECTIVE: The purposes of the study were threefold: (a) to determine whether a measurement system based on facial expression would be useful in the assessment of post-operative pain in young children; (b) to examine construct validity in terms of structure, consistency, and dynamics of the facial display; and (c) to evaluate concurrent validity in terms of associations with global judgments of the children's pain. PATIENTS: One hundred children between the ages of 13 and 74 months were video-taped for a maximum of 1 hour after arrival in the postanesthesia care unit (PACU) at British Columbia's Children's Hospital. OUTCOME MEASURES: Videotapes were edited into 20-second blocks, randomly selected from each 2-minute time period taped during the hour following surgery, and coded for the presence or absence of 13 facial actions in the Child Facial Coding System (CFCS). RESULTS: Facial expressions were characterized primarily by the following constellation of actions: open lips, lowered brows, a deepened nasolabial furrow, mouth stretched wide in both horizontal and vertical directions, eyes squeezed shut or squinted, and raised cheeks. A principal components analysis indicated that these actions comprised a single factor, accounting for 55% of the variance in CFCS actions. Facial action summary scores were correlated with a visual analog rating of global pain, confirming that the CFCS has convergent validity. Facial action summary scores, i.e., pain displays, were at their lowest immediately after admittance to the PACU and just before the child's release from the PACU. CONCLUSIONS: The present study demonstrated that the CFCS serves as a valid measurement tool for persistent pain in children.

Facial expression during induced pain.

Facial expressions contribute substantially to judgments of sufferer's pain but have not been rigorously described. We obtained a detailed description of 72 female volunteers' facial reactions to the cold pressor experience, using Ekman and Friesen's (1978a) objective, anatomically based Facial Action Coding System. In addition, we examined the impact of exposure to social models tolerant or intolerant to pain. The facial actions systematically provoked by cold pressor exposure comprised a narrowing of the eye aperture from below, raising the upper lip, pulling the lip corners, parting of the lips, or dropping the jaw, and eyes closing or frequently blinking; however, there was rich individual variation in the facial displays. The reactions were most salient at onset, indicating blends of startle, adaptive reaction, emotional expression, and pain, but they declined in vigor over time, although self-report of pain continued to mount. The relation between subjective distress and facial expression was greatest at the beginning of noxious stimulation. The social models had a potent impact on verbal report and pain tolerance but not on facial expression, indicating relative independence of components within the rich range of expressive reactions of painful experience.

Judgments of genuine, suppressed, and faked facial expressions of pain.

The process of discriminating among genuine, suppressed, and faked expressions of pain was examined. Untrained judges estimated the severity of pain being experienced when viewing videotaped facial expressions of chronic pain patients undergoing a painful diagnostic test or dissimulating reactions. Verbal feedback as to whether pain was experienced also was provided, so as to be either consistent or inconsistent with the facial expression. Judges were able to distinguish genuine pain faces from baseline expressions but, relative to genuine pain faces, attributed more pain to faked faces and less pain to suppressed ones. Advance warning of deception did not improve discrimination but led to a more conservative or nonempathic judging style. Verbal feedback increased or decreased judgments, as appropriate, but facial information consistently was assigned greater weight. An augmenting model of the judgment process that attaches considerable importance to the context in which information is provided was supported.

Social modeling influences on sensory decision theory and psychophysiological indexes of pain.

Subjects exposed to social models dissimulating tolerance or intolerance generally exhibit matching behavior in their verbal ratings of painful stimulation. It has been unclear, however, whether these changes reflect voluntary alteration of evidence or genuine changes in distress. This study used alternative measures and controlled for methodological limitations of earlier studies by examining nonpalmar skin potential in addition to palmar skin conductance and heart rate indexes of psychophysiological response to electric shock, and by evaluating verbal expressions of pain with sensory decision theory methodology. Of 20 female volunteer subjects, half served as controls, and half were exposed to a tolerant female model. Both the subject and the model verbalized ratings of discomfort provoked by a series of electric shocks of increasing intensity. Subjects then underwent a series of preselected random shocks. Sensory decision theory analyses revealed lower discriminability of the shocks among subjects exposed to a tolerant model. Several indexes of nonpalmar skin potential and heart rate reactivity exhibited lower reactivity in the tolerant group. Tolerant modeling was also associated with decreases in subjective stress. The results were consistent with the position that changes in pain indexes associated with exposure to a tolerant model represented variations in fundamental characteristics of painful experiences as opposed to suppression of information.

Observer judgments of acute pain: facial action determinants.

We provided a microanalytic description of facial reactions to a series of painful and nonpainful electric shocks and examined the impact of these as discrete facial cues for observer judgments of acute pain. Thirty female volunteers were videotaped and reported their discomfort in response to electric shocks after earlier exposure to one of three social influence conditions: a tolerant model, an intolerant model, or neutral peer presence. We coded the videotapes for facial activity using the Facial Action Coding System (Ekman & Friesen, 1978b), and peer judges rated them for painful discomfort. Subjects exposed to a tolerant model reported no more discomfort than did subjects exposed to an intolerant model, despite receiving more intense levels of shock, but were judged by observers to be in more pain. Analyses of facial activity yielded consistent findings: Tolerant-model subjects, though reporting discomfort equivalent to that reported in other groups, displayed more pain-related facial activity (brow lowering, narrowing of the eye aperture from below, raising the upper lip, and blinking). There was a substantial direct relation between observer judgments of distress and discrete, pain-related facial actions (mean multiple R = .74 for the various shock levels rated). These data indicate that nonverbal expression yields information about the response to noxious stimulation that is non-redundant with self-report.

Appearance-based information about coping with pain: valid or biased?

Previous research led to the conclusion that patient characteristics such as physical attractiveness and non-verbal expressiveness affected judgements of patient pain and distress. This study investigated whether this represents an intrusive bias or whether there indeed are psychological differences between physically attractive vs physically unattractive and expressive vs inexpressive pain patients. The findings led to the conclusion that both variables are related to the types of coping strategies pain patients use. Specifically, physically attractive and nonverbally expressive patients were found to be less likely to utilize passive coping strategies. Coping style also was found to be related to demographic characteristics of the patients. Theoretical reasons for the identified relationships are discussed as are the implications of these findings for the assessment of pain.

Developmental changes in infant pain expression during immunization injections.

Developmental changes in pain expression provoked by routine immunization injections during the first 2 years of life were examined. An interval-sampling, behavioral observation system was developed to code categories of expressive behavior in infants, their mothers and the nurse responsible for the injection. Qualitative changes were observed in the infants' behavior, with those less than 12 months of age responding in a more spontaneous, diffuse manner, whereas the older infants displayed more anticipatory distress, descriptive language and goal-directed movement. Mothers and the nurse actively interacted with each other and the infant with a range of vocal and nonvocal actions. The findings justified the use of unobtrusive, naturalistic observation as a means of assisting practitioners who suffer from an inadequate knowledge-base on pain in children.

Social influences on factored dimensions of the McGill Pain Questionnaire.

The McGill Pain Questionnaire (MPQ) was administered to 268 subjects following electrical stimulation to pain-tolerance limits. Subjects received stimulation under four social modeling conditions: tolerant, intolerant, control, and no model. The number of factors and degree of obliqueness most appropriate for the MPQ scores were determined using multiple criteria. Five factors, reflecting 46.6% of the total variance, were derived and labelled as follows: affective-arousal, sensory-pressure, perception of harm, somesthetic pressure, and cutaneous sensitivity. The various modeling conditions did not produce any significant between-group differences on the factors. The repeated demonstration that the MPQ assesses substantially more than the three components originally proposed suggests that considerable caution is warranted with respect to using the 'sensory-evaluative-affective' method of scoring this test. Considered in relation to previous research, the present findings are consistent with the conclusion that social influences affect fundamental components of subjective reactions to pain.

A theoretical framework for understanding self-report and observational measures of pain: a communications model.

Self-report and observational measures of pain are examined from the perspective of a model of human communication. This model examines the experience of pain as affected by intrapersonal and contextual factors, the process whereby it is encoded into expressive behaviour, and the process of decoding by observers prior to their engaging in action. Self-report measures primarily capture expressive pain behaviour that is under the control of higher mental processes, whereas observational measures capture behaviour that is less subject to voluntary control and more automatic. Automatic expressive behaviours are subject to less purposeful distortion than are behaviours dependent upon higher mental processes. Consequently, observational measures can be used and have clinical utility as indices of pain when self-report is not available, for example, in infants, young children, people with intellectual disabilities or brain damage, and seniors with dementia. These measures are also useful when the credibility of self-report is questioned and even when credible self-report is available. However, automatic behaviours may be more difficult for observers to decode. The model outlined herein takes into account the role of various human developmental stages in pain experience and expression and in understanding the utility of self-report and observational measures. We conclude that both observational and self-report measures are essential in the assessment of pain because of the unique information that each type contributes.