Which pain scale would the nurse use to measure the intensity of pain in toddlers

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Introduction
Section snippets
Participants
Study 2: validation of the FPS-R with a painful procedure
Study 3: validation of the FPS-R with a clinical sample
General discussion
Acknowledgements
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The purpose was to examine nurses' use of pediatric pain scales and to compare their estimate of the child's pain intensity and affect with the child's self-report. The Analog Chromatic Continuous Scale (ACCS) was used for pain intensity and the McGrath Affective Faces Scale (MAFS) for pain affect. Self-report of pain was obtained from 124 hospitalized postoperative children aged 5 to 17 years and compared with estimates of 44 pediatric nurses randomly assigned to either an experimental or control group. Experimental nurses used the ACCS and MAFS to obtain pain ratings whereas control nurses made estimates according to their customary method of assessment. Findings revealed that only 36% of the nurses had at any time used a pediatric pain scale. Correlations between the experimental nurses' ratings and the child's self-report were significantly higher than the control nurses' estimates and the child's self-report. The correlation between the child's self-report of pain intensity on the ACCS and of affect on the MAFS was r=.612, suggesting that nurses' use of both an intensity and affective pediatric pain scale would more accurately reflect the child's pain experience.

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Introduction

In the past decade, there has been an increased interest in the assessment and management of pain in pediatric populations. However, according to Kuttner (1996) “attempting to assess and measure another person's pain is like trying to speak a foreign language that you don't understand” (p. 76). Determining the best way to measure pain in children has been difficult, thus far, for two major reasons. First, the assessment of pain in children can present developmentally-specific difficulties due to potentially limited abilities in verbal communication and associative thinking (Champion et al., 1998). Second, although the International Association for the Study of Pain has made recommendations for regular charting of pain, in many settings no such practices have been put in place despite good intentions and the existence of many published scales. As a result of these two relatively independent factors, validated pain measures are not commonly used in pediatric care (Hester et al., 1998).

Without regular pain assessment, pain is often undertreated. Overcoming some of the challenges in assessing children's pain necessitates the development of reliable, valid and age-appropriate pain measures (Tesler et al., 1991). Such tools could be used both with acute pain when measures would be taken several times a day or chronic pain when measures could be taken less often, perhaps once a day. To be most effective, pain measurement tools must be simple, practical, and useful, without imposing a large burden on caregivers. Simplifying pain measurement may have multiple benefits including: (a) improved relief of pain in children; (b) decreased workload for nurses and other health care professionals related to improved patient pain relief; and (c) creation of a common pain language to facilitate communication about pain within and across settings.

More than 40 published pain measures are available for use with children (Finley and McGrath, 1998). Three types of measures are typically used in health care settings to measure pain: self-report, observational and physiological. Many different metrics are used to assess pain intensity (e.g. 0–5, 0–10, 0–42, and 0–100). In some institutions where different scales are simultaneously in use, because of the lack of a consistent practice of indicating which scale a given score refers to, it is often not possible to tell whether a recorded pain score of, say, 5, indicates severe pain (5/5), moderate pain (5/10) or minimal pain (5/100). As a result there can be significant inconsistency in how and when the measures are applied, if they are even used at all (von Baeyer et al., 1998). One way to eliminate such inconsistency would be the development of a common metric which could be used both within and across institutions. Communication of pain scores in standardized units, much like the intelligence quotient or the Celsius scale, would facilitate shared understanding of the meaning of the scores. A common metric would allow for a conventional and universal language for reporting scores, but would not be limited to a list of particular measurement instruments. It is important to note that the extent to which scores from various pain measures conform to this theoretical linear metric is a question to be answered separately for each tool and for each measurement situation (von Baeyer and Hicks, 2000).

If some consensus can be reached about the most desirable metric to be used, old measures can be adapted or new measures can be developed to fit within this framework. In order to reach a consensus, compromises will need to be made. Most self-report pain intensity measures designed for young children have four to six levels or divisions (e.g. Beyer, 1984, Hester, 1979, Whaley and Wong, 1987). On the other hand, self-report pain intensity measures designed for adults commonly have finer, more numerous divisions (e.g. the NRS-101, a common form of the numerical rating scale that provides a score from 0 to 100). Thus, if a common metric is to be adopted it will represent a compromise between the number of points necessary to measure pain intensity and applicability across the life-span (McCaffery and Pasero, 1999). Different instruments may be needed to accommodate the substantial variability across the pediatric age span, but pain intensity scored on the different instruments can be recorded on the same metric to facilitate communication.

Currently, a movement toward a consensus can be identified in that two metrics are most accepted: 0–5 and 0–10 (McCaffery and Pasero, 1999). Several pre-existing and developing systems in both research and clinical practice have become focused on these two most common metrics. For example, McCaffery and Pasero (1999) suggest a system, to be used throughout a clinical setting, that combines and standardizes a numerical rating scale and the Wong–Baker FACES scale on a 0–10 metric. While some observational and self-report measures already use these metrics, other measures will need to be adapted and validated.

Once measures have a shared metric, they can be more easily combined into measurement systems which employ multiple approaches, but are straightforward and simple to use. Improvement of the assessment and management of pain necessitates more user-friendly measurement tools for health care providers (Hester et al., 1998). Although there are other self-rating scales (e.g. numerical rating scales) that are already based on the 0–5 or 0–10 metric, a psychometrically sound facial expression scale would be an important addition to such a pain measurement system. Face scales are especially good for younger children because these measures are concrete and presumably easier for young children to follow, especially in the 4–8-year-old range (Champion et al., 1998). In order to use this tool, children would need the cognitive capacity to match pictures of facial expressions to their own internal state, but they would not need to be able to count or to use numbers in a categorical fashion. Children also report a preference for the faces scales, in part due to the ease of application (Champion et al., 2000).

One candidate for a simplified measurement system is the Faces Pain Scale (FPS; Bieri et al., 1990). It has several advantages over other facial expression scales. In creating this facial scale, Bieri et al. (1990) addressed the problems that had been encountered with other such scales. Specifically, they avoided the problems inherent in inclusion of smiles and tears in a pain scale: (a) the apparent confounding of affective distress with pain intensity (Champion et al., 1998, Chambers and Craig, 1998); and (b) the significantly higher pain ratings given on scales that have smiling ‘no pain’ faces compared with scales that have neutral ‘no pain’ faces (Chambers et al., 1999).

The development and psychometric refinement of the FPS occurred in several stages. The result of this multi-stage process is a straightforward measure that allows pain intensity to be measured in young children who may have difficulty with more cognitively demanding instruments. The original version of the scale consists of seven faces increasing in pain intensity and approximating equal intervals as assessed by children (Bieri et al., 1990). It must, of course, be acknowledged that a point on such a scale has no absolute meaning, but is relative to the rater's experience with pain, as well as other factors.

The original version of the FPS would require adaptation as it is a seven-point scale and therefore does not lend itself easily to scaling on either a 0–5 or 0–10 metric. A revision of the scale developed by Bieri et al. (1990) will allow the scores from the FPS to be on the same metric or scale as numerical self-report and observational measures of pain. For the current adaptation of the scale, six faces were considered more advantageous than 11 because of the challenge that the larger number of faces, and consequent finer distinctions, would pose for children aged 3–5 years (Shih and von Baeyer, 1994).

The Sydney Animated Facial Expressions (SAFE) Scale developed by Champion and colleagues (Goodenough et al., 1997) is a version of the FPS which was created in other research to explore the ways in which young children apply scales to estimate pain intensity (i.e. whether or not young children have a bias for the ends of a scale; cf. Chambers and Johnston, 2001). The SAFE scale is a computer animation in which a single face varies smoothly from ‘no pain’ to ‘most pain possible’ faces of the FPS (through 101 frames). In Study 1, this animated form of the scale was used in combination with printed copies of the anchor points (i.e. the first and last face as designated by Bieri et al., 1990) and adults were asked to identify the four intermediate faces to be included in the six-face adaptation of the FPS.

As suggested by McGrath (1987), cross-modality matching (CMM) methodology and related techniques may be ideally suited for psychometric refinement of pain measures. In Study 1, only one modality was used (i.e. the presentation of the pain faces). Two approaches related to CMM, the estimation and production methods, are suggested when examining only one modality. In magnitude estimation, a stimulus is presented and the participant is asked to assign a number to that presentation (Luce and Krumhansl, 1988). Magnitude production reverses the procedure used in magnitude estimation, in that the participant is given a number and asked to produce a matching intensity (Falmagne, 1985). For Study 1, the method of magnitude production was considered most appropriate for this investigation, as it allowed participants to match the pain intensity represented by a face to a number. Using this technique facilitated the reduction of the number of faces in the scale, while minimizing the number of trials required to obtain reliable results. Additionally, this method was more analogous to the way the scale will later be used in clinical practice (i.e. users will be asked to select a face matching the intensity of their pain experience).

In Studies 2 and 3, the CMM method was used with children matching their ratings of pain using pain faces and line length or color gradation (i.e. the visual analogue scale (VAS) and colored analogue scale (CAS), respectively). In CMM, the task for participants is to equate the perceived strength of two stimuli from two different modalities (Stevens, 1960). An experimenter selects a series of stimuli (e.g. sounds) and measures each by physical means (e.g. decibel meter). The participant might then adjust the intensity of a light to match each presented intensity of sound and the experimenter measures the responses (e.g. photometer). Such techniques have been used successfully even with children as young as age 4 because they do not depend on the understanding of numbers or words (McGrath, 1990).

The first aim of the present research was to revise the FPS from seven faces to six faces to make it practical to score it either 0-1-2-3-4-5 or 0-2-4-6-8-10, thereby allowing the FPS to be incorporated into a simplified pain assessment system that utilizes both self-report and observational measures employing the 0–5 or the 0–10 metric. The second aim was to evaluate the validity of the revised six-face version (Faces Pain Scale – Revised, FPS-R) by using the scale with children in actual pain situations, in both non-clinical and clinical settings. Ratings obtained on the revised scale were compared with those on the VAS which has been well-documented as a reliable and valid pain measurement tool (McGrath, 1987), and the CAS (McGrath et al., 1996).

Section snippets

Participants

Following the methods of Gracely et al. (1978) (see Section 2.2), a sample of 15 adults was obtained from the student population at the University of Saskatchewan. Participation was voluntary and some individuals received course credit for participating. Adults were selected for this phase because the task was considered too complex and abstract for children; however, all participants had extensive experience with children between the ages of 5 and 12. Parents, and others who had extensive

Study 2: validation of the FPS-R with a painful procedure

Study 1 demonstrated the psychometric qualities of the six-face FPS-R by establishing the linear progression of the faces and by presenting several comparisons (both within and between groups) based on 1200 ratings by adults. The next step in the development of the FPS-R was to determine the validity of the measure with children who are experiencing ‘real-life’ pain, namely ear piercing. The convergent validity of the FPS-R was assessed by correlating it with a VAS. As the age range selected

Study 3: validation of the FPS-R with a clinical sample

Study 2 demonstrated the validity of the FPS-R with children who are experiencing ‘real-life’ but non-clinical pain. The next step in the development of the FPS-R was to determine the validity of the measure with children experiencing clinical pain. The convergent validity of the FPS-R was assessed by correlating it with the VAS and CAS. As the age range selected for this phase was 4–12 years, possible age effects were also examined.

General discussion

The goal of the present research was to contribute to (a) the improvement of pain measurement methods used in pediatric populations and (b) the development of a common metric. In Study 1, a six-face adaptation of the FPS was developed for potential inclusion in a simplified system of pain assessment based on a 0–5 or 0–10 metric.

There are several reasons for choosing a face scale, and specifically the FPS, for adaptation to a common metric. Face scales are generally preferred, especially by

Acknowledgements

The authors would like to acknowledge the contributions of Duc Trieu (Faculty of Medicine, University of New South Wales), who was responsible for developing the 101 faces (from the original seven of the FPS) for the SAFE scale, and Robert Kovacic, who did the programming and Windows 95 applications. The contributions of Louise Alexitch, Tammy Marche, Kellie Hadden and Stephen Shaw are acknowledged. We would also like to express our appreciation to the staff of Ardene's for their commitment to,