Pressure Pain Threshold Values Research Articles

Examiner expectancy effects in the measurement of pressure pain thresholds

The ascending Method of Limits, used for the determination of pressure pain thresholds (PPT), is not a psychophysically robust method. The present study sought to determine if the examiner's expectancy, based on whether the measurement site was clinically `painful' or `non-painful', would bias the obtained PPT values. Twenty-eight patients with facial or temporal area pain served as subjects, and in each subject, a pain site and a control site were identified and marked. According to a randomization schedule, the pain and control sites were correctly marked in half of the subjects and were mis-labeled in the other half, thereby controlling the examiner's knowledge of a site and thus the examiner's expectancy of what the PPT should be. Two examiners, shown to be reliable with each other in both pre-clinical and post-clinical reliability studies, were blind to the true purpose of the study and to the marking procedures. Each examiner made one PPT measurement at each marked site in a counterbalanced measurement order. Manipulating the examiner's prior knowledge of the measurement site's characteristics significantly lowered the obtained PPT values for control sites but did not significantly alter the PPT at the clinically painful sites. Nevertheless, the pain sites still had significantly lower PPTs than did control sites. We conclude that: (i) PPTs at pain sites are robust to a major source of measurement bias associated with the ascending Method of Limits; (ii) measurement order and knowledge of measurement site characteristics can influence obtained PPT; and (iii) the common protocol in which the examiner monitors the amount of pressure during PPT measurement in order to control the force application rate may serve as a mechanism that can bias the obtained values.

Pressure algometry in manual therapy

SUMMARY. The pressure pain threshold (PPT), i.e. the least stimulus intensity at which a subject perceives pain, was studied in 30 patients with chronic unilateral pain in the shoulder and arm region.Fourteen trigger points were investigated on both sides of the body using pressure algometry. Eight paravertebral points and six points in the shoulder and arm region were evaluated. Each location was examined twice. The patients were tested by one examiner.The intraobserver reliability of PPT measurements was considered to be good. The Intraclass Correlation Coefficients of reliability (ICC), based on two repeated PPT measurements varied between 0.64 and 0.96. The painful side of the body was found to be more sensitive than the non-painful side, although there was not always a significant difference at the 0.05 level. The PPT was found to be higher in males than in females (P < 0.05). Females demonstrated lower PPTs than males at each trigger point. It was established that pressure tenderness varies over individual trigger points. Significant regional differences in PPT values were observed (P < 0.05). PPT values decreased in a cranial direction in the spine and in a caudal direction in the upper limb.Although the authors expected to find segmentally reduced PPT values on the painful side of the body, a generalized reduction of PPT values was present at all peripheral and spinal segmental sites. Some correlations between segmentally related trigger points were found by factor analysis.

Electronic pressure algometry of deep pain in healthy volunteers.

Deep pressure pain threshold (PPT) and pressure pain tolerance (PPtol) were measured by pressure algometry at the mastoid processes, external malleoli, and sternum in 24 healthy volunteers. The algometer consisted of a force displacement transducer with a 0.25 cm2 pressure tip linked to a recorder. The rate of force application was approximately 1kg/sec/0.25cm2. High intersubject variation was noted at all sites for both PPT and PPtol. Mean PPT and PPtol values at the sternum were 5.2kg +/- 2.1 and 8.1kg +/- 2.4, respectively, and significantly higher than at the other sites. PTT did not differ significantly between the sexes or between dominant and nondominant sides. PPtol, on the other hand, was lower in the women, but significantly so only at the malleoli. On repeat examination, comparison between the mean values at each site showed no statistical differences in any instance. Pressure algometry, as used in this study in healthy subjects, proved a reliable technique for the estimation of deep PPT and PPtol values. It may possibly serve for screening the response to experimental pain in various groups of pain patients.

Measurements of human pressure-pain thresholds on fingers and toes

Pressure-pain thresholds (PPT) were measured on fingers and toes with a hand-held electronic pressure algometer in 15 males and 15 females. The pressure algometer offered easy control of pressure application rate. The intra-individual coefficient of variation, based on repeated PPT measurements with a 1 week interval was 14%. The inter-individual coefficient of variation was 28% for females and 33% for males. In the course of 10 consecutive PPT measurements with short intervals (10 and 20 sec), no significant change in PPT was observed. PPT was found to be 50% higher in males than in females ( P < 0.0001). Slightly but significantly higher PPT values were found on the dominant compared to the non-dominant side ( P < 0.005).

Pressure-pain threshold in human temporal region. Evaluation of a new pressure algometer

A hand-held pressure algometer with a pressure sensitive strain gauge at the tip was used to measure the pressure-pain threshold (PPT) in the temporal region of healthy volunteers. Various sizes of circular tips and various application rates were tested before selecting an area of 0.5 cm 2 and a constant application rate of 0.68 N · sec -1 for future use. A highly significant correlation was found between PPT values obtained from the two sides (of the head) ( P < 0.001) and between PPT values obtained with a 3-week interval ( P < 0.001). In a series of 50 immediate consecutive measurements in the same individual, the mean PPT was 171 kP a (N = 6, 2 S.D. 24%). The mean relative change in PPT after a 3-week interval was 0 ± 51% (N = 11, 2 S.D.). In the course of 5 repeated determinations at weekly intervals there was a significant increase in PPT (ANOVA, P < 0.05). Subcutaneous lignocaine significantly elevated PPT compared to placebo. Due to the high inter-individual variation, determinations of PPT for group comparisons should include rather large population samples, whereas in paired studies, the intra-individual variation allows the investigation of much smaller groups (10–20 subjects). It is our experience that the pressure algometer is easy to operate in the hands of a skilled laboratory assistant.

Neurological Causes of Cervicobrachial Pain

The objective was to investigate the presence of cutaneous allodynia and hyperalgesia in the trigeminal and extra-trigeminal areas, as a surrogate for central sensitization (CS), in women with a painful temporomandibular disorder (TMD) and without other painful conditions. Painful TMDs, depression, and non-specific physical symptoms (NSPS) were classified according to the Research Diagnostic Criteria for Temporomandibular Disorders (RDC/TMD). The amount of pain in the trigeminal and extra-trigeminal areas was determined using a visual analogue scale (0–100 mm) after the application of a vibrotactile stimulus and assessment of the pressure pain threshold (PPT). Statistical tests (Fisher's, χ2, and Mann–Whitney) were performed, with a significance level of 5%. The sample comprised 45 women (mean age 37.5 years; 16 with a painful TMD) who were free of any headache, fibromyalgia, or other painful condition. Painful TMD was associated with higher pain sensitivity and lower PPT values in the trigeminal (P < 0.01) and extra-trigeminal regions (P < 0.01). The presence of depression contributed significantly to increased pain sensitivity. The presence of hyperalgesia and allodynia in both the trigeminal and extra-trigeminal regions among women with a painful TMD indicated the presence of CS. Changes involving the central nervous system should be considered during the evaluation and management of patients with a painful TMD.