Electronic Pressure Algometer Research Articles

Assessing mechanical allodynia in the rat paw with a new electronic algometer

Von Frey filaments used for testing mechanical thresholds are mechanically unstable and their use is difficult to standardize. We have therefore constructed a hand-held electronic pressure algometer. The pressure algometer is connected to a computerized data collection system, allowing on-line display of the applied force as well as the application rate. Data stored on the computer can be replayed and further analyzed. Using this apparatus, we have measured the pressure-induced withdrawal thresholds in rats with surgically induced neuropathy. The probe, with a circular tip of 1.0 mm diameter, was applied manually with a pressure increasing by approximately 0.05 N/s. Presurgical thresholds were normally distributed with a mean of 0.415 N, showing no significant difference between paws. During 2 weeks after surgery, the thresholds of the operated side were significantly reduced (range, 0.209–0.318 N), while the thresholds of the non-operated side remained at higher values (range, 0.432–0.491 N). Thresholds of control rats without surgery were in the 0.380–0.520 N range, with no significant difference between paws. In an additional experiment it was shown that interobserver reliability was high, both between withdrawal threshold values obtained and between rates of application used. In conclusion, the electronic algometer allows standardization of testing, detailed documentation of each experiment and provides an objective and accurate method for measuring the reactions of test animals to mechanical stimuli.

Effects of staphylococcus toxoid vaccine on pain and fatigue in patients with fibromyalgia/chronic fatigue syndrome

Positive results of pilot studies of the effect of staphylococcus toxoid vaccine in patients with fibromyalgia and chronic fatigue syndrome were the incitement to the present, placebo-controlled study. It included 28 patients who fulfilled the criteria for both fibromyalgia and chronic fatigue syndrome. The effect of vaccination with a staphylococcus toxoid was compared with the effect of injections of sterile water. Psychometric assessment was made using 15 items from the comprehensive psychopathological rating scale (CPRS), Zung's self-rating depression scale and clinical global impressions (CGI). The visual analogue scale (VAS) was used to measure pain levels, and a hand-held electronic pressure algometer was used to measure pressure pain thresholds. Significant improvement was seen in seven of the 15 CPRS items in the vaccine group when pretreatment values were compared to post-treatment values. In CPRS ‘fatiguability’, there were significant intergroup differences, and in CPRS ‘pain’ intergroup differences bordered on significance. There was no significant improvement in CPRS items in the placebo group. Clinical global impressions showed significant improvement in the vaccine-treated group, and VAS did so in both groups. In a follow-up study of 23 patients, the vaccine treatment was continued for 2–6 years. Fifty percent were rehabilitated successfully and resumed half-time or full-time work. The results of this study support the authors' hypothesis that treatment with staphylococcus toxoid may be a fruitful strategy in patients with fibromyalgia and chronic fatigue syndrome.

Decreased pain detection and tolerance thresholds in chronic tension-type headache.

To study nociceptive processing in patients with chronic tension-type headache. Forty patients with chronic tension-type headache and 40 healthy controls were examined. Pericranial tenderness was recorded by manual palpation, pressure pain detection and tolerance thresholds were recorded with an electronic pressure algometer, and the relative (pain detection minus sensory detection) electrical pain threshold was recorded with a constant current stimulator. Patients were considerably more tender than controls at all the locations examined by manual palpation (P<.001). Pressure pain detection and tolerance thresholds recorded in the finger were significantly lower in patients than in controls (P<.001). A nonsignificant similar trend was observed in the temple (P < or =.12). Detection and tolerance thresholds were decreased to a similar degree in patients compared with controls, and pain thresholds recorded in the finger and in the temple were highly correlated (r=.84, P<.001). The relative electrical pain threshold recorded at the labial commissure was significantly decreased in patients compared with controls (P=.03). All of the examined pain thresholds were significantly correlated to the pericranial tenderness recorded by palpation (r=-.35 to -.53, P < or = .03). The present finding of a general hypersensitivity to pain stimuli in chronic tension-type headache indicates that central factors play an important role in the pathogenesis of this disorder.

A comparison of pressure pain thresholds in different tissues and body regions. Long-term reliability of pressure algometry in healthy volunteers

Pressure pain thresholds (PPTs) were measured in 12 healthy female volunteers with a hand-held electronic pressure algometer (Somedic). The PPTs over 30 points, mainly located on the trunk, were measured in a randomized order. The measurements were repeated after one week and again 10-13 weeks later. Three spots over nerve tissue had lower PPTs than nearby muscle. There were no consistent differences between muscle and periosteum within the same region. Overall there was a tendency for points in the nape region to have the lowest PPT, and those in the lumbosacral region to have the highest. The shoulder points had intermediate values. The interindividual differences were great. There was no difference between the mean PPTs from the first session and those from the second session. However, at the third session, 10 weeks later, the average PPT value was substantially higher than in the previous sessions.

Cephalic muscle tenderness and pressure pain threshold in a general population

Tenderness and pain thresholds in pericranial muscles were studied in a general population. A random sample of 1000 adults aged 25–64 years was drawn as part of the Glostrup Population Studies, and 740 adults were examined. This study was part of a multifacetted, epidemiological study of different headache disorders according to the new headache classification. Manual palpation and pressure pain threshold with an electronic pressure algometer were performed by observers blinded to other information such as the person's history of headache, previous illness and mental state. The muscles most commonly tender to manual palpation were the lateral pterygoid (55%), the trapezius (52%), and the sternocleido-mastoid muscles (51%). Females were more tender than men in all the muscles examined by manual palpation. In total, the young age group was more tender than the old age group ( P = 0.03). Pressure pain thresholds on temporal muscles showed lower thresholds in women than in men ( P < 10 −3), and in the total population thresholds increased with age ( P < 0.05). No side-to-side difference in tenderness by manual palpation was found, while the right side showed increased pain thresholds in right-handed individuals ( P < 10 −4). No side-to-side difference was found in left-handed persons. This study provides data about the normal population and forms the neccesary basis for evaluating the importance of muscle tenderness in headache subjects and other selected groups.

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).