Pain threshold changes following acupuncture, measured with cutaneous argon laser and electrical tooth pulp stimulation, a comparative study

On the threshold - evaluation of variability in effects of acupuncture in a gender perspective

Variable results of pain alleviation in response to acupuncture have been reported, complicating its interpretation. Sources of variability are probably multi-factorial, including the contribution of gender related effects. Gender related variation in perceived pain has been discussed frequently, but documented effects of acupuncture referring to gender are sparse. Furthermore, factors such as operationalisation of the outcome variable and the statistical method for evaluation could also be sources of variability. When pain is regarded as subjective, the produced data should be treated as ordinal. The rank-based method by Svensson, taking the non-metric qualities of the ordinal data into account as well as the variability at the group and the individual level, is therefore an alternative. The present commentary aims to (1) evaluate changes in electrical sensory thresholds and electrical pain thresholds after low frequency electro-acupuncture separately in healthy women and men; (2) introduce and exemplify the method by Svensson in a user-friendly approach. To analyze the systematic patterns of change in thresholds, indicating evidence of treatment on a group level, the relative position (RP) and relative concentration (RC), were measured. The variation related to the individual, the relative rank variation (RV) was also measured. The results were divergent between women (n = 23) and men (n = 22), i.e. unchanged sensory threshold after acupuncture at the group level in women while changed in men. The assessed pain threshold after acupuncture on the other hand was changed towards higher levels in women and unchanged in men. The individual variation was apparent in both women and men but larger in women. For statistical analysis of the variability for both group and individual related effects, the rank-based method by Svensson could be used. The present study indicates that evaluation of sensory and pain threshold response should be analysed separately in women and men.

A comparison of effects on regional pressure pain threshold produced by deep needling of LI4 and LI11, individually and in combination

OBJECTIVES

To compare the effects of unilateral and bilateral needling of the same acupoint, and the effects of individual and combined needling of two distinct acupoints on pressure pain threshold (PPT).

DESIGN

22 subjects completed the randomised, dual blind (subject and evaluator) repeated measures study. PPT was measured before and after each intervention at ten sites (acupoints and nonacupoints) across the body with an algometer.

INTERVENTIONS

The same manual acupuncture techniques were applied to four interventions of large intestine 4 (LI4) unilaterally; LI4 bilaterally; large intestine 11 (LI 11) unilaterally; and LI4 in conjunction with LI11, both unilaterally.

MAIN OUTCOME MEASURES

(1) Percentage change in PPT from preintervention baseline measured at the 10 regional sites following every intervention; (2) participants' perceptions of pain; needling sensations; tension during, and anxiety prior to, each intervention; and changes in practitioner behaviour.

RESULTS

Following all four interventions, statistically significant increases in mean PPT were observed. These occurred at nine sites following the LI4 intervention either unilaterally or bilaterally; at six sites for LI11 intervention; and at five sites following the combined LI11 and LI4 intervention. These increases were significantly greater for the bilateral LI4 intervention than the unilateral LI4 intervention at only two sites (p < 0.02 and p < 0.0001). There were no statistically significant differences in the subjective perceptions among the four interventions.

CONCLUSION

The enhanced effects on PPT by the bilateral compared with the unilateral intervention at LI4 although limited, do provide some support for the traditional Chinese medicine (TCM) assumption that bilateral needling of the same point enhances the treatment effect. There was no support for the assumption that combined needling of points from the same channel should enhance the treatment effect and failure to obtain better effects by combined needling of points from the same channel could result from the interaction occurring during the combined needling.