Changes in insertion resistance of acupuncture accompanying respiratory cycle〔Abstract〕

Changes in insertion resistance of acupuncture accompanying respiratory cycle

Abstract

Introduction　
Needle penetration of the skin without pain and smooth insertion of needle to deep structures are considered important skills for adequate acupuncture therapy. Physical resistance during needle insertion has been considered an important factor for smooth needling, however no experimentation has been conducted. In the present study, the relationship between insertion resistance and respiratory rhythm was quantitatively analyzed.

Methods
Seven subjects (male 4, female 3,　average age: 36.1+/-14.5) who gave informed consent were used. Insertion resistance was measured by a specially developed device. The acupuncture needle was attached to the holder of the motor drive unit which inserted the needle at a constant rate of depth, and changes of resistance were monitored by the strain-gage attached to the base of the needle holder.
The subjects lay in prone position and the resistance meter was set on the back or thigh. They were asked to maintain a stable rhythmic respiration, or to hold at inspiratory or expiratory state during insertion resistance measurement. Surface electromyogram (EMG) and/or needle EMG were at the nearby needle insertion loci were recorded.

Results
Rhythmic changes in insertion resistance at the lumbar area accompanying respiratory rhythm were clearly detected. There is a high correlation between changes in respiration and insertion resistance and low insertion resistance during the expiration phase. These rhythmic changes of insertion resistance disappeared when the respiration was held and reappeared with rhythmic respiration. No change in insertion resistance accompanying respiration was observed at the femoral region. In general the insertion resistance increased with the depth of insertion. These phenomena were detected and reproduced in all subjects. No EMG activities accompanying rhythmic respiration was detected by surface nor needle electrodes at lumber areas.

Discussion　and Conclusion
The present study clearly demonstrated that needle insertion resistance rhythmically changed with respiration and low insertion resistance was observed during the expiration phase. These facts suggest that needle insertion during the expiration phase is easier than in the inspiration phase. These changes in insertion resistance disappeared with holding of the respiration. It is reasonable to assume these insertion resistance changes are caused by direct muscular tonus changes or through autonomic nervous functions during respiration. Our attempts at EMG recordings could not detect electrical activities of the lumber muscles, so other mechanical influences produced by the respiratory movement might be a possible factor in the insertion resistance changes.