The thermal performance of biological tissue under moxibustion therapy.

An understanding of the thermal performance of biological tissue under moxibustion with ash cleaning and distance adjustment (ACDA) is helpful for the optimization and standardization of moxibustion clinical treatment. This study compared surface temperature distribution of burning moxa stick with and without ash cleaning. The experimental of moxibustion treatment on in-vitro tissue and human abdomen were conducted and corresponding numerical models were developed. The effect of ACDA on thermal performance of biological tissue under moxibustion therapy were analyzed. The results show that the surface temperature of burning moxa stick with ash cleaning maintained at a higher range compared to that without ash cleaning. During moxibustion with ACDA process in in-vitro tissue experiment, the temperature increase (ΔT) at skin surface almost fluctuated in the same temperature range, and the ΔT in subcutaneous tissue (>11 mm) kept increasing. Relatively, these ΔT under moxibustion treatment without ACDA showed different trends and these values were all much smaller than those with ACDA. In addition, the position of maximum temperature of tissue under moxibustion with and without ACDA was fixed on treatment acupoint and moved away from treatment acupoint, respectively. Besides, the surface temperature of human abdomen tissue under moxibustion treatment with ACDA can be maintained at 46 °C-50 °C for a longer time compared to that under moxbustion without ACDA. In conclusion, moxibustion with ACDA can create a larger and more durable thermal effect on biological tissue. The results also suggest that ACDA may be helpful to improve moxibustion therapy efficacy in clinic treatments.

The Effect of Moxibustion Stimulation on Local and Distal Skin Temperature in Healthy Subjects.

The aim of this study is to investigate the response of local and distal skin temperature to moxibustion stimulation (MS) and explore the effects of MS on sympathetic nerve activity. The distal skin temperatures of fingertips, as an indicator for sympathetic reflex response, were recorded using infrared camera during resting period (10 min), MS period (10 min), and natural cooling period (15 min), respectively. The MS without ash cleaning (AC) was applied to acupoints Quze (PC3) (Group I) and Lao Gong (PC8) (Group II), respectively. In Group III, the MS with the operation of AC was performed on PC8. The temperature responses of the local stimulation points and corresponding control points were also investigated. At the beginning of MS period, a significant increase of temperature on the stimulation point accompanied by a simultaneous reduction of temperature on fingertips was observed. A marked negative correlation was also obtained between temperature changes in the stimulation point and in the fingertips. At the end of natural cooling period (t = 34 min), the temperature of stimulation point was obviously higher than baseline values. In contrast, the temperatures of fingertips increased and then returned to the baseline levels during the second minute of MS period. In Group III, the temperature of stimulation point increased every time with the operation of AC, accompanied by the temperature decrease of middle fingertip. The findings suggest that moxibustion may trigger the sympathetic nervous system and induce the reduction of microcirculation, accompanied by a reduction of fingertip temperature. In addition, the operation of AC caused repeated cycles of thermal stimulation on the stimulation point, which may repetitively activate cutaneous sympathetic nerve fibres and evoke the temperature reduction of fingertips.

An In Vitro and Numerical Study of Moxibustion Therapy on Biological Tissue.

OBJECTIVE: Moxibustion therapy achieves satisfactory therapeutic effects largely depending on the heat stimulation of burning moxa. Understanding the thermal characteristics of heating process is an effective way to reveal the underlying mechanisms of moxibustion therapy. METHODS: This paper performs experimental study on temperature distributions of burning moxa sticks and fresh in vitro porcine abdominal tissue using an infrared camera and thermocouples. Meanwhile, a moxibustion model incorporating moxa stick burning model and tissue heat transfer model was established with consideration of radiation propagation and water evaporation. RESULTS: The burning features of moxa sticks were acquired and the radiation energy generated by the burning moxa stick was absorbed and scattered in biological tissue, resulting in a large temperature gradient in the skin layer. And the water evaporation led to a mass loss and reduced skin surface temperature. The numerical model was verified by experimental results and the effects of moxibustion treatment distance and duration can be quantified based on model calculation. CONCLUSION: The detailed heat transfer process of moxibustion was obtained experimentally and numerically. During moxibustion, the radiation attenuation and water evaporation have a significant influence on the energy transport in biological tissue which cannot be ignored. The treatment distance of 3 cm is the recommended value to achieve the treatment efficacy without thermal damage and pain. SIGNIFICANCE: This research would reveal the underlying mechanisms of moxibustion therapy. Besides, the developed models are expected to establish a guideline for moxibustion clinical treatment.