- Email: [email protected]
A needle temperature microsensor for in vivo and real-time measurement of the temperature in acupoints
Sensors and Actuators A 119 (2005) 128–132
A needle temperature microsensor for in vivo and real-time measurement of the temperature in acupoints Renfa Cui, Jianhua Liu, Wentao Ma, Jiabing Hu, Xiaodong Zhou, Hongyi Li, Jiming Hu∗ College of Chemistry and Molecular Sciences, Wuhan University, Wuhan 430072, PR China Received 1 March 2004; received in revised form 15 September 2004; accepted 15 September 2004 Available online 27 October 2004
Abstracts A novel needle temperature microsensor measurement system was established to study the temperature characteristics in acupoints. Before used in vivo, the needle temperature microsensor was tested in vitro and proved stable, accurate and sensitive. Its measurement error was no more than ±0.1 ◦ C by calibration. Its resolution was 0.1 ◦ C and response time was less than 1 s. The measurement ranged from 20 to 40 ◦ C. The in vivo experiments showed that the temperature of the acupoints ascended significantly higher than that of the left and right non-acupoints (parallel to the detected acupoints and 1.0 cm apart from them) after electroacupuncture (EA) at other acupoints, which were located on the same meridian line with the detected acupoints but 6–10 cm away from them. The results indicated that the needle temperature microsensor had a good performance in vivo. Furthermore, it supplied a reliable tool for the study of the mechanism of acupuncture and meridians. © 2004 Elsevier B.V. All rights reserved. Keywords: Microsensor; Needle temperature sensor; Thermistor; Acupoints; Meridians; In vivo
1. Introduction Temperature is an important index of life activity. Many creatures including human, whose body temperature is about 37.0 ◦ C, have a relatively constant body temperature. If the body temperature is higher or lower than that, animals might be suffering from some diseases. Temperature is an important parameter associated with substance metabolism, energy transformation and signal transmission, which are the essence of life. Therefore, the measurement of temperature in vivo is considered as an important way to reveal some biophysical and physiological properties of life. Generally, the temperature in the tissue below the skin is more stable than that on the surface of the skin. The temperature in the tissues can act as a parameter to reflect the situations in them. Therefore it is more significant and meaningful to measure the temperature below the skin instead of on the skin. ∗
Corresponding author. Tel.: +86 27 8788 2136; fax: +86 27 8764 7617. E-mail address: [email protected] (J. Hu).
0924-4247/$ – see front matter © 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.sna.2004.09.016
There are all kinds of techniques and instruments for temperature measurement, such as thermistors, platinum resistors, thermocouples, bimetals, infrared-ray temperature sensors, quartz thermometers, optical fiber temperature sensors, etc. [1]. Each has its own advantages and disadvantages. The needle temperature microsensor prepared by us for the measurement of temperature in acupoints is based on the principle of thermistors for its high temperature coefficient, high sensitiveness, short response time and minimizability. Acupuncture is an important part of traditional Chinese medicine (TCM). It is a therapy of stimulating special points called acupoints over the human body and has been widely applied in the clinic to treat various diseases for its simple manipulation, low costs, no side effects and good curative effects [2]. According to the theory of the TCM, there are 14 main meridians running through the human body and joining the acupoints and the corresponding organs together [3]. The anatomical structure and substance basis of the acupoints and meridians remain largely unknown. Thus the in situ measurement of the physical and chemical properties of these loca-
R. Cui et al. / Sensors and Actuators A 119 (2005) 128–132
129
tions will benefit to clarify the mechanism of acupuncture and meridians in some extent. The needle temperature microsensor, whose shape is similar to that of an acupuncture needle, was established in the present study. Its sensitivity, accuracy and stability were evaluated in vitro. Afterwards the needle temperature microsensor was applied in vivo for the temperature measurement in acupoints and non-acupoints.
2. Experiments Twenty healthy rabbits weighting from 2.0 to 3.0 kg were chosen as experimental animals. The multi-purpose electroacupuncture apparatus (Model G6805-2, Shanghai Medical Instrumental High-TECK Co., China) were used for stimulating. The chosen acupoints included Zusanli (ST36), Shangjuxu (ST37), Xiajuxu (ST38), and Jiexi (ST39) points. The locating of the acupoints was based on the comparative anatomy. The locations of them were as follows: Zusanli (ST36) points, located about 1.2 cm below the capitulum of the fibular and 1.0 cm away from the anterior crista of the tibia; Dubi (ST35) points, located at the lower border of the patella and in the depression lateral to the patellar ligament when the knee is flexed; Shangjuxu (ST37) and Xiajuxu (ST38) points, located at about the 6/16, 9/16 of the distance from the Dubi (ST35) points to the highest point of the ankle, respectively; Jiexi points located at the crease of the instep and between the extensor hallucis longus of the first toe and second toe. The locating of the left and right non-acupoints were as follows: they were parallel to the detected acupoints and 1.0 cm apart from them. 2.1. The fabrication of the needle temperature microsensor and the experimental setup The fabrication of the needle temperature microsensor (Fig. 1) was divided into four stages. First, the two Pt–Ir silks (20 m diameter) of a thermistor were coated carefully
Fig. 1. The sketch map of the fabrication of needle-tip temperature microsensor.
with insulating materials in order to insulate themselves with each other and with the inner wall of the syringe needle. Then it was dried at a proper temperature. Secondly, the dried thermistor (200 m diameter) was drawn carefully through a syringe needle (500 m outer diameter, 250 m inner diameter) with the small thermistor just at the tip. Thirdly, the two Pt–Ir silks (20 m diameter) of the thermistor were connected with two copper silks, respectively. Finally, the leaving space of the hollow syringe needle was filled with insulating materials to immobilize the thermistor at the tip and the Pt–Ir silks in it. The experimental setup, which was composed of several parts, was shown in Fig. 2. The temperature analyzer was a three-channel potentiometric amplifier. The potentiometric signals were obtained by a computer equipped with PCL711B Multi-function Data Acquisition Card (Evoc Technology Co. Ltd.). 2.2. In vitro experiments The needle temperature microsensors were calibrated and evaluated in a thermostat bath at different temperatures. Three needle temperature microsensors and a standard thermometer were put together in a thermostat bath and were recorded simultaneously when the temperature were raised and dropped between 20 and 40 ◦ C.
Fig. 2. The setup of the temperature measurement system.
130
R. Cui et al. / Sensors and Actuators A 119 (2005) 128–132 Table 1 Some typical data obtained from the needle temperature microsensors in vitro when the temperature ascends and descends
Fig. 3. The sketch map of the depth of the needle temperature microsensor inserted in the tissues.
2.3. In vivo experiments Twenty healthy rabbits were divided randomly into two groups: group A, detecting the temperature in Zusanli (ST36) points and left and right non-acupoints after EA at Shangjuxu (ST37) and Xiajuxu (ST38) points, and group B, detecting the temperature in Shangjuxu (ST37) points and left and right non-acupoints after EA at Xiajuxu (ST38) and Jiexi (ST39) points. They remained conscious throughout the experiments, which was based on two considerations: first, the intensity of stimuli was rather mild; secondly, anaesthetization might influence the natural body temperature of the rabbits. The experiment were performed at a controlled room temperature (20 ± 1 ◦ C). After remaining stable for 10 min, changes of the temperature in acupoints and non-acupoints were recorded after EA at other acupoints. Three needle temperature microsensors (sheathed with thin plastic tubes and only left 5 mm outside) were inserted perpendicularly 5 mm below the skin (Fig. 3) to detect the temperature in the acupoints and non-acupoints simultaneously for several minutes under normal conditions. Afterwards two stainless acupuncture needles (0.28 mm outer diameter) were inserted 5–8 mm below the skin to stimulate the acupoints (located on the same meridian line with the detected acupoints but 6–10 cm away from them) for 20 min. The stimulation was elicited from the multi-purpose electroacupuncture apparatus. Parameters of the stimuli were as follows: the frequency was 5 Hz, and the intensity was strong enough to only elicit slight twitches of the lower limbs. There were no bleeding phenomena in the acupoints and nonacupoints during the experiment.
3. Results and discussion The characteristics of the needle temperature microsensors were evaluated in a long term in vitro, showing that it had a good accuracy and precision (Table 1). Its resolution was 0.1 ◦ C, response time less than 1 s, and measurement error less than ±0.1 ◦ C. The measurement ranged from 20 to 40 ◦ C. When the temperature of the thermostat bath was
Readings of the standard thermometer (◦ C)
1 (◦ C)
2 (◦ C)
3 (◦ C)
35.9 36.7 37.2 37.5 37.8 37.9 38.1 38.2 38.4 38.6 38.7 38.9 39.0 39.2 39.4 39.5 39.6 39.8
35.9 36.7 37.2 37.5 37.8 37.9 38.1 38.2 38.4 38.6 38.7 38.9 39.0 39.2 39.4 39.5 39.6 39.8
35.9 36.7 37.3 37.6 37.9 38.0 38.2 38.3 38.5 38.7 38.8 39.0 39.1 39.3 39.5 39.6 39.7 39.9
35.9 36.7 37.2 37.5 37.8 37.9 38.1 38.2 38.4 38.6 38.7 38.9 39.0 39.2 39.4 39.5 39.6 39.8
1–3 stands for readings of three needle temperature microsensors, respectively.
constant, the detecting temperature of the needle temperature microsensor was the same as that and maintained 20 h, indicating that it was very stable. The temperature change in acupoints and non-acupoints were recorded simultaneously after EA at other acupoints. Under natural conditions the temperature in Zusanli points and left and right non-acupoints were almost equal. Following EA at Shangjuxu and Xiajuxu points, all of them ascended quickly (at about 940 s) within a few seconds (<40 s). However, the temperature in Zusanli points ascended more higher than that in the non-acupoints. At about 1295 s, all of them reached their own peaks, and the temperature in Zusanli points was 0.4 ◦ C higher than that in the non-acupoints. Afterwards all of them started to descend and reached a constant value, respectively, at 2830 s after cessation of EA (Fig. 4). A similar phenomenon was observed in Shangjuxu points (Fig. 5). At about 964 s after EA, the temperature in Shangjuxu points and left and right non-acupoints reached their own peaks, and the temperature in Shangjuxu points was 0.3 ◦ C higher than that in the non-acupoints. Afterwards all of them started to descend and reached a constant value respectively at 2153 s after cessation of EA. The temperature increases (T, ◦ C) after 100, 200, 300, 400 s, . . . of the ascending of temperature (define the time at it as 0 s and regard it as the start of EA though actually there was a latent phase of no more than 40 s) were calculated (T = T100, 200, 300, 400, . . . − T0 ) and were expressed as the mean ± S.D. Differences were considered to be statistically significant for P < 0.05. The data were analyzed using the one-way ANOVA followed by the post-hoc multiple comparison test. The T in Zusanli points were significantly higher than that in the left and right non-acupoints within 700 s after EA at Shangjuxu and Xiajuxu points, while the
R. Cui et al. / Sensors and Actuators A 119 (2005) 128–132
Fig. 4. The temperature change in Zusanli points and the left and right nonacupoints during the process of EA at Shangjuxu and Xiajuxu points for 20 min.
131
Fig. 6. Effects of EA on the temperature in Zusanli points and the left and right non-acupoints. * P < 0.05, ** P < 0.01, *** P < 0.001 vs. the left and right non-acupoints.
T of the left and right non-acupoints were statistically no different (Fig. 6). In the first 200 s, T of the three increase d higher and higher. At about 300 s all reached their highest point and then decreased. The maximum T in Zusanli points was 1.89 ± 0.39 ◦ C (P < 0.01) versus the left and right non-acupoints 1.22 ± 0.25 and 1.07 ± 0.20 ◦ C, respectively. Gradually the T of the three became no difference (after 700 s). A similar curve was got at Shangjuxu (Fig. 7). Within 400 s the T in Shangjuxu were significant higher than that of the left and right non-acupoints after EA at Xiajuxu and Jiexi points, while the T of the left and right non-acupoints were statistically no different. In the first 200 s, T of the three increased higher and higher. At about 300 s all reached their highest point and then decreased. The maximum T in Shangjuxu points was 1.02 ± 0.21 ◦ C (P < 0.01) versus the left and right non-acupoints 0.74 ± 0.25 and 0.78 ± 0.21 ◦ C, respectively. Gradually the T of the three became no difference (after 700 s).
Maybe there are many kinds of possible reasons for this phenomenon. In our experiments we observed that the continuous stimuli of EA lead to muscles contraction, which, to our knowledge, may be directly responsible for the temperature ascending in the acupoints and non-acupoints. It is well known that muscles contraction will consume ATP, which is the direct energy provider for muscles, and ATP is transformed into ADP, accompanied with the release of chemical bond energy. Part of it will result in muscles contraction, and part of it will be released in the form of heat energy. Why did the temperature in acupoints ascend more higher than that in the non-acupoints? It may be regarded that the energy metabolism on the meridian line is much more active than that in the circumambient tissues and the acupoints consume more energy than the non-acupoints during the process of stimuli and thus release more heat. For another possible reason, EA at other acupoints may lead to the changes of the strain of the sympathetic nerves. This will
Fig. 5. The temperature change in Shangjuxu points and the left and right non-acupoints during the process EA at Xiajuxu and Jiexi points for 20 min.
Fig. 7. Effects of EA on the temperature in Shangjuxu points and the left and right non-acupoints. ** P < 0.01, *** P < 0.001 vs. the left and right nonacupoints.
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R. Cui et al. / Sensors and Actuators A 119 (2005) 128–132
result in the strengthening or inhibition of the capillary vessels, in which the calcitonin gene related peptide (CGRP) [4] and angiotensin II type (AII) [5] play an important role. In consequence it will increase the perfusion volume of the microcirculation of the tissues. It was reported that there were much more nerves and blood vessels in the acupoints than those in the circumambient tissues [6]. Maybe the perfusion volume of the microcirculation of the detected acupoints increases more than that of the circumambient tissues and thus it brings more blood to the acupoints than to the nonacupoints. The temperature of the blood is higher than that of the tissues and so such phenomena were observed in our experiments repeatedly. In our lab we have already observed that the partial oxygen pressure in acupoints is remarkably higher than that in the non-acupoints (1.0 cm away from the detected acupoints and parallel to them) under natural conditions [7]. Our experimental results are good agreement with this.
References [1] B. Lee, Review of the present status of optical fiber sensors, Opt. Fiber Technol. 9 (2003) 57–79. [2] M.W. Beal, Acupuncture and acupressure applications to women’s reproductive health care, J. Nurse-Midwifery 44 (1999) 217–229. [3] X. Cheng, Chinese Acupuncture and Moxibustion, Revised Edition, Foreign Languages Press, Beijing, 1987, pp. 1–3. [4] D. Van Rossum, U. Hanisch, R. Quirio, Neuroanatomical localization, pharmacological characterization and functions of CGRP, related peptides and their receptors, Neurosci. Biobehav. Rev. 21 (1997) 649–678. [5] H. Siragy, Angiotensin, receptor blockers, review of the binding characteristics, Am. J. Cardiol. 84 (1999) 3S–8S. [6] B. Zhu, Scientific Foundations of Acupuncture and Moxibustion, Qingdao Press, 1998, p. 64. [7] W. Xu, W. Ma, K. Li, J. Hu, L. Shen, H. Li, L. Cao, A needleelectrochemical microsensor for in vivo measurement of the partial pressure of oxygen in acupuncture points, Sens. Actuators B 86 (2002) 174–179.
Biographies 4. Conclusions The needle temperature microsensors and the instrumentations fabricated in our lab are suitable to measure the temperature in vivo and it supplies a useful and reliable tool for the research of acupuncture and meridians. As a result, the temperature in the acupoints ascends significantly higher than that in the non-acupoints after EA at other acupoints.
Acknowledgements This work was supported by the National Grand Fundamental Research Project, and the National Science Foundation of China grant 20375029 and 90409013, and the State Administration of Traditional Chinese Medicine of China foundation grant 02-03JP27.
Renfa Cui received his BS degree in 2001 from Hubei University, China. He is now doing his MS degree in analytical chemistry in Wuhan University, China. His interest lies in the research of the chemical, physical and biological properties of Meridians. Jianhua Liu received his BS, MS and PhD degrees from Hunan College of Traditional Chinese Medicine, China, in 1996, 1999 and 2002, respectively. He now focuses on the research of Meridian and acupuncture mechanism for his postdoctorate in Wuhan University. Jiabing Hu received his BS degree in 2002 from Wuhan University, China. Now he is a graduate major in measuring technology and instrument in Wuhan University. His interest lies in instrument design and programming. Jiming Hu received his PhD degree in chemistry from Wuhan University in 1988. Now he is a Professor of College of Chemistry and Molecular Science in Wuhan University. He has published more than 100 papers in international journals. His research areas lie in Laser Spectroscopy, Sensor, Meridian Research, and Analysis Instruments Research.
A needle temperature microsensor for in vivo and real-time measurement of the temperature in acupoints Renfa Cui, Jianhua Liu, Wentao Ma, Jiabing Hu, Xiaodong Zhou, Hongyi Li, Jiming Hu∗ College of Chemistry and Molecular Sciences, Wuhan University, Wuhan 430072, PR China Received 1 March 2004; received in revised form 15 September 2004; accepted 15 September 2004 Available online 27 October 2004
Abstracts A novel needle temperature microsensor measurement system was established to study the temperature characteristics in acupoints. Before used in vivo, the needle temperature microsensor was tested in vitro and proved stable, accurate and sensitive. Its measurement error was no more than ±0.1 ◦ C by calibration. Its resolution was 0.1 ◦ C and response time was less than 1 s. The measurement ranged from 20 to 40 ◦ C. The in vivo experiments showed that the temperature of the acupoints ascended significantly higher than that of the left and right non-acupoints (parallel to the detected acupoints and 1.0 cm apart from them) after electroacupuncture (EA) at other acupoints, which were located on the same meridian line with the detected acupoints but 6–10 cm away from them. The results indicated that the needle temperature microsensor had a good performance in vivo. Furthermore, it supplied a reliable tool for the study of the mechanism of acupuncture and meridians. © 2004 Elsevier B.V. All rights reserved. Keywords: Microsensor; Needle temperature sensor; Thermistor; Acupoints; Meridians; In vivo
1. Introduction Temperature is an important index of life activity. Many creatures including human, whose body temperature is about 37.0 ◦ C, have a relatively constant body temperature. If the body temperature is higher or lower than that, animals might be suffering from some diseases. Temperature is an important parameter associated with substance metabolism, energy transformation and signal transmission, which are the essence of life. Therefore, the measurement of temperature in vivo is considered as an important way to reveal some biophysical and physiological properties of life. Generally, the temperature in the tissue below the skin is more stable than that on the surface of the skin. The temperature in the tissues can act as a parameter to reflect the situations in them. Therefore it is more significant and meaningful to measure the temperature below the skin instead of on the skin. ∗
Corresponding author. Tel.: +86 27 8788 2136; fax: +86 27 8764 7617. E-mail address: [email protected] (J. Hu).
0924-4247/$ – see front matter © 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.sna.2004.09.016
There are all kinds of techniques and instruments for temperature measurement, such as thermistors, platinum resistors, thermocouples, bimetals, infrared-ray temperature sensors, quartz thermometers, optical fiber temperature sensors, etc. [1]. Each has its own advantages and disadvantages. The needle temperature microsensor prepared by us for the measurement of temperature in acupoints is based on the principle of thermistors for its high temperature coefficient, high sensitiveness, short response time and minimizability. Acupuncture is an important part of traditional Chinese medicine (TCM). It is a therapy of stimulating special points called acupoints over the human body and has been widely applied in the clinic to treat various diseases for its simple manipulation, low costs, no side effects and good curative effects [2]. According to the theory of the TCM, there are 14 main meridians running through the human body and joining the acupoints and the corresponding organs together [3]. The anatomical structure and substance basis of the acupoints and meridians remain largely unknown. Thus the in situ measurement of the physical and chemical properties of these loca-
R. Cui et al. / Sensors and Actuators A 119 (2005) 128–132
129
tions will benefit to clarify the mechanism of acupuncture and meridians in some extent. The needle temperature microsensor, whose shape is similar to that of an acupuncture needle, was established in the present study. Its sensitivity, accuracy and stability were evaluated in vitro. Afterwards the needle temperature microsensor was applied in vivo for the temperature measurement in acupoints and non-acupoints.
2. Experiments Twenty healthy rabbits weighting from 2.0 to 3.0 kg were chosen as experimental animals. The multi-purpose electroacupuncture apparatus (Model G6805-2, Shanghai Medical Instrumental High-TECK Co., China) were used for stimulating. The chosen acupoints included Zusanli (ST36), Shangjuxu (ST37), Xiajuxu (ST38), and Jiexi (ST39) points. The locating of the acupoints was based on the comparative anatomy. The locations of them were as follows: Zusanli (ST36) points, located about 1.2 cm below the capitulum of the fibular and 1.0 cm away from the anterior crista of the tibia; Dubi (ST35) points, located at the lower border of the patella and in the depression lateral to the patellar ligament when the knee is flexed; Shangjuxu (ST37) and Xiajuxu (ST38) points, located at about the 6/16, 9/16 of the distance from the Dubi (ST35) points to the highest point of the ankle, respectively; Jiexi points located at the crease of the instep and between the extensor hallucis longus of the first toe and second toe. The locating of the left and right non-acupoints were as follows: they were parallel to the detected acupoints and 1.0 cm apart from them. 2.1. The fabrication of the needle temperature microsensor and the experimental setup The fabrication of the needle temperature microsensor (Fig. 1) was divided into four stages. First, the two Pt–Ir silks (20 m diameter) of a thermistor were coated carefully
Fig. 1. The sketch map of the fabrication of needle-tip temperature microsensor.
with insulating materials in order to insulate themselves with each other and with the inner wall of the syringe needle. Then it was dried at a proper temperature. Secondly, the dried thermistor (200 m diameter) was drawn carefully through a syringe needle (500 m outer diameter, 250 m inner diameter) with the small thermistor just at the tip. Thirdly, the two Pt–Ir silks (20 m diameter) of the thermistor were connected with two copper silks, respectively. Finally, the leaving space of the hollow syringe needle was filled with insulating materials to immobilize the thermistor at the tip and the Pt–Ir silks in it. The experimental setup, which was composed of several parts, was shown in Fig. 2. The temperature analyzer was a three-channel potentiometric amplifier. The potentiometric signals were obtained by a computer equipped with PCL711B Multi-function Data Acquisition Card (Evoc Technology Co. Ltd.). 2.2. In vitro experiments The needle temperature microsensors were calibrated and evaluated in a thermostat bath at different temperatures. Three needle temperature microsensors and a standard thermometer were put together in a thermostat bath and were recorded simultaneously when the temperature were raised and dropped between 20 and 40 ◦ C.
Fig. 2. The setup of the temperature measurement system.
130
R. Cui et al. / Sensors and Actuators A 119 (2005) 128–132 Table 1 Some typical data obtained from the needle temperature microsensors in vitro when the temperature ascends and descends
Fig. 3. The sketch map of the depth of the needle temperature microsensor inserted in the tissues.
2.3. In vivo experiments Twenty healthy rabbits were divided randomly into two groups: group A, detecting the temperature in Zusanli (ST36) points and left and right non-acupoints after EA at Shangjuxu (ST37) and Xiajuxu (ST38) points, and group B, detecting the temperature in Shangjuxu (ST37) points and left and right non-acupoints after EA at Xiajuxu (ST38) and Jiexi (ST39) points. They remained conscious throughout the experiments, which was based on two considerations: first, the intensity of stimuli was rather mild; secondly, anaesthetization might influence the natural body temperature of the rabbits. The experiment were performed at a controlled room temperature (20 ± 1 ◦ C). After remaining stable for 10 min, changes of the temperature in acupoints and non-acupoints were recorded after EA at other acupoints. Three needle temperature microsensors (sheathed with thin plastic tubes and only left 5 mm outside) were inserted perpendicularly 5 mm below the skin (Fig. 3) to detect the temperature in the acupoints and non-acupoints simultaneously for several minutes under normal conditions. Afterwards two stainless acupuncture needles (0.28 mm outer diameter) were inserted 5–8 mm below the skin to stimulate the acupoints (located on the same meridian line with the detected acupoints but 6–10 cm away from them) for 20 min. The stimulation was elicited from the multi-purpose electroacupuncture apparatus. Parameters of the stimuli were as follows: the frequency was 5 Hz, and the intensity was strong enough to only elicit slight twitches of the lower limbs. There were no bleeding phenomena in the acupoints and nonacupoints during the experiment.
3. Results and discussion The characteristics of the needle temperature microsensors were evaluated in a long term in vitro, showing that it had a good accuracy and precision (Table 1). Its resolution was 0.1 ◦ C, response time less than 1 s, and measurement error less than ±0.1 ◦ C. The measurement ranged from 20 to 40 ◦ C. When the temperature of the thermostat bath was
Readings of the standard thermometer (◦ C)
1 (◦ C)
2 (◦ C)
3 (◦ C)
35.9 36.7 37.2 37.5 37.8 37.9 38.1 38.2 38.4 38.6 38.7 38.9 39.0 39.2 39.4 39.5 39.6 39.8
35.9 36.7 37.2 37.5 37.8 37.9 38.1 38.2 38.4 38.6 38.7 38.9 39.0 39.2 39.4 39.5 39.6 39.8
35.9 36.7 37.3 37.6 37.9 38.0 38.2 38.3 38.5 38.7 38.8 39.0 39.1 39.3 39.5 39.6 39.7 39.9
35.9 36.7 37.2 37.5 37.8 37.9 38.1 38.2 38.4 38.6 38.7 38.9 39.0 39.2 39.4 39.5 39.6 39.8
1–3 stands for readings of three needle temperature microsensors, respectively.
constant, the detecting temperature of the needle temperature microsensor was the same as that and maintained 20 h, indicating that it was very stable. The temperature change in acupoints and non-acupoints were recorded simultaneously after EA at other acupoints. Under natural conditions the temperature in Zusanli points and left and right non-acupoints were almost equal. Following EA at Shangjuxu and Xiajuxu points, all of them ascended quickly (at about 940 s) within a few seconds (<40 s). However, the temperature in Zusanli points ascended more higher than that in the non-acupoints. At about 1295 s, all of them reached their own peaks, and the temperature in Zusanli points was 0.4 ◦ C higher than that in the non-acupoints. Afterwards all of them started to descend and reached a constant value, respectively, at 2830 s after cessation of EA (Fig. 4). A similar phenomenon was observed in Shangjuxu points (Fig. 5). At about 964 s after EA, the temperature in Shangjuxu points and left and right non-acupoints reached their own peaks, and the temperature in Shangjuxu points was 0.3 ◦ C higher than that in the non-acupoints. Afterwards all of them started to descend and reached a constant value respectively at 2153 s after cessation of EA. The temperature increases (T, ◦ C) after 100, 200, 300, 400 s, . . . of the ascending of temperature (define the time at it as 0 s and regard it as the start of EA though actually there was a latent phase of no more than 40 s) were calculated (T = T100, 200, 300, 400, . . . − T0 ) and were expressed as the mean ± S.D. Differences were considered to be statistically significant for P < 0.05. The data were analyzed using the one-way ANOVA followed by the post-hoc multiple comparison test. The T in Zusanli points were significantly higher than that in the left and right non-acupoints within 700 s after EA at Shangjuxu and Xiajuxu points, while the
R. Cui et al. / Sensors and Actuators A 119 (2005) 128–132
Fig. 4. The temperature change in Zusanli points and the left and right nonacupoints during the process of EA at Shangjuxu and Xiajuxu points for 20 min.
131
Fig. 6. Effects of EA on the temperature in Zusanli points and the left and right non-acupoints. * P < 0.05, ** P < 0.01, *** P < 0.001 vs. the left and right non-acupoints.
T of the left and right non-acupoints were statistically no different (Fig. 6). In the first 200 s, T of the three increase d higher and higher. At about 300 s all reached their highest point and then decreased. The maximum T in Zusanli points was 1.89 ± 0.39 ◦ C (P < 0.01) versus the left and right non-acupoints 1.22 ± 0.25 and 1.07 ± 0.20 ◦ C, respectively. Gradually the T of the three became no difference (after 700 s). A similar curve was got at Shangjuxu (Fig. 7). Within 400 s the T in Shangjuxu were significant higher than that of the left and right non-acupoints after EA at Xiajuxu and Jiexi points, while the T of the left and right non-acupoints were statistically no different. In the first 200 s, T of the three increased higher and higher. At about 300 s all reached their highest point and then decreased. The maximum T in Shangjuxu points was 1.02 ± 0.21 ◦ C (P < 0.01) versus the left and right non-acupoints 0.74 ± 0.25 and 0.78 ± 0.21 ◦ C, respectively. Gradually the T of the three became no difference (after 700 s).
Maybe there are many kinds of possible reasons for this phenomenon. In our experiments we observed that the continuous stimuli of EA lead to muscles contraction, which, to our knowledge, may be directly responsible for the temperature ascending in the acupoints and non-acupoints. It is well known that muscles contraction will consume ATP, which is the direct energy provider for muscles, and ATP is transformed into ADP, accompanied with the release of chemical bond energy. Part of it will result in muscles contraction, and part of it will be released in the form of heat energy. Why did the temperature in acupoints ascend more higher than that in the non-acupoints? It may be regarded that the energy metabolism on the meridian line is much more active than that in the circumambient tissues and the acupoints consume more energy than the non-acupoints during the process of stimuli and thus release more heat. For another possible reason, EA at other acupoints may lead to the changes of the strain of the sympathetic nerves. This will
Fig. 5. The temperature change in Shangjuxu points and the left and right non-acupoints during the process EA at Xiajuxu and Jiexi points for 20 min.
Fig. 7. Effects of EA on the temperature in Shangjuxu points and the left and right non-acupoints. ** P < 0.01, *** P < 0.001 vs. the left and right nonacupoints.
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result in the strengthening or inhibition of the capillary vessels, in which the calcitonin gene related peptide (CGRP) [4] and angiotensin II type (AII) [5] play an important role. In consequence it will increase the perfusion volume of the microcirculation of the tissues. It was reported that there were much more nerves and blood vessels in the acupoints than those in the circumambient tissues [6]. Maybe the perfusion volume of the microcirculation of the detected acupoints increases more than that of the circumambient tissues and thus it brings more blood to the acupoints than to the nonacupoints. The temperature of the blood is higher than that of the tissues and so such phenomena were observed in our experiments repeatedly. In our lab we have already observed that the partial oxygen pressure in acupoints is remarkably higher than that in the non-acupoints (1.0 cm away from the detected acupoints and parallel to them) under natural conditions [7]. Our experimental results are good agreement with this.
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Biographies 4. Conclusions The needle temperature microsensors and the instrumentations fabricated in our lab are suitable to measure the temperature in vivo and it supplies a useful and reliable tool for the research of acupuncture and meridians. As a result, the temperature in the acupoints ascends significantly higher than that in the non-acupoints after EA at other acupoints.
Acknowledgements This work was supported by the National Grand Fundamental Research Project, and the National Science Foundation of China grant 20375029 and 90409013, and the State Administration of Traditional Chinese Medicine of China foundation grant 02-03JP27.
Renfa Cui received his BS degree in 2001 from Hubei University, China. He is now doing his MS degree in analytical chemistry in Wuhan University, China. His interest lies in the research of the chemical, physical and biological properties of Meridians. Jianhua Liu received his BS, MS and PhD degrees from Hunan College of Traditional Chinese Medicine, China, in 1996, 1999 and 2002, respectively. He now focuses on the research of Meridian and acupuncture mechanism for his postdoctorate in Wuhan University. Jiabing Hu received his BS degree in 2002 from Wuhan University, China. Now he is a graduate major in measuring technology and instrument in Wuhan University. His interest lies in instrument design and programming. Jiming Hu received his PhD degree in chemistry from Wuhan University in 1988. Now he is a Professor of College of Chemistry and Molecular Science in Wuhan University. He has published more than 100 papers in international journals. His research areas lie in Laser Spectroscopy, Sensor, Meridian Research, and Analysis Instruments Research.