Study on the body surface temperature variation patterns of the meridian acupoints related to the physiological status of the uterus

LiTian-yu (李天玉),Pan Li-jia (潘丽佳),Jia Chun-sheng (贾春生), Zhang Xiao-qi (张晓琪),She Yan-fen (佘延芬),Xu Yuan-yuan (徐媛媛),Song Xiao-dan (宋晓丹)

HebeiUniversity of Chinese Medicine,Shijiazhuang 050091,China

Abstract

Keywords:Uterus; MenstrualCycle; Thermography; Body Temperature; Research on Acupoints; Specificity of Acupoints;Point,Diji(SP 8);Women

Infrared thermal imaging technology has been used in the field of acupuncture and moxibustion for nearly 50 years w ith its convenience,intuitiveness,non- invasiveness and non-radiation.It uses infrared scanning to collect the infrared heat radiated by the human body;a visual infrared heat map accurately measuring the body temperature changes and thermal balance can be presented after processed by computer[1-2]. When a certain part of the human body undergoes physiological or pathological changes, the metabolism and blood circulation in that part w ill change,and the infrared radiation will change accordingly[3]. Therefore, the skin temperature can be used as an objective indicator to observe the physiological or pathological changes of the body[4]. At the same time,the change of the body surface temperature around the acupoints can also reflect the disease[5]. Studies have shown that the body surface temperature of acupoints is very susceptible to the external environment influence,especially closely related to the ambient temperature and airflow velocity,while the temperature difference of the acupoints w ith the same name has no significant relationship w ith the measurement environment[6-7]. Therefore, in this study,the skin temperature difference of the acupoints w ith the same name was used as the outcome index to observe the specific temperature changes of the body surface around the acupoints during the physiological changes of the uterus.

The somato-visceral reflex theory believes that the basis for the response function of the meridians is that the acupoints and the viscera have the same or adjacent segmental innervation of the nerves and spinal cords[8]. Our previous study found that the body surface temperature difference at Taixi (KI 3, the Yuan-Primary point of the Kidney Meridian) specifically responded to the menstruation onset in healthy female college students[9-10]. However, not all acupoints w ith the same or sim ilar segmental innervation of the visceral spinal cord show this response,which indicates that the somato-visceral reflex theory can't fully explain the above phenomenon.Our research group speculated that this discrepancy may be related to the characteristics of the acupoints and the meridians to which the acupoints belong.

In this study,we observed the body surface temperature and temperature difference of specific acupoints (the Yuan-Primary points and the Xi-Cleft points), the crossing points, the non-specific points, the unrelated meridian acupoints and the non-meridian non-acupoint points of the three yin meridians of foot closely related to uterus, also analyzed and summarized their specific change patterns during the menstrual cycle in healthy female college students,to lay a foundation for studying the mechanisms by which the meridian acupoints respond to the functions of Zang-fu organs and to confirm the hypothesis that the biophysical properties of the meridian acupoints respond to specific laws. The results will enrich the theory of the functional specificity of meridian acupoints,and provide a reference for clinical and scientific research on the biophysical properties of the meridian acupoints related to the menstrual cycle in healthy college students.

1 Materials and Methods

1.1 Inclusion criteria

Subjects w ith qualified medical exam ination; 18 to 26 years old; female college students without a history of pregnancy; reproductive system diseases excluded by B-mode ultrasound and gynecological examination;regular menstruation cycle of (28±7) d.

1.2 Exclusion criteria

Subjects who had breast tenderness,lumbosacral soreness,lower abdomen pain during the menstrual cycle,and visual analog scale(VAS)score ＞2 points lasted more than 1 d;patients with severe life- threatening primary diseases involving cardiovascular,cerebrovascular, liver, kidney or hematopoietic systems;mental disorders;subjects who had abnormal body temperature due to cold and other diseases in the past week;subjects w ith muscle pain,skin disease or peripheral nervous system disease; subjects with scars at the acupoints.

1.3 Term ination and exclusion criteria

Subject who found it intolerable or had serious adverse reactions during the test, should be term inated upon judgment; the subject unwilling to continue the test and requested to term inate; subjects mistakenly included but not meeting the inclusion criteria; subjects w ith a cold, diarrhea, insomnia or other diseases during the test;subjects whose results may be affected by failure to detect as required or incomplete data.

1.4 Dropout criteria

Subjects were w ithdrawn due to poor compliance or other reasons.

1.5 Statistical methods

Data were analyzed using SPSS version 19.0 statistical software. The measurement data were presented as mean± standard deviation(±s).Repeated measurement analysis of variance was used to investigate the change tendency of the same acupoint at different time points during one menstrual cycle. For comparison between different menstrual cycles, pairedt-test was used if the data conformed to normal distribution and homogeneity of variance,and rank- sum test was used if the data did not conform to the normal distribution or homogeneity of variance.Between different acupoints in the same menstrual phases,block analysis of variance was used to investigate the normally distributed data,and nonparametric rank-sum test was used to analyze the non-normally distributed data.P＜0.05 indicated that the difference was statistically significant.

1.6 General information

Our research group recruited the female college students and postgraduates as the observation subjects from Hebei University of Chinese Medicine between April 2018 and January 2019, who were screened in strict accordance w ith the inclusion and exclusion criteria, w ith the average age of (21.5±2.5) years old,the menarche of (13.5±1.2) years old, the menstrual phase of (5.54±0.98)d,and the menstrual cycle of (29.43±1.76)d.This trial was conducted in the Experimental Center of Xingyuan Campus,Hebei University of Chinese Medicine.The laboratory was located far away from noise and strong electromagnetic interference.The indoor temperature and hum idity were controlled at(25±2)℃and(40±5)% during detection. The indoor temperature was adjusted by the air conditioner, and the indoor hum idity was adjusted by the humidifier.

2 Methods

2.1 Acupoints and locations

Some specific acupoints including the Yuan-Primary points [Taixi (KI 3), Taibai (SP 3) and Taichong (LR 3)], the Xi-Cleft points [Shuiquan (KI 5), Diji (SP 8) and Zhongdu(LR 6), and the crossing point [Sanyinjiao (SP 6)] of the Spleen, Liver and Kidney Meridians closely related to the menstrual onset,as well as the non-specific acupoint [Xuehai(SP 10)],the unrelated meridian acupoint [Xuanzhong (GB 39)]and the non-meridian non-acupoint point beside Xuanzhong (GB 39) [at the outer side of the leg and the same level as Xuanzhong (GB 39),between the Stomach Meridian and the Gallbladder Meridian]were selected.All meridian acupoints were located according to theNomenclature and Location of Acupuncture Points(GB/T 12346-2006)[11](Figure 1 and Figure 2).

2.2 Observation items and time points

This study mainly detected the infrared temperature of the body surface at acupoints. The absolute value of the temperature difference between the two sides of the acupoints with the same name was used as the main outcome indicator.Measurements were performed for each subject during the four phases:menstrual(the day w ith the maximum menstrual volume, T1), follicular (the first day after the end of menstruation,T2),ovulatory (the first day after elevated basal body temperature, T3), and luteal (day 8 after elevated basal body temperature, T4) phases[12].The infrared temperature value of the body surface of at each selected acupoint was measured,and the absolute value of the temperature difference (the left side temperature m inus the right side temperature)between the two sides of the acupoint w ith the same name was statistically analyzed.

Figure 1. Acupoint locating at the inner side of the legs

Figure 2. Acupoint locating at the outer side of the legs

2.3 Infrared thermal imaging measurement method for the acupoint body surface

A WCHD research 780 long-wave uncooled portable thermal imaging camera(Infra Tec GmbH,Germany)was used.The instrument has a detectable spectral range of 7.5-14.0 µm,a thermal image of 1 280×960 pixel,a detectable temperature range of -40-1 200 ℃, and a thermal sensitivity of 0.05℃. The subject entered the laboratory to expose the test site 15 m in before the starting of the test, and rested in a natural state.For all the subjects, each acupoint was continuously tested for 5 m in w ith a detection range of 1 cm diameter circle set by a computer. The instrument automatically recorded the obtained value once every 1 m in and saved the data, which was further processed by IRBIS 3 standard software.

3 Results

3.1 Comparing the body temperature of the subjects and the environment

Morning body temperature comparison: The subjects measured their axillary temperature w ith a uniform mercury thermometer when waking up after a 6-8 h sleep before getting out of bed in the morning. The body temperature during ovulation was higher than during the other 3 phases (P＜0.05). Body temperature obtained by the infrared thermal test: The testing time was from 16:00 to 19:00. Before starting the infrared thermal test, the axillary temperature of each subject was measured w ith a uniform ly distributed mercury thermometer.The body temperature during the ovulation phase was higher than that during the menstrual phase and the follicular phase (P＜0.05), and there was no significant difference compared with the luteal phase(P＞0.05).The comparison of the body temperature and environment among the subjects is shown in Table 1.

Table 1.Com paring the body tem perature of the subjects and environment during different menstrual phases (±s)

Table 1.Com paring the body tem perature of the subjects and environment during different menstrual phases (±s)

Note: T1=Menstrual phase, T2=Follicular phase, T3=Ovulation phase, T4=Luteal phase

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3.2 Comparing the temperature differences of the Yuan-Primary points

The temperature differences of the same Yuan- Primary point during the different menstrual phases,and of different Yuan-Primary points during the same menstrual cycle were not statistically significant (P＞0.05), (Table 2).

3.3 Comparing the temperature differences of the Xi-Cleft points

Comparing the temperature differences of the same Xi-Cleft point during different menstrual phases showed that the temperature at Diji(SP 8)point during the ovulation phase was statistically significantly higher than those during the other three phases (P＜0.05).There were no statistically significant differences in the temperature of the remaining acupoints during each phase (allP＞0.05). The temperature differences were not statistically significant (P＞0.05) between the Xi-Cleft points during the same phase of the menstrual cycle(Table 3).

3.4 Comparing the temperature differences of different acupoints of the Spleen Meridian

The temperature differences of the same acupoint during different phases of the menstrual cycle were compared. The results showed that the temperature difference of Diji(SP 8)was statistically significantly higher during the ovulation phase than during the other three phases(P＜0.05).There was no statistically significant difference in the temperature of the remaining acupoints during different phases of the menstrual cycle (allP＞0.05). There was no statistically significant difference(P＞0.05)in the temperature difference between the acupoints during the same phase of the menstrual cycle (Table 4).

Table 2.Comparing the tem perature differences of the Yuan-Primary points during different phases of the menstrual cycle (±s, ℃)

Table 2.Comparing the tem perature differences of the Yuan-Primary points during different phases of the menstrual cycle (±s, ℃)

Note:T1=Menstrual phase,T2=Follicular phase,T3=Ovulation phase,T4=Luteal phase;1)comparing the temperature differences of the same acupoint during different phases of the menstrual cycle;2) comparing the temperature differences of different acupoints during the same phase of the menstrual cycle

Taichong (LR 3)0.52±0.36 0.47±0.39 0.52±0.37 0.50±0.46 1.144 0.862 Taibai(SP 3)0.50±0.36 0.53±0.43 0.58±0.42 0.53±0.46 0.967 0.580 Taixi (KI 3)0.56±0.43 0.66±0.60 0.67±0.59 0.57±0.46 1.112 0.310 Z-value2)-0.724 2.318-1.951 0.610 P-value2)0.733 0.838 0.749 0.866

Table 3.Com paring the temperature differences of Xi-Cleft points among different phases of the menstrual cycle (±s, ℃)

Table 3.Com paring the temperature differences of Xi-Cleft points among different phases of the menstrual cycle (±s, ℃)

Note:T1=Menstrual phase,T2=Follicular phase,T3=Ovulation phase,T4=Luteal phase;1)comparing the temperature differences of the same acupoint during different phases of the menstrual cycle;2) comparing the temperature differences of different acupoints during the same phase of the menstrual cycle

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Table 4. Comparing the temperature differences of the Spleen Meridian acupoints during the menstrual cycle ( ±s, ℃)

Table 4. Comparing the temperature differences of the Spleen Meridian acupoints during the menstrual cycle ( ±s, ℃)

Note:T1=Menstrual phase,T2=Follicular phase,T3=Ovulation phase,T4=Luteal phase;1)comparing temperature differences of the same acupoint during different phases of the menstrual cycle;2) comparing the temperature differences of different acupoints during the same phase of the menstrual cycle

Acupoints T1 T2 T3 T4 F-value1) P-value1) Xuehai (SP 10)0.41±0.35 0.40±0.33 0.40±0.33 0.39±0.31 0.045 0.987 Diji (SP 8) 0.38±0.28 0.37±0.31 0.54±0.39 0.39±0.33 6.008 0.001 Sanyinjiao (SP 6)0.44±0.34 0.45±0.50 0.55±0.58 0.43±0.33 1.300 0.276 Taibai (SP 3)0.50±0.36 0.53±0.43 0.58±0.42 0.53±0.46 0.967 0.580 Z-value2) 0.317-1.005-1.680 0.319 P-value2) 0.923 0.591 0.968 0.971

3.5 Comparing the temperature differences of the acupoints innervated by the L4 spinal cord segment

The temperature differences of the same acupoint innervated by the L4spinal segment during different menstrual phases were compared. The results showed that the temperature difference of Diji (SP 8) during the ovulation phase was significantly higher than that during the other three phases (P＜0.05). There was no statistically significant difference in the temperature of the remaining acupoints during different phases of the menstrual cycle (allP＞0.05). There was no statistically significant difference in body surface temperature between the acupoints innervated by the L4spinal cord segment during the same phase of the menstrual cycle(allP＞0.05), (Table 5).

3.6 Comparing the temperature differences of acupoints innervated by the L5 spinal cord segment

There were no statistically significant differences in the temperature of the same acupoint innervated by the L5spinal cord segment during different phases of the menstrual cycle(allP＞0.05),nor between the different acupoints during the same phase of the menstrual cycle (allP＞0.05), (Table 6).

Table 5.Com paring the temperature differences of acupoints innervated by the L4 spinal cord segment during the menstrual cycle ( ±s, ℃)

Table 5.Com paring the temperature differences of acupoints innervated by the L4 spinal cord segment during the menstrual cycle ( ±s, ℃)

Note:T1=Menstrual phase,T2=Follicular phase,T3=Ovulation phase,T4=Luteal phase;1)comparing the temperature differences of the same acupoint during different phases of the menstrual cycle;2) comparing the temperature differences of different acupoints during the same phase of the menstrual cycle

Acupoints T1 T2 T3 T4 F-value1) P-value1) Diji (SP 8)0.38±0.28 0.37±0.31 0.54±0.39 0.39±0.33 6.008 0.001 Zhongdu (LR 6)0.41±0.36 0.43±0.35 0.44±0.31 0.39±0.34 0.381 0.767 Sanyinjiao (SP 6)0.44±0.34 0.45±0.50 0.55±0.58 0.43±0.33 1.300 0.276 Taixi (KI 3)0.56±0.43 0.66±0.60 0.67±0.59 0.57±0.46 1.112 0.310 Shuiquan (KI 5) 0.60±0.48 0.62±0.56 0.64±0.52 0.68±0.53 0.324 0.808 Z-value2) -0.378 0.697 -0.283 0.101 P-value2) 0.828 0.955 0.964 0.988

Table 6.Com paring the temperature differences of acupoints innervated by the L5 spinal cord segment during the menstrual cycle (±s, ℃)

Table 6.Com paring the temperature differences of acupoints innervated by the L5 spinal cord segment during the menstrual cycle (±s, ℃)

Note:T1=Menstrual phase,T2=Follicular phase,T3=Ovulation phase,T4=Luteal phase;1)comparing the temperature differences of the same acupoint during different phases of the menstrual cycle;2) comparing the temperature differences of different acupoints during the same phase of the menstrual cycle

Acupoints T1 T2 T3 T4 F-value1) P-value1) Xuanzhong (GB 39)0.54±0.38 0.56±0.37 0.60±0.44 0.53±0.47 0.521 0.668 Taichong (LR 3)0.52±0.36 0.47±0.39 0.52±0.37 0.50±0.46 0.249 0.862 Taibai (SP 3)0.50±0.36 0.53±0.43 0.58±0.42 0.53±0.46 0.967 0.580 Non-meridian non-acupoint point 0.44±0.40 0.43±0.30 0.51±0.33 0.47±0.34 0.914 0.435 Z-value2) -1.051 0.425-1.372 0.212 P-value2) 0.895 0.850 0.935 0.942

3.7 Comparing the temperature differences of Diji(SP 8)

Paired comparisons of temperature differences of Diji(SP 8)during different phases were performed.The results showed that the temperature difference of Diji(SP 8)in the ovulation phase was statistically significantly higher than that in the other three phases(compared w ith the menstrual phase,t=-0.004,P=0.002; compared with the follicular phase,t=-0.740,P=0.001;compared w ith the luteal phase,t=0.241,P=0.003), while no statistically significant temperature difference was observed between the other three phases (the menstrual phase versus the follicular phase,t=0.887,P=0.751; the menstrual phase versus the luteal phase,t=0.256,P=0.838; the follicular phase versus the luteal phase,t=-0.440,P=0.601).

4 Discussion

The Yuan-Primary point is the special point through which the body's Yuan-Primordial qi circulates and stays,which can both treat and reflect the diseases of the five Zang organs[13]. The 66 Chapter ofNan Jing(Classic of Difficult Issues)records that the Yuan-Primordial qi passes through the three Jiao (Triple Energizer) around the body to warm and nourish the Zang-fu organs and the meridians.The physiological and pathological changes of the Zang-fu organs can manifest in the corresponding Yuan-Primary point through the meridians. The Xi-Cleft point is the point where the meridian qi is deeply concentrated,which was first found inZhen Jiu Jia Yi Jing(A-B Classic of Acupuncture and Moxibustion)[14].Therefore,our current work targeted the Yuan-Primary points and the Xi-Cleft points that could best reflect the physiological state and the pathological changes of the Zang-fu organs.

The twelve meridians of the human body connect the Zang-fu organs internally and the extrem ity joints externally.There is a close connection among the Zang-fu organs,the meridians and the acupoints.Located in the m iddle of the abdomen, the uterus is an important female internal reproductive organ w ith two main physiological functions: one for menstruation and the other for pregnancy[15]. The Spleen Meridian and its related Zang-fu organs are closely connected w ith the uterus. In terms of the meridians, the Spleen Meridian meets the Conception Vessel at Zhongji(CV 3),and meets the Thoroughfare Vessel at Sanyinjiao (SP 6); the Thoroughfare Vessel and the Conception Vessel govern the uterus; the Spleen Meridian is connected to the uterus through the Thoroughfare Vessel and the Conception Vessel.In terms of function,the spleen governs the hemogenesis,is the foundation of the acquired constitution and the source of generating qi and blood in the human body. At the same time, the spleen controls the qi of m iddle Jiao; the spleen qi governs the rise and controls the blood; meanwhile, the menstruation, pregnancy, and parturition in the uterus all need blood, so the blood generated and controlled by the spleen directly provides the material basis for menstruation and fetal development in the uterus. If the spleen qi is rich, the source of energy is sufficient,and the power to govern and regulate is strong, the menstrual blood w ill be stored and dispersed normally.Diji (SP 8) is the Xi-Cleft point of the Spleen Meridian. It has the effect of promoting the blood circulation for removing blood stasis, and regulating the menstruation for relieving pain, which is a commonly used point to treat the uterus-related diseases.

Studies in modern literatures have shown that the acupoints in the Spleen Meridian are mostly used to treat the uterus-related diseases(up to 74.5%)[16].Clinically, Xi-Cleft point is mostly used to treat pain and blood disorders, therefore, Li WJ,et al[17]used Diji (SP 8)to treat primary dysmenorrhea because dysmenorrhea is not only an emergency,but also pain and blood disorder. The Xi-Cleft point combined w ith the crossing point is also recorded in the prescription for the gynecological diseases in Gao Wu'sZhen Jiu Ju Ying(Collection of Gems of Acupuncture and Moxibustion) in the Ming Dynasty[18].

According to the somato-visceral reflex theory[8], the same or adjacent nerve segments innervating the viscera and the body surface are the basis for the connection between the body surface and the viscera.

Ancient literature believes that the shape of uterus includes not only the entity of the uterus, but also the appendages (fallopian tubes and ovaries) on both sides.The sympathetic segments of the sympathetic nerve efferent fibers of the uterus,fallopian tubes,and ovaries are located at T12-L1,T11-L1and T10-T11,respectively;the sympathetic segments of the sympathetic afferent fibers of the uterus, ovaries and appendages are located at T12and L1-3[19]. According to the cutaneous segmental innervation map[20], Diji (SP 8),Zhongdu(LR 6),Sanyinjiao (SP 6),Taixi(KI 3)and Shuiquan (KI 5) are located at L4, which is the adjacent spinal cord segment of the uterus[21-22].Only the temperature difference of Diji (SP 8) at the L4cutaneous segment can reflect the physiological changes in uterus.This result also validated the prelim inary speculation of our group:not all the acupoints,innervated by the same or similar spinal cord segment which innervates the viscera,can reflect the physiological changes in Zang-fu organs.This depends on the acupoint characteristics and the meridians to which they belong.

Regarding the meridians, among the three Xi-Cleft points of the three yin meridians of foot, only Diji (SP 8)of the Spleen Meridian has specific manifestation during the physiological changes during the ovulation phase,while the Xi-Cleft points of the other two meridians had no specific manifestations.The three Yuan-Primary points of the three yin meridians of foot also had no specific manifestations.Regarding the meridian acupoints, except for Diji (SP 8), the Xi-Cleft point of the Spleen Meridian, which showed specific performance, the temperature differences of the other same meridian acupoints[Xuehai(SP 10),Sanyinjiao(SP 6),Taibai(SP 3)]were not specific during the physiological changes during the ovulation phase. The temperature differences of the unrelated meridian acupoint [Xuanzhong (GB 39)]and the non-meridian non-acupoint point had no specific performance during the physiological changes during the ovulation phase.

It can be seen that the body surface temperature response of the acupoints in the Spleen Meridian is stronger than that of the Liver Meridian and Kidney Meridian; the body surface temperature response of the Xi-Cleft point of the Spleen Meridian is stronger than that of the Yuan-Primary point,the specific acupoints, and the crossing points; the body surface temperature response of the relevant meridian acupoints is stronger than that of the unrelated meridian acupoints,the non-meridian non-acupoint points. These results indicated the reflection function specificity of the meridian acupoints.

Our current study indicated that the thermal properties of Diji (SP 8), the Xi-Cleft point of the Spleen Meridian could specifically reflex the physiological changes in uterus-the onset of the ovulation phase. The manifestation of the meridian acupoints reflecting the function of Zang-fu organs is not only associated w ith the spinal cord segment to innervate the acupoints, but also associated w ith the acupoint characteristics and the meridians to which the acupoints belong.

C onflict of Interest The authors declare that there is no potential conflict of interest in this article.Acknow ledgments This work was supported by General Programs of National Natural Science Foundation of China (国家自然科学基金面上项目, No.81573884,No.81973755);Youth Program of National Natural Science Foundation of China (国家自然科学青年基金项目, No.81603542).Statement of Informed Consent Informed consent was obtained from all individual participants.

Received:22 January 2020/Accepted:5March 2020