The Distribution of Transcutaneous CO₂ Emission and Correlation With the Points Along the Pericardium Meridian

Article Outline

• Abstract
• 1.. Introduction
• 2.. Materials and Methods
• 3.. Results
• 4.. Discussion
• References
• Copyright

Abstract 

This study aimed to understand energy metabolism distribution along the pericardium meridian and verify the correlation between the body surface (points), and classic meridian theory. A highly sensitive CO₂ instrument was used to measure the transcutaneous CO₂ emission at 13 points along the pericardium meridian line (12 points on the line and one point beyond the line) and 13 control points beside them. Results showed that the distribution of transcutaneous CO₂ emission is highly related to the position on the body. Transcutaneous CO₂ emission is significantly higher at P7 and P3, than the control points beside them. The points along the meridian and the points beside them were clustered with relative distance by SAS statistics software. Two distance matrixes were then obtained. The correlation coefficients between the points along the line and between the control points were calculated. The results showed that the 13^th point beyond the line was far from the 12 points on the line (distance, 0.24), while acupoints on the line clustered earlier when compared with the non-acupoints. The average correlation coefficients among the acu-points was 0.65 which was significantly higher than 0.56, among the non-acupoints. No such characteristics were found among the control points. It was concluded that there is a strong correlativity of energy metabolism activity between the body surfaces along the meridian, and an even stronger correlativity between the acupoints on the meridian.

Key Words:  acupoint , cluster analysis , correlativity , meridian , pericardium meridian , transcutaneous CO₂ emission

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1. Introduction 

In classic meridian theory, meridians were discovered according to the phenomenon in which some body surfaces appear specifically related during acupuncture. The correlations between the body surfaces gradually became the acupoints and meridians. Such ancient law needs to be understood with scientific data in the present age. To obtain this data, a quantitative index which reflects physiological activity in loci should be used.

Transcutaneous CO₂ Emission (TCE) is the tiny amounts of carbon dioxide emitted from skin I, also called skin respiration in some early papers ¹, ². This small amount of CO_2, which is very difficult to measure, is related to the energy metabolism in local skin and also the tissue under the skin. In 1976, a highly sensitive CO₂ detector was invented by a Hungarian, F. William. The probe used to measure CO₂ from skin is small and easily operated (the hole is 7 mm in diameter, see Figure 1). A membrane of Ca(OH)₂ is made when putting the electrodes into the Ca(OH)₂ solution and pulling back. The probe is quickly placed on human skin with suitable pressure to isolate air that has entered the hole. The in itial CO₂ from the air is consumed by waiting until the resistance increases to a certain value. The increasing of resistance in the membrane at a certain time is measured as Ca(OH)₂ will change to CaCO₃ and deposit. The rate of change positively re lates with the rate of CO₂ released from skin which, in turn, reflects the energy metabolism of local tissue.

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• Figure 1. 

  CO₂ probe structure (A) and the measuring technique (B).

In 1984, William's student Eory, who owned an acupuncture clinic, tried the machine on a human body. He measured the TCE on P8 (Laogong) and found a higher TCE on the acupoint than the surrounding control area ^[1]. He also measured the changes of TCE along the Lung meridian during acu-puncture and found that there was a wave change of TCE along the line ^[2]. From 1992, we began to study the relationship between TCE and meridians using a series of experiments. The results showed that some acupoints or points on meridians have relatively higher TCE ^[3]. The TCE increased proximally along the pericardium meridian during acu-puncturing P6 (Neiguan) and recovered quicker on the meridian than outside the meridian ^[4]. The TCE correlated with the metabolism of tissue, the absorption of CO₂ by the circulatory system, the permeability of skin and the volume of extracellular fluid in the tissue ^[5]. The experiments implied that the TCE can provide significant physiological information and is related to Qi and blood, as described in Traditional Chinese Medicine. Therefore, the ancient law of correlativity of body surfaces may be able to be proven by measuring TCE and calculating the correlativity using cluster analysis.

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2. Materials and Methods 

A highly sensitive CO₂ instrument (FREWIL-QF, China) was used to measure the TCE on 13 points along the pericardium meridian (12 points on the meridian and one point beyond it, group A) and 13 con trol points outside the meridian (group B; Figure 2). The positions, point name and standard acupuncture nomenclature (SAN) of group A are shown in Table 1.

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• Figure 2. 

  Position of measured points along the pericardium meridian, ○ are the points on the meridian, ▴ are the points beside the meridian. × is a point beyond the meridian.

Table 1. The positions, point name and standard acupuncture nomenclature (SAN)

Room temperature was kept between 22 and 25°C. Twenty two healthy volunteers (14 males and eight females, with an average of 38) participated in this study. The subjects were asked to lie on a bed and relax for about 5 minutes. The pericardium meridian was determined using the percussion active point (PAP) method ^[6] combined with classic acupoint location. All the measured points were marked with a colored pen after referring to a standard acupuncture chart. The distance of the 13^th point was 2 cm beyond P1 (Tianquan) at the lengthen line of the meridian. The 13 control points (group B) were alternatively beside (about 1 cm away) the 13 points of group A. All the points were measured three times and the average values were calculated. The room CO₂ level was also monitored to keep a low level (less than 0.05%) which was controlled by ventilation. The correlative coefficient (CC) between the 13 points along the meridian line (Group A, including the point beyond the meridian) and the 13 control points outside the meridian (Group B) were calculated respectively to produce two CC matrixes. SAS statistic software was used to cluster the matrixes in which the CC(r) were replaced by the correlative distance (d = 1 - r) in the cluster tree. Wilcoxon Rank Sums test was used to compare the two mean coefficients to obtain p < 0.05.

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3. Results 

The average values at these points are shown in Table 2.

Table 2. The average values at 13 control points

Comparing group A with group B.

At point 3, which is P7 (Daling), referred to as a source point and point 5, which is P3 (Quze), referred to as a sea point, the TCE was significantly higher than the control points. The correlative coefficient between the two groups is 0.95. The distribution of TCE on the meridian and control points is shown on Figure 2.

The cluster results of the two groups using an average linkage method are shown in Figure 3, Figure 4.

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• Figure 3. 

  The distribution of TCE on the meridian and control points.

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• Figure 4. 

  Cluster tree shown by correlative distance between the points of group A. * are the acupoints and × is the point on lengthen line of P meridian.

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• Figure 5. 

  Cluster tree shown by correlative distance between the points of group B. * are the control points beside the acupoints.

From the cluster of group A, we could see that the 13^th point beyond the meridian was obviously further than points on the meridian. It clustered last. The distance between CL2 and the 13^th point was 0.24. In group A, the acupoints seem to be closer than non-acupoints. For instance, the 4^th point (P6 Neiguan), 8^th point (P2 Tianquan), and 5^th point (P3 Quze) were clustered in the 8^th cluster (CL8). The 6^th cluster (CL6) had six points, including five acupoints. The mean CC between acupoints was 0.65, but only 0.56 between non-acupoints. The rank sums test was used to examine the difference because of the non normal distribution. The result showed significant difference (p< 0.05). In group B, although the 13^th point still clustered last, the distance between CL2 and the 13^th point was only 0.1. The average CC between the points beside the acupoints and between the points beside the non-acupoints were 0.58 and 0.60 respectively, which was not a significant difference.

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4. Discussion 

According to the classic theory, Qi flows along channels and becomes rich at several main points. Result showed that TCE was higher on a source and sea point than the control points beside the meridian. The distribution of TCM is also gradually higher with the points close to the position of lung. This positioning may influence the TCE due to a higher concentration of CO₂ in the lung. The high correlativity between the points on meridian and control points imply that the TCE is highly related to the position on the body.

The meridian line may have two meanings. One is the channel in which Qi and blood flow. The propagated sensation can also move along the channel whenever some points are stimulated. The other meaning is that the acupoints on the line belong to the meridian. Usually the acupoints have similar treatment functions and may have a certain correlation. We have now revealed the correlation by calculating CC between these points. At first, we assumed that the pericardium meridian would lengthen beyond P1 and that the 13^th point had similar correlation with other points on the meridian. But results showed that only the points on the peri-cardium meridian had stronger correlation and the 13^th point beyond P1 was far from other points. This result proved that the end point of the pericardium meridian was P1 which corresponded to traditional meridian theory.

The high correlation of TCE along the meridian may illustrate that the metabolism on the meridian has similar changes or relationships. The acupoints on the meridian have even stronger correlation than the non-acupoints. These results illustrated that the acupoints on the meridian may be a group of special points which are strongly associated with each other. These associations may exist not only in one meridian. Other TCE research has found that the left and right source acupoints on the same meridian have very strong correlativity, with a mean CC of 0.814 ^[7]. Also, the correlativity between the source points in exterior and internal meridians and between the source points on the meridian with the same name are also strong. The mean CC was 0.65 and 0.514, respectively, which was significantly higher than the mean CC of 0.379 between normal source acupoints. These results proved that a complicated connection in meridian and collateral network existed on the human body. The rule of treating certain acupoints according to the meridian system can be understood by our studies.

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References 

1. Eory A . In-vivo skin respiration (CO₂) measurments in the acupuncture loci* . Acupunct Electrother Res . 1984;9:217–223
   • View In Article
   • MEDLINE
2. Eory A , Tamar K . Skin respiration changes along the LPSC line . ATTA . 1986;4:15–18 [In Italian]
   • View In Article
3. Zhang WB , Jing XH , Xu RM , Zu ZX , Li CH , Li H . Studies on skin respiration of CO₂ on stomach meridian and large intestine meridian in limbs . Chin J Inter Med . 1995;15:625–627 [In Chinese]
   • View In Article
4. Zhang WB , Li H , Xu RM . The influence to the skin respiration of CO₂ on meridian during acupuncture . Chinese Acupuncture & Moxibustion . 1996;16:39–42 [In Chinese]
   • View In Article
5. Zhang WB , Li H . Studies to the mechanism of transcutaneous CO₂ emission . Beijing Biomed Eng . 1996;15:221–225 [In Chinese]
   • View In Article
6. Zhu Zong-xiang , Hao Jin-kai . In: Biophysics in Acupuncture & Meridian . Beijing: Beijing Publishing House; 1988;p. 233–235
   • View In Article
7. Zhang W . Cluster analysis to the correlativity of skin respiration of CO₂ on source points of twelve meridians on human body . J Biomathematics . 1997;12:261–264 [In Chinese]
   • View In Article