Downloaded from http://aim.bmj.com/ on November 30, 2015 - Published by group.bmj.com
Original paper
Investigation of the electrical impedance of acupuncture points and non-acupuncture points before and after acupuncture, using a four-electrode device Ali Khorsand,1,2 Jiang Zhu,1 Hamidreza Bahrami-Taghanaki,2,3 Sara Baghani,3 Liangxiao Ma,1 Shima Rezaei2,4
▸ Additional material is published online only. To view please visit the journal online (http://dx.doi.org/10.1136/ acupmed-2014-010697). For numbered affiliations see end of article. Correspondence to Dr Shima Rezaei, Acupuncture Clinic, Imam Reza Hospital, Mashhad, 9137913316, Islamic Republic of Iran; [email protected] Accepted 6 March 2015 Published Online First 31 March 2015
To cite: Khorsand A, Zhu J, Bahrami-Taghanaki H, et al. Acupunct Med 2015;33: 230–236.
230
ABSTRACT Aim To evaluate the effect of acupuncture on skin electrical impedance of selected points, before and after acupuncture on one acupuncture point (PC6), using a four-electrode device. Methods Six acupuncture and non-acupuncture points on both sides of the body were selected to evaluate the effects of acupuncture on electrical properties of these points. Results There were no results significant differences of electrical impedance before and after acupuncture in the selected points. Conclusions According to our experimental setup, acupuncture at one point without stimulation does not alter skin electrical impedance in healthy volunteers and there is no difference between acupuncture points and non-acupuncture points.
INTRODUCTION Acupuncture is considered to be a complementary medicine. This ancient practice is used to treat many disorders, diseases and pain conditions. In recent years, the use of acupuncture by physicians in the field of clinical medicine has been increasing. Scientists have also started to study the properties of acupuncture points (APs) and meridians. Researchers are trying to determine the effectiveness of acupuncture and its physiological and biological mechanisms.1 In modern medicine, many studies have been conducted to explain the mechanism of acupuncture. The effect of acupuncture on the release of neurotransmitters2 3 and opioids in the brain,4 its impact on sensory receptors through affecting the nervous system,5 causing vasodilatation in peripheral vessels and removing toxins,6 7
its effect on the entire body through interstitial fluid and connective tissues,8 9 its influence on the gate control mechanism of pain,10 11 and its effectiveness via the autonomic nervous system12 13 are among the theories presented in relation to its mechanism of action. Another theory, which has attracted scientists’ attention since 1950s, explains the mechanism of acupuncture via the electrical properties of skin.14 According to this theory, APs and meridians have different electrical properties, compared to their surrounding areas.15–17 Various studies have addressed this issue. Some have supported this theory,15 18 and others have rejected it.19–21 The theory states that skin impedance at APs should be changed by acupuncture, but skin impedance away from the acupuncture is not changed. It has been shown that physical and psychological conditions alter the electrical impedance of APs.22 If acupuncture alters the electrical impedance of APs and meridians, it is possible that the affect of acupuncture on improving medical conditions can be explained by this theory. Over the years, researchers have employed different devices for measuring the electrical impedance of skin. However, many confounding variables, including environmental conditions, physiological parameters, and factors such as the size and angle of the device, pressure and contact area of electrodes, and skin moisture have reduced the validity of these studies.23 In 2008, in a systematic study, Ahn concluded that further research is
Khorsand A, et al. Acupunct Med 2015;33:230–236. doi:10.1136/acupmed-2014-010697
Downloaded from http://aim.bmj.com/ on November 30, 2015 - Published by group.bmj.com
Original paper required to confirm or refute this hypothesis.24 The aim of the present study was to evaluate the effect of acupuncture on skin electrical impedance and compare impedance variations between APs and non-APs, before and after acupuncture. In most recent studies, devices with two electrodes have been used; usually, one of these electrodes is manually used by the researcher and is pressed against the patient’s skin.19 25 In order to more accuracy, a device with four electrodes was designed. MATERIALS AND METHODS Participants
Zhang et al26 found the mean impedance on the meridian and control points before the needling to be 52.8±11.0 (mean±SD) and 61.7±10.3, respectively; the required sample size was calculated to be 20 by the following formula: N¼
(Z1ðA=2Þ þ Z1b )2 (S2Diff ) D2
Twenty healthy volunteers were selected from students of Beijing University of Chinese Medicine (mean age 26±7 years; 12 female and 8 male). Participants were Chinese, Iranian, Russian and Korean. Evaluation was performed at the Research Centre of the Acupuncture Department at Beijing University of Chinese Medicine from June to September 2010 (from 9:00 to 12:00). This study was approved by the Ethics Committee of Beijing University of Chinese Medicine, and verbal and written informed consent was obtained from all participants. Inclusion and exclusion criteria
Inclusion criteria were: (1) age range of 18–40 years; (2) good general health; and (3) the ability to rest calmly during measurements. Exclusion criteria were: (1) current use of medications; (2) chronic or acute health problems; (3) visually observable skin irregularities such as cracking, lacerations, bruises, and dermatological conditions; (4) pregnancy; and (5) recent orthopaedic surgery and body implants. Acupuncture points
APs were located by anatomical landmarks, based on textbook descriptions and charts, palpation, the Elastic Cun meter device and visual inspection (the location of points is detailed in the online supplementary file). Neiguan (PC6) on the left forearm was selected for needling, and six points on both sides of the body were selected to measure electrical skin impedance, including Ximen (PC4), Daling (PC7), Shousanli (LI10), Lingdao (HT4), non-APs on meridians (NAM), and non-APs not on meridians (NANM). PC4 and PC7 were chosen on the pericardium meridian to evaluate the effect of acupuncture on PC6 below and above it.
Khorsand A, et al. Acupunct Med 2015;33:230–236. doi:10.1136/acupmed-2014-010697
Two APs on two other meridians beside the pericardium meridian were selected to compare the effects of acupuncture on the stimulated meridian and other meridians (LI10 on the large intestine meridian as a Yang meridian and HT4 on the heart meridian as a Yin meridian). Two points which were not recognised as APs were also selected. We chose NAM at the midpoint between PC3 and PC4, to compare the changes of electrical impedance between APs on the pericardium meridian and non-APs on this meridian. NANM was located at the midpoint of PC4 and NAM, and 1 cm lateral to the middle side of the forearm (between the pericardium and heart meridians). This point was selected to determine any difference between APs and non-APs. The four-electrode device was equipped with 12 available probes; thus, six points in each forearm were selected. A distance of at least 4 cm was required between the 2 points, considering the dimensions of the probes. All these points were selected on the other side of the body, as control points, to compare the effect of acupuncture on both sides. Instruments
In order to use the four-electrode technique, an impedance meter was specifically designed for this study (model LRM30-R). The impedance meter outputs a regulated AC 5 kHz sinusoidal current of variable amplitude (30 μa) between the two outer electrodes ( justification for using 5 kHz is available in the online supplementary file). As schematically shown, the arrangement of skin electrodes ensures that the device only measures the impedance of the small subcutaneous region (a schematic figure is available in the online supplementary file). The system used in the present study was also modified and computerised in so that it consisted of 12 four-electrode probes with a reference electrode, shared by the probes.27 Settings and procedures
This study was carried out in a standardised setting in the Acupuncture Department of Beijing University of Chinese Medicine, Beijing, China. Subjects were asked to shave the needling sites before measurements, if necessary. Participants were advised to lie down quietly for 10 min before and during the measurements. The points for each evaluation were marked on the skin with non-toxic, washable ink by an expert acupuncturist. Ethyl alcohol was used to clean the probe tips at the beginning of each session. The probes were attached to the skin using adhesive tape. The reference lead was attached to the inner side of the left ankle. All environmental factors such as temperature, relative air humidity, body temperature, skin humidity, electromagnetic devices and noise were controlled. 231
Downloaded from http://aim.bmj.com/ on November 30, 2015 - Published by group.bmj.com
Original paper Temperature was set at 22–24°C and humidity at 30– 40%, which were, respectively, controlled by an air conditioner and evaporation humidifier, and measured by a hygrometer and thermometer. The device had previously been shown not to be affected by confounding factors such as cleaning the skin with alcohol, exfoliation and pressure. According to the specific study for device reliability, the results were found to be repeatable in several measurements during a specific period of time.28 Each selected point was allocated an identification number. The computer screen was positioned out of sight of the researcher and operator and it was not possible to manipulate the results of electrical skin impedance. Electrical impedance was measured for 50 min (once per minute). PC6 was punctured 20 min after the measurement, starting with a 1.5 Cun (40 mm×0.25 mm) stainless steel acupuncture needle which was inserted 2 mm under the skin by a guide tube and the needle was not stimulated. The needle was removed 40 min after starting the measurements (20 min after puncture).
data were analysed by repeated measures analysis of variance. 2. We selected six significant periods during the measurements: Minute 1: beginning of the measurement, Minute 20: last minute before inserting the needle, Minute 21: first minute after inserting the needle, Minute 40: last minute before removing the needle, Minute 41: first minute after removing the needle, and Minute 50: last minute of the measurement. 3. Linear charts were drawn to indicate changes of electrical impedance during 50 min.
RESULTS For 20 healthy volunteers, electrical impedance was measured in 12 points, 50 times during 50 min. Using the first method of data analysis showed that there were no significant differences between electrical impedance of the 12 points in the three periods (table 1). This means that the electrical impedance of neither APs nor APs changed after acupuncture during these times. Using the second method of data analysis also showed that there were no statistically significant differences between electrical impedance of the 12 points in the six special times (table 2). This means that needle insertion and removal did not alter electrical impedance of all 12 selected points detected by the four-electrode device. With regard to the linear charts drawn to indicate changes of electrical impedance during 50 min, we were not able to see any specific changes in the charts (figures 1 and 2).
Statistical analysis
Data were analysed using Microsoft Excel and SPSS V.13. To study the differences between various points and times, we used repeated measures analysis of variance. All p values were two-tailed and the significance value was set at 0.05. Since we could not use repeated measurements during the set period, three methods were used for data analysis: 1. The 50 min period was divided into three periods. During the first 20 min, no stimulation was performed. Within the second 20 min, the needle was inserted (and remained for 20 min) in the acupuncture point PC6. Within the second 40 min, the needle was removed and measurement continued during the last 10 min. The mean of each period was calculated and the obtained
Table 1 Points
DISCUSSION Our results showed that there is no significant change in electrical impedance during 20 min of acupuncture or after the removal of the needle at all selected points.
Electrical impedance in three periods Period 1 (minutes 1–20) Mean (SD)
Period 2 (minutes 21–40) Mean (SD)
PC7 (left) 31.46 (0.28) 31.12 (0.31) HT4 (left) 42.01 (0.37) 41.90 (0.32) NANM (left) 41.39 (0.47) 41.64 (0.24) NAM (left) 50.14 (0.39) 50.20 (0.16) LI10 (left) 52.01 (0.44) 52.10 (0.22) PC4 (left) 42.35 (0.81) 42.06 (0.17) PC7 (right) 31.24 (0.03) 33.45 (1.10) HT4 (right) 37.13 (1.14) 36.95 (0.30) NANM (right) 43.36 (0.46) 43.29 (0.17) NAM (right) 52.64 (1.26) 52.27 (0.32) LI10 (right) 51.74 (0.91) 51.25 (0.07) PC4 (right) 43.60 (0.56) 43.58 (0.12) NAM, non-APs on meridians; NANM, non-acupuncture points not on meridian.
232
Period 3 (minutes 41–50) Mean (SD)
p Value
30.30 (0.71) 41.95 (0.68) 41.76 (0.43) 50.17 (0.64) 51.97 (0.57) 42.04 (0.59) 34.62 (0.71) 37.15 (0.56) 43.57 (0.69) 52.14 (1.04) 51.31 (0.60) 43.73 (0.65)
0.111 0.931 0.392 0.699 0.971 0.628 0.508 0.52 0.117 0.599 0.109 0.343
Khorsand A, et al. Acupunct Med 2015;33:230–236. doi:10.1136/acupmed-2014-010697
Downloaded from http://aim.bmj.com/ on November 30, 2015 - Published by group.bmj.com
Original paper Table 2
Electrical impedance at six different times Minute 1 Mean (SD)
Minute 20 Mean (SD)
Minute 21 Mean (SD)
PC7 (left) 31.70 (5.07) 31.30 (6.49) 31.34 (6.69) HT4 (left) 42.70 (11.29) 42.17 (11.86) 42.32 (11.37) NANM (left) 41.94 (15.31) 41.27 (14.57) 41.37 (14.52) NAM (left) 50.62 (11.24) 50.08 (10.93) 50.40 (10.87) LI10 (left) 52.53 (19.90) 51.90 (19.15) 51.82 (19.02) PC4 (left) 43.17 (12.33) 42.02 (11.16) 42.27 (11.01) PC7 (right) 31.27 (8.73) 31.23 (10.54) 31.73 (10.64) HT4 (right) 37.96 (11.18) 36.35 (10.69) 36.45 (10.60) NANM (right) 43.94 (10.73) 43.30 (10.74) 43.17 (10.71) NAM (right) 53.70 (11.98) 51.92 (10.54) 52.27 (10.46) LI10 (right) 52.50 (12.76) 51.20 (12.03) 51.24 (12.08) PC4 (right) 44.09 (10.13) 43.29 (8.64) 43.36 (8.65) *Analysis of variance repeated measurement. NAM, non-APs on meridians; NANM, non-acupuncture points not on meridian.
We eliminated the known confounding factors in this study; hence, the validity of the results is acceptable. By applying age limits and using control points on the other side of each person’s body, the effects of some confounding factors such as age and race on impedance were minimised.28 We used a fourelectrode device which was designed and tested for this study. This device had just 12 probes, so only six points on each side of the body could be chosen; this was a limitation of our research. Many studies have compared the electrical properties of APs and meridians to their surrounding areas; however, of all conducted studies, only a few have assessed the effects of acupuncture on electrical impedance of APs. For example, the effect of acupuncture on skin electrical impedance in Litscher’s study showed that acupuncture on LU6 causes changes in electrical resistance in the surrounding points.29 In this study a two-electrode device with 48 probes was used. The different devices used in the two studies (four- and two-electrode) can explain the different results. Also
Figure 1
Minute 40 Mean (SD)
Minute 41 Mean (SD)
Minute 50 Mean (SD)
p Value*
30.83 42.39 41.90 50.19 52.55 42.21 34.92 37.12 43.49 52.05 51.32 43.72
30.93 (10.18) 42.58 (10.50) 42.16 (15.04) 50.39 (10.52) 52.71 (19.42) 42.45 (11.14) 34.82 (19.12) 37.41 (10.07) 43.61 (10.79) 53.92 (12.41) 51.48 (11.77) 44.03 (8.78)
28.49 (9.80) 42.41 (11.04) 42.86 (14.48) 48.39 (9.85) 53.48 (18.11) 42.57 (11.38) 32.75 (18.75) 37.61 (10.16) 44.12 (11.17) 52.45 (11.51) 49.62 (11.25) 44.45 (8.43)
0.128 0.738 0.180 0.318 0.610 0.245 0.342 0.061 0.661 0.503 0.076 0.252
(10.01) (10.58) (15.12) (10.89) (19.43) (11.35) (19.68) (9.89) (10.69) (11.38) (11.98) (8.81)
the timing of measurements and distance from APs were different. In Litscher’s study electrical resistance was measured exactly after needling and again after manual stimulation of the needle. All 48 selected points were within a distance of 2.5×3 cm from the needling point. The most marked change in impedance during insertion and stimulation could be found in one electrode next to (2.5 mm) the needling point. Based on this study, electrical resistance changed after acupuncture for a short time and close to the insertion point. In our study the distance between needling point and measurement area was at least 4 cm, and the first measurement was recorded 1 min after needling. Zhang’s findings were inconsistent with the results of the current study. In his study, before the insertion of the needle, the mean impedance of meridians and control points were 52.8 Ω±11.0 (mean±SD) and 61.7 Ω±10.3, respectively, and the difference was statistically significant. However, during the acupuncture, the decrease in the mean was only significant in the intervention group; moreover, after 5–10 min of
Electrical impedance of six points on the right forearm during 50 min.
Khorsand A, et al. Acupunct Med 2015;33:230–236. doi:10.1136/acupmed-2014-010697
233
Downloaded from http://aim.bmj.com/ on November 30, 2015 - Published by group.bmj.com
Original paper
Figure 2
Electrical impedance of six points on the left forearm during 50 min.
acupuncture, meridian impedance went back to 51.1 Ω±11.3 in the intervention group and to 59.9 Ω ±11.0 in the control group.26 One reason for the discrepancy in the results might be device variations between Zhang’s study and the current one. Zhang used a one-probe device to measure impedance. The device was moved to different sites for each measurement and had no direct connection to a computer; it also did not provide a digital presentation of electrical impedance. In the present study, we eliminated these factors by using a device with 12 probes, which were fixed on measuring points. In 2012, Shirley used a two-electrode device to measure the electrical impedance of 10 APs on lung meridians of 18 healthy volunteers before and after 45 min of acupuncture transcutaneous electrical nerve stimulation (Acu-TENS) on the BL13 point; the subjects were divided into control (with Acu-TENS) and placebo (without Acu-TENS) groups. It was concluded that the electrical impedance of all points had significantly reduced after the intervention. However, since Shirley did not use Acu-TENS in the placebo group and there was no difference in electrical skin impedance in patients of this group, the results seem to be consistent with those of the present study.30 The impact of other factors on electrical impedance has been observed in some other studies. Voll suggests that skin electrical resistance of 53–95 kilo-ohm indicates healthy organs. Resistance >95 indicates inflammation, and resistance
Original paper
Investigation of the electrical impedance of acupuncture points and non-acupuncture points before and after acupuncture, using a four-electrode device Ali Khorsand,1,2 Jiang Zhu,1 Hamidreza Bahrami-Taghanaki,2,3 Sara Baghani,3 Liangxiao Ma,1 Shima Rezaei2,4
▸ Additional material is published online only. To view please visit the journal online (http://dx.doi.org/10.1136/ acupmed-2014-010697). For numbered affiliations see end of article. Correspondence to Dr Shima Rezaei, Acupuncture Clinic, Imam Reza Hospital, Mashhad, 9137913316, Islamic Republic of Iran; [email protected] Accepted 6 March 2015 Published Online First 31 March 2015
To cite: Khorsand A, Zhu J, Bahrami-Taghanaki H, et al. Acupunct Med 2015;33: 230–236.
230
ABSTRACT Aim To evaluate the effect of acupuncture on skin electrical impedance of selected points, before and after acupuncture on one acupuncture point (PC6), using a four-electrode device. Methods Six acupuncture and non-acupuncture points on both sides of the body were selected to evaluate the effects of acupuncture on electrical properties of these points. Results There were no results significant differences of electrical impedance before and after acupuncture in the selected points. Conclusions According to our experimental setup, acupuncture at one point without stimulation does not alter skin electrical impedance in healthy volunteers and there is no difference between acupuncture points and non-acupuncture points.
INTRODUCTION Acupuncture is considered to be a complementary medicine. This ancient practice is used to treat many disorders, diseases and pain conditions. In recent years, the use of acupuncture by physicians in the field of clinical medicine has been increasing. Scientists have also started to study the properties of acupuncture points (APs) and meridians. Researchers are trying to determine the effectiveness of acupuncture and its physiological and biological mechanisms.1 In modern medicine, many studies have been conducted to explain the mechanism of acupuncture. The effect of acupuncture on the release of neurotransmitters2 3 and opioids in the brain,4 its impact on sensory receptors through affecting the nervous system,5 causing vasodilatation in peripheral vessels and removing toxins,6 7
its effect on the entire body through interstitial fluid and connective tissues,8 9 its influence on the gate control mechanism of pain,10 11 and its effectiveness via the autonomic nervous system12 13 are among the theories presented in relation to its mechanism of action. Another theory, which has attracted scientists’ attention since 1950s, explains the mechanism of acupuncture via the electrical properties of skin.14 According to this theory, APs and meridians have different electrical properties, compared to their surrounding areas.15–17 Various studies have addressed this issue. Some have supported this theory,15 18 and others have rejected it.19–21 The theory states that skin impedance at APs should be changed by acupuncture, but skin impedance away from the acupuncture is not changed. It has been shown that physical and psychological conditions alter the electrical impedance of APs.22 If acupuncture alters the electrical impedance of APs and meridians, it is possible that the affect of acupuncture on improving medical conditions can be explained by this theory. Over the years, researchers have employed different devices for measuring the electrical impedance of skin. However, many confounding variables, including environmental conditions, physiological parameters, and factors such as the size and angle of the device, pressure and contact area of electrodes, and skin moisture have reduced the validity of these studies.23 In 2008, in a systematic study, Ahn concluded that further research is
Khorsand A, et al. Acupunct Med 2015;33:230–236. doi:10.1136/acupmed-2014-010697
Downloaded from http://aim.bmj.com/ on November 30, 2015 - Published by group.bmj.com
Original paper required to confirm or refute this hypothesis.24 The aim of the present study was to evaluate the effect of acupuncture on skin electrical impedance and compare impedance variations between APs and non-APs, before and after acupuncture. In most recent studies, devices with two electrodes have been used; usually, one of these electrodes is manually used by the researcher and is pressed against the patient’s skin.19 25 In order to more accuracy, a device with four electrodes was designed. MATERIALS AND METHODS Participants
Zhang et al26 found the mean impedance on the meridian and control points before the needling to be 52.8±11.0 (mean±SD) and 61.7±10.3, respectively; the required sample size was calculated to be 20 by the following formula: N¼
(Z1ðA=2Þ þ Z1b )2 (S2Diff ) D2
Twenty healthy volunteers were selected from students of Beijing University of Chinese Medicine (mean age 26±7 years; 12 female and 8 male). Participants were Chinese, Iranian, Russian and Korean. Evaluation was performed at the Research Centre of the Acupuncture Department at Beijing University of Chinese Medicine from June to September 2010 (from 9:00 to 12:00). This study was approved by the Ethics Committee of Beijing University of Chinese Medicine, and verbal and written informed consent was obtained from all participants. Inclusion and exclusion criteria
Inclusion criteria were: (1) age range of 18–40 years; (2) good general health; and (3) the ability to rest calmly during measurements. Exclusion criteria were: (1) current use of medications; (2) chronic or acute health problems; (3) visually observable skin irregularities such as cracking, lacerations, bruises, and dermatological conditions; (4) pregnancy; and (5) recent orthopaedic surgery and body implants. Acupuncture points
APs were located by anatomical landmarks, based on textbook descriptions and charts, palpation, the Elastic Cun meter device and visual inspection (the location of points is detailed in the online supplementary file). Neiguan (PC6) on the left forearm was selected for needling, and six points on both sides of the body were selected to measure electrical skin impedance, including Ximen (PC4), Daling (PC7), Shousanli (LI10), Lingdao (HT4), non-APs on meridians (NAM), and non-APs not on meridians (NANM). PC4 and PC7 were chosen on the pericardium meridian to evaluate the effect of acupuncture on PC6 below and above it.
Khorsand A, et al. Acupunct Med 2015;33:230–236. doi:10.1136/acupmed-2014-010697
Two APs on two other meridians beside the pericardium meridian were selected to compare the effects of acupuncture on the stimulated meridian and other meridians (LI10 on the large intestine meridian as a Yang meridian and HT4 on the heart meridian as a Yin meridian). Two points which were not recognised as APs were also selected. We chose NAM at the midpoint between PC3 and PC4, to compare the changes of electrical impedance between APs on the pericardium meridian and non-APs on this meridian. NANM was located at the midpoint of PC4 and NAM, and 1 cm lateral to the middle side of the forearm (between the pericardium and heart meridians). This point was selected to determine any difference between APs and non-APs. The four-electrode device was equipped with 12 available probes; thus, six points in each forearm were selected. A distance of at least 4 cm was required between the 2 points, considering the dimensions of the probes. All these points were selected on the other side of the body, as control points, to compare the effect of acupuncture on both sides. Instruments
In order to use the four-electrode technique, an impedance meter was specifically designed for this study (model LRM30-R). The impedance meter outputs a regulated AC 5 kHz sinusoidal current of variable amplitude (30 μa) between the two outer electrodes ( justification for using 5 kHz is available in the online supplementary file). As schematically shown, the arrangement of skin electrodes ensures that the device only measures the impedance of the small subcutaneous region (a schematic figure is available in the online supplementary file). The system used in the present study was also modified and computerised in so that it consisted of 12 four-electrode probes with a reference electrode, shared by the probes.27 Settings and procedures
This study was carried out in a standardised setting in the Acupuncture Department of Beijing University of Chinese Medicine, Beijing, China. Subjects were asked to shave the needling sites before measurements, if necessary. Participants were advised to lie down quietly for 10 min before and during the measurements. The points for each evaluation were marked on the skin with non-toxic, washable ink by an expert acupuncturist. Ethyl alcohol was used to clean the probe tips at the beginning of each session. The probes were attached to the skin using adhesive tape. The reference lead was attached to the inner side of the left ankle. All environmental factors such as temperature, relative air humidity, body temperature, skin humidity, electromagnetic devices and noise were controlled. 231
Downloaded from http://aim.bmj.com/ on November 30, 2015 - Published by group.bmj.com
Original paper Temperature was set at 22–24°C and humidity at 30– 40%, which were, respectively, controlled by an air conditioner and evaporation humidifier, and measured by a hygrometer and thermometer. The device had previously been shown not to be affected by confounding factors such as cleaning the skin with alcohol, exfoliation and pressure. According to the specific study for device reliability, the results were found to be repeatable in several measurements during a specific period of time.28 Each selected point was allocated an identification number. The computer screen was positioned out of sight of the researcher and operator and it was not possible to manipulate the results of electrical skin impedance. Electrical impedance was measured for 50 min (once per minute). PC6 was punctured 20 min after the measurement, starting with a 1.5 Cun (40 mm×0.25 mm) stainless steel acupuncture needle which was inserted 2 mm under the skin by a guide tube and the needle was not stimulated. The needle was removed 40 min after starting the measurements (20 min after puncture).
data were analysed by repeated measures analysis of variance. 2. We selected six significant periods during the measurements: Minute 1: beginning of the measurement, Minute 20: last minute before inserting the needle, Minute 21: first minute after inserting the needle, Minute 40: last minute before removing the needle, Minute 41: first minute after removing the needle, and Minute 50: last minute of the measurement. 3. Linear charts were drawn to indicate changes of electrical impedance during 50 min.
RESULTS For 20 healthy volunteers, electrical impedance was measured in 12 points, 50 times during 50 min. Using the first method of data analysis showed that there were no significant differences between electrical impedance of the 12 points in the three periods (table 1). This means that the electrical impedance of neither APs nor APs changed after acupuncture during these times. Using the second method of data analysis also showed that there were no statistically significant differences between electrical impedance of the 12 points in the six special times (table 2). This means that needle insertion and removal did not alter electrical impedance of all 12 selected points detected by the four-electrode device. With regard to the linear charts drawn to indicate changes of electrical impedance during 50 min, we were not able to see any specific changes in the charts (figures 1 and 2).
Statistical analysis
Data were analysed using Microsoft Excel and SPSS V.13. To study the differences between various points and times, we used repeated measures analysis of variance. All p values were two-tailed and the significance value was set at 0.05. Since we could not use repeated measurements during the set period, three methods were used for data analysis: 1. The 50 min period was divided into three periods. During the first 20 min, no stimulation was performed. Within the second 20 min, the needle was inserted (and remained for 20 min) in the acupuncture point PC6. Within the second 40 min, the needle was removed and measurement continued during the last 10 min. The mean of each period was calculated and the obtained
Table 1 Points
DISCUSSION Our results showed that there is no significant change in electrical impedance during 20 min of acupuncture or after the removal of the needle at all selected points.
Electrical impedance in three periods Period 1 (minutes 1–20) Mean (SD)
Period 2 (minutes 21–40) Mean (SD)
PC7 (left) 31.46 (0.28) 31.12 (0.31) HT4 (left) 42.01 (0.37) 41.90 (0.32) NANM (left) 41.39 (0.47) 41.64 (0.24) NAM (left) 50.14 (0.39) 50.20 (0.16) LI10 (left) 52.01 (0.44) 52.10 (0.22) PC4 (left) 42.35 (0.81) 42.06 (0.17) PC7 (right) 31.24 (0.03) 33.45 (1.10) HT4 (right) 37.13 (1.14) 36.95 (0.30) NANM (right) 43.36 (0.46) 43.29 (0.17) NAM (right) 52.64 (1.26) 52.27 (0.32) LI10 (right) 51.74 (0.91) 51.25 (0.07) PC4 (right) 43.60 (0.56) 43.58 (0.12) NAM, non-APs on meridians; NANM, non-acupuncture points not on meridian.
232
Period 3 (minutes 41–50) Mean (SD)
p Value
30.30 (0.71) 41.95 (0.68) 41.76 (0.43) 50.17 (0.64) 51.97 (0.57) 42.04 (0.59) 34.62 (0.71) 37.15 (0.56) 43.57 (0.69) 52.14 (1.04) 51.31 (0.60) 43.73 (0.65)
0.111 0.931 0.392 0.699 0.971 0.628 0.508 0.52 0.117 0.599 0.109 0.343
Khorsand A, et al. Acupunct Med 2015;33:230–236. doi:10.1136/acupmed-2014-010697
Downloaded from http://aim.bmj.com/ on November 30, 2015 - Published by group.bmj.com
Original paper Table 2
Electrical impedance at six different times Minute 1 Mean (SD)
Minute 20 Mean (SD)
Minute 21 Mean (SD)
PC7 (left) 31.70 (5.07) 31.30 (6.49) 31.34 (6.69) HT4 (left) 42.70 (11.29) 42.17 (11.86) 42.32 (11.37) NANM (left) 41.94 (15.31) 41.27 (14.57) 41.37 (14.52) NAM (left) 50.62 (11.24) 50.08 (10.93) 50.40 (10.87) LI10 (left) 52.53 (19.90) 51.90 (19.15) 51.82 (19.02) PC4 (left) 43.17 (12.33) 42.02 (11.16) 42.27 (11.01) PC7 (right) 31.27 (8.73) 31.23 (10.54) 31.73 (10.64) HT4 (right) 37.96 (11.18) 36.35 (10.69) 36.45 (10.60) NANM (right) 43.94 (10.73) 43.30 (10.74) 43.17 (10.71) NAM (right) 53.70 (11.98) 51.92 (10.54) 52.27 (10.46) LI10 (right) 52.50 (12.76) 51.20 (12.03) 51.24 (12.08) PC4 (right) 44.09 (10.13) 43.29 (8.64) 43.36 (8.65) *Analysis of variance repeated measurement. NAM, non-APs on meridians; NANM, non-acupuncture points not on meridian.
We eliminated the known confounding factors in this study; hence, the validity of the results is acceptable. By applying age limits and using control points on the other side of each person’s body, the effects of some confounding factors such as age and race on impedance were minimised.28 We used a fourelectrode device which was designed and tested for this study. This device had just 12 probes, so only six points on each side of the body could be chosen; this was a limitation of our research. Many studies have compared the electrical properties of APs and meridians to their surrounding areas; however, of all conducted studies, only a few have assessed the effects of acupuncture on electrical impedance of APs. For example, the effect of acupuncture on skin electrical impedance in Litscher’s study showed that acupuncture on LU6 causes changes in electrical resistance in the surrounding points.29 In this study a two-electrode device with 48 probes was used. The different devices used in the two studies (four- and two-electrode) can explain the different results. Also
Figure 1
Minute 40 Mean (SD)
Minute 41 Mean (SD)
Minute 50 Mean (SD)
p Value*
30.83 42.39 41.90 50.19 52.55 42.21 34.92 37.12 43.49 52.05 51.32 43.72
30.93 (10.18) 42.58 (10.50) 42.16 (15.04) 50.39 (10.52) 52.71 (19.42) 42.45 (11.14) 34.82 (19.12) 37.41 (10.07) 43.61 (10.79) 53.92 (12.41) 51.48 (11.77) 44.03 (8.78)
28.49 (9.80) 42.41 (11.04) 42.86 (14.48) 48.39 (9.85) 53.48 (18.11) 42.57 (11.38) 32.75 (18.75) 37.61 (10.16) 44.12 (11.17) 52.45 (11.51) 49.62 (11.25) 44.45 (8.43)
0.128 0.738 0.180 0.318 0.610 0.245 0.342 0.061 0.661 0.503 0.076 0.252
(10.01) (10.58) (15.12) (10.89) (19.43) (11.35) (19.68) (9.89) (10.69) (11.38) (11.98) (8.81)
the timing of measurements and distance from APs were different. In Litscher’s study electrical resistance was measured exactly after needling and again after manual stimulation of the needle. All 48 selected points were within a distance of 2.5×3 cm from the needling point. The most marked change in impedance during insertion and stimulation could be found in one electrode next to (2.5 mm) the needling point. Based on this study, electrical resistance changed after acupuncture for a short time and close to the insertion point. In our study the distance between needling point and measurement area was at least 4 cm, and the first measurement was recorded 1 min after needling. Zhang’s findings were inconsistent with the results of the current study. In his study, before the insertion of the needle, the mean impedance of meridians and control points were 52.8 Ω±11.0 (mean±SD) and 61.7 Ω±10.3, respectively, and the difference was statistically significant. However, during the acupuncture, the decrease in the mean was only significant in the intervention group; moreover, after 5–10 min of
Electrical impedance of six points on the right forearm during 50 min.
Khorsand A, et al. Acupunct Med 2015;33:230–236. doi:10.1136/acupmed-2014-010697
233
Downloaded from http://aim.bmj.com/ on November 30, 2015 - Published by group.bmj.com
Original paper
Figure 2
Electrical impedance of six points on the left forearm during 50 min.
acupuncture, meridian impedance went back to 51.1 Ω±11.3 in the intervention group and to 59.9 Ω ±11.0 in the control group.26 One reason for the discrepancy in the results might be device variations between Zhang’s study and the current one. Zhang used a one-probe device to measure impedance. The device was moved to different sites for each measurement and had no direct connection to a computer; it also did not provide a digital presentation of electrical impedance. In the present study, we eliminated these factors by using a device with 12 probes, which were fixed on measuring points. In 2012, Shirley used a two-electrode device to measure the electrical impedance of 10 APs on lung meridians of 18 healthy volunteers before and after 45 min of acupuncture transcutaneous electrical nerve stimulation (Acu-TENS) on the BL13 point; the subjects were divided into control (with Acu-TENS) and placebo (without Acu-TENS) groups. It was concluded that the electrical impedance of all points had significantly reduced after the intervention. However, since Shirley did not use Acu-TENS in the placebo group and there was no difference in electrical skin impedance in patients of this group, the results seem to be consistent with those of the present study.30 The impact of other factors on electrical impedance has been observed in some other studies. Voll suggests that skin electrical resistance of 53–95 kilo-ohm indicates healthy organs. Resistance >95 indicates inflammation, and resistance
