Moxibustion, one of the classical therapies of Traditional Chinese Medicine (TCM), uses the heat generated by burning moxa floss (usually made by
A moxibustion session typically lasts 20–30 minutes, and patients are often treated several times a week for several weeks. Patients are exposed to the smoke during treatment, while acupuncturists are commonly exposed for prolonged periods during clinical practice. Because of recent concerns as to the safety of the therapy, specifically the potential toxicity of the smoke, many clinics no longer use moxibustion, thus depriving patients of the benefits of this unique treatment. Evaluation of the safety and the effects of moxa smoke is imperative.
Concerns about moxa smoke are similar to those regarding tobacco smoke and air pollutants. Many studies show that exposure to tobacco smoke and air pollutants is positively associated with adverse effects in the respiratory, immune, nervous, and cardiovascular systems [
HRV refers to the time variation coefficient between successive heart beat cycles. It is one of the most promising quantitative markers of autonomic nerve system activity [
Participants, most of them students of Beijing University of Chinese Medicine or other nearby universities plus some residents of the area around the University, were recruited between March 2012 and July 2012. The study protocol was approved by the Human Medical Ethics Committee of Beijing University of Chinese Medicine and was registered in the Chinese Clinical Trial Registry (ChiCTR-TRC-12002445). Written informed consent was secured from all participants.
Inclusion criteria required that subjects be normal and healthy according to the American Society of Anesthesiologists Physical Status Classification System, that is, that they have no organic, physiologic, biochemical, or psychiatric disorders, smoke
Individuals were excluded if they (1) had a history of addiction to alcohol or drugs, (2) had had contact with moxa smoke within one month of the test, (3) had used medications within two weeks of the test, (4) had had a cold or other illnesses within one week of the test, (5) had ingested food or drink containing caffeine or alcohol, smoked, or done strenuous exercise within four hours of the test, and (6) were pregnant or lactating.
Participants were instructed to refrain from tobacco, alcohol, medications, and strenuous exercise and to avoid contacting moxa smoke or any other abnormal gas during the two-week test.
The trial was performed at the Beijing University of Chinese Medicine in two adjacent, bright, quiet, and similarly laid-out rooms equipped with beds. Ambient temperature and humidity were kept between 24°C
Room 1 had normal indoor air. In Room 2, moxa smoke was generated by burning moxa sticks (three-year-old pure moxa, 1.8 cm × 20 cm, Nanyang Hanyi Moxa Co., Ltd., China). A digital dust indicator (P5L2C, Binta Green Technology Co., Ltd., Beijing, China) that detects particulate matter <10
This was a two-arm, open, and randomized study (
Testing consisted of three phases, one immediately after the other. In phase 1, subjects entered Room 1 and were encouraged to relax in a supine position. After 5–10 minutes of rest, ECG monitoring was performed for 5 minutes. In phase 2, they entered Room 2. After a 5-minute rest in a supine position, ECG monitoring was performed for 20 minutes. In phase 3, they returned to Room 1 for another 5-minute ECG recording (see Figure
Experimental procedures for tests 1 and 2.
Control subjects were similarly monitored but remained in Room 1 during phase 2 (see Figure
The test was performed on each subject twice in a single week to accord with routine clinic practice. One week later, subjects in both groups returned for another 5-minute ECG (see Figure
Flow of participants through the whole trial.
With the subjects supine, three ECG electrodes were placed on their right subclavian and double costal arch regions. A data acquisition instrument (DATAQ Instrument Inc., MODEL:DI-720-USB, USA) was connected to the electrodes and a computer. To allow the heart beat to become steady, ECG recording was started 5–10 minutes after they lay down.
ECGs were analyzed by a specialist blinded to group assignment. After removal of extraneous noise, normal-to-normal beat intervals were analyzed for time- and frequency-domain parameters in 5-minute epochs using standard algorithms and HRV analysis software (Catholic University of Leuven). Time-domain analysis estimates the variation of differences between successive RR intervals through statistically developed indices. Frequency-domain analysis estimates respiratory-dependent, high- and low-frequency power through spectral analysis. Widely used HRV parameters [
HRV parameters used in this trial.
Variable | Units | Description |
---|---|---|
Time-domain |
||
| ||
SDNN | msec | the standard deviation of all NN intervals, an estimate of overall variability |
rMSSD | msec | the square root of the mean of the squared differences between adjacent NN intervals, an estimate of the short-term components of variability |
pNN50 | % | the proportion derived by dividing NN50 (the number of interval differences of successive normal-to-normal intervals greater than 50 ms) count by the total number of normal-to-normal intervals |
| ||
Frequency- domain |
||
| ||
TP | msec2 | total power, frequency range <0.4 Hz |
HF | msec2 | power in the high-frequency range (0.15–0.4 Hz), considered to be mediated mainly by vagal activity |
LF | msec2 | power in the low-frequency range (0.04–0.15 Hz), suggested to be mediated by both sympathetic and parasympathetic activities |
LF/HF | Ratio | an indicator of the balance of the sympathetic and parasympathetic systems |
SPSS17.0 statistical software was used for data analysis. The paired
TP, HF, and LF data were transformed into natural logarithms (ln) for better analysis. The four-segment data of phase 2 were calculated into one mean value for comparison with data from the other two phases. Percentage changes ((mean value in phase 2/value in phase 3 − value in phase 1)/value in phase 1 × 100%) or changes (mean value in phase 2/value in phase 3 − value in phase 1) of all data were used for comparisons between the groups.
There were no statistically significant baseline differences between the groups (Table
Baseline characteristics of study subjects.
Variables | Experimental group |
Control group |
|
---|---|---|---|
Gendera | Male/female | 12/16 | 12/15 |
Age b | Years |
|
|
BMIb | kg/m2 |
|
|
Ethnic groupa | Han/others | 27/1 | 26/1 |
Nationalitya | China/Singapore | 26/2 | 26/1 |
Smoking historya | Yes/no | 0/28 | 0/27 |
Regular exercisea | Yes/no | 11/17 | 7/20 |
Emotional conditiona | Good/ok/bad | 11/17/0 | 13/14/0 |
Mean HRb | bpm |
|
|
SDNNc | ms | 40.43 (12.89) | 43.02 (26.26) |
RMSSDc | ms | 35.08 (24.80) | 34.02 (13.8) |
PNN50c | % | 14.93 (32.12) | 14.02 (17.21) |
lnTPc | 7.17 (0.77) | 7.17 (1.18) | |
lnHFc | 6.31 (1.21) | 6.02 (1.36) | |
lnLFc | 5.77 (0.8) | 5.99 (0.96) | |
LF/HFc | 0.76 (0.82) | 0.83 (0.72) |
In phases 2 and 3, during and after exposure, HR (
Changes in all indicators in the first test of the week. Values are expressed as (a) mean and (b)–(h) median. * indicates a significant difference (
Comparison of the percentage changes/changes in HR and HRV parameters showed no significant differences between groups (Table
Comparison of the percentage changes/changes in HR and HRV parameters between the groups in the first test of the week.
Experimental group | Control group |
|
|
---|---|---|---|
HR1,a | |||
Before-during |
|
|
0.75 |
Before-after |
|
|
0.92 |
SDNN1,b | |||
Before-during | 0.19 (0.35) | 0.20 (0.29) | 0.74 |
Before-after | 0.22 (0.42) | 0.14 (0.33) | 0.62 |
RMSSD1,b | |||
Before-during | 0.18 (0.38) | 0.09 (0.35) | 0.78 |
Before-after | 0.18 (0.36) | 0.15 (0.42) | 0.89 |
PNN502,b | |||
Before-during | 4.03 (10.34) | 4.88 (11.44) | 0.56 |
Before-after | 4.32 (8.46) | 5.26 (15.3) | 0.72 |
lnTP1,b | |||
Before-during | 0.03 (0.09) | 0.04 (0.09) | 0.58 |
Before-after | 0.05 (0.08) | 0.04 (0.07) | 0.60 |
lnHF1,b | |||
Before-during | 0.05 (0.1) | 0.04 (0.11) | 0.46 |
Before-after | 0.05 (0.09) | 0.04 (0.11) | 0.45 |
lnLF1,b | |||
Before-during | 0.03 (0.15) | 0.04 (0.09) | 0.57 |
Before-after | 0.03 (0.17) | 0.04 (0.18) | 0.82 |
LF/HF2,b | |||
Before-during | 0.11 (0.51) | 0.09 (0.34) | 0.89 |
Before-after |
|
|
0.79 |
Number 1 indicates percentage changes; number 2 indicates data changes. Values are expressed as amean ± standard deviation and bmedian (interquartile range). No significant differences were found between the groups using aindependent two-sample
In phases 2 and 3, during and after exposure, each group had significant reductions in HR (
Changes in all indicators in the second test of the week. Values are expressed as (a) mean and (b)–(h) median. *indicates a significant difference (
In phase 2, the experimental group’s percentage decrease in HR (
Test 2: percentage changes/changes in HR and HRV parameters.
Experimental group | Control group |
|
|
---|---|---|---|
HR1,a | |||
Before-during |
|
|
|
Before-after |
|
|
0.63 |
SDNN1,b | |||
Before-during | 0.21 (0.32) | 0.15 (0.41) | 0.76 |
Before-after | 0.16 (0.36) | 0.28 (0.57) | 0.56 |
RMSSD1,b | |||
Before-during | 0.42 (0.29)* | 0.19 (0.30) |
|
Before-after | 0.12 (0.37) | 0.24 (0.57) | 0.47 |
PNN502,b | |||
Before-during | 9.78 (17.32)△ | 5.02 (7.81) | 0.02 |
Before-after | 4.26 (13.59) | 10.59 (17.26) | 0.34 |
lnTP1,b | |||
Before-during | 0.3 (0.09)* | 0.05 (0.08) |
|
Before-after | 0.04 (0.09) | 0.09 (0.13) | 0.18 |
lnHF1,b | |||
Before-during | 0.29 (0.07)* | 0.03 (0.09) |
|
Before-after | 0.06 (0.1) | 0.06 (0.19) | 0.71 |
lnLF1,b | |||
Before-during | 0.31 (0.21)* | 0.07 (0.15) |
|
Before-after | 0.10 (0.19) | 0.15 (0.23) | 0.15 |
LF/HF2,b | |||
Before-during | 0.18 (0.34) | 0.32 (0.84) | 0.30 |
Before-after | 0.13 (0.69)△ | 0.44 (1.19) | 0.005 |
Number 1 indicates percentage changes; number 2 indicates data changes. Values are expressed as amean ± standard deviation and bmedian (interquartile range). The symbols * and △ indicate significant differences (
Mean HR (
HR and HRV parameters, follow-up test.
HRa | SDNNb | RMSSDb | PNN50b | lnTPb | lnHFb | lnLFb | LF/HFb | |
---|---|---|---|---|---|---|---|---|
Control group |
|
44.07 (22.26) | 34.01 (21.12) | 12.37 (21.9) | 7.22 (1.04) | 5.94 (1.62) | 5.83 (1.04) | 0.93 (1.17) |
Experimental group |
|
52.72 (26.91) | 46.16 (38.15) | 29.75 (45.16) | 7.56 (1.07) | 6.73 (1.54) | 6.19 (1.35) | 1.01 (1.45) |
Values are expressed as amean ± standard deviation and bmedian (interquartile range). The symbol *indicates a significant difference (
During moxa smoke exposure, seventeen experimental group subjects felt sleepy and relaxed. One felt refreshed; stomach and bowel movement improved in another. Ten complained of choking and irritation in nose, pharynx, and eyes. One had difficulty in breathing. Eight had no unusual sensations.
In the control group, two subjects felt sleepy; one had neck discomfort; one had numbness in the hand. Twenty-three felt nothing unusual.
No harmful HR and HRV effects were observed during exposure to clinical levels of moxa smoke. Evidence for this is that there were no differences in HR and HRV, either immediately (after 10 minutes) or at followup a week after exposure, between the experimental group exposed to moxa smoke and the control group without such exposure. These results might explain why reports of adverse reactions associated with smoke produced in this ancient therapy are so rare.
In contrast to retrospective studies based on clinical observation, our present study was a well-controlled, randomized, and prospective study to examine possible adverse effects of moxa smoke. The study is unique in moxa smoke concentration, length of exposure to the smoke, and its carefully controlled and monitored experimental environment, all of which mimic actual clinical moxibustion practice. The sample size is comparable to those reported in similar studies on exposure to other types of potentially hazardous smoke [
The HRV effects that we observed in this moxa smoke study contrast with findings of air pollution and tobacco smoke studies, which show harmful effects on human health [
Interestingly, in the second test we observed positive HR and HRV parameter changes in the experimental group compared to control. These include decrease in mean HR and increases in both time-domain analysis HRV (RMSSD, PNN50) and frequency-domain (TP, HF, and LF) during the 25-minute moxa smoke exposure (Table
Moxa smoke effects and mechanisms have not been well investigated. We speculate that the effects are similar to those of aromatherapy, as a number of studies [
We are aware of the limitations of the present study. Our data only show HRV effects from short-term exposure to moxa smoke; in normal acupuncture practice, patients usually receive multiple moxibustion treatments, and practitioners are usually exposed to the smoke for years. These factors warrant a long-term observational study. Furthermore, because the participants in our study were not blinded, we cannot rule out the possibility of placebo effect. Additionally, our subjects were young and healthy; these results might not reflect how moxa smoke affects the elderly or chronically ill.
Nevertheless, this study is an important step toward understanding the effects of moxa smoke. Our results provide useful information on the feasibility of a future, larger trial and will make it possible to calculate adequate sample sizes for such research.
In conclusion, our data show that short-term moxa smoke exposure at clinical concentrations poses no hazards to patients’ HR and HRV and suggest that moxa smoke has a positive regulating effect on human autonomic function. Future studies are needed to further investigate the effects and the safety of moxa smoke.
The authors have no conflict of interests.
The research was supported by the National 973 Project (2009CB522906), National Natural Science Fund Project (no. 81072862), and Beijing University of Chinese Medicine Graduate Student Fund Project (JYBZZ-XS043). The authors wish to thank Dr. Lyn Lowry for her editorial assistance.