Effects of Transcutaneous Electrical Acupoint Stimulation on Patients with Stable Chronic Obstructive Pulmonary Disease: A Prospective,Single-Blind,Randomized,Placebo-Controlled Study

Abstract

Objectives:

To evaluate the clinical effect of transcutaneous electrical nerve stimulation over acupoints (acu-TENS) on patients with stable chronic obstructive pulmonary disease (COPD).

Design:

Prospective, single-blind, randomized, placebo-controlled study.

Settings/Locations:

Outpatient center of West China Hospital, Sichuan University.

Patients:

Fifty patients with stable COPD enrolled in the study.

Interventions:

Patients were randomly assigned to one of two groups: the acu-TENS group (n=25), who underwent acu-TENS over acupoints of bilateral EX-B-1(Dingchuan), BL-13 (Feishu), BL-23 (Shenshu), ST-36 (Zusanli), and the placebo acu-TENS control group (n=25), who had the same electrode placement but no electrical output. Treatments were performed for 40-minute sessions every 2 days for 4 weeks.

Outcome measures:

Lung function (forced expiratory volume in 1 second, percentage predicted (FEV₁% predicted); forced vital capacity, percentage predicted (FVC% predicted), 6-minute walk distance (6MWD) and oxygen saturation (SpO₂), COPD assessment test (CAT), and Dyspnea Visual Analogue Scale (DVAS) were assessed before and after the intervention.

Results:

Compared to control group, FEV₁% predicted was improved and CAT score was decreased significantly in the acu-TENS group after treatment (p<0.05). The DVAS score decreased significantly in the acu-TENS group (p=0.039), with a slight but insignificant improve in 6MWD, SpO₂, and FVC% predicted after treatment.

Conclusions:

Acu-TENS over acupoints of bilateral EX-B-1 (Dingchuan), BL-13 (Feishu), BL-23 (Shenshu), and ST-36 (Zusanli) improved FEV₁% predicted and reduced DVAS and CAT scores on patients with stable COPD. This may be a novel treatment strategy in COPD.

Introduction

Chronic obstructive pulmonary disease (COPD) is characterized by incompletely reversible airflow limitation, with high morbidity and mortality,¹ leading to increasing social and economic burden.² Many develop this disease and die of the complications.^3,4

Respiratory symptoms of dyspnea, cough, and chronic sputum production are common in patients with COPD and strongly affect quality of life. Pharmacologic treatments recommended by guidelines such as those from the Global Initiative for Chronic Obstructive Lung Disease (GOLD)¹ to improve clinical symptoms and reduce the frequency of exacerbation. However, patients who are receiving the maximum treatment for COPD can also present with severe symptoms and frequent exacerbations. In addition, adverse effects of current medications are increasingly being reported; for example, the use of inhaled corticosteroids increases the risk for pneumonia and muscle weakness.⁵

Therefore, nonpharmacologic therapies, which may be an alternative treatment option for stable COPD and have fewer side effects, have recently emerged and been accepted for use. Acupuncture is a Traditional Chinese Medicine therapy with subtantial effects on various diseases. It has been recently reported to reduce dyspnea,^6

–9, improve quality of life, and improve performance on the 6-minute walking distance (6MWD) test^10,11 in patients with COPD.

As an invasive treatment, puncturing in the body may cause adverse effects (e.g., pneumothorax, subcutaneous hematoma).^12
–14 Alternatively, transcutaneous electrical nerve stimulation (TENS) is an electrotherapy method that exerts a specific low-frequency pulse current to treat diseases. It arose in the 1970s and was mainly used to alleviate pain^15

–18 and for rehabilitation.¹⁹ Bourjeily-Habr²⁰ and Neder²¹ reported that TENS might be a new rehabilitative treatment for COPD. Recently, TENS has been applied over acupoints (acu-TENS). Studies demonstrated that acu-TENS improves lung function and quality of life in patients with COPD.^22
–24 Lau et al.²³ found that a single session of acu-TENS on EX-B-1 (Dingchuan) could improve forced expiratory volume in 1 second, percentage predicted (FEV₁% predicted), and reduce dyspnea severity in patients with stable COPD, and Ngai et al.²⁴ showed that acu-TENS on EX-B-1 (Dingchuan) improves physical function and quality of life with increased sessions.

In clinical studies of COPD, while acupoints have cooperative effects,²⁵ apart from EX-B-1 (Dingchuan), other acupoints of EX-B-1 (Dingchuan), BL-13 (Feishu), BL-23 (Shenshu), and ST-36 (Zusanli) were also frequently chosen to treat COPD.^{8

–11,23,24,26

–36} The cooperative effects of EX-B-1 (Dingchuan), BL-13 (Feishu), BL-23 (Shenshu), and ST-36 (Zusanli) by acu-TENS on COPD have not been studied. Therefore, the current study was designed to detect the clinical effects of acu-TENS over multiple acupoints on patients with stable COPD.

Materials and Methods

The departmental ethic review committee of West China Hospital approved the study, and the study was conducted in accordance with the Declaration of Helsinki (registration no.: ChiCTR-TRC-14004500).

Patients

Patients were recruited from the outpatient center of West China Hospital from May to July 2014 and were diagnosed with COPD according to the GOLD guidelines.¹ Inclusion criteria were clear consciousness, ability to walk independently, no previous experience with acu-TENS, and willingness to sign the informed consent form. Exclusion criteria were a history of cardiovascular, endocrine, or neurologic disease; allergy to the adhesive agent; pregnancy or lactation; upper respiratory tract disease; an acute exacerbation of COPD in the preceding 3 months; and participation in other clinical trials in the past 6 months. Patients who had COPD exacerbations during the study were excluded. Patients were free to withdraw from the study; the reasons were recorded by telephone.

Study design

Sample size calculation

The sample size was determined by using Package for Encyclopaedia Medical Statistics 3.2 software (PEMS 3.2, Guangzhou Jing far Pharmaceutical Research Co., Ltd. GuangZhou, China.) with 90% power and an α value of 0.05 (two-sided). According to Suzuki et al.,¹¹ the standard deviation of FEV₁% predicted in the placebo group is 15.4%; thus, 15.4% was set as the overall standard deviation, and 16% as the overall mean difference. Therefore, the sample size had be 20 cases for each group. Considering the potential 20% loss of patients, the number of participants recruited had to be 25 per group, and a total of 50 patients were recruited for this trial.

Randomization and blinding

Both patients and program assessors were blinded to the intervention. Patients were randomly assigned to the acu-TENS group or control group (placebo acu-TENS) by the statistician, who was blinded to the intervention, using SPSS software, version 16.0 (SPSS Inc., Chicago, IL). This software randomly generated a total of 50 numbers, from Arabic digital numbers 1 to 50; each code was printed on a separate piece of paper and placed in separate sealed opaque envelopes. When a patient was enrolled in the study, the patient was asked to pick one of the envelopes randomly. An odd number indicated the control group, and an even number indicated the treatment group. After allocation, patients in different groups were separated and received different treatments until the end of the study. Three acupuncturists with more than 3 years' working experience with clinical acupuncture were involved in this study.

Intervention program

All the points were located by the same acupuncturist, and patients received the treatment at the same time and same place each session by the other two acupuncturists (one for the acu-TENS group and one for the control group during the study).

For basic treatment, patients continued to receive the treatments they had been receving for the past 6 months. In the acu-TENS group, patients were seated for their procedure. An acupuncturist wiped the skin of the points with a cotton ball soaked in 75% alcohol. Four pairs of electrodes for TENS (6805-D model, Shantou City Medical Equipment Co., Ltd., Shantou City, China) were placed on the acupoints and fixed with adhesive tape. Treatment frequency was set for 2Hz according to the study by Franco et al.³⁷ Electrodes of the same pair can only be connected at the same side to avoid direct contact across the body. In the control group (placebo acu-TENS), the devices were set as mentioned for the active treatment group, but no electrical current was applied. For both groups, treatment was performed for 40 minutes every 2 days for 4 weeks (14 sessions).

Outcome measurement

Before the study, patient data were collected, including sex, age, body–mass index, smoking history, COPD history, and medication history. Before the first session and after the 14th session, the following indicators were measured at the same time and the same place.

6MWD and oxygen saturation

The 6MWD test was performed according to American Thoracic Society (ATS) guidelines.³⁸ During the test, patients wore a fingertip oximeter (PC-60A, Ke Ruikang Industrial Co., Ltd., Shenzhen City, China) to record oxygen saturation (SpO₂) every minute.

Lung function

According to the recommendation of ATS,³⁹ the predicted values of forced vital capacity (FVC% predicted) and FEV₁% predicted by spirometry (AS-501, Guangzhou Aoxun Trading Co. Ltd. GuangZhou, China.).

Dyspnea Visual Analogue Scale

According to ATS guidelines³⁸ for 6MWD, every patient had to rest for at least 10 minutes before walking; the 6MWD test began after confirmation that the patient had no difficulty breathing. All patients could walk independently. Therefore, the difference in the Dyspnea Visual Analogue Scale (DVAS) score was assessed only after the 6MWD test, which follows the method used by Suzuki et al.^10,11

The DVAS score was recorded according to ATS guidelines.⁴⁰ Scores range from 0 to 100 mm; 0 means no breathing difficulties, while 100 represents the maximum dyspnea imaginable. Patients marked DVAS score immediately after completing the 6MWD test.

COPD Assessment Test

The COPD Assessment Test (CAT) is divided into eight questions. Points for each answer range from 0 to 5; 0 represents no impact, and 5 means the worst effect imaginable. The final score score is the sum of points for each question.⁴¹

Statistical analysis

Data are presented as the mean±standard deviation. Changes in exercise tolerance (6MWD and SpO₂), lung function (FEV1%, FVC%), and symptoms (CAT, DVAS) were compared and analyzed by independent t-test or non-independent t-test. All data were analyzed by a statistician who was blinded to the intervention with SPSS software, version 16.0. A p-value <0.05 was considered to represent a statistically significant difference.

Results

Fifty-five patients were initially recruited into the study; five were excluded because FEV1% predicted was <20%. Thus, 50 patients (25 in the acu-TENS group and 25 in the control group) were allocated to a study group (Fig. 1).

FIG. 1.

Flowchart. Fifty-five patients were initially recruited into the study; 5 were excluded. Thus, 50 patients (25 in the acu-TENS group and 25 in the control group) completed the study. After 4 weeks treatment, the data were collected and conclusions were drawn.

Baseline characteristics

The main age of the study population was 66.3±9.0 years. There were non-significant differences between groups in the baseline data (p>0.05) (Table 1).

Table 1.

Baseline Data

Variable	Acu-TENS group (n=25)	Control group (n=25)	p-Value
Men/women (n/n)	10/15	15/10	–
Age (y)	66.04±8.815	66.48±9.368	0.833
Body–mass index (kg/m²)	22.37±4.025	23.2720±5.198	0.496
GOLD grade (n)
I	0	0	–
II	13	11	–
III	6	7	–
IV	6	7	–
Smoking history (y)	22.80±18.15	22.20±18.49	0.908
COPD history (y)	8.504±7.11	9.51±9.93	0.351
Pharmacologic treatment (n)
ICS+LABA	6	6	–
LABA	2	4	–
LAMA	0	1	–
Leukotriene RA	1	0	–
Exercise tolerance
6MWD (m)	383.76±98.42	395.20±76.14	0.648
SaO₂ (%)
0 min	95.48±2.76	95.04±3.02	0.593
1 min	93.24±3.66	93.76±3.65	0.618
2 min	92.48±3.85	92.16±3.98	0.774
3 min	92.32±5.19	92.40±4.42	0.953
4 min	91.60±5.49	92.56±4.18	0.490
5 min	92.64±5.41	92.28±4.41	0.798
6 min	92.24±6.37	92.48±4.00	0.874
Lung function
FEV1%	47.08±19.19	38.36±18.73	0.111
FVC%	56.28±19.52	50.52±16.13	0.261
FEV1/FVC	65.41±12.53	61.98±14.39	0.373
Symptoms
CAT score	16.56±5.83	14.56±6.028	0.239
DVAS score	22.80±19.48	18.00±17.56	0.365

Values expressed with a plus/minus sign are the mean±standard deviation.

AcuTENS, transcutaneous electrical nerve stimulation over acupoints; GOLD, Global Initiative for Chronic Obstructive Lung Disease; COPD, chronic obstructive pulmonary disease; ICS, inhaled glucocorticosteroids; LABA, long-acting β₂-agonists; LAMA, long-acting anticholinergics; RA, receptor antagonist; 6MWD, 6-minute walk distance; SaO₂, oxygen saturation; FEV1%, the ratio of the measured values of predicted values of forced expiratory volume in 1 second; FVC%, the ratio of the measured values of predicted values of force vital capacity; CAT, COPD assessment test; DVAS, Dyspnea Visual Analogue Scale.

6MWD and SpO₂

After the 4-week intervention, the 6MWD changed 30.5±37.4 m in the acu-TENS group compared with 23.5±58.0 in the control group (Table 2). However, the differences between or within groups were not significant (p=0.961). Compared with baseline data, SpO₂ tended to decrease in the acu-TENS group but increased in the control group after the intervention; the changes within and between groups were not significant (Fig. 2).

FIG. 2.

Oxygen saturation (SpO₂) during the 6-minute walk distance test (6MWT) before and after treatment. SpO₂ was recorded every minute during the test by fingertip oximeter. Before treatment, SpO₂ was at the baseline in both groups (p>0.05). After treatment, SpO₂ showed different trends between the two groups; it increased in the acu-TENS group and decreased in the control group, but there were no statistically significant difference within or between groups (p>0.05).

Table 2.

Changes in Exercise Tolerance, Lung Function, and Symptoms

	Acu-TENS group (n=25)			Control group (n=25)
Variable	Before	After	p-value	Before	After	p-Value	p-Value for between-group difference
Exercise tolerance (m)
6MWD	383.8±98.4	418.3±90.6	0.203	395.2±76.1	418.7±57.1	0.096	0.961
Lung function (%)
FEV1%	47.1±19.2	53.6±19.5	0.243	38.4±18.7	39.0±16.8	0.698	0.046^*
FVC%	56.3±19.5	60.3±13.9	0.408	50.5±16.1	49.4±13.8	0.793	0.137
Symptoms
CAT	16.6±5.8	8.9±6.1	0.001^**	14.6±6.0	10.8±5.9	0.032^*	0.028^*
DVAS	22.8±19.5 (20)	11.2±11.7 (10)	0.039^*	18.0±17.6 (10)	11.6±12.8 (10)	0.192	0.358

Values in parentheses are the median.

p<0.05.

p<0.01.

Effect of acu-TENS on lung function

At the end of the intervention, the changes in FEV₁% predicted were significant between groups (p=0.046). FEV1% predicted slightly but insignificantly improved in the acu-TENS group (improvement, 6.7±8.0; p=0.243) (Table 2) and the control group (0.7±10.4; p=0.698). FVC% predicted nonsignificantly improved between groups (p=0.137).

Effect of acu-TENS on symptoms

After the treatment program, CAT score decreased significantly in both groups: by 7.64±4.65 in the acu-TENS group (p=0.001) and by 3.72±5.18 in the control group (P=0.032). Moreover, the difference between group was also obvious (p=0.028). The DVAS score decreased significantly in the acu-TENS group –(change, −11.60±18.41; p=0.039) and nonsignificantly decreased in the control group (change, −6.40±17.77;p=0.192) by the end of the intervention. The differences between groups were not significant (p=0.358).

Adverse events

During the trial, no adverse events occurred.

Discussion

To the authors' knowledge, this is the first report on the effect of applying acu-TENS over multiple acupoints on patients with stable COPD. The findings showed that acu-TENS over bilateral EX-B-1 (Dingchuan), BL-13 (Feishu), BL-23 (Shenshu), ST-36 (Zusanli) can improve 6MWD in patients with stable COPD. The 6MWD seems to have improved more (30.5 m) than with single EX-B-1 (8.5 m),²⁴ but the improvement was not significant, which is contrary to the finding with a single point. Compared to Suzuki and colleagues' findings,¹¹ the improvement in 6MWD by acupuncture was 45.4 m, much better than the current finding. Since this was a prospective study, the difference may due to the following: (1) Acu-TENS may not has as positive effects 6MWD in patients with stable COPD as acupuncture; (2) because of the small sample size and the fact that patients had stage II–IV COPD according to the GOLD guidelines¹ (a group whose exercise tolerance level was lower), the results may not fully prove the effect of acu-TENS on COPD; (3) the selected points—treatment session and time—may not be the best optimal solutions for transcutaneous electrical acupoint stimulation (TEAS) on stable COPD.

After the treatment, the trend toward decrease in SpO₂ was reduced in the acu-TENS group and improved in control group. Ngai et al.²⁴ reported that acu-TENS applied to EX-B-1 (Dingchuan) for 40 minutes a session 5 days a week for 4 weeks may slow the tendency in SpO₂ decline, which is similar to the current findings. Moreover, FEV₁% predicted improved impressively in the acu-TENS group, while FVC% predicted increased more in the acu-TENS group than the control group. This is also consistent with the findings by Lau and Jones²³and Ngai et al.²⁴ After the intervention, the CAT score decreased in both groups, but the trend was better in the acu-TENS group (7.64) than in the control group (3.72); it was more than the score of 2 that is recommended to be a credible clinical effect.⁴² The DVAS score reduced in both groups, but the decrease was greater in the acu-TENS group than in the control group.

According to Traditional Chinese Medicine, COPD is a “lung distention” syndrome. When the lung is attacked by evil qi, ascension or descension of lung qi will be disturbed, leading to cough, sputum, and lung distention. It is treated by expelling evil qi and enriching the foundation. The pathogenesis of stable COPD is an insufficient foundation, including lung deficiency, spleen deficiency, and kidney deficiency.

Acupuncture is widely used for chronic disease in clinical. According to the literature, the number of points selected for COPD have ranged from 1 to 13;^{8

–11,23,24,26

–36} the points chosen most frequently were EX-B-1 (Dingchuan), BL-13 (Feishu), BL-23 (Shenshu), and ST-36 (Zusanli). EX-B-1 (Dingchuan) is an extraordinary point, with the function of regular lung qi, while BL-13 (Feishu), BL-23 (Shenshu), and ST-36 (Zusanli) reinforce the lung, spleen, and kidney. Meanwhile, the number of treatment sessions has ranged from 1 single to 20; a 4-week duration was more acceptable.^{8

–11,23,24,26

–36} Because acupuncture sessions have a cumulative effect,¹¹ the current study used a total of 14 sessions conducted every 2 days for 4 weeks.

Compared with acupuncture, acu-TENS is noninvasive and safe. Currently, the mechanism of acu-TENS on the treatment of COPD is still unknown. Ngai et al.²⁴ and Jones et al.⁴³ demonstrated that acu-TENS may affect the afferent hypothalamus through the nerve impulse and promote the release of β-endorphin, eventually relaxing airways and reducing dyspnea. There are three asumptions: (1) Because functional magnetic resonance imaging has confirmed that specific parts of the brain may react during acupuncture,⁴⁴ acu-TENS may initiate nerve stimulation of hypothalamus and directly or indirectly cause the respiratory center to release endorphins, thus expanding the bronchi and ease breathing difficulties; (2) acu-TENS may lead to changes in the hypothalamus parasympathetic output signal, causing the release of acetylcholine in the parasympathetic nervous endings and inhibiting the release of inflammatory cells;⁴⁵ (3) acupoint stimulation may stimulate muscles, thereby triggering the body's sympathetic nervous system through afferent stimulation, inducing the release of endorphins substances, and reducing airway resistance.

The study had some limitations. The first limitation is the small sample size. The second is that the selected points, treatment sessions, and time may not be the best optimal solutions for TEAS on stable COPD. Third, no effect was seen on patients with adverse events of COPD. Articles had demonstrated that acu-TENS can alleviate symptoms in patients with these adverse events,^22,46 but Wen et al.⁴⁷ found the effect of acu-TENS on these patients may not obvious and still require further study. Because of budgetary and time constraints and laboratory and economic indicators, follow-up assessment was not included in this study.

In conclusion, this study showed that acu-TENS over bilateral EX-B-1 (Dingchuan), BL-13 (Feishu), BL-23 (Shenshu), and ST-36 (Zusanli) conducted in 40-minute sessions every 2 days for 4 weeks in patients with stable COPD, may improve FEV1% and reduce DVAS and CAT scores, withou any adverse effect or invasive procedures; effects on 6MWD and SpO₂ require further study. Acu-TENS is an noninvasive and safe treatment, and crossover and multicenter studies with larger sample sizes are needed in the future.

Footnotes

Acknowledgment

This study was supported by a project of Sichuan Provincial Health Department (project no. 130085). The authors thank all patients who devoted their time to this study.

Author Disclosure Statement

No competing financial interests exist.

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Effects of Transcutaneous Electrical Acupoint Stimulation on Patients with Stable Chronic Obstructive Pulmonary Disease: A Prospective,Single-Blind,Randomized,Placebo-Controlled Study

Abstract

Objectives:

Design:

Settings/Locations:

Patients:

Interventions:

Outcome measures:

Results:

Conclusions:

Introduction

Materials and Methods

Patients

Study design

Sample size calculation

Randomization and blinding

Intervention program

Outcome measurement

6MWD and oxygen saturation

Lung function

Dyspnea Visual Analogue Scale

COPD Assessment Test

Statistical analysis

Results

Baseline characteristics

6MWD and SpO2

Effect of acu-TENS on lung function

Effect of acu-TENS on symptoms

Adverse events

Discussion

Footnotes

Acknowledgment

Author Disclosure Statement

References

6MWD and SpO₂