Heart Rate Variability during Acupuncture Treatment of Lumbosacral Pain

Yan Yang ^{1, 2, †}, Gerhard Litscher ^{1, 2, †, *}, Zemin Sheng ^{2, 3}, Lu Wang ^{1, 2}

1. Research Unit of Biomedical Engineering in Anesthesia and Intensive Care Medicine, Research Unit for Complementary and Integrative Laser Medicine, and Traditional Chinese Medicine (TCM) Research Center Graz, Medical University of Graz, 8036 Graz, Austria

2. Heilongjiang University of Chinese Medicine, Harbin 150040, China

3. Privatclinic Lassnitzhoehe, 8075 Lassnitzhoehe, Austria

† These authors contributed equally to this work.

* Correspondence: Gerhard Litscher

Academic Editor: Hegyi Gabriella

Special Issue: Modernization of Acupuncture Education and Research

Received: February 12, 2020 | Accepted: March 16, 2020 | Published: March 20, 2020

OBM Integrative and Complementary Medicine 2020, Volume 5, Issue 1, doi:10.21926/obm.icm.2001015

Recommended citation: Yang Y, Litscher G, Sheng Z, Wang L. Heart Rate Variability during Acupuncture Treatment of Lumbosacral Pain. OBM Integrative and Complementary Medicine 2020; 5(1): 015; doi:10.21926/obm.icm.2001015.

© 2020 by the authors. This is an open access article distributed under the conditions of the Creative Commons by Attribution License, which permits unrestricted use, distribution, and reproduction in any medium or format, provided the original work is correctly cited.

1. Introduction

Treatment of Lower Back Pain (LBP) using acupuncture mainly involves controlling or reducing pain to return to normal life activities as soon as possible. The most recent international guidelines regarding the topic recommend pharmacological management for pain relief in LBP, which includes paracetamol, non-steroidal anti-inflammatory drugs, muscle relaxants, opioid analgesics, epidural steroids, anticonvulsants, antidepressants, and corticosteroids, among others [1]. However, most of these pharmacological treatments provide limited pain relief and are accompanied by serious side effects, such as drowsiness, dizziness, addiction, allergic responses, reversible reduction in the liver function, and negative impacts on gastrointestinal functions [1]. This raises the requirement for complementary treatments for LBP. Such treatments include multidisciplinary rehabilitation based on physiotherapy, spinal manipulation, exercise therapy, massage therapy, cognitive-behavior therapy, yoga, tai-chi, and acupuncture [1].

The aim of the present study was to investigate the short-term effects of heart rate (HR) and heart rate variability (HRV) during the acupuncture treatment in patients with LBP.

2. Methods

2.1. Patients

A total of 18 patients (mean age + SD: 60.2 ±12.0 years; age range: 38–84 years; mean height + SD: 167.9 ±7.8 cm; mean weight + SD: 82.9 ±14.1 kg; mean body mass index (BMI) + SD: 29.4 + 4.9 kg/m²; 15 females and 3 males) were enrolled in the study. The enrolled patients did not have any severe neurological or orthopedic disorders. Therefore, no numerical rating scale was used. All the investigations were performed at the Privatclinic Lassnitzhoehe in Austria. The recruitment of the patients for the study was conducted by an experienced neurologist. It was the first acupuncture session for each of the enrolled patients, as none had undergone acupuncture therapy previously. All the patients provided oral informed consent for participation in the study, and the study was performed in accordance with the principles of the Declaration of Helsinki. Ethical permission for the study was obtained from the institutional review board of the Privatclinic Lassnitzhoehe [2].

2.2 Study Procedures

The study was performed and integrated into routine acupuncture therapeutic interventions. Therefore, there was no control group for the trial. All the patients were subjected to needle acupuncture. The HR and HRV data were analyzed during one single 30-minute-long acupuncture session.

2.3 Acupuncture Points and Needling Technique

The acupuncture points used for LBP treatment in the present study for each patient are listed in Table 1. The description of the acupuncture points is provided in Table 2. The main acupuncture points are depicted in Figure 1.

Table 1 Acupuncture points for LBP used in the present study.

Table 2 Description of the acupuncture points for LBP used in this study (approx.: approximate; 1 cun = one thumb width) [3].

Figure 1 Main acupuncture points for low back pain (LBP).

Needling was performed in accordance with the Chinese standard procedures (with respect to depth and direction), using single-use needles (0.30 × 30 mm and/or 0.30 × 40 mm; Huan Qiu, Suzhou, China). Needle stimulation was performed clockwise as well as counter-clockwise, each for 15 s, with two rotations per second, resulting in 30 rotations per stimulation. Stimulation was performed immediately after inserting the needle, 10 min later, and immediately before removing the needles (Figure 2).

Figure 2 Measurement procedure (before acupuncture (a); during acupuncture (b–e); after acupuncture (f)).

2.4 Evaluation Parameters

HR and HRV, which have been used successfully in numerous acupuncture studies conducted previously, were the primary target parameters for the present study [4]. The parameters were measured in a quiet room after a resting period of at least 5 min. The HRV analysis was performed using Medilog® AR12 HRV system (Huntleigh Healthcare, Cardiff, UK) from the TCM research center of the Medical University in Graz. Registration was performed using three adhesive electrodes (Skintact Premier F–55; Leonhard Lang GmbH, Innsbruck, Austria) applied to the chest of each patient. Six measuring phases (a–f; Figure 2), each being 5-min long, were compared, one prior to stimulation (a), four during the acupuncture treatment (b–e), and one after the acupuncture treatment (f).

HR and HRV were measured continuously during the acupuncture treatment. The sampling rate of the HRV system was 4,096 Hz. The raw electrocardiographic data were stored on a memory card, and were subsequently read out using a card reader connected to a standard computer. HRV was presented in such a manner that the function of the autonomic nervous system was assessable [4]. Low frequency/high frequency (LF/HF) and the mean value of the heart rate (HR), recommended by the Task Force of the European Society of Cardiology and the North American Society for Stimulation and Electrophysiology, were quantified as the electrocardiographic variables [5].

2.5 Statistical Analysis

Data analysis was performed using SigmaPlot 14.0 software (Systat Software Inc., Chicago, IL). Graphic presentation of the results was achieved using box plot illustrations. Testing was performed using a one-way repeated measures analysis of variance, Kruskal-Wallis one-way analysis of variance on ranks, and Tukey’s test. The significance threshold was set at P < 0.05.

3. Results

The mean HR prior to, during, and after the acupuncture treatment of the 18 patients are presented in Figure 3. No significant alterations were observed either among the different conditions (a–f) or prior to and after the acupuncture treatment (P = 0.975). HR did not appear to change significantly during the first phase (b) after the insertion of needles.

Figure 3 Mean heart rate (HR). Box plot illustration for the 18 patients with lower-back pain prior to (a), during (b–e), and after (f) the needle acupuncture treatment. No significant changes were observed. The dotted horizontal lines in the boxes depict the position of the median. The end of the box defines the 25^th and 75^th percentiles, and the error bars mark the 10^th and 90^th percentiles (n.s.: not significant).

The results for the analysis of total HRV are depicted in Figure 4. A significant decrease in total HRV was observed during and immediately after the acupuncture treatment.

Figure 4 Total heart rate variability (HRV). Box plot illustration for 18 patients with low-back pain before (a), during (b–e), and after (f) needle acupuncture. The graphic shows significant changes during the phases c–f (a.u. = arbitrary unit). Further explanations are given in Figure 3.

Furthermore, during and after the acupuncture treatment, significant reductions in the LF/HF ratio of the HRV were observed (Figure 5).

Figure 5 LF (low frequency)/HF (high frequency) ratio. Box plot illustration for the 18 patients with low-back pain before (a), during (b–e), and after (f) needle acupuncture. Further explanations are given in again Figure 3.

4. Discussion

HRV is an index representing the function of the autonomic nervous system (ANS), and serves as a reliable method for obtaining information regarding the sympathetic and parasympathetic nervous systems. Recent studies have demonstrated that changes in sympathovagal balance could be related to acupuncture treatment [4].

The present exploratory study was aimed to evaluate the effect of acupuncture treatment on the ANS reactivity in patients with lumbosacral pain. The results revealed that compared to the only existing study on the topic of HRV, acupuncture, and lumbosacral pain [2], similar HR and LF/HF-HRV pattern changes were observed in the present study as well, while certain slightly different HRVtotal changes were also observed.

There is evidence that acupuncture is capable of affecting the balance of the ANS. Generally, acupuncture is able to improve either vagal or sympathetic tone, depending on which acupuncture points have been stimulated [4]. In the present study, the LF/HF value during and after the acupuncture treatment increased significantly compared to the initial values before the treatment. A possible reason for the statistical significance of the results of the present study, as well as the previous study [2], could be that acupuncture, as a kind of external stimulation, stimulates the human body to elicit its reflex defense reaction. However, a stress response caused by adequate needling may gradually disappear and turn into positive stimulation.

Acupuncture has been used frequently in the past for the treatment of lower back pain [1]. The underlying mechanism could be related to the activation of endogenous opioids and neuropeptides through the stimulation of specific structures in the brain. It has been reported that acupuncture could be applied as a supplementary procedure to reduce pain and thereby improve the quality of life in patients [1].

The ANS comprises two components the sympathetic nervous system which is responsible for the flight and stress reactions, and the parasympathetic nervous system, which dominates when a person relaxes. The low-frequency band LF (0.04–0.15 Hz) in HRV mainly reflects the sympathetic activity, while the high-frequency component HF (0.15–0.4 Hz) is regarded as an index of parasympathetic nerve activity. The LF/HF ratio, therefore, reflects the sympathovagal balance [1,2,4,5,6].

The patients suffering from pain could have impaired ANS function. A previous study conducted by our research group demonstrated that the LF/HF ratio was significantly increased in patients after treatment of the lumbosacral pain [2]. Although the present study did not exactly demonstrate this type of outcome, there nonetheless exists a parallel to this previous study. The results clarified that the LF/HF ratio, and not the mean HR, could be modulated through the acupuncture treatment using different acupuncture points. ANS modulation is closely related to the ANS tone (medium HR), and is, therefore, associated with an increase in the sympathetic activity and a decrease in the vagal tone, and consequently with an increase in HR and a decrease in its variability [6]. This implies that a physiological correlation exists between HRV and HR. However, in a simulation study, it was demonstrated that the changes in the ANS modulation should be independent of the changes in the mean HR [7]. This is consistent with the findings of the present study. Acupuncture is able to modulate the ANS through the activation of the sympathetic and parasympathetic nervous systems.

The present study also has certain limitations. Firstly, the sample size was relatively small, which limits the significance of the possible different effects of using different acupuncture methods (points). Since there is only one similar study reported previously [2], it was not possible to calculate the sample size on the basis of differences in the HRV modulated using needle acupuncture treatment. Secondly, registration of a control group was not possible in this preliminary trial because, as stated in the introduction section, the tests were integrated into the routine acupuncture therapeutic interventions in a rehabilitation clinic. Thirdly, it would be interesting for future studies to evaluate how the duration of the acupuncture treatment (at least 6 to 10 sessions) would affect the clinical outcomes. It is possible that more prolonged acupuncture treatment would be more beneficial for pain relief. Finally, although the acupuncture points commonly used to treat LBP are Yaoyu (GV2), Huantiao (GB30), Yanglingquan (GB34), Shenshu (BL23), Dachangshu (BL25), Yaoyangguan (GV3), and Weizhong (BL40) [8,9], a slightly modified acupuncture scheme was used in the present study. Since no control group was used, it appeared at first that it was unclear whether the changes being observed were a result of the acupuncture treatment, the act of lying down for 30 min, or the psychological factors such as hoping to achieve pain relief from the treatment or all of the above. However, in relation to previous works [2,4], the possibility of the measured effects arising only from lying down or from psychological factors could be excluded.

In 2010, Lee et al. [10] summarized the important references in the literature and stated that sham-controlled randomized controlled studies presented variable results and no clear evidence that acupuncture exerted any specific effects on HRV. Therefore, more rigorous research is warranted. Meanwhile, extensive basic research has been conducted regarding this topic, which clearly demonstrates that acupuncture and, for example, moxibustion could exert effects on HR and HRV, respectively [6,11].

The results of the present study, which represent a low vagal tone, could be associated with qi deficiency based on the TCM theory, according to a previous study [12]. Moreover, qi deficiency is one of the significant diagnoses made by the traditional Chinese medical acupuncturists for patients with lower back pain [13]. Therefore, the change in the HRV of patients observed in the present study possibly reflects that acupuncture has a therapeutic effect on the patients with lower back pain through the regulation of the balance of qi.

Future research could include other assessment variables and the investigation of the long-term HRV effects of different acupuncture schemes on patients with lumbosacral pain.

5. Conclusion

The present study revealed that HR did not change significantly, while there were significant changes in HRVtotal and the LF/HF ratio of HRV during a single acupuncture session in the patients with LBP. There was a significant alteration in HRV between the time points of the beginning and the completion of the acupuncture treatment. Current studies related to this topic are limited in number and have been conducted in very small groups, rendering it difficult to draw reliable conclusions. Therefore, future studies using the same standardized acupuncture scheme in all patients and involving a greater number of acupuncture sessions shall assist in elucidating certain open questions in this field of study.

Acknowledgments

The article has been written during a 6-month research stay of Mrs. Yan Yang, MA at Medical University of Graz under supervision of Prof. Gerhard Litscher which was supported by a scholarship from Eurasia-Pacific Uninet. Prof. Litscher, Priv.Doz. Dr.med. Lu Wang and Dr.med. Zemin Sheng are also Visiting Professors at the Heilongjiang University of Chinese Medicine in Harbin, China. All authors would like to thank Prim. Walter Kreuzig, MD, Head of Medical Affairs at the Privatclinic Lassnitzhoehe, for his support for this study.

Author Contributions

All authors (Y.Y., G.L., Z.S., and L.W.) designed the study. Z.S. and Y.Y. performed the acupuncture and the HRV measurements in the clinic. Y.Y. and G.L. analysed the data. G.L. wrote the paper with input from all authors (Y.Y., Z.S., L.W.).

Funding

Eurasia Pacific Uninet, Austria and TCM Research Center Graz, Medical University of Graz, Austria, Europe.

Competing Interests

The authors have declared that no competing interests exist.