Acupuncture and Heart Rate Variability Research
Acupuncture and Sound Assisted
Autonomic Modulation Technique
Brief Scientific Background and Clinical Applications
In the author’s facility, a variety of conditions that are considered to be associated with autonomic dysfunctions, (e.g. insomnia, IBS, migraine, irregular menstruation, etc.) have been treated using acupuncture. This paper briefly describes the background and rationale of incorporating heart rate variability biofeedback into acupuncture procedure. It is part of an exploration to enhance the autonomic effect of acupuncture and further improve clinical outcomes.
Heart Rate Variability
Heart rate variability (HRV) refers to the beat-to-beat alterations in heart rate. Under resting conditions, the ECG of healthy individuals exhibits periodic variation in R-R intervals (Fig 1). HRV (time and frequency domain) analysis is well established and an accepted diagnostic procedure in cardiology1:
Studies have shown that reduced HRV is a strong and independent predictor of mortality following an acute myocardial infarction.2-4 Studies have also suggested a link between reduced HRV and conditions such as hypertension,5-7 diabetes,8, 9 obesity10 and emotional disorders.11-14 There is a significant inverse correlation between HRV and age (HRV decreases as a person gets older).15-17 HRV is affected by stress, mental and physical activities, and other factors. Figure 2 shows an example of HR fluctuations under different conditions.
Heart Rate Variability Biofeedback (HRV-BFB): Utilization in Acupuncture Practice
There are a variety of therapeutic interventions (pharmacological, exercise, behavioral) that positively influence HRV.18 A heart rate variability biofeedback (HRV-BFB) method has been increasingly utilized in the field of applied psychophysiology as one of the tools to help increase and maintain optimal HRV.
The method is designed to train patients to breathe at a specific rate in order to create slow heart rate oscillation and augment HRV.19 HRV-BFB and slow breathing have been shown to increase baroreceptor function.20, 21 Clinically, it has been shown to be efficacious in the treatment of various diseases such as asthma,22 depression,23 irritable bowel syndrome,24 fibromyalgia,25 and coronary artery disease.26
It could be useful to incorporate HRV-BFB in acupuncture sessions; however there are a few issues to consider when combining acupuncture with conventional BFB methods:
These methods are typically done by monitoring physiological signals (heart rate, respiration, R-R spectrum, etc.) on a PC screen. In order to let patients obtain this visual feedback, treatment position is generally limited to a seated position. Another concern is that some patients find following graphic tracing on a monitor to be stressful so they have difficulty relaxing in front of a computer. This may be due to sympathetic arousal and suppression of EEG alpha waves (EEG alpha, an indication of relaxed awareness is known to spontaneously diminish when a person’s eyes are in focus).
In order to more naturally guide patient’s breathing towards the targeted frequency as well as for practical incorporation of HRV-BFB during an acupuncture session, a specifically designed audio CD was created (HRV Trainer CD, non-commercial version, 2002).27 An audio CD includes voice commands, ocean sounds and classical music. The first 10 minutes of the CD contains voice commands of “Inhale”, “Exhale” and ocean wave sounds. Classical music starts after 10 minutes while the ocean sounds gradually diminish. After 20 minutes, the CD contains only classical music. Three versions of CDs with different rhythms (0.83 Hz, 0.1 Hz, and 0.12 Hz) have been initially created to accommodate the slight variance in each individual’s resonant frequency.
A preliminary study was conducted using the 0.1 Hz version (voice and ocean sound cues are repeated every 10 seconds). It was intended to test subjects’ compliance and response with the CD guided breathing training as a part of an exploration to enhance the autonomic effect of acupuncture.
Methods: Four healthy subjects were seated with their backs supported. The ECG signals were obtained through electrodes using a standard lead II configuration. In addition, strain gauge was attached to the subjects’ chests to monitor their respiration. After a 5 minute resting period, subjects were asked to breathe at a rate of 12 breaths per minute paced by visual cues on a computer screen for 5 minutes. Then the screen was masked and the CD was played. After 35 minutes, the CD was turned off and the computer screen was again shown to the subjects for the paced breathing. ECG signals were recorded continuously during the entire procedure using Biopac MP 150 with a sampling rate of 1000 Hz. Power spectral analysis was conducted by means of Fast Fourier Transform based on the stored ECG R-R interval data (Biosignals, Finland). The power spectra were divided into two frequency bands of interest: low frequency (LF: 0.04 to 0.15 Hz), and high frequency (HF: 0.15 to 0.4 Hz).
Results and Discussion:
Observation of respiration rate indicated that subjects had good compliance following the voice and wave cues. In regards to frequency domain HRV analysis, LF power sharply increased as subjects started to hear the CD through headphones (Fig. 3). LF increase was greatest and most steady during the CD track with ocean wave sounds; however the increase remained also during the tracks with only classical music. This suggests that subjects were generally able to “self train” to breathe at the low 0.1 Hz frequency rhythm. In contrast to the noticeable LF changes, high frequency power changed only slightly.
Figure 5 is example of HRV spectra, based on data during the 5 min. rest. There is activity in all frequency bands: VLF, LF, and HF. Figure 6 illustrates the spectrum of the same subject, based on data from 20-25 minutes after the CD started. On the spectrum, VLF and HF rhythm virtually disappeared, and a greatly augmented LF with a single peak spectrum can be seen. The respiratory linked HRV, often referred to as respiratory sinus arrhythmia (RSA), is usually seen in the HF range. However, in this instance it is shifted to the lower frequency range, overlapping with LF (*note).
Overall, as indicated by total power spectra during each period, the heart rate was oscillating with much greater amplitude during the CD session (compared to the rest period and the controlled respiration period at 12 breaths per minute). This suggests that the CD guided auditory breathing methods induced quite a different autonomic state compared to the period of quiet rest or relaxation. It should be noted that at the bottom spectrum, HR is oscillating with much greater amplitude (note the scale difference on the Y axis between the Fig. 5 and 6 spectra). The LF band of HRV is closely associated with blood pressure regulation. The spectral analysis indicates that the subject’s baroreceptor activity and autonomic reflexes were highly enhanced during the CD guided breathing. Administering acupuncture when a patient’s physiological state is in such a balance, holds great potential for highly positive clinical outcomes.
*Note: Heart rate fluctuation specifically associated with respiration (typically a high frequency rhythm of heart oscillation) is a respiratory linked natural cardiac variation and is referred to as respiratory sinus arrhythmia (RSA). It is generated by autonomic brainstem reflexes and is primarily mediated by vagal (parasympathetic) innervations of the heart. Thus, measurement of RSA has been suggested as a non-invasive index of vagal cardiac efferent activity.28, 29
RSA is usually observed in the high frequency component of HRV spectrum (between 0.15-0.4
Hz.). Therefore, the power of the HF component is considered to be a marker of vagal activity in frequency domain HRV analysis (LF component is considered to be a marker of both sympathetic and vagal modulation).30 It should be noted, however, that HF is associated with vagal modulation of the heart only when a subject’s respiration rate is within the HF range (between 9 to 24 cycles per minute).
HRV analysis has been increasingly utilized as a useful method to access efficacy of various therapeutic interventions such as acupuncture. When HRV frequency analysis is used as an evaluation tool, it is extremely important to pay close attention to the subject’s respiration (particularly rate and depth) to avoid misinterpretation of data. The data presented here, clearly demonstrate the profound influence of respiration rate on power frequencies of HRV. Such important respiration factors, however, have not been carefully controlled in many previous clinical trials using HRV analysis.31
In our facility, since 2002, we have been utilizing combined acupuncture and HRV-BFB based slow breathing application, in an attempt to further stimulate the autonomic nervous system. The Acupuncture and Sound Assisted Autonomic Modulation Technique utilizes a specific acupuncture method and the power of breath, both especially intended to modify and optimize the autonomic nervous system and enhance the patient’s innate healing system. Utilizing the knowledge and technique derived from previous research, acupuncture is applied while carefully considering the stimulation points, depth, respiratory phases and other important variables in order to effectively guide the autonomic state in the desired direction.32-34 Simultaneously, patients actively participate in the acupuncture session by performing rhythmic breathing, with the aid of the CD, while acupuncture needles are inserted. HRV is recorded during the session to monitor compliance and the physiological response.
The autonomic nervous system coordinates virtually every function of the visceral organs and glands. The type of acupuncture technique and breathing exercise used in this procedure is believed to enhance the autonomic reflex, which plays a critical role in maintaining our proper homeostatic balance. Thus, the procedure can be useful on a wide range of conditions and disorders. In our clinical practice, we have particularly noted a profound effect using the procedure for conditions that resulted from or are triggered by the autonomic deregulation or disturbance of normal biological rhythm (e.g. some types of chronic pain, headache, stress, anxiety, IBS and other digestive problems, insomnia, chronic fatigue, depression, irregular menstrual cycles, hormonal imbalances, etc.)
Conclusion: With the aid of the CD, subjects were able to create increased HRV and generally maintain the peak oscillation around 0.1Hz, without visual feedback. The combined HRV-BFB and acupuncture approach potentially provides a powerful stimulus to the autonomic nervous system.
Part of this paper was presented at the ICMART XIII World Congress: Medical Acupuncture Science and Techniques, Oct 10th – 12th, 2008, Budapest, Hungary and World Health Organization (WHO) Congress on Traditional Medicine, Nov 7th – 8th, 2008, Beijing, China.
Acupuncture, Heart Rate Variability and Breathing Effects
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