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"Non-linear
analysis of heart rate variability in acupuncture
practice"
Abstract of Poster Presentation for 2005 Society for
Acupuncture Research Meeting
Albuquerque, New Mexico
Kristen T. Sparrow, M.D.
The purpose of this study was to explore and evaluate the
applicability of non-linear and/or fractal analysis of
Heart Rate Variability (HRV) in acupuncture practice.
HRV analysis has gained traction as a research and
clinical tool because it is a non-invasive method of
observing sympathovagal tone. HRV decreases with age,
disease, and increased sympathetic input to the autonomic
nervous system. HRV monitoring has become topical because
it is now well established that stress and elevated
cortisol have an incalculable impact on pain, mood,
immunity, and health in general. The autonomic nervous
system is thought to be involved, in part, in patients'
responses to acupuncture. In previous pilot studies, HRV
was analyzed using power spectra analysis during patients'
acupuncture sessions. It appeared that the patients, who
ultimately benefited from acupuncture, tended to have a
decrease in their LFR/HFR ratio during the course of their
treatment session. This signified a relative increase in
their parasympathetic activity and a decrease in their
sympathetic activity. Subsequently, there have been other
studies performed in unrelated clinical settings, which
showed similar findings of an increase in vagal tone
associated with positive outcomes.
Non-linear and fractal analysis are methods applied to HRV
to expose patterns in the autonomic nervous system which
not might be revealed by linear analytical systems.
Overall, it seems clear that the cardiovascular signals
from healthy subjects possess a greater complexity and
lower predictability than pathological ones. This greater
complexity may be a sign of the ability of the system to
respond to changes in the input signals, which allows a
more effective response of the system to new physiological
situations. Acupuncture may represent just such a new
physiological situation. It is also known that increased
parasympathetic input to the vagus nerve increases the
fractal component and increases complexity. Whether HRV
analysis can help improve outcomes in acupuncture practice
by either identifying patients who are likely to benefit,
or by actually increasing patients' vagal tone is the
overarching purpose of this line of investigation.
The first goal of this particular study was to determine
whether there was a reproducible system to analyze HRV
data in a non-linear or fractal way that could be used in
the acupuncture clinic setting, with the unique time
constraints, and patient positioning requirements. The
second goal was to determine whether non-linear or fractal
analysis would simply reinforce the spectral analysis data
of individual patients, or would reveal additional
information.
For this study patients coming into the clinic for
acupuncture were randomly selected for HRV monitoring.
Monitors were placed, needles inserted according to the
tenets of TCM, and the recording was started. 20-minute
recordings were the norm. In addition to the routine
spectral analysis, both fractal and non-linear analysis
systems were applied to the HRV data obtained from
patients during acupuncture treatment. The J and J
Engineering Biofeedback Monitoring HRV data obtained for
spectral analysis, was extracted (intrabeat intervals) and
subjected to fractal analysis using Benoit Trusoft fractal
analysis software, and to non-linear HRV analysis using
shareware from the University of Kuopio in Finland. The
data was analyzed for the whole treatment, and then for
each half. At the time of submission 35 patients had been
studied, often with multiple runs.
The results of this study showed that the fractal analysis
system was not reproducible and did not lead to any
consistent data. The data produced by the non-linear
analysis system, using the HRV shareware, seemed to
confirm the findings of the spectral analysis, and were
reproducible and coherent. More evaluation of the data
generated will be needed to determine whether the second
goal of this study will be met; whether non-linear
analysis will give more precise feedback as to the
patient's autonomic state.
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