Effects of spinal manipulative therapy on autonomic activity and the cardiovascular system: A case study using the electrocardiogram and arterial tonometry

Objective: To determine if there is alteration in the autonomic nervous and cardiovascular systems after. chiropractic manipulative therapy (CMT). A n ovel approach was used to quantitatively plc,be for changes in the activity of the autonomic nervous system, in blood pressure, and in pressure pulse transmission time. This approach uses the electrocardiogram and arterial to nometry equipment. Design: This case study involves 1 subject treated over a 6-week period (2 visits/week). Respiration, electrocardiogram,:and loft and light radial art ery blood pressures were measured during the baseline (2 visits) and treatm ent (10 visits) phases. Measurements were obtained before (n = 3) and after (n = 3) a break period (baseline) or before: and after CMT. High-velocity, low-amplitude CMT that produced joint cavitation was used. Setting: The study was performed at the Parker College Research Institute i n a temperature-controlled laboratory. Main Outcome Measures: Fourier analysis was performed on the electrocardiog ram-determined rest-redistribution intervals. The low frequency power betwe en 0.04 to 0.15 Hz and the high frequency power between 0.15 to 0.40 Hz rep resent the activity of the sympathetic anti parasympathetic nervous systems , respectively. The main outcome measure was the sympathovagal index, which is determined from the ratio of low frequency to high frequency. The arter ial pressure and the time for pressure pulses to travel from the heart to t he radial artery recording sites (pressure pulse transmission time) were st udied. Differences (average of 3 measurements after treatment minus measure ments before treatment) for each variable were calculated. Results: After the ist CMT treatment, the difference between treatment and baseline decreased for both the low frequency/high frequency (-2.804 +/- 1. 273) and low frequency power (-0.135 +/- 0.056). These findings indicated t hat the parasympathetic nervous system predominated the sympathetic nervous system. After the 3rd, 3th, 6th, and 9th treatment, the difference between treatment and baseline increased for low frequency/high frequency (0.908 /- 0338, 2.313 +/- 0.300, 2.776 +/- 1.102, and 0.988 +/- 0.269, respectivel y) and indicated that the sympathetic nervous system predominated the paras ympathetic nervous system In addition, the difference between treatment and baseline for the pressure pulse transmission time decreased bilaterally af ter die 4th treatment (left, -13.52 +/- 3.70 ms; right, -9.75 +/- 3.76 ms) and 6th treatment (left, -9.53 +/- 3.60 ms; right, -9.24 +/- 3.50 ms), whic h indicated that arterial compliance had decreased. Furthermore, after the 6th treatment, the difference between treatment and baseline fur the rest-r edistribution interval time decreased (-0.084 +/- 0.014 s). The difference between treatment and baseline for the systolic, diastolic, and mean arteri al pressure for the above-mentioned treatments was not considered significa nt. Conclusion: This case study is the first to attempt to use electrocardiogra m and arterial tonometry data to study the effects of CMT on the autonomic nervous and cardiovascular systems over an extended period of time. These d evices allowed a more in-depth study of the cardiovascular and autonomic ch anges associated with CMT. Although changes in the autonomic nervous and ca rdiovascular systems can be detected, further development of a reliable and reproducible experimental protocol is required before validating the effec ts of CMT on these systems.