Heart Rate Variability
Pulse Wave ProfilerThe PWP Scanning modality measures Heart Rate Variability (HRV). HRV is the beat-to-beat variation in heart rate. This natural rise and fall of heart rate is caused by several physiologic phenomena, including breathing and autonomic nervous system activity.
Healthcare professionals utilize HRV for a wide variety of clinical applications. Chiropractors use HRV to get a window into how the autonomic nervous system (ANS) modulates heart rate in the baseline or resting state.
The PWP measures the variations in heart rate of a patient in a resting state. Under resting conditions, the ECG of healthy individuals exhibits periodic variation in the interbeat intervals.
Studies have shown that reduced HRV is a strong and independent predictor of mortality following an acute myocardial infarction (Bigger et al., 1992; Kleiger, Miller, Bigger, & Moss, 1987; Malik, Farrell, Cripps, & Camm, 1989).
Studies have also suggested a link between reduced HRV and conditions such as hypertension (Guzzetti et al., 1988; Langewitz, Ruddel, & Schachinger, 1994; Novak, Novak, de Champlain, & Nadeau, 1994), diabetes (Bernardi et al., 1992), obesity (Kupari, Virolainen, Koskinen, & Tikkanen, 1993) negative emotions (Kawachi, Sparrow, Vokonas, & Weiss, 1995; Sloan et al., 1994; Yeragani et al., 1990; Yeragani et al., 1993).
There is also a significant inverse correlation between HRV and age (Kohara et al., 1996; Yo et al., 1994). Some excellent HRV research information can be found at... www.macses.ucsf.edu/Research/Allostatic/notebook/heart.rate.html.
Chiropractic Care improves HRVHRV was used as the autonomic measurement in a recent independent research study headed by Dr John Zhang, M.D., Ph.D., in which 96 doctors of differing techniques adjusted 625 patients.
The study, published in the Journal of Chiropractic Education [Vol19, No 1, 2005] concluded that, based on the HRV results, "chiropractic care is associated with a shift to a healthy autonomic nervous system balance." For the first time, chiropractors are able to measure how a patient responds to their environment, by viewing sympathetic/parasympathetic balance. Chiropractors can demonstrate through their actions that subluxations affect more than the spine.
What information is gathered during the PWP scan?The Instantaneous Heart Rate (IHR) - This view shows the actual heart rate over the entire data collection period. As you can see from this graph, the average heart rate over this period is around 67, but the actual values range from less than 55 to over 85 - this variability is exactly what we are measuring with this protocol.
The Blue line at the bottom indicates the SCR (skin conductance response) values. In this scan, the SCR remains under the black line (threshold), indicating that there was no unexpected "spike" in nervous system arousal.