Laser Doppler flowmeter (LDF) has been used as a noninvasive device to quantify the components of the blood flow velocity oscillations, including the Traube-Hering (TH) wave and heart rate. The Traube-Hering component (0.1 Hz) of the oscillations represents baroreceptor activity; changes in this component reflect changes in autonomic tone. Currently, the “gold standard” for noninvasive measurement of autonomic tone is heart rate variability (HRV), as measured by EKG. We evaluated the accuracy of the LDF as a measuring device for changes in autonomic tone. LDF TH and cardiac component changes should be synchronous with EKG HRV changes. LDF blood flow velocity and EKG R to R intervals (RRI) were obtained from 13 healthy individuals. Both the Head-up tilt test and cold pressor test were employed as standard provocative autonomic procedures for increasing sympathetic activity. HRV was analyzed from both the RRI obtained from EKG and the cardiac component of the LDF wave. We compared the spectral analyses of HRV from both sources. Using paired-samples t-test, the overall correlation was .997(p < .001); this reflects LDF's ability to detect HRV accurately. The TH component, compared with HRV, demonstrated overall correlation of .623 (p = .003); this reflects simultaneous changes that take place between the TH component and HRV, with differences in magnitude. The cardiac component of the blood flow velocity oscillations as measured by the LDF can be used to accurately assess and quantify changes in autonomic tone. The TH component can be used to note changes in autonomic tone but does not appear to quantify it to the same degree. A larger sample size may be necessary to make a more definitive statement.
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