[Energy index of heart rate spectral analysis for the assessment of autonomic nerve activities].
Heart rate spectral analysis was performed in 17 male healthy volunteers by changing their positions (supine or standing) and respiratory rates (8, 10, 12, 15 and 20 bpm). Furthermore, analysis was made by a multiple regression method on parameters such as R-R interval, tidal volume, respiratory time and positions of the subjects which may contribute to the peak power values of high frequency components (HFC, synchronous with respiratory patterns and of low frequency components (LFC, about 0.1Hz). HFC power was found to be significantly dependent on R-R interval and respiratory time, but not on tidal volume or position. Following equation was obtained. HFCP = 11.3 X RTX (RR-0.246) HFCP: HFC power value (msec) RT: respiratory time (sec) RR: R-R interval (sec) Therefore, HFCP or area under the curve (AUC) of HFC is not appropriate for the assessment of autonomic nerve activities, especially when respiratory rate or heart rate is changing. The intensity of physical wave is in proportion to (amplitude X frequency). Consequently, in a case where frequency is changeable, (amplitude X frequency) is a good index of the oscillatory energy. Therefore, sigma (power X frequency) is proposed as a suitable index for a certain component of power-spectrum. Parasympathetic activity should be assessed by the following index induced from the previously mentioned equation. RR adjusted HFEI (high frequency energy index) = sigma (power X frequency)/(RR-0.246) (0.15Hz less than frequency less than 0.4Hz). Similarly, low frequency components which reflect the sympathetic activity should be assessed by the following equation. LFEI (low frequency energy index) = sigma (power X frequency) (0.05Hz less than frequency less than 0.15Hz). The assessment of autonomic nerve activities becomes more appropriate by using these indices especially when heart rate and respiratory rate are changing.
Naito
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Department of Anesthesiology, Tottori University School of Medicine.
D000328:Adult; D001341:Autonomic Nervous System / Q000502:physiology*; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D008297:Male