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Our aims were to use a chirp-type breathing maneuver to obtain a continuous relation between the high frequency component of HRV (HFRR) and respiratory frequency (RF), and to assess if it indicates the vagal withdrawal induced by a postural change. ECG and lung volume were registered from 30 subjects who performed, in sitting and standing, a 70-s continuous linear RF increase from 0.05 to 0.8 Hz at constant tidal volume. From the smoothed pseudo-Wigner-Ville distribution of the RR intervals and tidal volume series, HFRR and RF were computed to obtain the relation. After log-transformation, correlations were -0.88Â±0.03 in sitting and -0.89Â±0.04 in standing. With the postural change the intercept decreased (p<0.001) and the slope increased (p<0.009), indicating a vagal withdrawal. The continuous HFRR-RF relation we obtained can assess the vagal effect of the postural change independently from the RF influence, improving the interpretability of HFRR as vagal index.
Computers in Cardiology, 2009
Date of Conference: 13-16 Sept. 2009