Effect of respiration and vascular tone on heart rate variability in rats

Abstract

Basing on findings of a combined study (electrocardiography, pneumotachography, direct sphygmography) the paper discusses the effect of respiration and vascular tone on heart rate variability (HRV) in rats and presents a physiological interpretation of the selected spectral ranges. Studying the HRV in conscious rats showed the lower HF-wave range limit to be not higher than 0.8 Hz, and the upper one not less than 2.5 Hz; under stress this index increased up to 3 Hz. The experiments showed that conscious rats were characterized with the ‘package-like’ respiration (from 2 to 15-20 s). The respiratory rate in each ‘package’ was different, therefore two or more peaks might be recorded at high-frequency spectral range. This fact confirmed the existence of several oscillators-pacemakers of respiratory center. In the anaesthetised rats the vasomotor waves were established to affect the variability of respiratory and heart rates within the range of 0.25-0.5 Hz with 0.4 Hz peak. Therefore the lower limit of the average MF waves should not exceed 0.25 Hz.