Spectrum analysis of heart rate variability

The respiratory influence on heart-rate variability is investigated. The experiment took ECG and respiratory signals from ten normal healthy subjects. A matrix of tests was conducted in different postures (sitting and standing) and with different breathing patterns (paced and natural). Spectrum analysis was used on the interbeat interval signal (IBI) to obtain the heart rate spectrum. In the paced breathing condition, the relation between the magnitude of respiration in the IBI spectrum and the breathing frequency was found to be exponential. In natural breathing (sitting posture) the relation was weaker than in paced breathing. It was found that there is no significant difference in the relation between sitting data and standing data during either paced or natural breathing