RSA component extraction from heart rate signal by independent component analysis

Respiratory sinus arrhythmia (RSA) is a phenomenon where heart rate changes synchronously with respiration. It can be measured by high frequency power (HF power, 0.15-0,4 Hz) of heart rate interval (RRi) series, which is an important and widely used parameter in cardiovascular research. Due to the altering respiration rates, it is important to have methods to separate the RSA from the RRi. We applied Independent Component Analysis (ICA) to extract the RSA from the RRi series. The performance of ICA was evaluated with a simulation study where real 5 min RRi (n=20) and respiration data (n=2) of spontaneously breathing males were superimposed. According to residual analysis in time and frequency domain, the extracted RSA follows the shape of simulated RSA (3.3 - 5.4% RMS error of total variability), and ICA is able to remove RSA without changing the power content of RRi (p <0.05). Thus, ICA is a capable method to extract RSA from RRi series.