Analysis of heart rate and blood pressure variability during nasal continuous positive airway pressure therapy in patients with obstructive sleep apnea

We investigated the effect of a nasal continuous positive airway pressure (nCPAP) therapy on low frequency (LF) and high frequency (HF) parameters of the heart rate variability (HRV) and the systolic blood pressure variability (SBPV). All recordings were done one day before and two days after initiation of nCPAP during daytime and applied nasal ventilation. Fourier analysis was calculated with a developed software. The power spectral density (PSD) of beat to beat time series was given according to the method of Welch (1967). LF and HF parameters of HRV and SBPV were calculated by integration of spectral components. Within two nights of nCPAP therapy the HRV parameters changed significantly, but no changes were found on the SBPV parameters. The analysis of HRV and SBPV in the frequency domain appears to be a sensitive marker of the therapeutic effects of nCPAP on the autonomic tone.