L.I. Kalakutskiy, A.A.Fedotov, A.V. Shulyakov

The research of uncertainties at determining the spectral indices of pulse rate: total spectral power and ratio between spectral power in low frequency range and high frequency range was carried out. The uncertainties occur due to errors of conversion of consecutive recorded pulse beat-to-beat series into evenly sampled time series, errors of measuring durations of pulse beat-to-beat intervals, choosing parameters of biosignals registration. Using cubic spline functions for the transformation of pulse beat-to-beat series reduces uncertainties. Dependencies between uncertainties of diagnostic indices, due to errors of measuring durations of pulse beat-to-beat intervals, and average duration of pulse beat-to-beat intervals and modulation index were revealed. These dependencies allow us to set requirements for parameters of measuring convertor with due account taken of acceptable values of uncertainties of diagnostic indices. Dependencies between uncertainties of spectral indices and duration of biosignals registration were obtained. These dependencies allow us to set requirements for choosing parameters of biosignals registration with due regard for acceptable values of uncertainties of diagnostic indices. Thus when the acceptable uncertainty at determining of diagnostic indices