AN INSTRUMENT FOR REAL-TIME SPECTRAL ESTIMATION OF HEART-RATE-VARIABILITY SIGNALS

A Digital Signal Processor (DSP)-based instrument is proposed for esti mating and displaying the Heart Rate Variability (HRV) spectrum in rea l-time. It consists of an intelligent module which is properly interfa ced to an IBM PC and whose operations are independent from the compute r's other tasks. In this way, the simultaneous recording of the ECG se quence, needed for the more complete off-line analysis, can be perform ed by the same host. The employed hybrid spectral estimator (in which a classical FFT analysis follows the autoregressive extrapolation of d ata) appears to be the most apt for the present fixed point arithmetic s implementation. The reliability of the instrument and its accuracy a re checked both with suitable test signals and by comparison with the results obtained through off-line analysis of the same ECG tracks. The instrument is presently used for cardiovascular investigations, in pa rticular for quickly picking patients with cardiac autonomic neuropath y (CAN) out of a population of diabetic subjects.