LONG-TERM HEART-RATE FLUCTUATIONS IN POSTOPERATIVE AND BRAIN-DEAD PATIENTS

Long-term heart rate fluctuations in postoperative and brain-dead pati ents were investigated. Heart rates were monitored continuously, and t he data were stored, edited, and interpolated to allow for data lost d uring calibration and disconnection of the sensors for various treatme nts. Heart rate power spectra were calculated using the fast Fourier t ransform method. The power spectra of the patients who recovered showe d that the heart rate fluctuated and produced a 1/f relationship, term ed 1/f fluctuations, whereas those of patients who died in the intensi ve care unit (ICU) consisted of white-noise like signals. The power sp ectra in brain-dead patients showed a 1/f relationship under steady-st ate conditions, while the power density and variation of the frequency distribution were lower than those in a normal subject. Therefore, 1/ f fluctuations appear to be universal and occur independent of the cen tral nervous system.