SPECTRAL-ANALYSIS OF SYSTEMIC ARTERIAL-PRESSURE AND HEART-RATE SIGNALS AS A PROGNOSTIC TOOL FOR THE PREDICTION OF PATIENT OUTCOME IN THE INTENSIVE-CARE UNIT

Objectives: To evaluate the applicability of changes in spectra of sys temic arterial pressure and heart rate signals in the prediction of pa tient outcome in an adult intensive care unit (ICU). To compare the pr ognostic predictability of this method with the Acute Physiology and C hronic Health Evaluation II (APACHE II) scoring system. Design: Prospe ctive data collection from 52 ICU patients. Setting: Adult ICU at a la rge, university-affiliated, medical center. Patients: Consecutive pati ents who were admitted to the adult ICU due to noncardiac emergencies, and who remained for at least 2 days. Interventions: None. Measuremen ts and Main Results: The demographic data, diagnosis, and survival dat a were recorded for each patient enrolled in this study. For the perio d between admission and 24 hrs before discharge, the APACHE Il score w as tabulated daily. Likewise, continuous, on-line, and rear time spect ral analysis of systemic arterial pressure and heart rate signals was carried out every day for at least 30 mins at 2200 to 2400 hrs. The av eraged power density values during this 30-min recording period of the high-frequency (0.15 to 0.4 Hz), low-frequency (0.08 to 0.15 Hz), and very low-frequency (0.016 to 0.08 Hz) components of systemic arterial pressure and heart rate signals were subsequently computed. Systemic vascular resistance index and cardiac index were also determined daily . We observed a trend of changes in the spectral components of systemi c arterial pressure and heart rate signals in patients who eventually survived (n = 25) or died (n = 27). Progressive increases in the power density; values of both the low-frequency and very low-frequency comp onents of systemic arterial pressure and heart rate signals appeared t o be related to recovery. Conversely, progressive decreases in the pow er density values of these spectral components was indicative of deter ioration and fatality. The pre dieted outcome based on the trend of ch anges in the low-frequency and very law-frequency components of system ic arterial pressure and heart rate signals correlated positively with daily APACHE II scores. No direct correlation, however, was indicated by mean systemic arterial pressure, heart rate, systemic vascular res istance index, and cardiac index. We also confirmed that the different ial trend of spectral changes in patients who survived or died was not due to circadian rhythm, nor alterations in the responsiveness of the blood Vessels to intravenous infusion of dopamine. Conclusion: Power spectral analysis of systemic arterial pressure and heart rate signals offers a reasonable means of monitoring acute, critically iii patient s, and may be used as an alternative prognostic tool far the predictio n of patient outcome in the ICU.