Spectral analysis of systemic arterial pressure and heart rate signals of patients with acute respiratory failure induced by severe organophosphate poisoning

Abstract

OBJECTIVE: Spectral analysis of systemic arterial pressure (BP) and heart rate (HR) signals may be an alternative prognostic tool for predicting patient outcome in the intensive care unit (ICU). We evaluated the applicability of the same analysis in the emergency department for predicting mortality in patients with acute respiratory failure induced by severe organophosphate poisoning. DESIGN: Prospective collection of data from 14 emergency service patients. SETTING: Emergency service at a large, university-affiliated medical center. PATIENTS: Consecutive patients who, after attempting suicide by ingesting organophosphates, were admitted to the ICU of the emergency service with acute respiratory failure and remained for > or =2 days INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Demographic and survival data and day 1 Acute Physiology and Chronic Health Evaluation (APACHE) II and Glasgow Coma Scale scores were recorded. Continuous, on-line, real-time spectral analysis of BP and HR signals was carried out during the first 12 hrs after admission. We then computed the total sum of power density during this period of the low-frequency (0.04-0.15 Hz) and very low-frequency (0.004-0.04 Hz) components in the BP and HR spectra, along with the averaged values of mean BP and HR. Eight patients who recovered exhibited vigorous power in the low-frequency and very low-frequency components of their BP and HR signals. There was a significant reduction in the power density of those four spectral components in three patients who eventually died. Three patients discharged in a vegetative state manifested significantly reduced power in the low-frequency component in their BP spectra, with maintained power in the other three spectral components. APACHE II and Glasgow Coma Scale scores of the recovered patients were discernibly different from those of patients who eventually died or who became vegetative. None of the 14 patients showed appreciable differences in mean BP, mean HR, erythrocyte or plasma cholinesterase concentration, or atropine requirement during the first 24 hrs. CONCLUSION: The low-frequency and very low-frequency components of BP and HR signals may be a sensitive alternative index for early prediction of mortality in patients with acute respiratory failure induced by severe organophosphate poisoning.