Studies the usefulness of cardiovascular variability parameters for monitoring intensive-care unit (ICU) patients, and discusses assessing ICU patient status using spectral analysis parameters. Both short-term and long-term spectral parameters were employed for the assessment of patient status in the ICU. Short-term parameters were sensitive to the airway suction (AWS) and may also be employed to monitor the response to different therapeutic interventions. Long-term parameters showed significantly increased /spl alpha/-slope values in nonsurviving patients. This result suggests that the /spl alpha/-slope value on 24-hour RR spectra obtained from the ECG signal may be a relevant prognostic index.