Summer Research Description: Heart rate variability (HRV), the variation in beat-to-beat, interval of the heart has been proposed as an early predictor of mortality in ICU patients (Norris 2006). Lower variability in heart rate in these patients has generally been associated with higher rates of mortality. Through Spectral analysis, the HRV signal has shown associations between the high-frequency component of the signal and parasympathetic activity and low-frequency component and both sympathetic and parasympathetic activity. Previously, normal heart rate variability has not been described in the trauma ICU and remains a limitation in studies of HRV in the trauma ICU. In addition, the effect of mechanical ventilation, drug administration, and physical manipulation are all poorly described. Within this study many patients within the trauma ICU setting will be observed by taking an accurate record of all patient-care activities occurring during a 15-minute observation widow. Through this, the main aims of the study are the establish a baseline measure of undisturbed patient heart rate variability for patients in the Trauma ICU, as well as the examine the effect of patient care activities including drug administration, physical manipulation, and mechanical ventilation on heart rate variability in ICU patients.