It has become standard practice in inpatient and intensive care settings to monitor systolic, diastolic and mean arterial blood pressure by oscillometric technique. Several studies have confirmed the accuracy and precision of the oscillometric technique in ambulatory patients at both the level of the brachial and radial arteries. Multiple clinical research studies have demonstrated that when blood pressures (systolic, diastolic and mean arterial pressures) determined by non-invasive blood pressure monitors (NIBP) from various manufacturers are compared to direct invasive arterial pressure monitors, the two values are on average within 5 mm Hg of each other. There is limited data in critically ill patients. To date, there are no studies evaluating the accuracy or precision of these devices in intensive care patients for alternative sites (calf, thigh). In addition, there are no large clinical studies evaluating oscillometric NIBP monitoring in a complex medical intensive care population with varying hemodynamics. The goal of this study is to validate the oscillometric technique in measurement of blood pressure in the calf and thigh regions when compared to a gold standard. We may also be able to evaluate more specifically which situations for our patient population the blood pressure will be accurately portrayed as compared with the arterial pressure tracing. It has possible clinical value in either validating non-invasive blood pressure monitoring and eliminating/decreasing the need for invasive arterial blood pressure monitoring. Our hypothesis is that NIBP in the medical intensive care patients is highly variable and not a reliable means of arterial blood pressure monitoring.