 Continuous pulse oximetry monitoring is the standard of care in critically ill patients in emergency departments, operating rooms and intensive care units. In patients with poor peripheral perfusion low blood flow due to peripheral vascular disease, low body temperature, or shock and the use of medications to raise the blood pressure, clinicians have difficulty obtaining an accurate measurement. Several studies have demonstrated the utility of forehead sensor measurements under these clinical conditions. Forehead sensor measurement is considered to be a more central measurement than with digit or ear sensors. However the sensor requires a head band for accurate measurement. On a regular basis, the forehead sensor has led to pressure ulcer development at Barnes-Jewish Hospital despite following vendor recommendations for alternating placement every 8 hours from one side of the forehead to the other. An alternate sensor placed on the nose has recently demonstrated rapid detection of induced drops in oxygen saturation. It has also demonstrated correlation with arterial oxygen saturation measured in a clinical laboratory. The oxygen saturation measurement from the nose is also considered a central measurement. However, studies of the nose sensor were conducted in healthy subjects or during anesthesia care over several hours. Therefore, research is needed to examine the accuracy of the nose sensor in the ICU patient population. In addition, due to concerns for sensor related pressure ulcers in patients with decreased perfusion, the sensor needs to be evaluated for extended periods of time. 