 Critically ill patients in the emergency department commonly require arterial line placement for continuous direct blood pressure monitoring, frequent arterial blood gas sampling, and frequent blood sampling. Trans-radial catheterization has been shown to reduce access site complications and increase patient comfort compared to trans-femoral access. Radial artery access on the first attempt is optimal; attempts at reentry delay care and increase the risk of vascular spasm, hematoma, infection, neurovascular injury, and pain. The traditional pulse palpation method of radial artery cannulation can be challenging, especially in patients with weak pulses i.e. morbidly obese or hypotensive individuals. 