The most common aery for invasive blood pressure monitoring:-

The radial aery is commonly cannulated because of its superficial location and substantial collateral flow. The radial aery is chosen for cannulation primarily because of the superficial nature of the vessel and ease of maintenance of the site. The radial aery lies between the brachioradialis tendons and flexor carpi radialis tendons, approximately 1-2 cm from the wrist, medial to the bony head of the distal radius. Before cannulation of radial aery The Modified Allen's Test has been the most frequently used method to clinically assess adequacy of ulnar aery collateral flow despite the lack of evidence that it can predict ischemic complications in the setting of radial aery occlusion. Doppler ultrasound can be used to evaluate collateral hand perfusion in an effo to stratify risk of potential ischemic injury from cannulation.