Ankle–brachial pressure index grossly overestimate the ABI (by approximately 0.3). A Doppler ultrasound blood flow detector, commonly called Doppler wand or Doppler probe, and a sphygmomanometer (blood pressure cuff) are usually needed. The blood pressure cuff is inflated proximal to the artery in question. Measured by the Doppler wand, the inflation continues until the pulse in the artery ceases. The blood pressure cuff is then slowly deflated. When the artery's pulse is re-detected through the Doppler probe the pressure in the cuff at that moment indicates the systolic pressure of that artery. The higher systolic reading of the left and right arm brachial
Brachial plexus block collapse. In severe cases, cardiac dysrhythmia, cardiac arrest and death may occur. Other rare but serious complications from brachial plexus block include pneumothorax and persistent paresis of the phrenic nerve. Complications associated with interscalene and supraclavicular blocks include inadvertent subarachnoid or epidural injection of local anesthetic, which can result in respiratory failure. Because of the close proximity of the lung to the brachial plexus at the level of the clavicle, the complication most often associated with this block is pneumothorax — with a risk as high as 6.1%. Further complications of supraclavicular block include subclavian artery puncture, and spread of