#ortho > **ABI** = injured SBP / uninjurged brachial SBP > API = arterial pressure index > API > 0.9 : unlikely to have vascular injury and can be observed/discharged > API <0.9 : possible vascular injury *upper limb* - ipsilateral brachial artery detected with doppler device until brachial artery heard - cuff pumped up 20 mmHg past point where doppler sound disappears. cuff released until doppler picks up sound again (systolic pressure) - the pressure at which this sound occurs is recorded and the procedure is repeated for opposite uninjured upper extremity *lower limb* - pt supine with cuff on injured lower extremity - ipsilateral DP or PT detected with doppler until arteyr heard - cuff pumped 20 mmHg past where doppler sound disappears - cuff slowly released until doppler device picks up arterial sound again (systolic pressure) - pressure at which this sound occurs is recorded and procedure repeated on opposite uninjured extremity or brachial artery