Since this patient has developed gangrene of the toe ankle to brachial presure ratio should be less than 0.3. Ratio of ankle to brachial systolic pressure (ankle brachial index) is obtained to determine the presence and magnitude of occlusive disease. The ankle brachial index of 0.9 - 1.0 indicates normalcy or minimal aerial occlusive disease. ABI of 0-5 -0.9 signifies claudication level. ABI less than 0.5 signifies presence of ischemic rest pain or severe occlusive aerial disease. ABI less than 0.3 is compatible with trophic changes over the lower extremity.