ABI & Physiologic Segmental Pressures

1. 1

   Patient supine, 10 min rest. Place appropriate cuffs: bilateral brachial, high thigh, above-knee, below-knee, ankle.

2. 2

   Bilateral brachial pressures: use handheld Doppler over brachial artery. Record the higher value as reference.

3. 3

   Segmental pressures: inflate each cuff to suprasystolic, then slowly deflate. Use Doppler over DP or PT to detect return of signal.

4. 4

   Ankle pressures: DP and PT on each side. Use the higher ankle value for ABI calculation.

5. 5

   ABI = highest ankle pressure ÷ highest brachial pressure. Normal ≥0.9; PAD ≤0.9; Critical ischemia <0.4.

6. 6

   If ABI >1.4 (incompressible): measure toe pressures using photoplethysmography (PPG). TBI <0.6 = PAD.

7. 7

   Document waveforms at each level: triphasic = normal, biphasic = mild disease, monophasic = significant disease.

• Bilateral brachial pressures (baseline)
• High thigh cuff pressure
• Above-knee (AK) cuff pressure
• Below-knee (BK) cuff pressure
• Ankle pressures (DP + PT bilateral)
• Toe pressures (TBI) if indicated

• ABI calculation (ankle ÷ brachial)
• Segmental pressure gradients
• Waveform character at each level
• TBI for calcified vessels

• Calcified vessels (diabetics, ESRD): ABI >1.4 is non-compressible — use TBI instead
• ABI 0.91–1.0 = borderline; 0.71–0.90 = mild PAD; 0.41–0.70 = moderate; ≤0.40 = severe
• Exercise ABI adds sensitivity when resting ABI is normal

Always take the higher of DP and PT for the ankle pressure. ABI ≤0.9 is diagnostic of PAD. ABI >1.4 = incompressible — order TBI.