How to Perform a PPG Toe Pressure and Toe Brachial Index (TBI)
The PPG (photoplethysmography) Toe Pressure and related Toe Brachial Index (TBI) are performed to assess the vascular condition of the foot by obtaining systolic pressures at the toe. PPG toe pressure studies are considered reimbursable when performed using a bidirectional Doppler with hard-copy output. PPG probes are available for the Bidop® 3, Smartdop® 45, Smartdop® 30EX, and Smartdop® 50EXF Dopplers.
Take a blood pressure reading at the arm
Place a blood pressure cuff around the patient's arm. Place ultrasound gel on the tip of the probe and apply the probe at a 45 to 60 degree angle over the brachial or radial artery.
Wait for Doppler sounds to become stable. If your Doppler has an LCD display, watch the waveform on the display until it becomes rhythmic and stable.
Inflate the cuff to 20 mmHg over pressure cessation. Then, slowly deflate the cuff until the first Doppler sound is heard.
Record the systolic pressure when the first sound is heard and repeat the test on the other arm. Use the highest arm pressure to calculate the ABI to rule out subclavean steal syndrome.
Take a systolic pressure at the toe
Prior to taking the systolic pressure(s) at the toe, take a printout of the PPG waveform for documentation.
Make sure the patient's foot is warm and placed at heart level. A warm foot is necessary to minimize vasoconstriction.
Place a digit cuff comfortably snug around the base of the patient's toe and affix the PPG probe to the pad of the big toe using double-sided clear tape.
Turn the Doppler on and wait for steady cyclic waveform motion to appear on the LCD display. Then, inflate the cuff to 20 mmHg above the anticipated systolic pressure. Waveform motion will cease. Deflate the cuff slowly until cyclic waveform motion returns.
Record the systolic pressure and repeat the test on the other foot
Interpreting the Results
To calculate the TBI, divide the toe pressure by the highest arm pressure
Interpretation ¹
0.64 +/- .20 in normal limbs
0.52 +/- .20 in claudicating limbs
0.23 +/- .19 in limbs with ischemic rest pain or ulcers
A toe pressure of greater than 30 mmHg may be an indicator of healing potential in foot ulcers¹
A PPG waveform that does not have swift recovery may indicate poor perfusion
¹ Zierler RE, Sumner DS. Physiologic Assessment of Peripheral Arterial Occlusive Disease. Vasc Surg 4th Edition 1:65-117 WB Saunders Co., PA, USA, 1995
The instructions provided above are intended as general guidelines. For specific instructions on performing a PPG Toe Pressure and Toe Brachial Index using your Doppler, please refer to the operation manual and/or inservice video provided.
