The Ankle Brachial Index (ABI) is the ratio of the blood pressure at the bottom of the leg or ankle to the blood pressure in the arm. Knowing the ABI is important because it can be used as an indicator of Peripheral Arterial Disease (PAD). Peripheral arteries of the body can be affected in the same way as coronary arteries (heart arteries). These blood vessels can become clogged with cholesterol or stiffen due to calcification. Significant differences in blood pressure in the lower legs and arms can signal peripheral arterial disease. This disease can progress to more serious diseases such as stroke and heart failure.
Step
Part 1 of 3: Measuring Brachial Pressure
Step 1. Ask the patient to lie on his back
The patient needs to lie on his back so that his brachial pressure can be measured. Make sure the patient is lying on a flat surface so that his arms and legs are at heart level. Give at least 10 minutes of rest before taking heart rate levels. Rest will help normalize blood pressure, especially if the patient is restless, while allowing the heart and brachial pulses to calm down.
The patient's arms should be open. So, sleeves should be rolled up
Step 2. Locate the brachial artery
Use your index and middle fingers to find the pulse point. Do not use your thumb as this finger has its own pulse making it more difficult to find the patient's pulse. The brachial pulse is usually just above the antecubital fossa, which is the center of the elbow flexion.
Step 3. Wrap the blood pressure measuring cuff around the patient's left arm
Ensure that the cuff is 5 cm above the point of the brachial pulse. To ensure an accurate measurement, make sure the cuff is loose enough so that it can be turned slightly on the arm, but not so much that it can sag off the arm.
If possible, use a blood pressure cuff that is approximately the length of the patient's arm
Step 4. Inflate the cuff to find the systolic blood pressure of the arm
To measure the blood pressure level, place the diaphragm of the stethoscope on the brachial pulse. Close the pump valve and use it to fill the cuff with air to about 20 mm Hg above normal blood pressure or until the patient's pulse is no longer audible.
- Systolic blood pressure represents the maximum arterial pressure produced by contraction of the left ventricle of the heart.
- Diastolic pressure indicates the minimum amount of pressure produced when the chambers fill with blood during the beginning of the cardiac/cardiac cycle.
Step 5. Deflate the cuff
Release the pressure slowly at a rate of 2-3 mmHg by opening the valve while closely monitoring the manometer (pressure meter.). Note when the pulse is heard again, and note again when it disappears. The systolic blood pressure is the point at which the pulsating sound returns and the diastolic blood pressure is the point at which the pulse disappears. Systolic blood pressure is the pressure that will be used later to calculate the ABI.
Part 2 of 3: Measuring Ankle Pressure
Step 1. Ask the patient to remain supine
Your goal is to keep the arms and legs at heart level so you can get the most accurate measurement possible. Remove the blood pressure cuff from the patient's arm.
Step 2. Wrap the blood pressure cuff around the patient's left ankle
Position the cuff 5 cm above the malleolus (round protrusion of the bone) of the ankle. Make sure the cuff is not wrapped too tightly. Check the tightness by inserting two fingers. If it can't be inserted, it means the bandage is too tight.
Make sure the cuff is the right size for the patient. The width of the cuff should be slightly larger than the diameter of the lower leg
Step 3. Locate the dorsalis pedis artery
The dorsalis pedis (DP) artery is located on the upper surface of the foot just near the point where the sole and the ankle meet. Rub the ultrasound gel on the top area of the foot. Use the Doppler probe to find the strongest point of DP. Move the probe until you find the point with the strongest pulsating sound. You may also hear a pulsating or swishing sound.
Step 4. Record the arterial blood pressure of the DP
Inflate the blood pressure cuff to about 20 mm Hg above the patient's normal systolic pressure, or until the Doppler whirring sound disappears. Deflate the cuff and take it back when the swish sound returns. This is the ankle systolic blood pressure.
Step 5. Locate the posterior tibial artery (PT)
For the most accurate ABI measurement results, you will need to measure the dorsalis pedis and posterior tibial artery blood pressures. The PT artery is in the upper of the back of the calf. Rub the ultrasound gel over this area and use the Doppler probe to find the point of the strongest PT pulse.
Step 6. Record the arterial blood pressure of PT
Repeat the same process as when measuring the DP artery. If so, record the results and move the cuff to the right leg. Record the dorsalis pedis and posterior tibial artery blood pressures in the right leg.
Part 3 of 3: Calculating the Ankle Brachial Index (ABI)
Step 1. Record the higher systolic blood pressure at the ankle
Compare the results of the right and left ankles, and the DP and PT arteries of both ankles. The highest number of each wrist will be used to calculate the ABI.
Step 2. Divide the ankle systolic blood pressure by the arm systolic blood pressure
You will calculate the ABI for each leg individually. Use the highest value from the left ankle artery measurement and divide by the arterial value. Then, repeat the process with the result on the right ankle.
For example: Left ankle systolic blood pressure is 120 and arm systolic blood pressure is 100. 120/100=1, 20
Step 3. Record and interpret the results
The normal ABI rate is 1.0 to 1. 4. The closer the patient's ABI to 1, the better the results. This means that the arm blood pressure should be as close to the ankle blood pressure as possible.
- An ABI of less than 0.4 indicates severe peripheral arterial disease. Patients may develop ulcers or gangrene that do not heal.
- An ABI of 0.41-0.90 indicates mild to moderate peripheral arterial disease and requires further testing such as CT, MRI, or angiography.
- An ABI of 0.91-1.30 indicates normal blood vessels. However, values between 0.9-0.99 can cause pain during exercise.
- An ABI >1, 3 indicates a blood vessel that cannot be compressed and is very calcified so that it raises blood pressure. Sustained diabetes or chronic kidney disease can be the cause of this condition.
Tips
- Some of the symptoms of arterial disease include calf pain when walking, ulcers that don't heal on the toes or feet, discoloration and hair loss on the feet, cold and clammy skin, etc.
- Patients who are asymptomatic should measure the Ankle Brachial Index to rule out peripheral vascular disease including cigarette addicts, diabetics over 50 years of age, those with a family history of heart disease, and people with high cholesterol levels.
- If the patient has a wound in the brachial or pedal area, use sterile gauze to protect the wound before dressing the cuff.
- Check the doctor's orders or special considerations that need to be made before undergoing the procedure. Dialysis can negate the measurement of brachial blood pressure in the patient.
- Check the overall condition of the patient. Other pathological conditions can affect the accuracy of the procedure.
