What is the primary purpose of the Ankle Brachial Index (ABI)?

The primary purpose of the Ankle Brachial Index (ABI) is to evaluate peripheral arterial disease (PAD). The ABI is a simple, non-invasive test that compares the blood pressure in a patient's ankle with the blood pressure in the arm. By measuring these pressures, healthcare providers can assess the degree of arterial obstruction and determine the presence of PAD, which is characterized by narrowed arteries that reduce blood flow to the limbs. A lower ABI value indicates more severe blockage and poorer blood flow, which can help guide treatment options for patients at risk for cardiovascular complications.

The other options do not align with the purpose of the ABI. Measuring heart rate or assessing blood pressure does not provide specific information about peripheral artery function. Analyzing respiratory function is a completely different area of assessment and is not related to vascular health or PAD evaluation. Hence, the correct answer highlights the specific role of the ABI in diagnosing and managing peripheral arterial disease.