Pulsatility Index Calculator

Calculate the Pulsatility Index (PI) to assess blood flow characteristics in Doppler ultrasound examinations. The PI measures the variability of blood flow velocity and is used to evaluate vascular resistance.

How to Use This Calculator

Enter the Peak Systolic Velocity (PSV) value from your Doppler measurement
Enter the End Diastolic Velocity (EDV) value
Enter the Mean Velocity (MV) value
Click Calculate to see the Pulsatility Index and interpretation

Formula Used

PI = (PSV - EDV) / MV

Where:

PSV = Peak Systolic Velocity - Maximum blood flow velocity during systole
EDV = End Diastolic Velocity - Minimum blood flow velocity during diastole
MV = Mean Velocity - Average blood flow velocity over the cardiac cycle

Example Calculation

Real-World Scenario:

Assessing blood flow in the middle cerebral artery of a patient to evaluate cerebrovascular resistance.

Given:

Peak Systolic Velocity (PSV) = 120 cm/s
End Diastolic Velocity (EDV) = 40 cm/s
Mean Velocity (MV) = 80 cm/s

Calculation:

PI = (120 - 40) / 80 = 80 / 80 = 1.0

Result: Pulsatility Index = 1.0 (Normal flow characteristics)

Why This Calculation Matters

Practical Applications

Assessing cerebrovascular resistance in stroke patients
Evaluating placental blood flow in obstetrics
Monitoring renal artery stenosis
Assessing peripheral vascular disease

Key Benefits

Non-invasive assessment of vascular resistance
Helps identify abnormal blood flow patterns
Aids in diagnosis of various vascular conditions
Supports treatment monitoring and decision making

Common Mistakes & Tips

Ensure accurate angle correction when measuring velocities. Doppler measurements should be taken at an angle of 60° or less to the vessel, and angle correction should be properly applied to avoid underestimation of true velocities.

Normal PI values vary by vessel and patient condition. What's normal for the middle cerebral artery (PI 0.6-1.1) differs from renal arteries (PI 0.7-1.5). Always compare with age-matched normal values and consider the specific clinical context.

Frequently Asked Questions

A high PI (typically >1.3-1.5) indicates increased vascular resistance. This can be seen in conditions like severe stenosis, increased intracranial pressure, or advanced peripheral artery disease. It suggests that blood flow is more pulsatile and less continuous.

A low PI (typically <0.6-0.7) indicates decreased vascular resistance and more continuous blood flow. This is often seen in low-resistance vascular beds like the internal carotid artery, placental circulation, or in conditions with vasodilation. Extremely low values may suggest arteriovenous malformations or high-flow states.

Both PI and RI measure vascular resistance, but they use different formulas. RI = (PSV - EDV) / PSV, while PI = (PSV - EDV) / MV. RI is more commonly used and ranges from 0 to 1, while PI can theoretically range from 0 to infinity. PI is more sensitive to changes in mean velocity and is preferred in some clinical scenarios.

References & Disclaimer

Medical Disclaimer

This pulsatility index calculator is for educational and informational purposes only. It should not be used for diagnostic or treatment decisions. Always consult with qualified healthcare professionals for medical advice and diagnosis. The calculator provides estimates based on the input values and standard formulas, but actual clinical interpretation requires consideration of the patient's complete medical history, examination findings, and other diagnostic tests.

References

Gosling RG, King DH. - Arterial assessment by Doppler ultrasound
Aaslid R, et al. - Clinical monitoring of cerebral hemodynamics
Vasquez J, et al. - Pulsatility index in vascular assessment

Accuracy Notice

This calculator provides accurate mathematical calculations based on the input values. However, the clinical interpretation of pulsatility index values depends on multiple factors including the specific vessel being examined, patient age, and underlying medical conditions. Always interpret results in the context of comprehensive clinical evaluation.

About the Author

Kumaravel Madhavan

Web developer and data researcher creating accurate, easy-to-use calculators across health, finance, education, and construction and more. Works with subject-matter experts to ensure formulas meet trusted standards like WHO, NIH, and ISO.

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