Enter the peak systolic velocity and the end-diastolic velocity into the Calculator. The calculator will evaluate the Resistive Index.
Resistive Index Formula
RI = (PSV - EDV) / PSV
Variables:
- RI is the Resistive Index ()
- PSV is the peak systolic velocity
- EDV is the end-diastolic velocity
To calculate Resistive Index, subtract the end-diastolic velocity from the peak systolic velocity, then divide by the peak systolic velocity.
How to Calculate Resistive Index?
The following steps outline how to calculate the Resistive Index.
- First, determine the peak systolic velocity.
- Next, determine the end-diastolic velocity.
- Next, gather the formula from above = RI = (PSV – EDV) / PSV.
- Finally, calculate the Resistive Index.
- After inserting the variables and calculating the result, check your answer with the calculator above.
Example Problem :
Use the following variables as an example problem to test your knowledge.
peak systolic velocity = 5
end-diastolic velocity = 14
Frequently Asked Questions
What is the clinical significance of the Resistive Index (RI)?
The Resistive Index (RI) is a Doppler ultrasound parameter that is used to assess the resistance to blood flow within a vessel. It is particularly useful in evaluating the renal arteries for conditions such as renal artery stenosis and can help in assessing the severity of disease in organs like the liver and kidneys.
How can peak systolic velocity (PSV) and end-diastolic velocity (EDV) vary between patients?
PSV and EDV can vary significantly between patients depending on factors such as age, cardiovascular health, and the presence of any vascular diseases. These velocities are influenced by the elasticity of the blood vessels and the cardiac output, which can be affected by numerous physiological and pathological conditions.
Can the Resistive Index (RI) be used to diagnose specific conditions?
While the Resistive Index (RI) is a valuable tool in assessing vascular resistance and can indicate abnormalities in blood flow, it is not diagnostic of specific conditions on its own. It is typically used in conjunction with other diagnostic tests and clinical findings to help diagnose conditions like renal artery stenosis or hepatic fibrosis.
Are there any limitations to using the Resistive Index (RI) in clinical practice?
Yes, there are limitations to using the Resistive Index (RI). The accuracy of RI measurements can be affected by technical factors such as the angle of insonation and patient positioning. Additionally, RI values can be influenced by physiological variations and may not always reflect the severity of disease in some cases. It is important for clinicians to interpret RI values within the context of the overall clinical picture.
