Umbilical Artery PI Calculator

Actual umbilical-artery PI=(systolic−diastolic)/cycle-mean velocity, matching units and acquisition. Negative end-diastolic flow retained; actual cycle mean supplied, not an assumed arithmetic mean. No clinical diagnosis or universal gestational reference.

Description

Umbilical-artery pulsatility index expresses waveform velocity excursion relative to its cycle mean.

Umbilical-artery pulsatility index expresses waveform velocity excursion relative to its cycle mean.^[1]

It differs from a resistance index whose denominator is peak systolic velocity.

When to use Umbilical Artery PI Calculator

Use this tool to calculate or review the supplied observations under the stated rules. Establish the observation date, units, measurement context and independently applicable clinical reference or calibrated model.

How to use Umbilical Artery PI Calculator and understand its results

Establish the observation date, units, measurement context and independently applicable clinical reference or calibrated model.
Enter independentlyMeasuredSystolicVelocity, independentlyMeasuredEndDiastolicVelocity, independentlyMeasuredCycleMeanVelocity, using the field meanings and rules below, then run the tool.
Read result.observedPulsatilityIndex. Use the units and sign conventions below.
Correct any reported input issue and run again. Before using a successful result, check the stated units, signs, reference scope and observation coverage.

Input field	Meaning	Value type	Requirement
independentlyMeasuredSystolicVelocity	Independently measured systolic velocity	number	Required
independentlyMeasuredEndDiastolicVelocity	Independently measured end diastolic velocity	number	Required
independentlyMeasuredCycleMeanVelocity	Independently measured cycle mean velocity	number	Required

Require positive systolic peak and cycle-mean velocities. Diastolic velocity must be finite and no greater than systolic; negative diastolic flow is allowed. Divide systolic-minus-diastolic by cycle mean. The tool does not extract waveform velocities or apply a clinical threshold.

PI=(systolicVelocity−diastolicVelocity)/cycleMeanVelocity

Use the matching field units and the exact boundary, ordering and reference rules above.

Output field	Meaning	Value type
result	Structured result; its nested fields below contain the actual calculation or selected reference	object
result.observedPulsatilityIndex	Observed Pulsatility Index	number

json

{
  "input": {
    "independentlyMeasuredSystolicVelocity": 100,
    "independentlyMeasuredEndDiastolicVelocity": 40,
    "independentlyMeasuredCycleMeanVelocity": 70
  },
  "output": {
    "result": {
      "observedPulsatilityIndex": 0.8571428571428571
    }
  }
}

Limitations and assumptions

Dating evidence, acquisition conditions and applicable clinical references remain independently established. The output describes supplied observations or a conditional model without diagnosing an outcome, choosing a dose or verifying clinical applicability.

Missing required fields, unknown fields, wrong types and violated rules return input issues. Numeric values and outputs must be finite. Extremely large composite outputs are rejected.

Alternative or Complementary methods

For a related step, use Uterine Artery PI Calculator: Uterine-artery pulsatility index compares systolic-to-diastolic velocity excursion with a cycle-mean velocity. For a complementary comparison, use Mean Uterine Artery PI Calculator: Mean uterine-artery pulsatility index combines independently matched left and right measurements.

References

Umbilical Artery PI Calculator — tool.io

Similar or alternative tools

Uterine Artery PI Calculator
Uterine-artery pulsatility index compares systolic-to-diastolic velocity excursion with a cycle-mean velocity.
Mean Uterine Artery PI Calculator
Mean uterine-artery pulsatility index combines independently matched left and right measurements.