Cardiopulmonary Function Assessment Scores (CPET)

VO2/HR Ratio (Cardiac Efficiency) Calculator

Clinical calculation support · Verify results before clinical use

Oxygen Pulse Calculator

Calculate oxygen uptake per heartbeat from CPET measurements.

— mL/beat

Calculated oxygen pulse

Enter values to calculate

The result will appear here after valid VO₂ and heart rate values are entered.

Clinical interpretation

A single oxygen pulse value does not independently establish normal or abnormal cardiac function. Interpret it with the exercise-stage response and the rest of the CPET.

This calculator reports VO₂/HR only. It does not provide a diagnosis, predicted oxygen pulse, or validated risk score.

About Oxygen Pulse

Oxygen pulse (O₂ pulse) is oxygen uptake divided by heart rate. When VO₂ is entered in mL/min and heart rate in beats/min, the result is expressed in mL of oxygen per beat.

Formula

Oxygen pulse = VO₂ (mL/min) ÷ HR (beats/min)

Clinical context

Oxygen pulse reflects the product of stroke volume and the arteriovenous oxygen-content difference. It is therefore influenced by both oxygen delivery and peripheral oxygen extraction; it is not a direct measurement of stroke volume or a standalone measure of “cardiac efficiency.”

During incremental CPET, the shape of the oxygen-pulse trajectory may be informative. A low value or an early plateau or decline can raise concern for an abnormal exercise response, but these findings are not specific and should be interpreted alongside symptoms, effort level, VO₂, ECG, blood pressure, ventilatory variables, haemoglobin, and the clinical context.

Interpretation cautions

No universal normal range is displayed because oxygen pulse varies with body size, sex, age, exercise intensity, and oxygen extraction.
Use VO₂ and HR measurements taken from the same CPET time point or exercise stage.
Do not use this calculation alone to diagnose myocardial ischaemia, heart failure, or impaired stroke volume.

References

Degani-Costa LH, Nery LE, Rodrigues MT, et al. Does oxygen pulse trajectory during incremental exercise discriminate impaired oxygen delivery from poor muscle oxygen utilisation? ERJ Open Research. 2019;5(2):00108-2018. doi:10.1183/23120541.00108-2018

Guazzi M, Arena R, Halle M, Piepoli MF, Myers J, Lavie CJ. Cardiopulmonary Exercise Testing: What Is its Value? Journal of the American College of Cardiology. 2017. doi:10.1016/j.jacc.2017.08.012

Radtke T, et al. Practical guide to cardiopulmonary exercise testing in adults. Respiratory Research. 2022. PubMed: 35022059

Clinical disclaimer: This tool performs a simple arithmetic calculation and is intended for educational and clinical-support use. It does not replace interpretation of the complete CPET by a qualified clinician. Clinical decisions should not be based on oxygen pulse alone.