Cardiopulmonary Function Assessment Scores (CPET)

CPX-AUC Index (Total Oxygen Uptake Area) Calculator

Clinical calculation support · Verify results before clinical use

VO₂ AUC estimate

Enter oxygen uptake at three exercise stages and the duration of each interval.

Exploratory estimate
Not a validated score

Method and interpretation

This calculator estimates the area under a simplified VO₂-versus-time curve by connecting resting VO₂, VO₂ at anaerobic threshold, and peak VO₂ with straight-line segments.

For each interval, the trapezoidal estimate is the mean of the two endpoint VO₂ values multiplied by the interval duration. The two interval areas are then added.

Important limitations

The estimate assumes a linear change in VO₂ within each interval and uses only three points, so it does not reproduce integration of the full breath-by-breath or time-series CPET data.
The result depends on the actual interval durations; total exercise duration alone is insufficient to locate the anaerobic threshold in time.
No validated reference range, risk category, diagnostic cutoff, or outcome prediction is provided for this calculated value.
Do not use this estimate alone to diagnose disease, stratify prognosis, or guide treatment. Interpret established CPET variables in their clinical context.

Scientific context

Guazzi M, Bandera F, Ozemek C, Systrom D, Arena R.
Cardiopulmonary Exercise Testing: What Is its Value? Journal of the American College of Cardiology. 2017;70(13):1618–1636.
doi:10.1016/j.jacc.2017.08.012
This review provides context for established CPET variables; it is not cited as validation of a CPX-AUC index.

Guazzi M, Adams V, Conraads V, et al.
Clinical recommendations for cardiopulmonary exercise testing data assessment in specific patient populations. European Heart Journal. 2012;33(23):2917–2927.
doi:10.1093/eurheartj/ehs221
Clinical recommendations on CPET assessment; not evidence for a validated AUC cutoff.

Clinical disclaimer: This tool provides a simplified mathematical estimate, not an independently validated clinical index. The term “CPX-AUC Index” and the claims of normal values, risk prediction, or prognostic utility in the original page could not be substantiated by the sources reviewed. Verify the intended method against a primary publication before clinical use.