Cardiopulmonary Function Assessment Scores (CPET)

PETCO2 at AT Index Calculator

Clinical calculation support · Verify results before clinical use

Measurement and interpretation

Enter PETCO₂ measured at the anaerobic/ventilatory threshold during CPET.

mmHgUnit

Clinical explanation

End-tidal carbon dioxide partial pressure (PETCO₂) measured at the ventilatory threshold reflects the interaction between pulmonary perfusion, ventilation, and carbon dioxide production during exercise. In heart failure cohorts, a lower value at threshold has been associated with impaired exercise haemodynamics and adverse cardiac outcomes.

Evidence-based threshold

A study of 130 patients with compensated heart failure reported an optimal PETCO₂-at-ventilatory-threshold cut point of 36.1 mmHg for separating higher- and lower-risk groups. In that study, values at or below the cut point identified the higher-risk group; this is a cohort-derived prognostic threshold, not a universal normal range.

PETCO₂ at VT	Study-based grouping	Meaning
≤36.1 mmHg	Higher risk group	Associated with greater risk of cardiac-related events in the cited compensated-HF cohort.
>36.1 mmHg	Lower risk group	Lower-risk group relative to the study cut point; does not exclude disease or future events.

Important limitations

The cut point was derived in a specific cohort of patients with compensated heart failure and should not be generalized uncritically to all CPET populations.
Threshold identification, protocol, respiratory pattern, pulmonary vascular disease, and other clinical factors may affect interpretation.
Use PETCO₂ alongside established CPET variables, including peak VO₂ and the VE/VCO₂ slope, rather than in isolation.

References

Arena R, Guazzi M, Myers J. Prognostic value of end-tidal carbon dioxide during exercise testing in heart failure. International Journal of Cardiology. 2007;117(1):103–108. The study reports a 36.1 mmHg cut point at ventilatory threshold in 130 patients with compensated heart failure. doi:10.1016/j.ijcard.2006.04.058 · PubMed PMID: 16843545

Original-file reference: bibliographic details not verified The original file cited a 2007 Journal of Cardiac Failure article with DOI 10.1016/j.cardfail.2007.08.003 and a title that could not be verified in the searched sources. It has therefore not been retained as a confirmed source for the threshold above.

Clinical disclaimer: For healthcare professional use. This calculator provides a simplified interpretation of one CPET variable and must not replace comprehensive clinical assessment or validated risk models. Prognostic associations do not establish an individual patient's outcome.