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Clinical contextWhy this tool matters and how to interpret it
Understand the result,
not just the number.
PETCO₂ at AT Index: Explanation and Clinical Context The PETCO₂ at Anaerobic Threshold (AT) Index measures the partial pressure of end-tidal CO₂ at the anaerobic threshold during cardiopulmonary exercise testing (CPET). This index reflects ventilatory efficiency and the balance between CO₂ production and elimination. Lower PETCO₂ at AT (<30 mmHg) indicates inefficient ventilation, often observed in patients with heart failure or pulmonary vascular disease, and correlates with worse prognosis.
Values between 30–36 mmHg are considered intermediate and require clinical correlation. Higher PETCO₂ at AT (>36 mmHg) reflects normal ventilatory efficiency and favorable prognosis. This tool assists clinicians in risk stratification, exercise prescription, and prognostic evaluation in patients undergoing CPET.
Evidence & references1 primary source mapped
- Source 1
Arena R, et al. "End-Tidal CO₂ at Anaerobic Threshold During Cardiopulmonary Exercise Testing: Clinical Significance in Heart Failure." J Card Fail. 2007;13:826-834. doi:10.1016/j.cardfail.2007.08.003
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