Verbeet, Eline (2025) The diagnostic value of the arterial to end-tidal CO2-gradient for a ventilation/perfusion mismatch during maximal cycling ergometry: A retrospective cohort study. thesis, Medicine.
Full text available on request.Abstract
Background: Cardiopulmonary exercise test (CPET) can help determine the cause of unexplained dyspnea on exertion. The arterial to end-tidal CO2 gradient (P(a-ET)CO2), measured during CPET, reflects the degree of dead space and can indicate a ventilation/perfusion (V/Q) mismatch. However, the positive predictive value (PPV) of an abnormal P(a-ET)CO2 (>0.4 kPa) for diagnosing a V/Q mismatch remains unclear. Methods: We retrospectively analyzed data of 122 patients who underwent CPET with blood gas analysis between January 2022 and July 2024. We examined their diagnostic imaging and diagnoses three months before and after CPET to assess the PPV, false omission rate (FOR) and performed a cut-off analysis. Logistic regression analyses were conducted to identify predictors of an abnormal P(a-ET)CO2 at maximal exercise. Results: Among the 52 with a P(a-ET)CO2 >0.4 kPa, 34 underwent diagnostic imaging and 7 were diagnosed with a V/Q mismatch. The current cut-off showed a minimal PPV of 13.5%, maximal PPV of 48.1% and minimal FOR of 4.3%. Increasing the cut-off from 0.4 kPa to 0.8 kPa improved the minimal PPV to 30.0% and reduced the FOR to 3.9%. Age (OR 1.07, p<0.001) and percentage of predicted DLCO (OR 0.93, p<0.001), independently predicted an abnormal P(a-ET)CO2 at maximal exercise, achieving 96% sensitivity, 39% specificity and 93% negative predictive value. Patients with a V/Q mismatch had significantly lower FEV1% and higher PETCO2, lower EqCO2 and higher PaCO2 at maximal exercise. Conclusion: P(a-ET)CO2 has limited diagnostic performance in diagnosing a V/Q mismatch. The cut-off value might be safely increased from 0.4 to 0.8 kPa. Age and percentage of predicted DLCO are independent predictors for an abnormal P(a-ET)CO2 at maximal exercise.
| Item Type: | Thesis (UNSPECIFIED) |
|---|---|
| Supervisor name: | Veen, Dr. H.P.A.A. van and Fabius, Dr. T. M. and Jongh, Dr. F.H.C. de |
| Faculty: | Medical Sciences |
| Date Deposited: | 13 May 2026 14:01 |
| Last Modified: | 13 May 2026 14:01 |
| URI: | https://umcg.studenttheses.ub.rug.nl/id/eprint/3953 |
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