Partial Pressure of End-Tidal Oxygen and Blood Lactate During Cardiopulmonary Exercise Testing in Healthy Older Participants and Patients at Risk of Cardiac Disease
Bibliographic record
Abstract
Background: The partial pressure of end-tidal oxygen (PETO 2 ) and end-tidal oxygen concentration (ETO 2 ) are among the indices that can be measured by exhaled gas analysis. Several observational studies have shown that skeletal muscle function is impaired in patients with cardiac disease; thus, the assessment of skeletal muscle function is important. Additionally, although it has recently been suggested that the difference in PETO 2 from rest to the ventilatory anaerobic threshold (VAT) reflects oxygen availability in peripheral factors, primarily skeletal muscle, the evidence for this is not well established. Therefore, we hypothesized and investigated whether increased blood lactate (BLa) levels, resulting from decreased skeletal muscle and mitochondrial oxygen availability, and PETO 2 dynamics during cardiopulmonary exercise testing (CPET) would be related. Methods: All participants performed the symptomatic limited CPET, and their BLa levels were measured. The difference in PETO 2 and ETO 2 from rest to VAT determined by the V-slope method (DeltaPETO 2 and DeltaETO 2 ) was calculated and compared with the increase in BLa due to exercise testing. Results: We recruited 22 healthy older participants (nine males; 69.4 ± 6.8 years) and 11 patients with cardiovascular risk (eight males; 73.0 ± 8.8 years). DeltaPETO 2 and DeltaETO 2 did not differ between the two groups (P = 0.355 and P = 0.369, respectively), showing no correlation between increase in BLa from rest to VAT, but were significantly correlated with an increase in BLa from rest to the end of exercise (DeltaPETO 2 , P = 0.030; DeltaETO 2 , P = 0.029). The correlation was particularly pronounced among those at cardiovascular risk (DeltaPETO 2 , P = 0.012; DeltaETO 2 , P = 0.011). Conclusions: DeltaPETO 2 and DeltaETO 2 from rest to VAT during CPET may be useful as indices reflecting skeletal muscle oxygen utilization capacity. Cardiol Res. 2024;15(1):29-36 doi: https://doi.org/10.14740/cr1597
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.002 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.001 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".