The Relationship Between Central and Peripheral Chemoreflex Sensitivities and V <sub>E</sub> ‐VCO <sub>2</sub> Slope Below and Above the Respiratory Compensation Point of Incremental Exercise
Bibliographic record
Abstract
During incremental exercise, the ventilation (V̇ E ) versus carbon dioxide production (V̇CO 2 ) relationship exhibits a double‐linear response with an inflection of slope at the transition from hyperpnea to hyperventilation (i.e., respiratory compensation point (RCP)). Whether peripheral or central chemoreflexes contribute to the hyperventilatory response to incremental exercise remains undetermined. This study tested the hypothesis that peripheral and not central chemoreflex sensitivity would relate to the magnitude of the V̇ E ‐V̇CO 2 slope above RCP and that neither would relate to the sub‐RCP V̇ E ‐V̇CO 2 slope. Seven healthy, caffeine‐free males (age: 27±5 years) performed a ramp‐incremental test to exhaustion on a cycle ergometer, during which ventilation and gas exchange were measured by metabolic cart. The V̇ E ‐V̇CO 2 slope above and below RCP were determined by linear regression from the estimated lactate threshold to RCP, and from RCP to end‐exercise, respectively. On four separate days, 12 modified rebreathing tests were performed: six in isoxic‐hyperoxia (PO 2 =150 mmHg) and six in isoxic‐hypoxia (PO 2 =50 mmHg). Using ensemble‐average data, central chemoreflex sensitivity was measured as the mean hyperoxic V̇ E versus end‐tidal partial pressure of carbon dioxide (P ET CO 2 ) slope (in L∙min ‐1 ∙mmHgP ET CO 2 ‐1 ) and the peripheral chemoreflex sensitivity was determined from the difference of hypoxic and hyperoxic slopes. The mean V̇ E ‐V̇CO 2 slopes above and below RCP were 35.0 + 3.7 (range: 28.3‐39.9) and 61.8 + 9.2 (range: 51.9‐78.3), respectively. Mean peripheral and central chemoreflex sensitivities were 1.6±1.3 L∙min ‐1 ∙mmHgP ET CO 2 ‐1 (range: 0.1‐3.7) and 4.1±2.1 L∙min ‐1 ∙mmHgP ET CO 2 ‐1 (range: 2.3‐8.4), respectively. Peripheral chemoreflex sensitivity did not relate to V̇ E ‐V̇CO 2 slope below (r=0.44, p=0.32) or above (r=‐0.02, p=0.96) RCP. No relationships were found between central chemoreflex sensitivity and V̇ E ‐V̇CO 2 slope below (r=0.06, p=0.90) or above (r=0.04, p=0.93) RCP. These preliminary observations suggest that neither central nor peripheral chemoreflex sensitivity factor into the magnitude of the hyperpneic or hyperventilatory response to incremental exercise.
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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 | 0.000 | 0.002 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 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".