Does the Respiratory System Limit Exercise in Mild Chronic Obstructive Pulmonary Disease?
Bibliographic record
Abstract
RATIONALE: It is not known if abnormal dynamic respiratory mechanics actually limit exercise in patients with mild chronic obstructive pulmonary disease (COPD). We reasoned that failure to increase peak ventilation and Vt in response to dead space (DS) loading during exercise would indicate true ventilatory limitation to exercise in mild COPD. OBJECTIVES: To compare the effects of DS loading during exercise on ventilation, breathing pattern, operating lung volumes, and dyspnea intensity in subjects with mild symptomatic COPD and age- and sex-matched healthy control subjects. METHODS: Twenty subjects with Global Initiative for Chronic Obstructive Lung Disease stage I COPD and 20 healthy subjects completed two symptom-limited incremental cycle exercise tests, in randomized order: unloaded control and added DS of 0.6 L. MEASUREMENTS AND MAIN RESULTS: Peak oxygen uptake and ventilation were significantly lower in COPD than in health by 36% and 41%, respectively. With added DS compared with control, both groups had small decreases in peak work rate and no significant increase in peak ventilation. In health, peak Vt and end-inspiratory lung volume increased significantly with DS. In contrast, the COPD group failed to increase peak end-inspiratory lung volume and had a significantly smaller increase in peak Vt during DS. At 60 W, a 50% smaller increase in Vt (P < 0.001) in response to added DS in COPD compared with health was associated with a greater increase in dyspnea intensity (P = 0.0005). CONCLUSIONS: These results show that the respiratory system reached or approached its physiologic limit in mild COPD at a lower peak work rate and ventilation than in healthy participants. Clinical trial registered with www.clinicaltrials.gov (NCT 00975403).
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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 | 0.003 |
| 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 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.001 | 0.001 |
| 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".