Physiological and perceptual responses to exercise according to the locus of symptom limitation in patients with COPD
Bibliographic record
Abstract
We tested the hypothesis that patients with chronic obstructive pulmonary disease (COPD) who stop exercise due to breathlessness (B) vs. leg discomfort (LD) have greater pathophysiological abnormalities in dynamic respiratory mechanics & pulmonary gas exchange efficiency at end-exercise. We compared physiological and perceptual responses at the symptom-limited peak of cycle exercise testing between 61 patients reporting B (43M; mean±SD FEV1, 42±22%pred) and 26 patients reporting LD (24M; FEV1, 60±27%pred, p<0.05 vs. B) as their main exercise-limiting symptom. At end-exercise in the B vs. LD group: O2 uptake (62±22 vs. 72±25%pred, p=0.06), breathing reserve (6±19 vs. 18±23%, p=0.01), intensity ratings of leg discomfort (3.7±2.6 vs. 6.0±2.2 Borg units, p<0.01) and inspiratory reserve volume (0.34±0.41 vs. 0.72±0.37 L, p<0.01) were lower; intensity ratings of breathlessness were higher (6.0±2.2 vs. 4.1±2.1 Borg units, p<0.01); and the magnitude of decline in inspiratory capacity from rest was greater (-0.53±0.76 vs. -0.26±0.55 L, p=0.11). Measures of pulmonary gas exchange efficiency at end-exercise, including blood O2 saturation (96±12 vs. 96±9%) and the ventilatory equivalent for CO2 (37.1±6.4 vs. 37.0±7.3), were similar between-groups. In conclusion, COPD patients reporting B vs. LD as their main exercise-limiting symptom had greater pathophysiological abnormalities in dynamic respiratory mechanics at end-exercise. These findings have potentially important clinical implications in terms of identifying patients whose exercise tolerance may be enhanced by improving dynamic respiratory mechanics vs. skeletal muscle function.
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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 | 0.004 |
| 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 | 0.001 |
| 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".