Tidal Flow-Volume Loop Enveloping at Rest in Advanced COPD
Bibliographic record
Abstract
BACKGROUND: Expiratory flow limitation (EFL) is a key physiological abnormality in COPD. Comparing tidal-to-maximum flow-volume (F-V) loops is a simple and widely available method to assess EFL in patients with COPD. We aimed to investigate whether subjects with COPD showing significant resting tidal F-V enveloping (ie, > 50% tidal volume) would present with higher exertional operating lung volumes, which would lead to greater burden of dyspnea and poorer exercise tolerance compared to their counterparts. METHODS: 37 subjects with COPD (21 males; 63.1 ± 9.2 years old; FEV 1 = 37 ± 12% predicted) and 9 paired controls (3 males; 55.9 ± 11.7 y old) performed an incremental cardiopulmonary exercise testing on a cycle ergometer. Dyspnea perception, inspiratory capacity maneuvers after 3–4 sequential tidal F-V loops, and esophageal and gastric pressures were measured during exercise. RESULTS: Most subjects (31 of 37, 84%) presented with significant tidal F-V enveloping. Critical inspiratory constraints and upward dyspnea inflection points (as a function of both work rate and ventilation) were reached earlier in these subjects, thereby leading to poorer exercise tolerance compared to their counterparts ( P = .01). Abdominal muscle recruitment (ie, increase in gastric pressure ≥ 15%) during tidal expiration was significantly higher in the EFL+ group. However, this did not bear an influence on the operating lung volumes, inspiratory constraints, dyspnea, cardiocirculatory responses, or exercise tolerance ( P > .05). CONCLUSIONS: Tidal F-V loop enveloping at rest should be valued as it is related to relevant clinical outcomes, such as dyspnea burden and exercise tolerance in subjects with COPD.
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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 | 0.001 |
| 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 | 0.000 | 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".