Dead-space ventilation is linked to exercise capacity and survival in distal chronic thromboembolic pulmonary hypertension
Bibliographic record
Abstract
Background Cardiopulmonary exercise testing (CPET) is frequently used for the evaluation of patients with pulmonary hypertension (PH). Non-operable distal chronic thromboembolic pulmonary hypertension (CTEPH) represents a unique subgroup of PH where microvascular disease resembling pulmonary arterial hypertension (PAH) may predominate and efficacious medical therapy is now available. However, little is known regarding the detailed CPET profile of patients with distal CTEPH, and whether ventilation and gas exchange responses are different from PAH. Methods Forty-nine consecutive patients with non-operable distal CTEPH according to multidisciplinary team assessment and 45 PAH patients underwent CPET and right heart catheterization. Patients were followed up for a median of 3.2 years (interquartile range: 1.8 to 4.4). Results Pulmonary hemodynamics were similar in distal CTEPH and PAH groups, but patients with distal CTEPH achieved a lower percent predicted peak oxygen consumption (59 ± 13% vs 66 ± 14%, p < 0.05). At peak exercise, higher physiologic dead-space fraction (VD/VT) (0.45 ± 0.07 vs 0.35 ± 0.07, p < 0.0001) and higher arterial-to-end-tidal carbon dioxide gradient (9 ± 3 vs 5 ± 3 mm Hg, p < 0.0001) were observed in distal CTEPH compared with PAH. Ventilatory efficiency, expressed as VE/VCO 2 slope, was also more impaired in distal CTEPH (52.2 ± 10.1 vs 43.8 ± 8.4 liters/min, p < 0.0001). In the distal CTEPH group only, higher VD/VT was associated with lower peak oxygen consumption ( r = −0.46, p = 0.003) and worse survival. Conclusions Compared with PAH, a distinct pattern of response to exercise was observed in distal CTEPH, characterized by increased dead-space ventilation that resulted in worse ventilatory efficiency and greater impairment of exercise capacity. In distal CTEPH, dead-space ventilation correlated with exercise capacity and was associated with survival.
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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 | 0.003 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.001 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| 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".