Abstract 16687: Abnormal Peripheral Muscle Oxygenation During Submaximal Exercise Contributes to Exercise Intolerance in Pulmonary Arterial Hypertension
Bibliographic record
Abstract
Introduction: Pulmonary arterial hypertension (PAH) is a vascular remodeling disease leading to right ventricular failure. Despite the most modern therapies, most patients display persistent and significant exercise intolerance. Many observations suggest that exercise limitation in PAH is not simply due to pulmonary hemodynamic impairment, but that other determinants intrinsic to the skeletal muscle are involved. Hypothesis: We hypothesized that O2 delivery to skeletal muscles during exercise is impaired in PAH independently of cardiac output. Methods and Results: Ten PAH patients performed a submaximal exercise at 70% of their peak workload (mean workload = 58 (15) W). Ten healthy controls performed the same exercise at the same workload as the PAH patients with whom they were paired. The increase in muscle deoxyhemoglobin concentration [HHb] (near-infrared spectroscopy, ISS) of the dominant quadriceps was significantly higher in PAH patients compared to healthy controls (29.6 (3.7) vs 9.7 (2.5) %; p<0.01) at the end of the submaximal exercise. This was not related to differences in cardiac output increases during exercise (+4.0 (0.7) vs +3.2 (0.4) L/min; p=0.29) (Nexfin BMEYE) or hemoglobin level (138.4 (2.4) vs 138.1 (3.7) g/L; p=0.94) for PAH patients and controls, respectively. Conversely, exercise-induced arterial O2 desaturation was more pronounced for PAH patients (-5.5 (1.8) vs -0.2 (0.6) %; p=0.03). Adding O2 supplementation did not significantly modified end-exercise muscle [HHb] (p=0.53), cardiac output increases (p=0.72) and arterial O2 desaturation (p=0.18). Quadriceps muscle biopsy confirmed that PAH patients had lower capillarity density compared to healthy controls (202 (27) vs 304 (23) #cap/mm2; p=0.01) that correlated with end-exercise muscle [HHb] (R2=0.37; p<0.01). Finally, muscle [HHb] during submaximal exercise correlated with VO2 max (R2=0.65; p<0.01) and 6 minutes walk test distance (R2=0.54; p=0.01). Conclusions: Our results demonstrate that PAH patients exhibit a lower skeletal muscle capillarity density that contributes to inadequate muscle O2 supply during exercise and exercise intolerance.
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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 | 0.000 | 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) | 0.007 | 0.001 |
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".