Ventilatory and sensory responses to incremental exercise in adults with a Fontan circulation
Bibliographic record
Abstract
Many adults with single-ventricle congenital heart disease who have undergone a Fontan procedure have abnormal pulmonary function resembling restrictive lung disease. Whether this contributes to ventilatory limitations and increased dyspnea has not been comprehensively studied. We recruited 17 Fontan participants and 17 healthy age- and sex-matched sedentary controls. All participants underwent complete pulmonary function testing followed by a symptom-limited incremental cardiopulmonary cycle exercise test with detailed assessments of dyspnea and operating lung volumes. Fontan participants and controls were well matched for age, sex, body mass index, height, and self-reported physical activity levels (all P > 0.05), although Fontan participants had markedly reduced cardiorespiratory fitness and peak work rates ( P < 0.001). Fontan participants had lower values for most pulmonary function measurements relative to controls with 65% of Fontan participants showing evidence of a restrictive ventilatory defect. Relative to controls, Fontan participants had significantly higher breathing frequency, end-inspiratory lung volume (% total lung capacity), ventilatory inefficiency (high ventilatory equivalent for CO2), and dyspnea intensity ratings at standardized absolute submaximal work rates. There were no between-group differences in qualitative descriptors of dyspnea. The restrictive ventilatory defect in Fontan participants likely contributes to their increased breathing frequency and end-inspiratory lung volume during exercise. This abnormal ventilatory response coupled with greater ventilatory inefficiency may explain the increased dyspnea intensity ratings in those with a Fontan circulation. Interventions that enhance the ventilatory response to exercise in Fontan patients may help optimize exercise rehabilitation interventions, resulting in improved exercise tolerance and exertional symptoms. NEW & NOTEWORTHY This is the first study to comprehensively characterize both ventilatory and sensory responses to exercise in adults that have undergone the Fontan procedure. The majority of Fontan participants had a restrictive ventilatory defect. Compared with well-matched controls, Fontan participants had increased breathing frequency, end-inspiratory lung volume, and ventilatory inefficiency. These abnormal ventilatory responses likely form the mechanistic basis for the increased dyspnea intensity ratings observed in our Fontan participants during exercise.
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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) | 0.001 | 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".