Exercise Recruits Dormant Intrapulmonary Arteriovenous Shunts in Healthy Subjects
Bibliographic record
Abstract
0857 There is morphologic evidence for arteriovenous intrapulmonary shunts that bypass the pulmonary capillaries in healthy humans. We postulated that these vessels are dormant at rest, but are then recruited during exercise as cardiac output and pulmonary vascular pressures rise. PURPOSE: To determine whether whole-body endurance exercise results in the recruitment of direct intrapulmonary arteriovenous connections in healthy humans. METHODS: 13 healthy males (31 yr; 178 cm; 73 kg) and 10 healthy females (27 yr; 165 cm; 59 kg) with normal lung function and a range of fitness levels (mean VO2max = 126% predicted; range = 78–200% predicted) completed a maximal progressive exercise test on a bicycle ergometer. Agitated saline contrast echocardiography (4-chamber apical view) was used to test for the presence of intrapulmonary shunting at rest and during each exercise level. This technique entails infusion of saline microbubbles (diameter = 30–90 microns) into a peripheral vein. The contrast microbubbles are highly echogenic and are readily visualized as they enter the right heart. If there is no intracardiac or intrapulmonary shunting the microbubbles are filtered completely by the pulmonary microcirculation. A delayed appearance (>3 cardiac cycles) of contrast in the left heart is consistent with passage of microbubbles through distinct intrapulmonary arteriovenous conduits. RESULTS: Intrapulmonary shunting was not evident at rest. However, twenty-one of the twenty-three subjects demonstrated a delayed trans-pulmonary passage of microbubbles during exercise. The shunting appeared at an average power output of 133 watts, at a metabolic rate of 1.9 L/min (60% VO2max), a minute ventilation of 47.6 L/min, and a heart rate of 128 bpm. Three min following exercise the transpulmonary passage of microbubbles was not evident. CONCLUSION: The transpulmonary passage of microbubbles during exercise provides evidence that dormant intrapulmonary arteriovenous shunts open as cardiac output and pulmonary vascular pressures rise. These shunts may contribute to the decreased efficiency of gas exchange and reduction in pulmonary vascular resistance during exercise. NHLBI
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
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) | 0.002 | 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".