Anatomic Intrapulmonary Arteriovenous Anastomoses And Right‐To‐Left Shunt As Evaluated By The Multiple Inert Gas Elimination Technique
Bibliographic record
Abstract
Background Previous work using agitated saline contrast echocardiography suggests anatomic intrapulmonary arteriovenous anastomoses (IPAVAs) can be recruited during exercise, in hypoxia and when cardiac output is increased pharmacologically. These observations are in contrast to the considerable work using the multiple inert gas elimination technique (MIGET) which has not found significant right‐to‐left intrapulmonary shunt at rest or during exercise. The purpose of the present study was to evaluate anatomical intra‐pulmonary arteriovenous connections using agitated saline contrast echocardiography and 25μm microspheres and compare to right to left gas exchange shunt quantified by MIGET in the dog. Methods Dogs were anaesthetized (I.V. propofol), ventilated (5 cm H 2 O PEEP) and evaluated during the following conditions: 1) Baseline, 2) 10 μg/kg/min I.V. dobutamine, 3) 2 μg/kg/min I.V. dopamine, 4) hypoxia (FIO 2 = 0.125). Within each condition, pulmonary mixed venous blood was obtained via a Swan‐Ganz catheter, and arterial blood via indwelling femoral catheter. Ventilation‐perfusion mismatch (V A /Q.), diffusion limitation and right‐to‐left shunt was quantified by MIGET and cardiac output by direct Fick. Presence of IPAVAs was evaluated by agitated saline contrast echocardiography, as well as contrast echocardiography using 25μm microspheres. Results At baseline, no animal demonstrated a positive contrast echocardiogram suggestive of IPAVAs, and calculated right‐to‐left shunt from MIGET was 0.3±0.1% of cardiac output. Across the three experimental conditions, saline contrast bubbles were detected in the left ventricle 83% of the time, while 25μm microspheres were detected in the left ventricle by echocardiography 67% of the time. No diffusion limitation or low V A /Q. regions (i.e. V. A /Q. ratio of 0.005–0.1) were detected at any point, and right‐to‐left shunt was below 1% during dobutamine, dopamine, and hypoxia (0.6±0.3%, 0.6±0.3%, 0.8±0.6%, respectively). Conclusion Anatomic arteriovenous anastomoses of approximately 25 μm in diameter can be recruited during hypoxia and pharmacologically in the healthy intact lung; however, their functional contribution to right‐to‐left shunt or gas exchange impairment is minimal. Support or Funding Information Natural Sciences and Engineering Council of Canada (NSERC)
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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 | 0.000 |
| 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".