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Anatomic Intrapulmonary Arteriovenous Anastomoses And Right‐To‐Left Shunt As Evaluated By The Multiple Inert Gas Elimination Technique
Author(s) -
Stickland Michael K,
Wagner Peter D,
Tedjasaputra Vincent,
Fuhr Desi P,
Collins Sophie E,
Wagner Harrieth,
Diepen Sean,
Byers Brad W,
Hopkins Susan R
Publication year - 2016
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.30.1_supplement.1230.8
Subject(s) - medicine , ventricle , shunt (medical) , perfusion , cardiac output , saline , dobutamine , right to left shunt , catheter , arterial catheter , cardiology , arterial blood , hemodynamics , anesthesia , radiology , patent foramen ovale , migraine
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)