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Reduction in Edema Cuff Size is not the Mechanism of Lung Protection Afforded by Airway Pressure Release Ventilation (APRV)
Author(s) -
Jain Sumeet Vidya,
KollischSingule Michaela,
Roy Shreyas,
Pasquale Gabriella,
Sweeney Tara,
Satalin Josh,
Andrews Penny,
Habashi Nader,
Nieman Gary,
Gatto Louis A
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.981.1
Subject(s) - medicine , lumen (anatomy) , cuff , tunica media , adventitia , ards , edema , lung , anesthesia , surgery , pathology , carotid arteries
We have shown that preemptive application of APRV significantly reduces the incidence of acute respiratory distress syndrome (ARDS). The exact protective mechanism is currently not known. Objective To determine if the mechanism of this protection was a reduction in the size of pulmonary vascular edema cuffing. Methods 14 swine were randomized into three groups: naïve (n=5), non‐protective ventilation (NPV; n=5), and airway pressure release ventilation (APRV; n=4). Naïve pigs did not receive lung injury. A fecal clot and gut ischemia/reperfusion‐induced ARDS model was used in both the NPV and APRV groups. Following injury, both groups were managed on their respective ventilator settings and sacrificed after 48 hours. Lung tissue was fixed and histology examined at 10× and 40× magnification. Lumen, tunica media, tunica adventitia, and lymphatics were identified, outlined, colored, and then quantified ( Figure). The following parameters were further evaluated for each vessel: lumen area, lumen roundness, tunica media area, tunica adventitia area, and lymphatic area. Clinical parameters and histologic lung injury scoring were analyzed. Results Vessel lumen roundness and tunica media area did not vary between groups (p>0.05). Lumen area was smaller in the injury groups (NPV/APRV) than in the naïve animals (p<0.05). The perivascular cuff, i.e. tunica adventitia and lymphatic vessels, was larger in the injured animals compared with naïve (p<0.05), without difference between ventilatory strategy. The tunica adventitia occupied a larger percent of total vessel area in the injured animals; however, lymphatics did not occupy a larger percent of the cuff compared with naïve, correlating instead with vessel size. Naïve pigs had lower wet/dry ratio compared with NPV pigs (5.47 vs. 8.82; p<0.05) without difference between Naïve and APRV groups (5.47 vs. 7.11, p>0.05) or APRV and NPV groups (7.11 vs 8.82; p>0.05). PaO 2 /FiO 2 ratio was higher in the APRV vs. NPV group (p<0.05), and histologic scoring showed decreased lung injury. Conclusion Despite increased lung protection using APRV, there was no difference in edema cuff size. Therefore, changes in edema cuff size do not contribute to APRV‐induced lung protection.