PURPOSE: To compare airway pressure release ventilation (APRV) to conventional mechanical ventilation (CMV) with respect to oxygenation, true shunt, ventilation-perfusion (V/Q) matching, and lung density distributions in swine with acute respiratory distress syndrome (ARDS) due to smoke inhalation injury (SII).
METHODS: Anesthetized swine inhaled wood-bark smoke and were randomized to APRV (n=6) or CMV (n=8). Time controls (CTRL, n=6) were uninjured. Animals were ventilated for 48 hrs. Multiple inert gas elimination technique quantified blood flow (% cardiac output) to V/Q compartments, including true shunt (Qshunt) and normal (Qnormal) lung. Fractional volumes of abnormal lung (VOL) were calculated from CT scans as the sum of poorly and non-aerated lung. Statistical significance is p<0.05.
RESULTS: PaO2-to-FiO2 ratio (PFR) was lower in APRV than CMV at 24 hrs (126 vs 238) and not different at 48 hrs (120 vs 98). Qshunt was low (<1) before smoke, and higher in APRV than in CMV at 1 hr (16 vs 9) and 24 hrs (35 vs 12). Qnormal decreased as Qshunt increased and was lower in APRV than in CMV at 1 hr (80 vs 93). VOL was higher in both APRV and CMV than CTRL at all times after injury. Qshunt and VOL changed inversely with PFR, r2=0.44.
CONCLUSIONS: APRV did not demonstrate an advantage over CMV with respect to oxygenation, true shunt, V/Q matching, or lung aeration in early management of smoke inhalation injury in this model. All pathological changes were accelerated in the APRV group.
CLINICAL IMPLICATIONS: Further study is needed before APRV can be routinely advocated for early treatment of severe smoke inhalation injury.
DISCLOSURE: The following authors have nothing to disclose: Andriy Batchinsky, Kevin Chung, Bryan Jordan, Corina Necsoiu, Ruth Nguyen, Dara Regn, Samuell Burkett, Thomas Zanders, Michael Morris, Leopoldo Cancio
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