Abstract
BackgroundSevere hypoperfusion can cause lung damage. We studied the effects of regional perfusion block in normal lungs and in the lungs that had been conditioned by lavage with 500 ml saline and high VT (20 ml kg−1) ventilation.MethodsNineteen pigs (61.2 ± 2.5 kg) were randomized to five groups: controls (n = 3), the right lower lobe block alone (n = 3), lavage and high VT (n = 4), lung lavage, and high VT plus perfusion block of the right (n = 5) or left (n = 4) lower lobe. Gas exchange, respiratory mechanics, and hemodynamics were measured hourly. After an 8-h observation period, CT scans were obtained at 0 and 15 cmH2O airway pressure.ResultsPerfusion block did not damage healthy lungs. In conditioned lungs, the left perfusion block caused more edema in the contralateral lung (777 ± 62 g right lung vs 484 ± 204 g left; p < 0.05) than the right perfusion block did (581 ± 103 g right lung vs 484 ± 204 g left; p n.s.). The gas/tissue ratio, however, was similar (0.5 ± 0.3 and 0.8 ± 0.5; p n.s.). The lobes with perfusion block were not affected (gas/tissue ratio right 1.6 ± 0.9; left 1.7 ± 0.5, respectively). Pulmonary artery pressure, PaO2/FiO2, dead space, and lung mechanics were more markedly affected in animals with left perfusion block, while the gas/tissue ratios were similar in the non-occluded lobes.ConclusionsThe right and left perfusion blocks caused the same “intensity” of edema in conditioned lungs. The total amount of edema in the two lungs differed because of differences in lung size. If capillary permeability is altered, increased blood flow may induce or increase edema.
Highlights
We established a model of the lower lobe perfusion block, and in the second, we investigated whether the pathological changes in the non-perfused lobe could be prevented by ventilation with a CO2-enriched gas mixture
The branch of the pulmonary artery supplying the lower lobe of the left or right lung was selectively occluded with a 6F AMPLATZER occluder device, introduced by Seldinger technique and confirmed by angiography. (Additional file 2: Movie S1 and Additional file 3: Movie S2)
Venous admixture did not change during the experiment, which suggests that the flow diverted from the non-perfused to the perfused lung tissue was accompanied by a similar increase in ventilation, resulting in an unchanged ventilation/perfusion (V/Q)
Summary
Ligation of the left pulmonary artery and the left main bronchus led to massive hemorrhagic lung injury, shock, and death [2]. This effect was attenuated when the lung was ventilated with a gas mixture containing 5% CO2 [3, 4]. We added two moderate insults to the model to render the lung more susceptible perfusion block effects. These were lung lavage with 500 ml saline and ventilation with a tidal volume of 20 ml kg−1
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