Relationship between airway microvascular leakage, edema, and baseline airway functions

Matheson, Melissa, Ann-Christine Rynell, Melissa McClean,and Norbert Berend. Relationship between airway microvascular leakage, edema, and baseline airway functions. J. Appl. Physiol. 84(1): 77-81, 1998.This study wasdesigned to examine the relationship among microvascular leakage,edema, and baseline airway function. Microvascular leakage was inducedin the airways of anesthetized, tracheostomized New Zealand Whiterabbits (n = 22) by using nebulized N-formyl-methionyl-leucyl-phenylalanine(10 mg) and was measured in the trachea by using the Evans blue dyetechnique. Airway wall thickness was assessed morphometrically in theright main bronchus after Formalin fixation at a pressure of 25 cmH₂O. Areas calculated includedthe mucosal wall area, the adventitial wall area, the total wall area,and the percentage of total wall area consisting of blood vessels. Aneutrophil count was also performed by analyzing numbers of cells inboth the mucosal wall area and the adventitial wall area. Airwayfunction was assessed before and 30 min after challenge withN-formyl-methionyl-leucyl-phenylalanineby determining airway resistance, functional residual capacity,specific airway resistance, and flow-volume and pressure-volume curves(after paralysis of the animals with suxamethonium). The concentration of Evans blue dye in tracheal tissue ranged from 31.3 to 131.2 µg.There was a significant correlation between this concentration and boththe adventitial wall area (P < 0.01)and mucosal neutrophil numbers (P < 0.005). There was no correlation between Evans blue concentration andeither blood vessel area or changes in respiratory physiologyparameters before and after challenge. There was no significantdifference between any respiratory physiology measurements before andafter challenge. We conclude that an increase in microvascular leakagecorrelates with airway edema in the adventitia; however, these airwaychanges have no significant effect on airway elastic or resistiveproperties.