Bronchovascular cuff formation and lung lymph flow in edema formation of anesthetized sheep

The relationship between bronchovascular cuff formation and lung lymph flow in hydrostatic edema was evaluated. After a balloon was inserted into the left atrium to increase left atrial pressure for 5 hrs, peripheral lung tissues were resected for analysis of the wet-dry ratio and cuff formation. The degree of cuff formation was expressed as the cuff ratio (outer diameter of cuff/outer diameter of microvessel or airway) in three size categories: 80-200, 200-400, and 400-750 microm in diameter. The amount of excess lung lymph (Ex LL) for 5 hrs was calculated from the recorded data for the whole lymph flow wave. The wet-dry ratio showed a significant correlation with ALAP and lung lymph flow increased significantly (flow rate, 0.67 +/- 0.46 ml/min (mean +/- SD); Ex LL, 56.4 +/- 47.6 ml). Cuff formation was found at all levels of the bronchovascular tree, with a larger cuff ratio (> 1.3) observed at arteries and veins of 80-200 microm in diameter, but a significant correlation with Ex LL was found only for arteries of 80-200 microm. Fluid accumulation in lung interstitium first occurred at smaller extra-alveolar arteries even under mild hydrostatic pressure elevation with a significant increase in lymph flow.