Intravascular volume loading reversibly decreases airway cross-sectional area.

High-resolution computed tomography was used to directly determine the short-term effects of intravascular volume expansion on airway caliber. The change in airway cross-sectional area caused by intravascular volume expansion (30 ml/kg, Ringer's lactate) was studied in six anesthetized mini-pigs within 5 min. Twenty-five of 27 large airways (diameter, 2.01 to 5.0 mm) demonstrated decreased internal cross-sectional area (10.56 +/- 1.26 vs 8.66 +/- 1.03 mm2, p < 0.001). Twenty of 24 small airways (diameter, 0.75 to 2.0 mm) showed decreased internal cross-sectional area (1.82 +/- 0.16 vs 1.44 +/- 0.16 mm2, p < 0.001). These changes were rapidly (< 6 min) reversed by intravascular volume reduction. The external airway cross-sectional area did not change. These data suggest rapid, reversible bronchial mucosal vascular engorgement as a cause of increased airway resistance in heart failure.