Respiratory bronchioles as the pathway for collateral ventilation.

Abstract

Left upper lobes from the dog were subjected to 3 different procedures to study the pathways for collateral ventilation. The 1st procedure involved measuring the pressure required to initiate collateral ventilation in a completely collapsed lobe. In the 2nd procedure, polystyrene spheres between 60 and 7[mu] in diameter were passed through the lobe and an estimate made of the size of the largest to pass through. Finally, in a 3rd lobe aerosolized India ink was deposited along the pathways of flow which later served to outline them for identification in histological sections. The pressure required to start collateral ventilation in 6 collapsed lobes varied from 17 to 28 cm of water. Polystyrene spheres as large as 120 u were able to pass through to the outflow side of the lobe. Serial sections from the aerosolized material indicated respiratory bronchioles connecting terminal bronchioles from adjacent lung segments. The data thus obtained from 3 experimental procedures indicate that collateral respiration occurred through respiratory bronchioles but not through smaller pathways such as the alveolar pores of Kohn.