Demonstration of intersegmental respiratory bronchioles in normal human lungs

Intercommunications between small airways of adjacent bronchopulmonary segments were studied morphologically in six normal human lungs. Following fixation 3 mm-wide catheters were wedged through the segmental bronchi and corrosion casts were made using different colours of a cold-curing resin (Technovit). The lung tissue was corroded away with concentrated hydrochloric acid and the intersegmental area studied. The resin had crossed from one segment to another in most casts especially in the lower lobe, and in some the junctions between different colours were apparent in small airways with a diameter of 80 to 150 micrometers. These airways had a few alveolar openings in their walls and presumably are intersegmental respiratory bronchioles. This study suggests free communication between small airways of neighbouring segments. It further suggests that collateral ventilation might be of importance even in normal lungs.