The damage caused by the introduction of acid into the pulmonary parenchyma is repaired rapidly.
The depth of the necrosis determines which elements will participate in the repair. If epithelium alone is injured, epithelium alone takes part in the repair. When the damage involves the deeper tissue, organization by granulation competes with and impedes the development of the epithelium.
An overproduction of the epithelium occurs and may form bronchiolar polypi or extend into the peribronchial tissue.