The Annals of Thoracic Surgery, Vol 32, 235-243, Copyright © 1981 by The Society of Thoracic Surgeons
Mechanical and cellular bacterial clearance in lung atelectasis
DC Drinkwater Jr, C Wittnich, DS Mulder, GK Richards and RC Chiu
A pig model with aerosolized pneumococcal bacteria was used to establish
that bacterial clearance in a collapsed lung in the perioperative period
was decreased compared with the opposite, aerated lung. Cannulation of the
right lymphatic duct revealed a significant increase in both lymph flow and
ratio of lymph to plasma protein, indicating the development of a
high-permeability edema in the collapsed, infected lung. Only 22% of the
efferent lymph and blood was positive for the infecting organism.
Examination of the T cells obtained by bronchopulmonary lavage showed an
initial fall in the numbers of alveolar macrophages at 6 hours after
collapse and infection, relative to the opposite, control lung. However, at
24 hours, the collapsed lung had replenished its alveolar macrophage
population to such a degree that it was greater than the control. Electron
microscopy revealed that the macrophages in the collapsed lung were more
activated with increased lysosomal and pseudopodial activity. The in vitro
chemotactic function of the macrophages appeared depressed, but
phagocytosis and intracellular bactericidal activity were increased in the
atelectatic lung. We conclude that there is a decreased bacterial clearance
capacity in atelectasis. This finding indicates that impaired mucociliary
clearance plays the dominant role in susceptibility to infection.
