UWOMJ Volume 18 No 4 November 1948

Page 1

MEDICAL JOURNAL University of Western Ontario November, 1948

Vol. 18

No.4

THE SIGNIFICANCE OF PULMONARY ATELECTASIS By F.

s.

KENNEDY,

M.D.

normal respiratory function of the lung is dependep.t upon an T HEuninterrupted airway from the larynx to the pulmonary air sac. Interruption of this airway produces abnormal physiologic and pathologic changes in the portion of the lung distal to the interruption, the magnitude of which varies from minor changes to major respiratory dysfunction occasionally resulting in sudden death. In the latter instance where the airway is obstructed above the bifurcation we are in the habit of applying the term asphyxia. However, when the obstruction occurs below the bifurcation of the trachea the term commonly applied to the process distal to the obstruction is atelectasis, obstructive atelectasis or absorption collapse, the latter term being preferred by Robert Coope of the Liverpool Royal Infirmary. Certain physiologic and pathologic changes occur in the portion of the lung and bronchial tree involved in the atelectatic process. The resulting degree of systemic effect produced is in direct proportion to the area of lung involved, the rate of occurrence and degree of obstruction and the presence of infection in the involved area as well as the effect that the obstructing agent may produce. Complete obstruction of a bronchus results in a reduction of the vital capacity of that lung immediately. The air in the pulmonary ~lveoli distal to the obstruction is absorbed by the pulmonary capillaries and the affected segment of the lung becomes atelectatic either rapidly or slowly depending on the presence of collateral aeration through the alvolar pores. The segment of lung becomes very much smaller than normal, reducing the volume of the lung within the unyielding chest wall and creating a potential vacuum. The normal intrapleural negative chest pressure of minus 5 to 8 em. of water may be increased to as high as minus 40 em. of water. The movable parts of the chest compensate for this lowered volume, the mediastinum shifting to the affected side, the diaphragm moving upward and the intercostal spaces of the affected 151


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