Effect of dynamic intrathoracic airway obstruction

(A) During forced expiration, the intrathoracic intratracheal pressure (P_tr) is less than the pleural pressure (P_pl), worsening the obstruction.

(B) During forced inspiration, P_tr exceeds P_pl, lessening the degree of obstruction.

Redrawn from: Kryger M, Bode F, Antic R, et al. Am J Med 1976; 61:85.

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