Fig. 5.

Flow-volume curves in different situations. (A) Normal patient; (B) patient with COPD and dynamic hyperinflation and auto-PEEP and after bronchodilator treatment; (C) sudden interruption of exhalation flow representing an important gas leak from the patient (bronchopleural fistulae) or from the ventilator circuit; (D) a sawtooth pattern is observed in both inspiratory and expiratory limbs and indicates the presence of secretions in the airways.

(In: Cordioli, R and Brochard, L, Respiratory system compliance and resistance in the critically ill, Oxford Textbook of Critical Care, ISBN: 9780198855439.)