Figure 5
From: Clinical review: Patient-ventilator interaction in chronic obstructive pulmonary disease
Airway and flow-time tracings illustrating the concept of delayed cycling. (a) Normal mechanics. The expiratory trigger (ET) setting is 0.25. Cycling is ideal, that is, the inspiratory flow (V') decreases to the 0.25 cycling level at the end of the patient's neural inspiration (tin). (b) Obstructive mechanics. The change in inspiratory flow curve derived from Figure 3 leads to the 0.25 level being reached later, well after the end of tin. The magnitude of delayed cycling (tiexcess) is illustrated by the double arrow. Increasing the level of ET to 0.6 of peak inspiratory flow corrects this problem, and cycling occurs once more at the end of tin. Exp., expiration; Insp., inspiration; V'peak, peak inspiratory flow.