maintenance of a desired Paco , such as with an acute
ramp. A descending ramp flow pattern produces a longer
overdistention in the lungs. Also, because the inspiratory flow is fixed, VCV can cause patient–ventilator asynchrony, particularly if the inspiratory flow is set too low. With VCV, the set flow can be constant or a descending
(Figure 22–6), the airway pressure is set and remains constant despite changes in resistance and compliance. Box 22–5 lists factors that affect the tidal volume with PCV. The principal advantage of PCV is that it prevents
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FIGURE 22–31 Auto-PEEP. Note the amount of effort required to trigger the ventilator, represented by the amount of decrease in esophageal pressure required for triggering. Also note the presence of an inspiratory effort that does not trigger the ventilator.