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Chapter 2 – Intensive care: mechanical ventilation and HFPV
release ventilation (IMPRV): like SIMV, the mandatory breaths can be synchronized to the
patient’s inspiratory effort.
2.2.7 Pressure-Controlled Ventilation (PCV)
In PCV, the physician only indirectly controls the tidal volume. A certain pressure limit is
set. During a ventilator delivered inspiration, as air is driven into the lungs, airway pressure
rises, rapidly reaching the preset pressure control level. This pressure is maintained for the
duration of inspiration (Fig. 2.5). The pressure limit, the respiratory frequency, and the
inspiratory time are physician-preset. Within a given inspiratory time, a higher set pressure
limit will allow greater filling of the lungs: more air can enter the lungs before the airflow
begins to slow, and so the tidal volumes are larger. Thus in a given patient with stable lung
mechanics, the tidal volume increases if the upper pressure limit has been set high and
decreases if it has been set at a low level.
Figure 2.5 Pressure Controlled Ventilation (PCV).
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