In which of the following situations is pressure-controlled ventilation sometimes used?

1. When a precise PaCO2 has to be maintained (some closed-head injuries)
2. When more even distribution of ventilation is required
3. When ventilating patients with severe, refractory hypoxemia
4. When tidal volume in unstable due to leaks
a. 1 and 2 only
b. 3 and 4 only
c. 1, 2, and 3 only
d. 1, 3, and 4 only

ANS: B
Pressure-controlled continuous mandatory ventilation is indicated when adequate oxygenation has been difficult to achieve in other modes of ventilation. The instability of tidal volume caused by airway leaks can be minimized by using pressure-controlled ventilation rather than vol-ume-controlled ventilation.