Q: In Tension pneumothorax, atelectasis, pulmonary edema, and pneumonia (Choose one)

A) Both static and dynamic compliance fall

B) Only dynamic compliance fall

C) Only static compliance fall

D) Both static and dynamic compliance remain unchanged

Answer is A

Formulae for compliances are as follows

Static compliance is based on plateau pressure (no air is flowing)

Cstat = Vt/(Pplat - PEEP)

Dynamic compliance is based on peak pressure (air is flowing)

Cdyn = Vt/(Ppeak - PEEP)

In tension pneumothorax, atelectasis, pulmonary edema, and pneumonia both peak and plateau pressures rise and so cause both compliances to fall.