Which of the following concepts apply to zone I under positive pressure ventilation?
I.It constitutes shunt.
II.In healthy individuals zone I does not exist.
III.It constitutes alveolar dead space ventilation.
IV.Arterial pressures exceed alveolar pressures.

Question

Quizplus · Accepted Answer

In zone I alveoli are ventilated but have no blood flow, which constitutes alveolar dead space ventilation. In spontaneously breathing healthy individuals with normal cardiac outputs and blood pressures, arterial pressures always exceed alveolar pressures, even in the uppermost apical lung regions, and zone I does not exist. However, a severe decrease in blood pressure can lower PAP so much that zone I conditions are created in the lung.

Which of the Following Concepts Apply to Zone I Under