Figure 17-17
Pressure gradients across the airways. The airways consist
of a thin-walled intrathoracic portion (near the alveoli) and a more rigid (cartilaginous)
intrathoracic and extrathoracic portion. During expiration, the pressure from elastic
recoil is assumed to be +2 cm H2
O in normal lungs (A–D)
and +1 cm H2
O in abnormal lungs (E and
F). The total pressure inside the alveolus is pleural
pressure plus elastic recoil. The arrows indicate
the direction of airflow. EPP, equal pressure point. See the text for an explanation.
(Redrawn with modification from Benumof JL: Anesthesia for Thoracic Surgery,
2nd ed. Philadelphia, WB Saunders, 1995, Chapter 8.)
