Distribution of aerated lung follows cephalocaudal and anteroposterior gradients

Distribution (expressed as a percentage) of aerated (open part of bars), poorly aerated (hatched part of bars), and nonaerated (closed part of bars) lung areas along the anteroposterior and the cephalocaudal axis. Each bar represents the lung parenchyma located at a given distance (in centimeters) from the anterior chest wall or from the pulmonary apex. Aerated lung decreases and nonaerated lung increases along the anteroposterior and cephalocaudal axis.