What types of atelectasis may occur?
Atelectasis can be passive, compressive, resorptive, cicatricial, or discoid.
Passive atelectasis occurs when the lung is allowed to retract (e.g., due to presence of a pneumothorax).
Compressive atelectasis results from extrinsic compression of the lung by a space occupying process (e.g., a bulla or lung mass).
Resorptive (or obstructive) atelectasis occurs due to airway obstruction (e.g., from mucus plugging or endobronchial tumor) that results in peripheral alveolar gas resorption.
Cicatricial atelectasis results from lung fibrosis (e.g., from prior mycobacterial infection or radiation therapy).
Discoid (or platelike) atelectasis is a form of adhesive atelectasis due to hypoventilation, and it has a bandlike or linear configuration, most often seen in the lung bases.