Atelectasis Atelectasis is the medical term for collapse of areas of the alveoli in the lungs.  In simple terms, areas of lung normally involved with the exchange of air collapse and no longer function (this is not the same as a Collapsed Lung, which is called a Pneumothorax). Atelectasis may occur because part of the airway above the atelectasis becomes obstructed (for example, from a lung tumor), or from simple disuse (often after surgery, patients tend not to breathe as deeply, and part of the airways collapses).  It may also occur in small areas of the lung for unknown reasons.  The only symptom is usually shortness of breath, and diagnosis can be made by chest X-ray. Post-operative (after surgery) -- an incentive spirometer is a device used to "exercise" the lungs in order to keep airways open. Bronchodilator therapy given as an aerosol may help in some cases. Treat the underlying cause, such as a Pneumonia or tumor.