What does atelectasis mean in medical terminology?

Atelectasis means the collapse or incomplete expansion of lung tissue, resulting in reduced gas exchange. The term breaks into atel meaning incomplete and ectasis meaning expansion or stretching. It commonly occurs after surgery when patients breathe shallowly due to pain, allowing sections of lung to collapse. Other causes include airway obstruction by mucus plugs or tumors, pleural effusion compressing the lung, and prolonged bed rest. Incentive spirometry, deep breathing exercises, and early ambulation after surgery prevent atelectasis.