noun. collapse of an expanded lung (especially in infants); also failure of pulmonary alveoli to expand at birth.
1. Noun, singular or mass These air sacs are responsible for exchanging oxygen and carbon dioxide with the bloodstream, and atelectasis can reduce the amount of oxygen that your blood can carry to your tissues. 2. Adverb This is called atelectasis 552920-6/pdf 'inline-reference::Chest: Deep-Breathing Exercises Reduce Atelectasis and Improve Pulmonary Function After Coronary Artery Bypass Surgery').