Answer: The condition is called Atelectasis.
Explanation: Atelectasis is the complete or partial collapse or closure of a lung resulting in reduced or absent gas exchange. It is usually unilateral, affecting part or all of one lung.
Atelectasis is a condition where the alveoli have been deflated down to little or no volume, it is different from pulmonary consolidation, whereby the alveoli are filled with liquid.
Atelectasis will occur when an airway is blocked (obstructive) or when there is pressure from outside of the lung (nonobstructive).
General anesthesia is a common cause of atelectasis because it will usually change the regular pattern of breathing, and will affect the exchange of lung gases, which will then lead to the alveoli deflating.