A recent review article summarizing the available published evidence on the association between atelectasis and post-op fever concluded that there is no clinical evidence supporting this speculation. Causes
The most common cause is post-surgical atelectasis, characterized by splinting, i.e. restricted breathing after abdominal surgery. Atelectasis develops in 75–90% of people undergoing general anesthesia for a surgical procedure.Another common cause is pulmonary tuberculosis. Smokers and the elderly are also at an increased risk. Outside of this context, atelectasis implies some blockage of a bronchiole or bronchus, which can be within the airway (foreign body, mucus plug), from the wall (tumor, usually squamous cell carcinoma) or compressing from the outside (tumor, lymph node, tubercle). Another cause is poor surfactant spreading during inspiration, causing the surface tension to be at its highest which tends to collapse smaller alveoli. Atelectasis may also occur during suction, as along with sputum, air is withdrawn from the lungs. There are several types of atelectasis according to their underlying mechanisms or the distribution of alveolar collapse; resorption, compression, microatelectasis and contraction atelectasis. Relaxation atelectasis (also called passive atelectasis) is when a pleural effusion or a pneumothorax disrupts the contact between the parietal and visceral pleurae.Risk factors associated with increased likelihood of the development of atelectasis include: type of surgery (thoracic, cardiopulmonary surgeries), use of muscle relaxation, obesity, high oxygen, the lower lung segments. Factors also associated with the development of atelectasis include: age, presence of chronic obstructive pulmonary disease or asthma, and type of anesthetic.
Antibiotics are given for an infection. Chronic atelectasis is often treated with antibiotics because infection is almost inevitable. In certain cases, the affected part of the lung may be surgically removed when recurring or chronic infections become disabling or bleeding is significant. If a tumor is blocking the airway, relieving the obstruction by surgery, radiation therapy, chemotherapy, or laser therapy may prevent atelectasis from progressing and recurrent obstructive pneumonia from developing. See also
Alveolar capillary dysplasia, a very rare type of diffuse congenital disorder of the lung
Flat-chested kitten syndrome or FCKS: atelectasis in neo-natal kittens
Tympanic membrane atelectasis: Retraction of the ear drum into the middle ear can also be referred to as atelectasis. William Pasteur, pioneer pulmonologist

References
External links

04-048a. at Merck Manual of Diagnosis and Therapy Home Edition
Atelectasis at Merck Manual of Diagnosis and Therapy Professional Edition