Perioperative respiratory failure is usually caused by atelectasis Atelectasis Atelectasis is collapse of lung tissue with loss of volume. Patients may have dyspnea or respiratory failure if atelectasis is extensive. They may also develop pneumonia. Atelectasis is usually... read more 
(collapse of lung tissue with loss of volume). (See also Overview of Mechanical Ventilation Overview of Mechanical Ventilation Mechanical ventilation can be Noninvasive, involving various types of face masks Invasive, involving endotracheal intubation Selection and use of appropriate techniques require an understanding... read more .)
Effective means of preventing or treating atelectasis include
Incentive spirometry
Ensuring adequate analgesia for chest and abdominal incisions
Upright positioning
Early mobilization
Atelectasis caused by abdominal distention should be alleviated according to the cause (eg, nasogastric suction for excessive intraluminal air, paracentesis to evacuate tense ascites).
Hypoperfusion, regardless of cause, may result in respiratory failure through inadequate delivery of oxygen to respiratory muscles coupled with excess respiratory muscle load (eg, acidosis, sepsis). Mechanical ventilation is useful for diverting blood flow from overworked respiratory muscles to critical organs such as the brain, kidney, and gut.
