Pneumonia ranks as the third most common postoperative infection behind urinary tract infection (UTI) and wound infection.

With hypercapnic respiratory failure, the most common cause of insufficient ventilatory drive is medication effect. Opioids are the most potent suppressor of both hypoxic and hypercapnic ventilatory drive, but other sedatives and hypnotics also cause respiratory depression.

Drive failure results when the patient’s ventilatory effort is insufficient and can be caused by drug overdoses, general anesthesia, central nervous system (CNS) disease, and obesity hypoventilation syndrome. The most common contributors in the perioperative setting are residual sedation from general anesthesia or the effects of opioid analgesics on respiratory drive and level of consciousness. Pump failure results when ventilatory demand exceeds the patient’s capability and can be caused by prolonged effect of neuromuscular blocking agents, underlying neuromuscular disorders, electrolyte abnormalities and metabolic disturbances, pleural disorders, chest wall abnormalities, and respiratory muscle fatigue.

Respiratory failure can be broadly categorized as hypoxemic respiratory failure (respiratory insufficiency) or hypercapnic respiratory failure (ventilatory failure), and the two forms may coexist

Acute respiratory failure is defined as the requirement for mechanical ventilation longer than 48 hours postoperatively or unplanned reintubation for cardiac or respiratory failure.

There is currently no role for methylxanthines or chest physical therapy (PT). NIV is the preferred method of ventilatory support and has been shown to improve outcomes in COPD exacerbations