Incidence of postoperative pneumonia in various surgical subspecialties: a retrospective study.

Postoperative pneumonia (POP) can be defined as either hospital-acquired pneumonia (HAP, pneumonia developing 48-72 h after admission) or ventilator-associated pneumonia (VAP, pneumonia developing 48-72 h after endotracheal intubation)' or within 30 days in postoperative patients. POP accounts for 2.7-3.