Abstract
Nosocomial or hospital-acquired pneumonias are infections of the lung parenchyma occurring more than 48 hours after hospital admission and excluding infections incubating at the time of admission. Environmental sources (air, water, food, fomites), medical devices (endotracheal tubes, suction catheters, bronchoscopes, respiratory therapy equipment), other patients, and hospital staff can serve as vectors for nosocomial infection. Pneumonia is the most common nosocomial infection in the ICU and the second most common hospital-acquired infection. Occurrence ranges from 0.4% in unselected hospitalized patients to 23% in the ICU. The risk of ventilator-associated pneumonia (VAP; a subset of nosocomial pneumonia) is estimated to be 1% per day of mechanical ventilation. More than half of patients with ventilator-associated pneumonia die during the same hospitalization, although not all deaths are directly related to pneumonia. The attributable mortality (percentage of deaths that would not have occurred in the absence of infection) is lower. In a case-control study of 41 patients who developed nosocomial pneumonia, 44% of the deaths were attributed to infection. ICU patients with any nosocomial infection have 2.5 times the death rate of uninfected patients. Even after adjustment is made for confounding factors such as organ system dysfunction, APACHE II score and intensity of therapy, the mortality risk is at least doubled. Nosocomial infection has its greatest mortality impact in younger, less severely ill patients, where failure to accurately diagnose and treat infection plays a larger role than in elderly patients with multiple mortality risks. Nosocomial pneumonia also prolongs hospital stay by an average of 7-9 days, and increases hospital expenses.