GOAL

The goal of this Clinical Practice Guideline (CPG) is to provide guidance for the diagnosis, treatment, prevention, and mitigation of Ventilator Associated Pneumonia (VAP). These guidelines are not intended solely for clinical care, but also to help unit commanders and supporting medical components to consider the unique challenges of the management of a common healthcare associated infection in both traditional and expeditionary settings.

BACKGROUND

VAP is a common healthcare-associated infection (HAI), but what defines VAP and how it is diagnosed have remained moving targets. Due to wide variations in the surveillance and diagnosis of VAP, the true rate of VAP is unknown, but it is believed to occur in at least 5-15% of patients placed on a ventilator.1-2

While much of combat casualty care in the intensive care unit setting is largely similar to the care of trauma patients in civilian centers, there are several challenges unique to expeditionary care, chief among them being microbiological variabilities. Military operations in Iraq and Afghanistan are notable for a high number of multi-drug resistant (MDR) bacterial infections in combat casualties, particularly Acinetobacter calcoaceticus-baumannii complex (ABC).3

Several benchmark studies, along with other data, implicate nosocomial transmission as the major contributing source of these infections.4-6  An outbreak of multi-drug resistant Acinetobacter baumannii-calcoaceticus complex infections in the U.S. military health-care system associated with military operations in Iraq described cluster outbreak strains of ABC within the military healthcare system suggesting that, at least in the case of ABC, the bacteria has spread from field hospitals in Iraq to those within the continental U.S.7  Additionally, bacteria identical to those found in clinical isolates have been cultured from numerous environmental surfaces from U.S. medical treatment facilities within Iraq.  These experiences have been replicated in more recent times with similar results, indicating that this issue is endemic and not related to individuals or groups of service members.

DIAGNOSIS

The diagnosis of VAP is difficult and varies across institutions. American Thoracic Society and Infectious Disease Society of America guidelines define VAP as a “new lung infiltrate plus clinical evidence that the infiltrate is of an infectious origin, which include the new onset of fever, purulent sputum, leukocytosis, and decline in oxygenation” which develops >48 hours after endotracheal intubation.8

Determination of whether a pulmonary abnormality is of infectious origin is particularly challenging, especially in trauma patients. Blast injury and penetrating chest injury patients are highly likely to have injury-related chest radiography findings that may obscure or mimic infections.

Patients on mechanical ventilation are at risk for a variety of serious complications in addition to VAP, including acute respiratory distress syndrome, pneumothorax, pulmonary embolism, lobar atelectasis, and pulmonary edema. The Centers for Disease Control have large scale, ongoing quality projects designed to validate and streamline surveillance measures, though these have yet to be validated for a priori diagnosis of various ventilator associated conditions.  Despite the changing language surrounding ventilator associated conditions, the strongest and most consistent evidence continues to support daily sedation interruptions and spontaneous breathing trials for aggressive liberation from mechanical ventilation as the factors most likely to reduce all ventilator associated conditions.9