Chapter 72: Clinical Controversies: Ventilator-Associated Pneumonia: Does It Exist?

CLINICAL CONTROVERSIES: VAP: DOES VAP EXIST?

In the United States, ventilator-associated pneumonia (VAP) is the most commonly diagnosed hospital-acquired infection in intensive care units (ICUs), affecting upward of 20% of ventilated patients with varyingly estimated attributable mortality ranging from 10% to 55%.¹ Acquisition of VAP is responsible for prolonged ICU and hospital length of stay (LOS), increased hospital costs, and increased utilization of antibiotics. In a post hoc retrospective-matched cohort analysis of microbiologically confirmed cases of VAP in the North American Silver-Coated Endotracheal Tube study, the authors calculate median total charges for patients with VAP were almost $200,000 compared to under $100,000 for patients without VAP. This was accounted for by the patients requiring intubation up to 5 days longer and as a consequence, significantly prolonging their ICU and hospital stays by 11 and 13 days, respectively.² A subsequent large, retrospective study comparing 2144 patients who had VAP as determined by International Classification of Diseases, Ninth Revision code to a matched cohort of patients without VAP showed similar findings. The patients with VAP had longer mean durations of mechanical ventilation (21.8 vs 10.3 days), prolonged ICU and hospital LOS (20.5 vs 11.6 and 32.6 vs 19.5, respectively), and an increase in hospital costs of almost $40,000.³ The high attributable mortality and costs associated with VAP have garnered much attention from national patient safety organizations as well as state and federal health agencies, mandating compliance with preventive measures and reporting metrics.

However, to begin any discussion about VAP, one must first consider by which criteria VAP is defined. Until recently, there was significant discrepancy between medical professional society’s definition of VAP and the Centers for Disease Control (CDC)/National Healthcare Safety Network’s reportable surveillance definition (Table 72–1). Crucial differences in timing of the onset of pneumonia in a mechanically ventilated patient and whether microbiologic criteria were necessary for diagnosis left these competing criteria at odds. As clinical and reporting definitions of VAP diverged, our ability to reliably estimate rates, costs, and impact of VAP diminished. This is demonstrated in a study by Klompas, where 3 infection control personnel (following the CDC surveillance definition) and 1 physician (used clinical judgment), independently reviewed 50 cases and were only able to agree on a diagnosis of VAP in 3 patients while the range of cases identified varied from 7 to 20 depending on the reviewer.⁴ In response to widespread confusion and concern over the discrepancy leading to misleading VAP rates and unclear VAP-associated mortality, the CDC altered its definition to include solely objective data for diagnosis and limited the diagnosis to onset after a minimum of 48 hours of ventilation with stable ventilator settings. This led to an entirely new classification of reportable ventilator-associated events (VAEs): ventilator-associated condition (VAC), infection-related ventilator-associated complication (iVAC), and finally possible VAP and probable VAP.⁵ Some would argue, however, that these new diagnoses, VAE, VAC, iVAC, and their criteria have yet to be ...