The "last breath" of the ventilator-associated pneumonia surveillance definition*.

722 www.ccmjournal. org March 2014 • Volume 42 • Number 3 Bedside clinicians know better than anyone that diagnosing ventilator-associated pneumonia (VAP) can be devilishly difficult. Intensivists admitted to being less than 50% confident about more than 30% of patients they diagnose with VAP (1). Their uncertainty is well placed. Autopsy series affirm that clinical diagnostic criteria miss a third or more of true cases and wrongly suggest VAP in almost one half of all cases (2). Requiring microbiological confirmation does little to improve confidence. The sensitivity and positive predictive value of quantitative bronchoalveolar lavage cultures are only about 50% and 70%, respectively, relative to histology (3–7). As with clinical diagnoses, so too with surveillance designations. Infection preventionists are just as likely to get it wrong. In fact, infection preventionists may be more prone to error because they often rely on indirect evidence, such as radiographic reports rather than images, to make their determinations. The problem is further compounded by subjectivity. There are no official standards for concepts such as worsening oxygenation, increased secretions, or progressive infiltrates. Surveyors are instead left to their own discretion. Not surprisingly, reasonable practitioners often disagree (8, 9). In this issue of Critical Care Medicine, the article by Stevens et al (10) reminds us just how unreliable and variable VAP classifications can be. Stevens et al (10) developed six clinical vignettes describing possible cases of VAP. They distributed the vignettes to a nationally representative sample of infection preventionists and hospital epidemiologists and asked them to rate whether each patient has VAP or not. They found almost no agreement between survey respondents. Answers followed a near normal distribution suggesting near random variation in VAP assignments. Although it is possible that agreement may have been better if respondents had had access to the full medical charts or bedside evaluations rather than just vignettes alone, the findings by Stevens et al (10)are consistent with other published surveys using different methodologies (8, 9). These sobering results remind us yet again that VAP is a fundamentally unreliable outcome measure. This is true regardless of whether the application is benchmarking hospitals, determining remuneration, studying the impact of different prevention strategies, or evaluating the efficacy of new treatments. VAP is simply too subjective, inaccurate, and prone to bias to yield dependable answers in any of these spheres. Furthermore, the use of this VAP surveillance definition had led to the misinterpretation and misuse of pneumonia bundles of care (11). These results also remind us of why the Centers for Disease Control and Prevention (CDC) retired their longstanding clinical surveillance definitions for VAP and created ventilator-associated event (VAE) definitions instead (12). VAE definitions were designed to enhance objectivity and facilitate automated surveillance by eliminating subjective criteria (such as “worsening oxygenation” or “increased secretions”) and substituting quantitative alternatives instead (e.g., an increase in the daily minimum positive end-expiratory pressure [PEEP] of ≥ 3 cm H 2 O sustained for ≥ 2 d) (13). More broadly, the VAE framework was designed to overcome the limited accuracy of VAP definitions by shifting from diagnosis-specific surveillance to syndrome-based surveillance. Ventilator-associated conditions (VAC), the core concept within the VAE framework, can be thought of as a surveillance marker for the syndrome of nosocomial respiratory deteriorations. To get the most out of VAE surveillance, however, we have to appreciate its unique strengths and respect its limitations. First and foremost, VAC is not VAP. Pneumonia only accounts for a small fraction of VACs just as pneumonia only accounts for a small fraction of attributable mortality in ICUs (14). Acute respiratory distress syndrome, severe sepsis, pulmonary Copyright © 2013 by the Society of Critical Care Medicine and Lippincott Williams & Wilkins DOI: 10.1097/CCM.0000436119. 32758.69 *See also p. 497.