Abstract & Commentary
Ventilator-Associated Events (VAE): An Attempt to Step Out of the Mire
By Richard H. Kallet, MS, RRT, FAARC, FCCM
Director of Quality Assurance, Respiratory Care Services, San Francisco General Hospital
Mr. Kallet reports no financial relationships relevant to this field of study.
SYNOPSIS: Hospital-based infection surveillance experts nationwide participated in a survey to access the level of agreement in diagnosing ventilator-associated pneumonia by evaluating six identical case studies. The level of agreement between participants was poor.SOURCE:
The objective of this study was to confirm or disconfirm the perception that subjectivity in the National Health Safety Network’s (NHSN) surveillance definition for ventilator-associated pneumonia (VAP) has rendered such data meaningless and unsuitable for use as a quality measure of hospital performance. Investigators constructed six hypothetical cases and asked participants to judge the likely presence of VAP. Forty-three infection specialists representing a cross-section of U.S. hospitals participated. Most participants were either directors of infection control (23%) or infection preventionists (66%). Virtually all (98%) participants used the NHSN surveillance definition for VAP.
Overall, there was poor agreement among participants, with a Fleiss K score of 0.13 (K scores < 0.40 represent poor agreement, and values < 0 signify no agreement). Even in the two vignettes intended to represent "VAP" and "Not-VAP" unambiguously, the K score was only 0.25. Neither the educational background nor job position was associated with the respondents’ judgments. However, the frequency of VAP determination was significantly lower among respondents who worked in suburban hospitals (31%) compared to those working in an urban (42%) or rural (67%) setting. It appeared that the interpretation of chest radiographs was a particularly important factor in the participants’ determinations.
Concluding that a patient has VAP has always been problematic because a gold standard for diagnosis does not exist. Clinical criteria used to diagnose VAP are based on nonspecific signs common to many other conditions, and some of them are highly subjective. Approximately 60% of clinically diagnosed VAP cases cannot be confirmed by microbiologic cultures.1
When surveillance data for VAP are compared, the incidence in Europe (using virtually the same preventive measures) is five times higher than that in the United States.2 The lower U.S. surveillance rates are widely suspected to be driven by public reporting requirements of infectious complications during hospitalization. Public reporting reflects growing socioeconomic pressures to reign in health care costs, which also entails shifting financial incentives to reward "performance" and punish "preventable complications." Recently, Medicare and Medicaid have considered not reimbursing care related to VAP, while the Joint Commission has contemplated incorporating VAP rates as a factor in rating and accreditation.
Unsurprisingly, more than 50% of non-academic medical ICUs now report VAP rates of zero. This has been widely attributed to the adoption of the "ventilator bundle." Such extraordinarily low VAP rates have been met with pervasive skepticism and insinuations that hospitals are "gaming the system." Understandably, there is enormous pressure on infection surveillance experts to interpret clinical evidence as conservatively as possible. Likewise, government bureaucrats and hospital administrators (with different motivations) may harbor unrealistic expectations on the effectiveness to the VAP bundle.
The VAP bundle represents a credible strategy to reduce modifiable risk factors. Its components are simple, add little if any cost, and are easy to implement. However, the belief that these bundles can achieve a zero VAP rate is highly improbable. Even the most compelling components have limited efficacy in randomized clinical trials (e.g., chlorhexidine reduces VAP by an average of 40%, and the optional use of subglottic drainage tubes reduces VAP by 50%). In the seminal observational study, 95% adherence to the bundle was needed to achieve a 59% decrease in VAP rate.3
In contrast, there are considerable, non-modifiable factors that increase the propensity for developing VAP (e.g., trauma, neurologic injury, chronic disease) by a factor of 3- to 10-fold. Therefore, hospitals treating primarily high-risk patients could conceivably be exposed to considerable economic liability. It is also not believable that prevention measures, no matter how well executed, could eliminate VAP in these high-risk patient populations.
The study by Stevens and colleagues demonstrates the unsuitability of current VAP surveillance data for benchmarking hospital performance. By comparison, the new surveillance model of ventilator-associated events (VAE)4 that will be used in the future for public reporting and benchmarking is objective and less prone to manipulation. VAE will bring its own set of problems. But, if evaluating quality of care more objectively brings us closer to extricating ourselves from the current mire, it will be welcomed.
1. Chastre J, Fagon JY. Ventilator-associated pneumonia. Am J Respir Crit Care Med 2002;165: 867-903.
2. Klompas M. What can we learn from international ventilator-associated pneumonia rates? Crit Care Med 2012;40:3303-3304.
3. Resar R, et al. Using a bundle approach to improve ventilator care processes and reduce ventilator-associated pneumonia. Jt Comm J Qual Patient Saf 2005;31:243-248.
4. Magill SS, et al. Developing a new, national approach to surveillance for ventilator-associated events: Executive summary. Respir Care 2013;58:1985-1989.Stevens JP, et al. When policy gets it right: Variability in U.S. hospitals’ diagnosis of ventilator-associated pneumonia. Crit Care Med 2014; 42:497-503.