Online Letters to the Editor

What Is the Clinical Significance of National Health Safety Network Ventilator-Associated Pneumonia? To the Editor:

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n a recent issue of Critical Care Medicine, we read with great interest the article by Lilly et al (1), which investigated the prevalence and test characteristics of National Health Safety Network (NHSN) ventilator-associated event (VAE)/ventilator-associated condition (VAC). They found that this novel VAE/VAC surveillance only detect less than one third of ventilator-associated pneumonia (VAP), which was diagnosed by conventional methods (2). It is consistent with another recent prospective cohort study, including 2,080 patients with 2,296 admission, that found that VAE algorithm detect at most 32% of the patients with VAP identified by traditional surveillance (3). Based on this finding, the authors suggest that NHSN VAE/VAC only provide limited benefit to prevent the VAP-associated complications as most of the conventional VAPs were not detected by this novel surveillance paradigm. However, we have one serious concern about this conclusion. There was a huge disagreement between NHSN VAP and conventional VAP in the study by Lilly et al (1); however, it remains unclear which one is a true VAP. In fact, a total of 243 and 62 cases were identified as NHSN possible and probable VAP, respectively, in the present work. In contrast, only 83 cases were defined as VAP by conventional diagnostic methods from the same study population. Therefore, NHSN VAE surveillance detected much more VAP based on the novel algorithm than conventional method in this study. Before the impact of ventilator bundle for VAP prevention on NHSN VAP is confirmed, it seems that NHSN VAE surveillance find much more NHSN VAP cases, and the effect of NHSN VAE program for preventable mortality may not be less than conventional VAP-focus program. Therefore, it should suggest that further study is warranted to demonstrate the clinical impact of VAP prevention bundle on NHSN VAP. If it is effective, NHSN VAE surveillance may provide more benefit than conventional VAP program. If not, the conclusion by Lilly et al (1) is right. The authors have disclosed that they do not have any potential conflicts of interest. Hui-Ying Hsu, RN, Department of Critical Care Medicine, Tainan Municipal Hospital, Tainan, Taiwan; Shu-Chen Kung, RRT, Hui-Chun Chang, RRT, Section of Respiratory Therapy, Chi Mei Medical Center, Liouying, Tainan, Taiwan; Chien-Ming Chao, MD, Department of Intensive Care Medicine, Chi Mei Medical Center, Liouying, Tainan, Taiwan Copyright © 2014 by the Society of Critical Care Medicine and Lippincott Williams & Wilkins

Critical Care Medicine

REFERENCES

1. Lilly CM, Landry KE, Sood RN, et al; for the UMass Memorial Critical Care Operations Group: Prevalence and Test Characteristics of National Health Safety Network Ventilator-Associated Events. Crit Care Med 2014; 42:2019–2028 2. Horan TC, Andrus M, Dudeck MA: CDC/NHSN surveillance definition of health care-associated infection and criteria for specific types of infections in the acute care setting. Am J Infect Control 2008; 36:309–332 3. Klein Klouwenberg PM, van Mourik MS, Ong DS, et al; MARS Consortium: Electronic implementation of a novel surveillance paradigm for ventilator-associated events. Feasibility and validation. Am J Respir Crit Care Med 2014; 189:947–955 DOI: 10.1097/CCM.0000000000000529

The authors reply:

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n their correspondence, Hsu et al (1) correctly point out that although the prevalence of ventilator-associated pneumonia (VAP) and National Health Safety Network (NHSN) probable VAP were similar, the prevalence of NHSN probable VAP was much higher in our (2) and other study populations (3). Furthermore, they assert that knowing whether VAP or NHSN probable VAP rates are lower when nosocomial lower respiratory tract infection preventive measures are in place is helpful for assessing the utility of the new constructs for preventing nosocomial infections. We have previously reported (4) that the application of off-site monitoring and electronic detection tools to this population resulted in significantly improved rates of adherence to VAP preventive measures and reductions in rates of VAP rates to very low levels. These same measures were in place during the current study. Although these measures likely also reduced the rates of NHSN probable VAP, the application of measures that significantly reduced VAP rates was associated with rates of NHSN possible VAP that were four-fold higher than those of VAP. The ineffectiveness of measures that prevent infections is not surprising because most patients classified as having NHSN possible VAP did not have a nosocomial lower airway infection. We agree with Hsu et al (1) that clinical trials of preventive measures would generate new and interesting information. However, we respectfully point out that clinical trial data will not change the fact that most cases of NHSN probable VAP are not prevented by measures that significantly reduce VAP cases in clinical practice. The authors have disclosed that they do not have any potential conflicts of interest. Craig M. Lilly, MD, Departments of Medicine, Anesthesiology, and Surgery, University of Massachusetts, Worcester, MA; Rahul N. Sood, MD, Department of Medicine, UMass Memorial Medical Center, University of Massachusetts Medical School, Worcester, MA www.ccmjournal.org

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