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Managing Ventilator Complications in a “VACuum” of DataA “VACuum” of Data to Guide Us FREE TO VIEW

Michael S. Niederman, MD, FCCP; Girish B. Nair, MD
Author and Funding Information

From the Department of Medicine, Winthrop-University Hospital, SUNY at Stony Brook.

CORRESPONDENCE TO: Michael S. Niederman, MD, FCCP, Department of Medicine, Winthrop-University Hospital, SUNY at Stony Brook, 222 Station Plaza N, Ste 509, Mineola, NY 11501; e-mail: mniederman@winthrop.org


FINANCIAL/NONFINANCIAL DISCLOSURES: The authors have reported to CHEST that no potential conflicts of interest exist with any companies/organizations whose products or services may be discussed in this article.

Reproduction of this article is prohibited without written permission from the American College of Chest Physicians. See online for more details.


Chest. 2015;147(1):5-6. doi:10.1378/chest.14-1496
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Ventilator-associated pneumonia (VAP) has been a major complication of mechanical ventilation that in years past has led to excess morbidity and mortality and has led to vigorous efforts at prevention. In the past decade, we have seen a dramatic decline in the reported frequency of VAP in the United States, with the advent of the “ventilator bundle” and with a belief that this simple, multimodality intervention could result in “zero VAP,” making pneumonia in patients on mechanical ventilation a potentially nonreimbursable medical error. However, a number of investigators have pointed out that the concept of zero VAP is biologically implausible and is the result of the manipulation of an imperfect clinical definition of pneumonia.1 In an effort to avoid this “gaming” of publicly reported data, the Centers for Disease Control and Prevention and multiple professional organizations have proposed a more “objective” process to monitor, namely that of ventilator-associated events (VAEs), which includes ventilator-associated conditions (VACs), infection-related ventilator-associated complications (IVACs), and VAP.2

The definition of a VAC requires a stable or decreasing positive end-expiratory pressure (PEEP) and supplemental Fio2 for at least 2 days, followed by an increase in Fio2 of at least 0.2 or an increase in PEEP of at least 3 cm H2O, for a minimum of 2 days. When a VAC is accompanied by signs of infection (fever, elevated WBC count, or neutropenia) and the addition of antibiotics for at least 4 days, an IVAC is present. Based on culture data, patients with an IVAC are further divided into possible or probable VAP. The putative “advantages” of the VAE concept are its objectivity, its lack of reliance on a chest radiograph (which is not used in the definition), and the ability to collect data rapidly with an electronic medical record, rather than through the laborious efforts of an infection control practitioner.

Despite these well-meaning intentions, the practical clinical validity of VACs has not been established, and it is quite surprising that we have been asked to monitor for these events. For example, although not all VACs are VAP, we do not know how many cases of VAP are defined as VACs. In an early study of 600 patients in six US centers, Klompas et al3 found that 135 had VACs, whereas 55 had VAP. Similarly, an Australian study found that 153 of 543 patients had VACs, whereas only 40 patients with VACs had positive respiratory cultures and were treated with antibiotics,4 so that both studies found VACs to be more common than VAP. In contrast to these data are the findings of a Canadian study of 1,320 patients who were mechanically ventilated, of which the prevalence of VACs was 10.5%, whereas the prevalence of VAP was 11.2%.5 Of the patients with VAP, 79% had neither a VAC nor an IVAC. Similarly, Klein Klouwenberg et al6 found that the prevalence of VACs and the prevalence of VAP were similar in a group of 2,080 patients, but that the VAE algorithm identified only 32% of the patients with VAP. In the current issue of CHEST (see page 68), Boyer et al7 report their experience with a VAC in a prospective 1-year study of 1,209 patients who were mechanically ventilated. Their study had 67 VACs but 86 episodes of VAP, making VAP a more common event. In addition, most of the 86 episodes of VAP were not VACs, with only 15 probable cases of VAP and six possible cases of VAP being classified as IVACs.

In addition to questions about the frequency of infection as a cause of VACs, there are many other issues related to the definition of a VAC. Concerns include the fact that a VAC can be diagnosed only after a 2-day period of stability, followed by 2 days of worsened oxygenation, making diagnosis only possible after a minimum of 4 days. In the study by Boyer et al,7 the median time of VAC onset was 6.2 days, even though the researchers used an adjudication method to include patients who died before the 2 calendar days of deterioration were met. Another concern with the definition of a VAC is that it depends on changes in Fio2 and PEEP (physician behavior) and not on a physiologic parameter, even though prior studies have shown that the Pao2/Fio2 ratio is a good predictor of the clinical course of VAP.8 Presumably the ventilator settings were chosen for the VAC definition to facilitate easy monitoring via electronic means. However, it is easy to eliminate most VACs by deciding to initially ventilate all patients with a higher Fio2 and PEEP than is needed, and thus it would not be necessary to increase the PEEP or Fio2 when the patient had a physiologic decline in oxygenation.

Although most studies do show that there is an adverse outcome for patients with VAEs, few convincing data exist that show we currently have the means to prevent these episodes. Boyer et al7 found that patients with VACs had a mortality rate of 66%, compared with 14% in those without VACs, whereas Hayashi et al4 found a 20.3% mortality rate that was not higher than that of patients without VACs. In both of these studies, the duration of mechanical ventilation was longer for patients with VACs than for those without, but the real impact of a VAC probably needs to be measured from the day of its onset and not from the first day of ventilation. The currently available data do not show that it is possible to prevent VACs by existing ICU care strategies, and that if there is a “VAC bundle,” it should be defined, developed, and tested before we agree to monitor for VACs. Muscedere et al5 found that over a 24-month period, the application of VAP-prevention recommendations increased, with a drop in the rate of VACs but with no change in the frequency of IVACs. In their current study in CHEST, Boyer et al7 defined the “preventability” of VACs, based on diagnosis, and as assessed by an adjudication committee.7 They judged that only 37.3% were preventable, but this dropped to 14.9% if probable VAP (which occurred despite documented adherence to a VAP-prevention bundle) was excluded. The preventable diagnoses included infection with inappropriate therapy, insufficient PEEP, excess IV fluids, aspiration, iatrogenic esophageal perforation, and postoperative bleeding necessitating resuscitation.

Currently, there are not enough data to endorse the measurement of VACs as a reflection of quality of care, particularly because most episodes of a VAC are not VAP, and we do not have a prevention strategy that is able to prevent IVACs. In addition, the new data from Boyer et al7 have nicely defined the causes of VACs and have shown that very few episodes are preventable using our current prophylactic strategies. Until this “VACuum” of data is filled with convincing information about the preventability of VACs, the methods for prevention, and the relation of VACs to quality of care, we urge a reevaluation of the VAC concept and consideration of a moratorium on its measurement.

References

Klompas M. Is a ventilator-associated pneumonia rate of zero really possible? Curr Opin Infect Dis. 2012;25(2):176-182. [CrossRef] [PubMed]
 
Magill SS, Klompas M, Balk R, et al. Developing a new, national approach to surveillance for ventilator-associated events. Crit Care Med. 2013;41(11):2467-2475. [CrossRef] [PubMed]
 
Klompas M, Khan Y, Kleinman K, et al; CDC Prevention Epicenters Program. Multicenter evaluation of a novel surveillance paradigm for complications of mechanical ventilation. PLoS ONE. 2011;6(3):e18062. [CrossRef] [PubMed]
 
Hayashi Y, Morisawa K, Klompas M, et al. Toward improved surveillance: the impact of ventilator-associated complications on length of stay and antibiotic use in patients in intensive care units. Clin Infect Dis. 2013;56(4):471-477. [CrossRef] [PubMed]
 
Muscedere J, Sinuff T, Heyland DK, et al; Canadian Critical Care Trials Group. The clinical impact and preventability of ventilator-associated conditions in critically ill patients who are mechanically ventilated. Chest. 2013;144(5):1453-1460. [CrossRef] [PubMed]
 
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(8):947-955. [CrossRef] [PubMed]
 
Boyer AF, Schoenberg N, Babcock H, McMullen KM, Micek ST, Kollef MH. A prospective evaluation of ventilator-associated conditions and infection-related ventilator-associated conditions. Chest. 2015;147(1):68-81.
 
Luna CM, Blanzaco D, Niederman MS, et al. Resolution of ventilator-associated pneumonia: prospective evaluation of the clinical pulmonary infection score as an early clinical predictor of outcome. Crit Care Med. 2003;31(3):676-682. [CrossRef] [PubMed]
 

Figures

Tables

References

Klompas M. Is a ventilator-associated pneumonia rate of zero really possible? Curr Opin Infect Dis. 2012;25(2):176-182. [CrossRef] [PubMed]
 
Magill SS, Klompas M, Balk R, et al. Developing a new, national approach to surveillance for ventilator-associated events. Crit Care Med. 2013;41(11):2467-2475. [CrossRef] [PubMed]
 
Klompas M, Khan Y, Kleinman K, et al; CDC Prevention Epicenters Program. Multicenter evaluation of a novel surveillance paradigm for complications of mechanical ventilation. PLoS ONE. 2011;6(3):e18062. [CrossRef] [PubMed]
 
Hayashi Y, Morisawa K, Klompas M, et al. Toward improved surveillance: the impact of ventilator-associated complications on length of stay and antibiotic use in patients in intensive care units. Clin Infect Dis. 2013;56(4):471-477. [CrossRef] [PubMed]
 
Muscedere J, Sinuff T, Heyland DK, et al; Canadian Critical Care Trials Group. The clinical impact and preventability of ventilator-associated conditions in critically ill patients who are mechanically ventilated. Chest. 2013;144(5):1453-1460. [CrossRef] [PubMed]
 
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(8):947-955. [CrossRef] [PubMed]
 
Boyer AF, Schoenberg N, Babcock H, McMullen KM, Micek ST, Kollef MH. A prospective evaluation of ventilator-associated conditions and infection-related ventilator-associated conditions. Chest. 2015;147(1):68-81.
 
Luna CM, Blanzaco D, Niederman MS, et al. Resolution of ventilator-associated pneumonia: prospective evaluation of the clinical pulmonary infection score as an early clinical predictor of outcome. Crit Care Med. 2003;31(3):676-682. [CrossRef] [PubMed]
 
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