Even before the pandemic, an estimated 250,000-plus patients contracted VAP each year in the US, but effective strategies for infection control and ventilator management can reduce ventilator-associated pneumonia (VAP), as well as hospital-acquired pneumonia (HAP) and ventilator-associated events (VAEs)

By Bill Pruitt, MBA, RRT, CPFT, AE-C, FAARC


Strategies to manage patients receiving mechanical ventilation are always evolving. New guidelines are tested and released then reevaluated. With ongoing scrutiny over time, guidelines are altered or dropped, and new ones come to practice. For many years there has been a focus on preventing hospital-acquired pneumonia (HAP) and ventilator-associated pneumonia (VAP).1 Hospital acquired pneumonia (HAP) are described as pneumonias that appear more than 48 hours after admission. Ventilator-associated pneumonia was defined as a pneumonia that began more than 48 hours after endotracheal intubation.

VAP surveillance and the strategies to reduce ventilator-associated pneumonia put forward by the CDC years ago have moved to a newer approach from the CDC to begin surveillance for ventilator-associated events (VAE) starting in 2013.This article will look at this change from VAP to VAE and examine the strategies for improving patient-ventilator care.

Moving from Ventilator-associated Pneumonia to VAE

Reducing VAP had been the standard of care for years and has generated a vast number of research articles, but the criteria defining VAP were very subjective and non-specific. In particular, research lacked a clear standardized definition of pneumonia based on radiologic evidence and a lack of agreement on the diagnosis of pneumonia associated with intubation/mechanical ventilation.3 The problems with subjectivity and non-specificity were highlighted in a 2014 study published in Critical Care Medicine, which presented six case vignettes identified by a number (1 to 6) to 43 infection control experts from all parts of the US. The experts determined which, if any, cases would be considered VAP by the CDC criteria. The number of cases identified as ventilator-associated pneumonia by the 43 experts ranged from just one to all six with, each individual numbered case getting almost equal support from the experts—showing no consensus among the group.4 Another published study presented 50 patient cases to 3 different surveyors who were asked to use the CDC VAP criteria to determine which cases reflected VAP. VAP was determined in 11, 15, and 20 cases respectively, and only 7 cases were identified by all three reviewers as being VAP.5

Ventilator-associated event surveillance was developed and released by the CDC to try and establish more objective, measurable, and more encompassing measures of the complications of mechanical ventilation.6 Rather than focusing on pneumonia, VAE monitoring looks for all major causes of pulmonary deterioration in patients receiving mechanical ventilation. The new approach also tends to shift the focus to the more serious cases of pneumonia involving higher levels of support in terms of ventilator management and use of antibiotics.

VAE and the Subsets

VAE is defined a change in patient condition that calls for increases in either positive end-expiratory pressure (PEEP) and/or the fraction of inspired oxygen (FiO2). Specifically, VAE is determined if, after an established baseline of 2 days of stable or decreasing PEEP and/or FiO2, >2 days occur where PEEP must be increased by >3 cmH2O (daily minimum values) above baseline and/or FiO2 must be increased by >20% above baseline (daily minimum values).2,6 

Ventilator-associated complications (VACs) are subsets of VAEs. The first is described as infection-related ventilator associated complications (IVACs). IVACs are determined by an abnormal body temperature (too high or too low), or white blood cell count (too high or too low), along with >4 days of new antibiotics starting within 2 days of the onset of VAE. The second subset of VAE is described as possible (or probable) ventilator associated pneumonia (PVAP). PVAP may also be a subset to IVACs if antibiotics have been started, or may be determined by histology.2

Triggers and Risk Factors for VAE

Many studies have looked at what triggers a VAE and almost all point to one of four primary triggers. In some 25 to 40% of cases, pneumonia is the cause, followed by fluid overload including pulmonary edema (15 to 50% of cases), atelectasis (10 to 15% of cases), and ARDS (5 to 20% of cases). 

Beyond these primary triggers, the following are included as contributing factors: mucus plugs, pulmonary embolism, pneumothorax, poor pulmonary toilet, stroke, extrapulmonary sepsis syndromes, and transfusion-associated lung injury. Still, in some 10 to 20% of VAE, no apparent cause is found as a reason for the increase in PEEP and/or FiO2.2 

Risk factors for VAEs include use of benzodiazepines or propofol for sedation, large tidal volumes, high inspiratory pressures, blood transfusions, and patient transport.2-4 

Strategies for Reducing Ventilator-associated Pneumonia, VAE and Subsets

Traditional strategies for ventilator-associated pneumonia include ventilator bundles which include specific actions to reduce incidence. The first major ventilator bundle to address VAP came from the Institute for Healthcare Improvement (IHI) and included four actions: 

  • Head of bed elevation to 30-45 degrees;
  • Daily sedation interruption (“sedation vacation”) and assessment of readiness to extubate;
  • Peptic ulcer prophylaxis;
  • Deep vein thrombosis (DVT) prophylaxis.7 

Several other actions were added to ventilator bundles as research on reducing VAP continued. These included daily spontaneous breathing trails (SBTs), use of subglottic suction, oral care with chlorhexidine, stress ulcer prophylaxis, use of special endotracheal tubes (ETTs), including silver coating, tapered cuff, polyurethane materials), reduction in “breaking-the-circuit” (opening the patient-ventilator circuit), and use of heat-moisture exchangers.8 

The effectiveness of the traditional ventilator-associated pneumonia ventilator bundle on reducing VAE is being questioned and it appears that some of the actions in the traditional approach may actually increase the risk for VAE (specifically, stress ulcer prophylaxis and oral care with chlorhexidine).2,8 In a 2019 Respiratory Care article, Kallet states, “At this juncture, no high-level evidence supports the notion that current ventilator bundles reduce VAE risk.”8 Research is underway to examine the most effective actions to reduce VAE and a new bundle may be introduced as more evidence is produced that supports a revised approach. 

One strategy that is gaining strength is to initiate mechanical ventilation using a PEEP set at 8 cmH2O as opposed to the conventional approach of PEEP set at 5 cmH2O. Comparing a pre-intervention group of 419 mechanically ventilated patients to 427 patients in the post-intervention group, the researchers found an approximate 50% reduction in VAE and reductions in IVAC and PVAP by 25-30%. This change was thought to be related to increasing FRC and reduction in atelectasis.9 Since the duration of mechanical ventilation is a contributing factor to many issues that could result in a VAE or VAC, actions that reduce time on mechanical ventilation (ie daily sedation interruption, SBTs) continue to be supported actions and will very likely be a key piece in any new VAE bundle. Careful fluid monitoring and management is needed since a positive fluid balance tends to increase VAC risk.8 Other considerations have been examined to reduce VAE as all of these are implicated in the VAE problem. These include careful use of sedatives (especially benzodiazepines and propofol), reducing use of opioids, avoiding use of mandatory modes of ventilation with large tidal volumes or high inspiratory pressure, careful use of blood transfusions, reducing gastric retention, avoiding reintubation, and careful use of neuromuscular blockade.2 

Another factor that may bring about an effective VAE bundle is the development of a fully automated VAE surveillance tool linked to the electronic medical record/patient data management system. A study from 2021 analyzed data from January 2008 to May 2016 on 22,442 ventilated patients and a total of 37,221 ventilator days. The automated system found 592 VAE in 2.5% of all the patients. Performance was checked by using three means: 

  • A convenience sample of 131 admissions with prolonged ventilation (21-27 days) was used to determine sensitivity and specificity for VAC detection compared to gold standard;
  • A random sample of 100 VAC cases out of all VAC cases was used to check specificity compared to gold standard for VAC detection; and
  • A random sample of 100 VAC cases (verified by gold standard) was used to evaluate the sensitivity and specificity for detecting IVAC.10 

In the first group of 131, researchers found a sensitivity of 98%, a specificity of 100%, a negative predictive value (NPV) of 99% and a positive predictive value (PPV) of 100%. In the second group of 100 VAC cases, specificity was 99% and PPV 99% when compared to the gold standard. In the third group, the sensitivity of automated surveillance for IVAC detection was 100% and the specificity 100% compared to the gold standard.10

Another automated system that can bring data together at the bedside has been evaluated and found to allow this near real-time information to be better used in a clinical setting to improve patient care and reduce VAEs. In the conclusion, the authors stated, “this observational study suggests that the direct incorporation of RKP into daily multidisciplinary rounds, rather than as a consultant technology at the central workstation, may improve care by decreasing VAEs and potentially improving patient weaning from the ventilator.”11

Conclusion

Surveillance of VAEs, VACs, and HAPs has increased awareness of these problems and has moved research away from solely looking at pneumonia to look at all causes of respiratory deterioration. Examining the traditional approaches to care is ongoing to see what may prove to be effective and small changes (ie starting PEEP at 8 cmH2O) may be enough to have a significant impact. Automated detection may allow for quick, accurate reviews and help find effective approaches. Having coordinated, real-time data available at the bedside may also be effective in reducing VAE.

Looking back at the widespread acceptance and use of the VAP bundle through past years, development of a VAE bundle may prove to be a widely adopted and effective means to put best practices and evidence-based approaches in to use.


RT

Bill Pruitt, MBA, RRT, CPFT, AE-C, FAARC, is a writer, lecturer, and consultant. He has over 40 years of experience in respiratory care, and has over 20 years teaching at the University of South Alabama in Cardiorespiratory Care. Now retired from teaching, he continues to provide guest lectures and write. For more info, contact [email protected]


References

  1. From the UpToDate website: https://www.uptodate.com/contents/treatment-of-hospital-acquired-and-ventilator-associated-pneumonia-in-adults. Accessed 4/10/22.
  2. Klompas M. Ventilator-associated events: what they are and what they are not. Respiratory Care. 2019 Aug 1;64(8):953-61.
  3. Ramirez-Estrada S, Pena-Lopez Y, Eshwara VK, Rello J. Ventilator-associated events versus ventilator-associated respiratory infections—moving into a new paradigm or merging both concepts, instead?. Annals of Translational Medicine. 2018 Nov;6(21).
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  9. Gekas, Bridget, Courtney Mitchell, Kevin Trethaway, and Erika J. Yoo. “Optimizing PEEP to Improve Rates of Ventilator Associated Events in the Medical Intensive Care Unit.” Respiratory Care (2021) 66 (Suppl 10) 3570769.
  10. Wolffers O, Faltys M, Thomann J, Jakob SM, Marschall J, Merz TM, Sommerstein R. An automated retrospective VAE-surveillance tool for future quality improvement studies. Scientific reports. 2021 Nov 15;11(1):1-7.
  11. Oglesby, H.J.A., Cataldo, S.H. and Pedro, M.J., 2021. Automated Near Real-Time Ventilator Data Feedback Reduces Incidence of Ventilator-Associated Events: A Retrospective Observational Study. Critical Care Explorations, 3(4)