Ventilator-Associated Events


For decades, ventilator-associated pneumonia (VAP) has been the bane of many ICUs, with a massive impact, both physically and economically. It has been estimated to strike around a quarter of a million patients annually in the U.S., which represents about 5-10 out of every 1,000 overall hospital admissions.1 The mortality rate associated with VAP has been estimated at up to 50%, and is approximately double that of non-ventilator pneumonia. VAP significantly increases the patient’s length of stay in the ICU, and can add $40,000 or more to the cost of that stay.2 Hospitals have spent millions more not only in direct patient care, but in quality control processes, the development of new policies and procedures, and the auditing of those programs, all in order to reduce or eliminate the number of VAPs found in their critical care areas.

Historical Context of VAP Research
While nobody disputes the impact VAP has had on the healthcare system, there is significant debate over what exactly constitutes a VAP, which is why there is such debate on prevalence and cost. Problems like subjective interpretation of chest X-rays, variability in calculating scores from various formulae, and lack of predicative accuracy from a statistical perspective have hampered VAP assessment ever since the first attempts to quantify the problem in the 1970s.

Even with the lack of an effective, objective standard for diagnosing VAP, clinicians were able to develop many new practices in order to lower its prevalence. The use of non-invasive ventilation grew, in order to avoid the ventilator component of VAP altogether. So-called “ventilator bundles,” including closed suction systems, improved oral care, and even patient positioning rules were created and put into practice. New equipment, like endotracheal tubes coated with silver or designed with continuous subglottic suctioning ports, were developed and promoted. With all these new interventions, VAP rates appeared to be on decline. However, researchers began to notice something odd about the data from various VAP-related studies: Even with the decline in reported VAPs, objective patient outcomes data, such as ventilator-free days or overall length of stay, were remaining generally stable. Questions began to arise about how much of the numerical improvement in VAPs was actually due to better policies and practices, and how much was due to statistical anomalies, observational biases, or outright “fudging” of the numbers by using different interpretations or alternate definitions. After all, the concept of VAP was not originally intended to be tied to reputation scores or reimbursement criteria, and despite being shoehorned into the healthcare system’s growing desire for hard data, there was still plenty of room for creative monitoring techniques.

A New Paradigm Is Born
With the troublesome nature of reporting a highly variable and subjectively described disease process in one hand, and the demands of governmental agencies, insurance providers, and even patients for enhanced data reporting in the other, the CDC realized it was time for a change in VAP reporting. In 2011, the CDC contacted a dozen professional groups and government agencies, including the American Association for Respiratory Care, and created the VAP Surveillance Definition Working Group. This group was tasked with looking at ventilator-associated pneumonia from their various perspectives (respiratory care, nursing, infection control, epidemiology, etc.) and coming up with a set of guidelines that would once and for all answer exactly how to find VAP. What they came up with was a bit surprising. The group determined that the best way to look for ventilator-associated pneumonia was to . stop looking for ventilator associated pneumonia.

While it seems strange indeed to have a multidisciplinary working group decide that their reason for coming into existence didn’t really matter after all, the decision highlighted a key (and heretofore forgotten) point: Pneumonia isn’t the only bad thing that can happen to a patient while being mechanically ventilated. Once this point was realized, the group determined there was very little to gain by focusing on something that medicine had been struggling to define for four decades, especially when there was plenty of other clinically relevant data to evaluate. Thus, the idea of ventilator-associated events, or VAEs, was developed,3 and VAPs were relegated from surveilled menace to simple internal quality-control measure.

Ventilator-Associated Conditions
VAEs can be broken down further into two additional groups, ventilator-associated conditions (VACs) and infection-related ventilator-associated conditions (IVACs). VACs are essentially any problem that causes a significant increase in a mechanically ventilated patient’s oxygen demand, defined as an increase in FiO2 of .20 or more (for example, going from .40 to .60) or an increase in PEEP of 3cm H2O or more. This increased demand is only considered a VAC if it occurs after at least two calendar days of mechanical ventilation with stable or decreasing oxygen needs, and it must be sustained for at least another two calendar days. The built-in time delay helps cut down on false positives by allowing time for pre-admission processes to fully manifest before blaming the ventilator.

There is no chest X-ray requirement for identifying a VAC, nor is there any lab work involved. This improves objectivity; since there can be significant variability between one interpretation of a chest X-ray and another, not to mention the difficulties inherent in shooting a clean film in an intensive care unit (like patient positioning, lack of breath coordination, and overlay of various ICU leads and accessories), chest x-rays are not particularly well-suited for the objective, repeatable requirements of the new reporting system. Leaving out the lab work is an effort to simplify things, as well as a nod to the fact that, at this initial level, the new criteria can represent things other than an active infection.

Infection-Related Ventilator-Associated Conditions
However, sometimes these events DO represent infection. For example, a VAC patient begins to show clinical signs of infection, such as a fever of greater than 38 degrees centigrade, or a temperature below 36 degrees centigrade, or a white blood cell count of greater than or equal to 12,000 cells per cubic millimeter or less than 4 cells per cubic millimeter. If the patient meets either of those criteria within two days of their increase in oxygen demand, AND is started on a new antimicrobial agent that continues for at least four days, that patient is declared to have an Infection-related IVAC. Although now laboratory work is required, chest radiography is still not part of the assessment. It’s also important to note that the two-day window does not necessarily START with the increased oxygen demand. According to the guidelines, if the new antibiotic and fever or WBC issues begin WITHIN two days of the increased oxygen, that’s still an IVAC. This allows for differences in patient response to the disease processes, as some people may have an elevated white cell count before their respiratory drive is impacted.

Inside the IVAC category there is once again mention of pneumonia, although it is strictly as an internal quality-control measurement to aid hospitals in patient care, NOT as a nationally-reported concern. IVACs can be split into two subcategories, both of which involve the presence of purulent respiratory secretions. These are defined as secretions from the trachea, bronchi or lungs that contain at least 25 neutrophils and fewer than 10 squamous epithelial cells per low power field. If the patient is found to have such secretions OR has a positive culture from a sample of sputum, endotracheal aspirate, bronchoalveolar lavage, specimen brushing, or the lung tissue itself, this is marked a POSSIBLE VAP. If your patient has purulent secretions AND a positive culture from any of those sources, the patient has a PROBABLE VAP. Alternatively, if the patient has a positive culture from pleural fluid drawn via thoracentesis or upon the initiation insertion of a chest tube, or positive lung histopathology showing the presence of fungi in the lung tissue, abscesses, or a viral infection, they can be considered to have probable VAP, even without the presence of purulent secretions. Positive blood tests for legionella, the flu virus, parainfluenza, adenovirus, or respiratory syncytial virus, can also shift them into the probable VAP category. Because this new paradigm does not specifically point at the ventilator as a causative agent, these pneumonias are no longer reported to the CDC for epidemiological tracking.

NOTE: The complete VAC/IVAC protocol, used to create this section, is available via the CDC website at http://www.cdc.gov/nhsn/PDFs/pscManual/10-VAE-FINAL.pdf

How Do These Changes Impact RTs?
In point of fact, many of the same techniques that were developed to reduce VAP rates will continue to be effective for controlling VAEs as well. After all, it’s important to remember that while the focus has expanded beyond pneumonia and the blame taken off the ventilator, the techniques used to minimize pneumonia are also effective at preventing respiratory complications in general.

Thus, the respiratory therapist can continue to significantly impact patient care by recommending the continued use of existing “vent bundle” protocols, using proper suction techniques, and working to cut down on the microaspiration of secretions around the endotracheal tube cuff, which is a leading contributor to pneumonia in ventilator patients, associated or not. In addition, the application of the latest theories and expert analyses in respiratory care can help reduce the impact of another one of the biggest contributors to VAEs, acute respiratory distress syndrome, or ARDS. The use of low tidal volume ventilatory strategies such as the ARDSnet recommendations, or alternative open-lung techniques like the use of airway pressure release ventilation, often help to reduce ventilator-induced lung injuries and maintain oxygenation status, even in the most critically ill. Respiratory therapists should also act as the first line of defense for the patient’s airway, ensuring other staff members are following good hand hygiene procedures and working safely around the oropharynx, without contaminating the area with pathogens from other sites around the body. Respiratory staff should also be providing regular educational opportunities to other staff members, helping ensure best practices are maintained. They can also take the lead on educating patient families and caregivers, which removes another potential failure point in infection control.

RTs also play a significant role in perhaps the single most important method to reduce the risk of VAEs: liberation from mechanical ventilation. It follows that a patient cannot have a VAE event if there is no ventilator, so aggressive liberation strategies may have a significant impact on event rates. Working closely with nurses and other ICU providers, RTs facilitate daily spontaneous breathing trials and encourage the early mobilization and even ambulation of ventilator patients. These strategies help decrease the reliance on the ventilator, work to strengthen the respiratory musculature, and push the patient to faster liberation.

Finally, with the shift in focus from pneumonia to more general hypoxic events, RTs should have an expanded role in research and data analysis. As respiratory therapists are at the forefront of ventilator management, they will likely be the first to identify the presence of a VAC, and will be in an ideal position to manage the treatment of those conditions. The knowledge and expertise of the respiratory therapist will also allow them to take a lead role in developing new prevention strategies, and RTs should become key members of VAE-related process improvement initiatives.

Mike Hess is a registered respiratory therapist, Department of Veterans Affairs, Battle Creek VA Medical Center, Kalamazoo, MI.


References

  1. Koenig S, Truwit J. Ventilator-associated pneumonia: Diagnosis, treatment, and prevention. Clin Microbiol Rev. 2006; 19(4):637-657
  2. Tablan OC, Anderson LJ, Besser R, et al. CDC healthcare infection control practices advisotry committee. Guidelines for preventing health care-associated pneumonia, 2003: Recommendations of CDC and the Healthcare Infection Control Practices Advisory Committee. MMWR Recomm Rep. 2004:53(RR-3):1-36
  3. Magill S, Klompas M, Balk R, et al. Developing a new national approach to ventilator-associated events. Crit Care Med. 2013;41(11):2467-2475

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