Introduction

Ventilator associated pneumonia (VAP) is defined as a hospital-acquired pneumonia that develops within 48 to 72 hours after endotracheal intubation; the diagnosis hinges on a lack of evidence suggesting that the infection developed prior to intubation. VAP is the most common intensive care unit (ICU)-acquired infection, accounting for 25 percent of all ICU infections and 50 percent of ICU antibiotic use. At least 250,000 VAPs occur in the United States (U.S.) each year. This condition causes complications in 8 to 28 percent of mechanically ventilated patients and carries a mortality risk of approximately 10 percent (range 6% to 27%), resulting in a possible 25,000 VAP-attributable deaths every year. Patients who develop VAP stay, on average, 4 days longer in the ICU. The per-case cost of VAP is estimated to be $23,000, and the total incremental costs to the U.S. health care system are high: $2.19 to 3.17 billion USD per year^1-3 The wide range of these estimates results from the lack of universally accepted, reliable diagnostic criteria for VAP is present. The diagnosis of VAP may be based on any of a variety of definitions, including a surveillance definition, a clinical definition, a microbiologically confirmed definition, or a combination of the three methods. Microbiologically confirmed definitions also may be differentially based on blind tracheal aspirates, directed bronco-alveolar lavage, or even protected brush specimens.²

The original “Making Health Care Safer” report examined four interventions related to VAP: variation of position (semi-recumbent positioning and continuous oscillation), continuous subglottic suctioning, selective decontamination of the gastro-intestinal tract and the use of sucralfate. While the data in favor of semi-recumbent positioning was limited (reduced VAP but did not change mortality), the practice was judged to be easy to implement and had essentially no cost or adverse effects. Oscillation was less clear in its benefit secondary to poor methodological quality of the studies. While no evidence for harm was found, there were increased costs, estimated to be about $100/day at the time of that report. Subglottic suctioning was judged to be a promising strategy. At the time of the report, it was infrequently used and there were only a few studies. Harmful effects were felt to be negligible but there were incremental costs for the specialized endotracheal tubes required for this strategy. Selective gastro-intestinal decontamination was found to have strong benefit for reducing VAP, though cost-effectiveness was unclear. Of the trials examined, none reported adverse events from this practice; however, there is continued concern that this practice may have a deleterious effect on antibiotic sensitivity in general, leading to more resistant organisms over time in individuals as well as on a population basis. Sucralfate as a VAP prevention strategy was judged to be inconclusive. Additionally, sucralfate is inferior compared with H-2 blockers for preventing gastro-intestinal bleeding. Given the increased risk of mortality with gastrointestinal bleeding and the increased costs should this complication occur, sucralfate can no longer be recommended for VAP prevention and H-2 blockers are the preferred agent for preventing gastro-intestinal bleeding in critically ill patients.

This updated review focuses on four strategies as well; elevation of the head of the bed, sedation vacations, oral care with chlorhexidine and subglottic suctioning.

What Are the Patient Safety Practices for Preventing Ventilator-Acquired Pneumonia?

We conducted a systematic review of the literature to update a 2001 review conducted for the original report. A recent study estimates that 14,000 to 20,000 lives could be saved each year in the U.S. if best practices to prevent VAP were universally applied to all patients on mechanical ventilation.³ The four primary recommended practices include: elevating the head of the bed to 30 degrees, sedation vacations, oral care with chlorhexidine (CHG), and subglottic suctioning endotracheal tubes. Ventilator “bundles” usually include other elements such as deep venous thrombosis (DVT)/pulmonary embolism (PE) prophylaxis and Peptic Ulcer Disease prophylaxis, but these procedures are designed to prevent other ventilator-associated conditions and do not address VAP prevention specifically. In fact, Peptic Ulcer Disease prophylaxis may increase the risk of VAP. Other VAP-specific preventive interventions may include use of closed suctioning circuits, scheduled circuit changes and a preference for orotracheal over nasotracheal intubation. The remainder of this section describes the evidence in support of the four primary VAP specific practices.

How Have Practices To Prevent Ventilator-Acquired Pneumonia Been Implemented and What Has Been Learned?

Practices to prevent VAP are usually “bundled” into a care package of several elements as described above. The package may also incorporate elements beyond the four discussed above, including closed in-line endotracheal suctioning systems, humidification systems, and non-VAP specific interventions such as DVT/PE prophylaxis, for which ventilated patients are at increased risk. In a 2005 pre-post study, Resar and colleagues reported a 45 percent reduction in VAP across 35 ICUs that used such a bundled approach in a collaborative. This particular bundle used only sedation vacations and head-of-bed elevation as VAP-specific elements.¹³ Subsequent pre-post studies have also found that bundled elements synergistically reduced the rate of VAP by as much as 40 percent in both adult and pediatric patient populations.^14,15

One factor that has been noted in most of these publications is the difficulty of ensuring that all patients who qualify for the bundle and the individual elements within the bundle (e.g., for some patients—such as spine surgery patients with a dural tear—head-of-bed elevation may be contraindicated,) actually receive the bundle's elements consistently. The Michigan Keystone Project addressed this quality gap through a process of developing and applying technical tools such as checklists and ensuring their use through improvements in teamwork and the safety climate within 112 ICUs. This pre-post study found a 71 percent risk reduction in VAP, while at the same time demonstrating an increase in the adherence to evidence-based practices from 32 percent at baseline to 84 percent after 30 months.¹⁶ This finding suggests that a combination of effective evidence-based bundle elements reinforced with strategies to improve teamwork and safety can ensure that patients receive appropriate care and that outcomes improve substantially.

Others have also noted this positive effect of collaboratives on closing the quality gap. In their evaluation of the routine use of VAP prevention practices, Krein and colleagues (2008)¹⁷ found that use of semi-recumbent positioning was much more prevalent than the use of subglottic drainage (73% vs. 21% of hospitals that reported use of VAP practices). They also found that use of semi-recumbent positioning was strongly influenced by participation in collaboratives (such as the Keystone Project) and is considered primarily a responsibility of nursing staff. In contrast, use of subglottic suctioning endotracheal tubes is not influenced very much by collaboratives and is primarily a physician decision. It is unclear whether these differences are secondary to the participation in collaboratives, depend on who has the primary responsibility for decisionmaking, or both. Interestingly, the authors also noted that whereas the prevalence of semi-recumbent positioning was dramatically higher than that of subglottic drainage, when the effectiveness of the techniques was compared, the supportive evidence for subglottic drainage was found to be much stronger than for semi-recumbent positioning (five randomized studies vs. two). More recently, Krein (2011)¹⁸ reported that the prevalence of use of VAP prevention measures was also strongly influenced by the threat of non-payment for this hospital-acquired infection, although the use of any one bundle component for preventing VAP varied across respondents to their survey. This finding would suggest that efforts to close the quality gap and improve the prevalence of use of prevention practices will need to be multi-factorial.

The cost-effectiveness of several VAP prevention practices—both subglottic suctioning endotracheal tubes and VAP bundles—has been assessed. For subglottic suctioning tubes, it is estimated that 11 people need to be treated (number needed to treat) in order to prevent one VAP. Although the cost of these endotracheal tubes is approximately $18 USD, one model of continuous washing tubes (inflow/outflow ports with pumping system) costs about $200 USD. In comparison, the cost of a standard endotracheal tube is approximately $1 USD. If the number needed to treat is accurate, these special endotracheal tubes (even the most expensive versions) are cost-effective, especially if reserved for patients likely to remain intubated for more than 48 to 72 hours (the risk for VAP in those requiring intubation less than 48- to 72 hours is considered low). This conclusion is further supported by Hallais and colleagues,¹⁹ who compared the cost of these tubes to the cost of VAP, using very conservative values. The authors found that averting only three VAPs would offset the cost of the special tubes. Based on this cost analysis, any ICU with at least 3 VAPs per year would find that switching to these tubes reduces harm as well as costs.

Ventilator bundles have also recently been evaluated for their cost-effectiveness. A Danish study²⁰ retrospectively examining ventilated patients in a single ICU found that the cost of preventing one VAP was 4451 € (approximately $6,000 USD), and the cost of preventing one death was 31792 € (approximately $42,000 USD). While the cost and incidence of each VAP varies across patient populations, the study concluded that the ventilator bundle would likely be cost-effective in most environments.

Conclusions and Comment

In conclusion, of the four key practices for preventing VAP, subglottic suctioning endotracheal tubes have strong evidence to support their ability to reduce VAP and to do it cost-effectively, based on a systematic review of multiple RCTs. Strong evidence from a recent systematic review of multiple RCTs also supports oral care using CHG. Evidence from a few non-randomized studies supports sedation vacations directly. This evidence is of moderate strength. The maintenance of a head-of-bed elevation of at least 30 degrees (a ubiquitous element of VAP prevention bundles) is supported by very little evidence, yet remains part of virtually all recommendations by U.S. quality and safety organizations. This tacit support is likely a result of its ease and lack of evidence of harm, although the ability to effectively implement this element consistently has been questioned. Other elements often advocated for VAP prevention but not specifically addressed in this chapter include using antimicrobial-coated endotracheal tubes (evidence supports effectiveness),²¹ closed circuit in-line suctioning systems (evidence does not support their effectiveness)²² and humidification circuits on ventilators (evidence does not support their benefit).²³

Evidence from multiple large pre-post studies also supports the effectiveness of VAP bundles. While the evidence for each specific VAP prevention bundle element may vary, two principles are clear. First, VAP is most effectively reduced by the bundling of several elements together for a potentially synergistic effect, and bundles should be developed locally based on both institutional expertise and evidence, with ongoing evaluation of the success of the interventions. Second, the consistent application of each of the bundle elements to all patients who qualify for them is essential to success. The use of teamwork tools and strategies to ensure this consistency can have a tremendous impact on closing this quality gap and improving patient outcomes. Technical work (the bundle) needs to be supported by adaptive work (the processes needed to apply the bundle consistently) for the best success.¹⁸ A summary table is located below (Table 1).

Table 1, Chapter 11

Summary table.

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