When analyzed as a dynamic factor over time, use of the ventilator bundle was not associated with the prevention of ventilator-associated pneumonia in a study of over 600 patients.
The finding raises doubts about the widespread use of the bundle among intensive care units and calls into question efforts to make ventilator-associated pneumonias a "never event," said lead author Dr. Martin A Croce and his associates.
"While quality improvement initiatives are extremely important in the care of critically ill and injured patients, any potential penalty for institutions that actively participate in such initiatives is unwarranted," they wrote.
Their study, appearing in the February issue of the Journal of Trauma and Acute Care Surgery, involved 630 patients at six level 1 trauma centers over a 16-month period (J. Trauma Acute Care Surg. 2013;74:354-62).
All trauma patients who were admitted to an intensive care unit and received mechanical ventilation for at least 48 hours were eligible for study inclusion (90% with blunt trauma). They were followed daily in the ICU until the development of ventilator-associated pneumonia (VAP), ICU discharge, or death.
Dr. Croce, chief of the trauma division at the University of Tennessee Health Science Center, Memphis, and colleagues assessed compliance among these patients with the Institute for Healthcare Improvement (IHI) ventilator bundle, which is a set of core measures to be assessed daily and designed to improve the outcomes of mechanical ventilation.
The four core measures assessed in this study were presence of stress ulcer prophylaxis, deep vein thrombosis prophylaxis, elevation of the head of the bed, and a daily sedation vacation with assessment of weaning.
"Oral chlorhexidine was not part of the bundle since it was added by the IHI after the study protocol was already approved," the authors wrote.
Overall, 36% of patients developed VAP (96% diagnosed with bronchoalveolar lavage), and the overall mortality was 15%.
Sixteen patients were censored from the final analysis since they developed VAP late – that is, after 16 days in the study – and the authors assumed that the efficacy of the ventilator bundle would be greatest early in an ICU stay. In the end, a total of 210 patients were available for analysis.
The investigators then looked at the impact of the ventilator bundle on VAP in two ways: by individual patient and by patient-days.
To assess individual patient compliance, the authors summed each patient’s bundle compliance score and then divided by the number of patients.
"Although this method is commonly used to calculate compliance, this method may not accurately measure bundle or component compliance because patients with either short or long stays are weighted equally," Dr. Croce and his associates said.
"Thus, equal weight is given to less severely injured patients with perfect or near-perfect compliance as is given to more severely injured patients with contraindications to some bundle components," they added.
Indeed, in this analysis, overall patient compliance with the bundle was significantly linked to a decrease in VAP.
"To avoid this bias toward short stays, compliance was also calculated by patient-days," they noted. In this method, they counted each day’s compliance as a unique event.
"Bundle compliance is a dynamic, time-dependent process during which an individual patient’s status may change from noncompliant to compliant ... depending on the patient’s condition," Dr. Croce and his associates wrote. For example, DVT prophylaxis may be held in advance of surgery and restarted again later.
In this analysis, ventilator bundle compliance was associated with neither the development nor the prevention of VAP, with a hazard ratio for bundle compliance of 1.26 (95% confidence interval, 0.845-1.877.
In fact, in this analysis, the only variable associated with VAP was male sex (hazard ratio, 1.75; 95% CI, 1.233-2.483).
"It is important that [the Centers for Medicare and Medicaid Services] and third-party payers realize that in trauma patients, VAP is closely associated with uncontrollable risk factors such as sex and injury severity and its prevention is not associated with the four components of the IHI ventilator bundle," they said.
Dr. Croce and his coinvestigators stated that the study was funded by the National Trauma Institute and the U.S. Army. They disclosed no relevant conflicts of interest.