Mark L. Metersky, MD1; Yun Wang, PhD2; Michael Klompas, MD3; et al

From 2006 to 2012, the incidence of ventilator-associated pneumonia (VAP) reported to the Centers for Disease Control and Prevention National Healthcare Safety Network (NHSN) decreased.1,2 In medical and surgical intensive care units, between 2006 and 2012, the reported incidence of VAP per 1000 ventilator-days decreased from 3.1 to 0.9 (71% decline) and 5.2 to 2.0 (62% decline), respectively. Whether the decrease was attributable to better care or stricter application of subjective surveillance criteria is unclear.3 The Medicare Patient Safety Monitoring System (MPSMS)4 has independently measured VAP rates since 2005, using a stable definition of VAP. Trends in MPSMS VAP rates from 2005 through 2013 were analyzed.

Methods

To track the national frequency of safety events in hospitalized patients, the MPSMS abstracted a random selection of acute-care hospital records from 2002-2013, except 2008 (because of a 1-year lapse in federal funding). Between 18 000 and 34 000 records were abstracted from between 730 and 4000 randomly selected hospitals across the nation each year. Detailed MPSMS methods have been previously reported.4 This analysis included MPSMS VAP rates during calendar years 2005 through 2013 among Medicare patients 65 years and older with principal diagnoses of acute myocardial infarction (AMI), heart failure, pneumonia (including a primary diagnosis of sepsis or respiratory failure and a secondary diagnosis of pneumonia), and selected major surgical procedures.

Determination of VAP required all of the following beginning 2 or more days after initiation of mechanical ventilation: chest radiograph with a new finding suggesting pneumonia, physician diagnosis of pneumonia, and an order for antibiotics to treat pneumonia.4 The denominator included all patients who received invasive mechanical ventilation for 2 or more consecutive days without a physician diagnosis of pneumonia prior to the onset of mechanical ventilation.

MPSMS was reviewed by Solutions IRB and determined not to be research involving human participants.

The cohort was divided into 4 periods (2005-2006, 2007 and 2009, 2010-2011, and 2012-2013). Because the proportions of patients with AMI, heart failure, pneumonia, and major surgery varied from year to year, the 2005-2006 condition-specific proportions served as a baseline. Then, a sample of patients with each condition was randomly selected (with replacement; 10% AMI, 15% heart failure, 20% pneumonia, 55% surgical) for each subsequent period to align the proportions in each period with the condition-specific proportions in 2005-2006. To reduce resampling variability, bootstrap resampling was performed, calculating VAP rates for each period 10 000 times, deriving means and 95% CIs. A mixed model with an ordinal time variable was fit, ranging from 0 to 7, corresponding to years 2005 (time = 0) to 2013 (time = 7), except 2008, to represent the annual change in VAP rates. Analyses were performed using SAS version 9.2 (SAS Institute Inc).

Results

The VAP rate was studied among 1856 patients. Numbers and characteristics of patients included in the sample during each period are reported in the Table. MPSMS VAP rates were stable over time (Figure), with an observed rate of 10.8% (95% CI, 7.4% to 14.4%) during 2005-2006, 9.7% (95% CI, 5.1% to 14.9%) during 2012-2013, and an adjusted average annual change of 0.00 (95% CI, −0.05 to 0.07).

Discussion

From 2005 through 2013, MPSMS VAP rates remained stable and substantial, affecting approximately 10% of ventilated patients. Persistently high VAP rates bolster concerns that most interventions purported to reduce VAP are supported by limited evidence.5

The data have limitations. The VAP rates were not measured in all hospitalized patients, just the subset included in the MPSMS (patients ≥65 years with 4 specific conditions).

The discordance between these findings and the significant declines in VAP rates reported by the NHSN1,2 could in part be due to differences in MPSMS and NHSN measure definitions, hospitals or patient groups, changes in characteristics of hospitals reporting to the NHSN over time, or preferential declines in VAP rates among hospitals reporting to the NHSN.

Nonetheless, the dichotomy between VAP rates reported to the NHSN and measured in the MPSMS supports the concern that surveillance using traditional definitions may be unreliable.3 The ongoing risk to patient safety represented by VAP supports the NHSN’s decision to explore more objective surveillance targets.6

JAMA