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Abstract

Introduction: Respiratory tract infection (RTI) is the major cause of Intensive Care Unit (ICU)-associated sepsis in Europe. To better inform healthcare improvement programmes, surveillance for VAP in Wales has been mandatory since 2008, coordinated by Public Health Wales and utilising HELICS criteria (1). Welsh VAP rates have been consistently low (2.3 per 1000 ventilator days) compared with Scottish (6.5 per 1000 ventilator days) and wider European data (12.2 per 1000 ventilator days). While possibly reflecting success of VAP-prevention measures, investigation into the reliability of the surveillance data appeared warranted. Our aims were to: prospectively capture episodes of ICU-acquired RTI occurring within Welsh ICUs using an alternative data collection tool, explore whether these episodes met HELICS criteria, identify reasons for episodes not meeting HELICS criteria, and compare numbers of VAP cases identified prospectively with numbers from the established surveillance system. Methods: Over a two-week study period, local investigators identified via WICSARG screened all invasively ventilated patients for new onset ICU-acquired RTI. When episodes occurred more than 48 hours after ICU admission, investigators evaluated whether they met HELICS criteria and estimated likelihood of infection according to a modified Clinical Pulmonary Infection Score (mCPIS). Established VAP surveillance processes continued in parallel. Results: Thirteen of 15 Welsh ICUs participated. Data was captured for 182 invasively ventilated patients on 1343 ventilator days. Antibiotics were commenced in 73 patients for new onset infection; respiratory tract was second most frequent source (17, 23.3%) after abdominal (23, 31.5%). Out of the 17 episodes of ICU-acquired RTI, 7 met HELICS criteria giving a VAP rate of 5.2 per 1000 ventilator days. In 36% episodes, HELICS criteria could not be fulfilled because chest radiography was not performed. Using a threshold mCPIS of 6 to diagnose ICU-acquired RTI, there were 3 further cases where RTI seemed likely, but HELICS criteria were not met. Interestingly, 2 VAPs fulfilled the HELICS criteria with a relatively low mCPIS of 4. Data was obtained for 1668 ventilator days in the same time period from the 13 ICUs using the established VAP surveillance mechanism. 5 episodes met HELICS criteria, giving a VAP rate of 3.0 per 1000 ventilator days. However, 5 other HELICS-defined episodes identified using the prospective data collection tool were not captured. Conclusions: Estimates of VAP incidence based on current surveillance mechanisms probably underestimate the true incidence of VAP in Wales. Use of HELICS criteria for VAP surveillance may exclude episodes likely to represent VAP, largely because chest radiography is not routine when antibiotics are commenced for suspected RTI in ICU. The use of mCPIS score could help to add reliability to the already collected data, however based on our results this score alone could not be used at a traditional cut-off of 6 points. We plan to re-audit our practice using the recently published CDC criteria to compare it’s effectiveness to the HELICS definition in capturing ICU acquired RTIs.