A program for sustained improvement in preventing ventilator associated pneumonia in an intensive care setting
© Caserta et al.; licensee BioMed Central Ltd. 2012
Received: 18 March 2012
Accepted: 24 September 2012
Published: 29 September 2012
Ventilator-associated pneumonia (VAP) is a common infection in the intensive care unit (ICU) and associated with a high mortality.
A quasi-experimental study was conducted in a medical-surgical ICU. Multiple interventions to optimize VAP prevention were performed from October 2008 to December 2010. All of these processes, including the Institute for Healthcare Improvement’s (IHI) ventilator bundle plus oral decontamination with chlorhexidine and continuous aspiration of subglottic secretions (CASS), were adopted for patients undergoing mechanical ventilation.
We evaluated a total of 21,984 patient-days, and a total of 6,052 ventilator-days (ventilator utilization rate of 0.27). We found VAP rates of 1.3 and 2.0 per 1,000 ventilator days respectively in 2009 and 2010, achieving zero incidence of VAP several times during 12 months, whenever VAP bundle compliance was over 90%.
These results suggest that it is possible to reduce VAP rates to near zero and sustain these rates, but it requires a complex process involving multiple performance measures and interventions that must be permanently monitored.
KeywordsVentilator associated pneumonia Prevention Intensive care VAP bundle
Ventilator-associated pneumonia (VAP) is a common infection in the ICU.  Recent studies describe a rate of 1 to 4 cases per 1,000 ventilator-days, although this can reach up to 10 cases per 1,000 cases ventilator-days in neonates and surgical patients [2, 3]. The improvement in outcomes associated with recent initiatives suggest that many cases of VAP can be prevented by adhering to bundles of infection prevention measures [4, 5].
The attributable mortality of VAP is around 4% to 9% varying with definitions, case-mix, causative microorganisms, and treatment adequacy [6, 7]. VAP is also associated with considerable morbidity, due to increased length of hospital and ICU stay, prolonged mechanical ventilation and increased hospital expenses [8–10], as well as excessive utilization of antimicrobials with correspondingly higher costs [8, 9].
As part of the 5 Million Lives campaign, endorsed by leading US agencies and professional societies, The Institute for Healthcare Improvement (IHI) recommends that all ICUs implement a ventilator bundle to reduce the incidence of VAP to zero . Since 2007, we have implemented the VAP bundle in our ICU, including oral hygiene with 0.12% chlorhexidine and continuous aspiration of subglottic secretions (CASS) . With these measures we were able to achieve zero incidence of VAP during a few months when a higher than 95% compliance rate with the VAP bundle was obtained . However, to date there are no reports of sustained low incidence of VAP  (near zero).
The purpose of this quasi-experimental study was to evaluate whether the sustained implementation of the VAP bundle in our ICU could effectively reduce the incidence of ventilator-associated pneumonia (VAP).
Setting and study design
An interrupted time series study was conducted in a 38-bed medical-surgical intensive care unit (ICU) of a tertiary care, private hospital in São Paulo, Brazil. This is an open staffing model ICU where approximately 2,200 patients are admitted annually. This study was a quality improvement study that was approved by the Institutional Review Board of Hospital Israelita Albert Einstein (IRB). The requirement for informed consent was waived by our IRB in accordance with the Code of Federal Regulations and the Privacy Rule. This project was carried out after our previously published study from April 2007 to September 2008 . Herein we report our observations for the period from October 2008 to December 2010 to evaluate whether the sustained implementation of the VAP bundle in our ICU could effectively reduce the incidence of VAP. All these hospital epidemiology data was analysed anonymously.
The VAP bundle included elevation of the head of the bed (HOB) (30–45 degrees); daily “sedation vacations” and assessment of readiness to extubate; peptic ulcer disease prophylaxis; and deep venous thrombosis/pulmonary thromboembolism (DVT/PE) prophylaxis for all ICU patients requiring mechanical ventilation. This ventilator bundle was monitored each weekday by an ICU nurse. She intervened in this process while performance monitoring was taking place at the bedside if non-compliance with an element of the bundle was detected (e.g., sedation was not stopped). We also intervened in other CDC evidence-based practices for prevention of ventilator associated pneumonia  including: 1) no routine changing of humidified ventilator circuits, 2) periodically draining and discarding condensate collecting in the ventilator tubing and, 3) changing the heat-and-moisture exchangers (HMEs) when they showed mechanical malfunction or became visibly soiled. These CDC process measures were audited twice yearly in a small sample of mechanically ventilated patients at random intervals.
Other interventions to control VAP in the ICU were implemented in October 2007 when oral decontamination with chlorhexidine 0.12% was introduced for all mechanically ventilated ICU patients . In February 2008, the continuous aspiration of subglottic secretions (CASS) endotracheal tube was implemented for patients requiring mechanical ventilation and expected to require ventilation for longer than 24 hours .
VAP surveillance was performed by trained infection control specialists using the US Center for Disease Control and Prevention/National Healthcare Safety Network (CDC/NHSN) definition  in an independence way from the treating ICU team, the incidence of VAP was expressed as cases of VAP per 1,000 ventilator-days and the incidence of ventilator associated tracheobronchitis (VAT) was expressed as cases of VAT per 1,000 ventilator-days.
VAP was defined as the sum of the clinical criteria as described the presence of fever (temperature >38°C), new or increased sputum production, in combination with radiologic evidence of a new or progressive pulmonary infiltrate, leukocytosis, a suggestive Gram’s stain, and grow of bacteria (not necessarily) in cultures of sputum, tracheal aspirate, pleural fluid, bronchoalveolar lavage (BAL), or blood . Per the CDC/NHSN definition, microbiological data are not necessary for the diagnosis.
VAT was defined as the presence of fever (temperature >38°C), new or increased sputum production, a microbiologically positive respiratory sample, and the absence of pulmonary infiltrates on chest radiography.
All isolates were identified by manual or automated methods and confirmed using the Vitek 2 system (bioMerieux Vitek, Inc., Hazelwood, MO).
The variables of interest were those that indicated compliance with the VAP prevention measures. We used segmented regression analysis of interrupted time series  to assess the changes in VAP before and after implementation of the ventilator bundle, oral decontamination with chlorhexidine 0.12%, and CASS endotracheal tube for patients requiring mechanical ventilation, according to the interventional phases (Figure 1).
We adjusted a segmented regression model that allowed us to analyze a reduction (or an increase) in VAP rate at each study phase separately: (1) ventilator bundle only, April 2007 to October 2007; (2) ventilator bundle + chlorhexidine, November 2007 to February 2008; (3) ventilator bundle + chlorhexidine + CASS endotracheal tube, March 2008 to December 2010 (Figure 1).
The intercept and slope are the two parameters which define each segment of a time series. The intercept is the value of the series at the beginning of a given time interval, the slope is the change of the measure (VAP rate) over a certain period (e.g., a month). A change in slope (β) is defined by an increase or decrease in the slope of the time step after the intervention, compared with the time step preceding the intervention. It is important to mention that this is not the same as constructing three models of simple linear regression, because the third partition parameters depend on the previous partitions’ parameters.
All tests of statistical significance were 2-sided with a significance level set at 0.05. All the data analyses were performed using SPSS 16.0 and SAS 9.1; SAS Institute Inc, Cary, NC, USA.
Compliance with process measures in each phase
Characteristics of the sustained period of “getting to zero” VAP prevention program in the ICU
Number of patients
Age, mean ± SD (in years)
Male, n (%)
APACHE, mean ± SD
Ventilator utilization ratio
MV days – median (IQR)
ICU LOS days – mean ± SD
Compliance with process measures, n (%)
Daily “sedation interruptions”
Ventilator circuits without changes
CASS endotracheal tube - n
Number of VAPs
Number of VATs
VAP rate per 1,000 ventilator-days
VAT rate per 1,000 ventilator-days
In-hospital mortality in VAP patients, n (%)
In-hospital mortality in ICU patients, n
In-hospital mortality in ICU patients per 10,000 patient days
In 2010, the analysis included 2,260 HOB elevation observations (91% compliance), 390 ventilator circuits without changes (99% compliance) and 390 observations of HMEs changes (94% compliance). Daily sedation vacations, gastric prophylaxis opportunities and DVT/PE prevention opportunities had 2,486 observations with 91% of compliance in all measurements (Table 1).
Incidence density of VAP and in-hospital mortality of VAP patients
The incidence density of VAP per 1,000 ventilator days in the ICU was 1.3 in 2009 (10,889 patient-days) and in 2010 the incidence was 2 (11,095 patients-days). The incidence density of VAT per 1,000 ventilator days in the ICU was 1.0 (10,889 patient-days) in 2009 and in 2010 the incidence was 2 (11,095 patient-days).
Mechanical ventilation days, ICU length of stay, ventilator utilization ratio, number of VAPs, number of VATs, ventilator-days, ventilator-free days, in-hospital mortality of VAP patients and in-hospital mortality ICU patients are shown in Table 1.
Characteristics of infections causing VAP during the sustained period of “getting to zero” VAP prevention program
MV time (days)
BAL + Tracheal aspirate
Correction of GERD
Liver failure/ liver transplant
Respiratory failure/ BCP
Carotid stenosis/ Endarterectomy
Acute respiratory failure/ BCP
K.pneumoniae + P.aeruginosa
E.aerogenes + A.baumannii
Pseudomonas aeruginosa accounted for over 40% of the gram-negative pathogens. The most prevalent pathogens overall were Pseudomonas aeruginosa and Acinetobacter baumannii. The majority of the pathogens were identified by tracheal aspiration. Only 25% of VAP patients (1/4) were investigate by BAL (Table 2).
The mortality rate was 100% for the patients with VAP in 2009 and 83.3% in 2010.
Since 2007, we have set as a priority in our hospital the eradication of nosocomial infections. To this end, we have developed a set of best practices for prevention of ventilator associated pneumonia (VAP). In order to achieve a reduction in VAP rates, we have applied the Institute for Healthcare Improvement bundle model and also implemented other preventive measures (oral chlorhexidine 0.12% and CASS endotracheal tube). Our VAP rates are discussed on a monthly basis at a multidisciplinary meeting with our hospital’s chief executive officer (CEO) and other senior management representatives responsible for ensuring that healthcare practices support a program for infection prevention and control that effectively prevents VAP.
Many hospitals have achieved the goal of getting VAP to zero [14, 15], while others have managed to substantially reduce VAP rates, but believe that eliminating VAP in the intensive care unit may be an unrealistic goal . In a previous publication , we have shown that this was only possible when the compliance with the VAP prevention bundle exceeded 95%, the CASS endotracheal tube was incorporated in daily practices and [17, 18] oral hygiene with chlorhexidine was implemented . In a recent systematic review and meta-analysis of patients at risk for ventilator-associated pneumonia, the use of endotracheal tubes with subglottic secretion drainage was shown to effectively prevent ventilator-associated pneumonia and to be possibly associated with reduced duration of mechanical ventilation and length of ICU stay . We believe this might be the reason for our reduced time and utilization rate of mechanical ventilation, together with the daily sedation vacation included in the VAP bundle. We also believe that obtaining the commitment of all members of the ICU team was ultimately a factor in our success in the implementation of these procedures over the years.
There are several limitations to this study. This is not a randomized trial but a quasi-experimental, interrupted time series study. Quasi-experimental study designs are frequently used when it is not logistically feasible to conduct a controlled trial. Thus, other unmeasured factors might have coincided with the interventions effective since April 2007 (implementation of the ventilator bundle), resulting in a decrease in VAP rates in our ICU. However, this seems unlikely because there had been no decrease in VAP rates over the previous several years (Figure 5). Data from our ICU in 2011 and in the first quarter of 2012 have shown that the VAP rate continues low (1.5 and 1.9, respectively). Finally, as this intervention was performed at a single medical center, it might be inappropriate to extrapolate our results (i.e. VAP mortality) to other hospitals. Even considering some aspects as the attributable mortality of VAP, other studies applying more sophisticated analysis such as multistate model that appropriately handle VAP as a time-dependent event or competing risk survival analysis have shown rates of attributable mortality as low as 10% [6, 24]. Despite these limitations, our study further support the assumption that controlling VAP rates can be a sustained with the monitoring of multiple performance measures and quality improvement efforts.
The process and the outcome measures for VAP presented here are derived from published guidelines and other relevant literature. While we recognize that the VAP definition may be subject to criticism due to its many subjective aspects, we managed to keep the whole team’s commitment to preventive measures for over two years, which demonstrates this is a sustainable program for preventing ventilator-associated pneumonia in the intensive care unit.
Ventilator associated tracheobronchitis
Intensive Care Unit
Institute for Healthcare Improvement
Institutional Review Board of Hospital Israelita Albert Einstein
National Nosocomial Infectious Surveillance System
Elevation of the head of the bed
Deep venous thrombosis/pulmonary thromboembolism
Center for Disease Control and Prevention/National Healthcare Safety Network
Continuous aspiration of subglottic secretions endotracheal tube
Chief executive officer.
We gratefully acknowledge all the healthcare workers Hospital Israelita Albert Einstein who continue working in VAP prevention.
No external funding was received for this work.
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