Pathogenesis

 

Ventilator-associated pneumonia (VAP) is defined as a nosocomial pneumonia in a patient on mechanical ventilatory support for >48 hours. It is the leading nosocomial infection in critically ill patients and is the second most common hospital-associated infection after that of the urinary tract.  The primary risk factor for the development of hospital-associated bacterial pneumonia is mechanical ventilation (with its requisite endotracheal intubation).

 

An understanding of its epidemiology/pathogenesis allows for the development of strategies to decrease its occurrence, as described by Safdar et al.

 

"The major route for acquiring endemic VAP is oropharyngeal colonization by the endogenous flora or by pathogens acquired exogenously from the intensive care unit environment, especially the hands or apparel of healthcare workers, contaminated respiratory equipment, hospital water, or air.  

 

The stomach represents a potential site of secondary colonization and reservoir of nosocomial Gram-negative bacilli.  Endotracheal-tube biofilm formation may play a contributory role in sustaining tracheal colonization and also have an important role in late-onset VAP caused by resistant organisms. Aspiration of microbe-laden oropharyngeal, gastric, or tracheal secretions around the cuffed endotracheal tube into the normally sterile lower respiratory tract results in most cases of endemic VAP.  In contrast, epidemic VAP is most often caused by contamination of respiratory therapy equipment, bronchoscopes, medical aerosols, water (e.g., Legionella) or air (e.g., Aspergillus or the severe acute respiratory syndrome virus)." (1)

 

Prevention

 

Strategies to prevent VAP have been developed and are currently one of IHIs major initiatives.  These measures represent an organized process that guarantees early recognition of pneumonia and consistent application of “best practices”.  


The Ventilator Bundle is a series of interventions related to ventilator care that, when implemented together, will achieve significantly better outcomes.


The key components of the Ventilator Bundle are:

  • Elevation of the Head of the Bed
  • Daily "Sedation Vacations" and Assessment of Readiness to Extubate
  • Peptic Ulcer Disease Prophylaxis
  • Deep Venous Thrombosis Prophylaxis 
  • Routine surveillance of VAP, to track endemic VAPs and facilitate early detection of outbreaks, is mandatory.

 

Intervention

 

When Prevention doesn’t work and ventilator-associated pneumonia occurs, the appropriate intervention is of utmost importance.

The first step is diagnosis of VAP.  As described by Mayhall, the diagnostic test that most accurately diagnoses VAP is quantitative culture and microscopic examination of lower respiratory tract secretions obtained by bronchoscopically directed techniques such as the protected specimen brush and bronchoalveolar lavage.(2)

 

As stated in the Guidelines (2005) for the management of adults with hospital-acquired, ventilator-associated, and healthcare-associated pneumonia:

 

"The clinical strategy emphasizes prompt empiric therapy for all patients suspected of having HAP.  The driving force behind this strategy is the consistent finding that delay in the initiation of appropriate antibiotic therapy for patients with HAP is associated with increased mortality.  The selection of initial antibiotic therapy is based on risk factors for specific pathogens, modified by knowledge of local patterns of antibiotic resistance and organism prevalence.  Therapy is modified on the basis of the clinical response on Days 2 and 3, and the findings of semiquantitative cultures of lower respiratory tract secretions. For a detailed discussion on treatment, as well as overall management of patients with VAP and HAP, review the Guidelines at Journal of Respiratory and Critical Care Medicine." (3)

 

 

References

(1) Safdar, N., Crnich, C.J., Maki, D.G. The pathogenesis of ventilator-associated pneumonia: its relevance to developing effective strategies for prevention.  Respiratory Care June 2005; Vol.50 No.6; 724-741.

 

(2) Mayhall G. C.  Special Issue: Ventilator-Associated Pneumonia or Not? Contemporary Diagnosis. Emerging Infectious Diseases Vol. 7, No. 2, March-April 2001 p. 201.

 

(3) American Thoracic Society and Infectious Diseases Society of America. Guidelines for the management of adults with hospital-acquired, ventilator-associated, and healthcare-associated pneumonia American.  Journal of Respiratory and Critical Care Medicine, Vol 171. pp. 388-416, (2005).



Related Links:

 

The American Association for Respiratory Care

The Science Journal of Respiratory Care


RESPIRATORY CARE
is the official science journal of the American Association for Respiratory Care (AARC).

 

Clinical Foundations

A Patient-Focused Education Program for Respiratory Care Professionals

 

 

 

 

Institute of Healthcare Improvement
5 million lives campaign

The 5 Million Lives Campaign is a voluntary initiative to protect patients from five million incidents of medical harm over the next two years (December 2006 – December 2008).

 


Center for Disease Control and Prevention (CDC)
Morbidity and Mortality Weekly Report

 

Recommendations of CDC and the Healthcare Infection Control Practices Advisory Committee

 

 

Other Resources: