Pneumonia (ventilator-associated or hospital-acquired)

Essential Evidence

Last Updated on 2023-04-11 © 2023 John Wiley & Sons, Inc.

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Christopher D. Jackson, MD, Assistant Professor of Medicine, University of Tennessee Health Science Center
Kristin A. Signater, MD, Medical Resident, University of Tennessee Health Science Center
Sarah Harirforoosh, Medical Student, University of Tennessee Health Science Center
William T. Prater, Medical Student, University of Tennessee Health Science Center
Ali Hassoun, MD, Clinical Assistant Professor, Alabama Infectious Diseases Center

Mark H. Ebell, MD, MS, Professor, College of Public Health, University of Georgia

Overall Bottom Line

  • Clinical criteria for ventilator-associated pneumonia (VAP) include new lung infiltrate in a ventilated patient and at least two of the following: temperature >38°C, leukopenia or leukocytosis, and purulent secretions. C Semi-quantitative culture is useful for the identifying causative organism; sampling by endotrachial aspiration is recommended for patients with VAP and using spontaneous sputum, induced sputum, or nasotracheal suctioning in non-ventilated patients with HAP.C
  • Antimicrobial therapy should be started promptly and based on local resistance patterns. The decision regarding single, dual or triple antibiotic therapy depends on patient mortality risk, risk factors for MDR pathogens, and whether HAP or VAP is treated. 27B
  • The recommended duration is 7 days for patients with HAP or VAP who have a good clinical response. 27B
  • Measures to prevent VAP include a bundle of services: oral decontamination, elevating head of bed to 30° to 45°, use of a new ventilator circuit for each patient and replacing it when soiled, suction of subglottic secretion, and minimizing the duration of intubation. A


Ventilator-associated pneumonia (VAP) is pneumonia that occur 48 to 72 hours after endotracheal intubation. Early onset VAP occur within 4 days of intubation, while late onset VAP occur 5 days or more after intubation. Hospital-acquired pneumonia (HAP) is pneumonia that begins after hospitalization but is not associated with mechanical ventilation.Nosocomial pneumonia encompasses both HAP and VAP.


  • VAP occurs in 8% to 28% of intubated patients. 12
  • The incidence is 1 to 4 per 1000 ventilator days. 11

Other Impact

  • VAP is the most common nosocomial infection in the ICU. 12
  • HAP and VAP, together, account for 21.8% of healthcare-associated infections, with 39.1% of those associated with a mechanical ventilator. 33
  • VAP has been shown to be associated with longer ICU and hospital lengths of stay. 34

Causes of the Condition

  • VAP is caused by a wide spectrum of organisms.
  • The most common organisms causing nosocomial pneumonia are KEEPS: klebsiella, enterobacter, e.coli, pseudomonas aeurignosa, and staphylococcus aureus.
  • Common bacteria include aerobic Gram-negative bacilli such as Pseudomonas aeruginosa, Escherichiacoli, Klebsiella pneumoniae, and Acinetobacter species.
  • Infections due to Gram-postive cocci such as Staphylococcus aureus including MRSA are increasing.


  • Most cases of VAP are caused by the aspiration of infected secretion from oropharynx, although a few cases occur secondary to blood stream infection.
  • Critical illness leads to rapid colonization of the oropharynx with pathogenic bacteria, caused by changes in the host defense, antibiotic exposure, and possible changes in bacterial adhesion and host surface receptors.
  • Many of the usual host defense mechanisms including immune function are less effective.
  • Profound changes occur in the function and structure of the alveoli.
  • Neutrophil dysfunction and inadequate phagocytosis increase susceptibility to infection.

Risk Factors

Risk Factor
Intubation duration
Mechanical ventilation duration
Colonization of the ventilator circuit
Supine body position
Enteral nutrition
Oropharyngeal colonization
Systemic antibiotics for prolong period
H2 blockers and antacids
Blood transfusion
Cigarette smoking
Male sex
SOFA score