Ventilator-Associated Pneumonia (VAP) 

1. Definition

Ventilator-Associated Pneumonia (VAP)

  • Pneumonia occurring ≥48 hours after endotracheal intubation and initiation of invasive mechanical ventilation
  • Infection not present or incubating at the time of intubation

Related Terms (CDC Surveillance)

Term

Definition

VAP

Clinical diagnosis

Ventilator-Associated Event (VAE)

Surveillance definition

VAC

Ventilator-associated condition

IVAC

Infection-related VAC

Possible VAP

IVAC + microbiology

 Exams focus: Clinical practice still uses VAP, not VAEs.


2. Epidemiology

  • Accounts for ~25–50% of ICU infections
  • Increases:
    • Ventilation duration
    • ICU stay
    • Cost
    • Antibiotic exposure


3. Pathogenesis 

Core Mechanism

Microaspiration of colonized secretions around ETT cuff into lower airways

Stepwise Pathogenesis

  1. Oropharyngeal colonization
    • ICU flora replaces normal flora
  1. Biofilm formation on ETT
    • Bacteria protected from antibiotics
  1. Microaspiration
    • Inadequate cuff pressure (<20 cmH₂O)
  1. Impaired host defenses
    • Sedation, paralysis, critical illness
  1. Direct inoculation
    • Suctioning, bronchoscopy

Other Mechanisms

  • Hematogenous spread (rare)
  • Gastric aspiration
  • Sinusitis (NG tubes)

4. Risk Factors

Patient-Related

  • Advanced age
  • Comorbidities (COPD, DM, CKD)
  • Immunosuppression
  • Malnutrition
  • Altered sensorium

ICU / Ventilation-Related

  • Prolonged ventilation
  • Reintubation
  • Supine position
  • Heavy sedation
  • Paralytics
  • Enteral feeding
  • Nasogastric tube
  • Stress ulcer prophylaxis (↑ gastric pH)

Microbiological

  • Prior antibiotics
  • Colonization with MDR organisms


5. Microbiology

 Antibiotic-sensitive pathogens

  • Streptococcus pneumoniae
  • Haemophilus influenzae
  • MSSA
  • Enteric Gram-negative bacilli

High risk of MDR pathogens

  • Pseudomonas aeruginosa
  • Acinetobacter baumannii
  • Klebsiella pneumoniae (ESBL / CRE)
  • MRSA
  • Stenotrophomonas maltophilia


6. Clinical Features

Systemic

  • Fever or hypothermia
  • Leukocytosis / leukopenia
  • Sepsis / septic shock

Respiratory

  • New or worsening hypoxemia
  • Increased ventilator requirements
  • Purulent tracheal secretions
  • Bronchial breath sounds

 Clinical signs alone are nonspecific


7. Diagnosis

No single gold standard

Diagnostic Criteria (Combination of):

1️⃣ Radiology

  • New or progressive infiltrate on chest X-ray / CT
  • Consolidation, cavitation

 Poor specificity in ARDS, atelectasis, pulmonary edema


2️⃣ Clinical Criteria

  • Fever
  • Leukocytosis
  • Purulent secretions
  • Worsening oxygenation


3️⃣ Microbiological Confirmation

Respiratory Samples

Method

Advantages

Limitations

Endotracheal aspirate (ETA)

Easy, non-invasive

Colonization

BAL

Higher specificity

Invasive

Protected specimen brush

Very specific

Rarely used

Quantitative Culture Cutoffs

Sample

Significant Growth

ETA

≥10⁵ CFU/mL

BAL

≥10⁴ CFU/mL

PSB

≥10³ CFU/mL

 ATS/IDSA: Prefer non-invasive sampling with semi-quantitative cultures


Biomarkers

  • Procalcitonin
    • Helps in antibiotic de-escalation
    • Not diagnostic alone
  • CRP – nonspecific


8. Differential Diagnosis

  • Pulmonary edema
  • ARDS
  • Atelectasis
  • Pulmonary embolism
  • Aspiration pneumonitis
  • Diffuse alveolar hemorrhage


9. Management

Principles

  1. Early empiric antibiotics
  2. Cover MDR organisms if risk present
  3. De-escalate based on cultures
  4. Shorter duration preferred


10. Empiric Antibiotic Therapy (ATS/IDSA 2016 )

Assess MDR Risk

  • Prior IV antibiotics (last 90 days)
  • Septic shock
  • ARDS preceding VAP
  • ≥5 days hospitalization
  • High local resistance rates


Empiric Regimens

WITHOUT MDR risk

 ONE anti-pseudomonal agent

  • Piperacillin-tazobactam
  • Cefepime
  • Levofloxacin
  • Imipenem / Meropenem


WITH MDR risk

 Two anti-pseudomonal agents + MRSA coverage

Anti-pseudomonal (choose 2 from different classes):

  • β-lactam:
    • Piperacillin-tazobactam
    • Cefepime
    • Meropenem
  • PLUS:
    • Aminoglycoside (amikacin)
    • OR Fluoroquinolone

MRSA coverage:

  • Vancomycin
  • Linezolid (preferred in renal failure)


Acinetobacter

  • Carbapenem (if sensitive)
  • Colistin / Polymyxin B
  • High-dose sulbactam

CRE

  • Ceftazidime-avibactam
  • Meropenem-vaborbactam
  • Colistin (last resort)


11. Duration of Therapy

Standard Duration

  • 7 days (strong recommendation)

Longer duration only if:

  • Non-fermenters (Pseudomonas, Acinetobacter)
  • Slow clinical response
  • Empyema / abscess
  • Immunosuppression

 Shorter duration ↓ resistance & toxicity


12. De-escalation Strategy 

  • Narrow antibiotics based on cultures
  • Stop MRSA coverage if cultures negative
  • Use Procalcitonin-guided discontinuation
  • Avoid “just in case” continuation


13. Adjunctive Therapy

  • Lung-protective ventilation
  • Adequate PEEP
  • Early mobilization
  • Glycemic control
  • Nutrition optimization

 No routine steroids for VAP


14. Prevention – VAP Bundle 

Ventilator Care Bundle

  1. Head-of-bed elevation (30–45°)
  2. Daily sedation interruption
  3. Daily assessment of extubation readiness
  4. Peptic ulcer prophylaxis (judicious)
  5. DVT prophylaxis
  6. Oral care with chlorhexidine(controversial)
  7. Subglottic secretion drainage
  8. Maintain ETT cuff pressure (20–30 cmH₂O)


Other Measures

  • Avoid unnecessary intubation
  • Prefer NIV / HFNC
  • Early tracheostomy (selected patients)
  • Strict hand hygiene


15. Complications

  • Septic shock
  • ARDS
  • Lung abscess
  • Empyema
  • Prolonged ventilation
  • MDR colonization


16. Prognostic Factors

Poor prognosis associated with:

  • Delay in appropriate antibiotics
  • MDR organisms
  • Septic shock
  • Advanced age
  • Organ failure
  • High APACHE II score