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)

• Hospital-acquired pneumonia (HAP):
  Pneumonia occurring ≥48 hours after hospital admission, not incubating at admission.
• Ventilator-associated pneumonia (VAP):
  Subset of HAP developing ≥48 hours after endotracheal intubation.

 Important Update (Guidelines – ATS/IDSA 2016, still current):

• Term Healthcare-associated pneumonia (HCAP) is obsolete → removed due to poor specificity for MDR pathogens.

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

2. Biofilm formation on ETT

• Bacteria protected from antibiotics

3. Microaspiration

• Inadequate cuff pressure (<20 cmH₂O)

4. Impaired host defenses

• Sedation, paralysis, critical illness

5. 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

Earlier (pre-2016), HAP/VAP was divided into:

• Early onset (<5 days) → low MDR risk
• Late onset (≥5 days) → high MDR risk

 This was used to decide:

• Narrow vs broad antibiotics

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

Quantitative Culture Cutoffs

 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
• Renal replacement therapy

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