What is ventilator-induced lung injury (VILI) in the Cardiovascular Intensive Care Unit (CVICU), its signs and symptoms, treatment, and relevant CVICU tips?

Ventilator-Induced Lung Injury in CVICU: Signs, Symptoms, Treatment, and Tips

Ventilator-induced lung injury (VILI) is a potentially life-threatening complication of mechanical ventilation that occurs when the ventilator strategy causes or worsens lung damage, contributing to increased morbidity and mortality in CVICU patients. 1

Definition and Mechanisms

VILI occurs through several key mechanisms:

• Volutrauma/Barotrauma: Lung injury caused by excessive tidal volumes and high inspiratory pressures that overstretch lung tissue 1, 2
• Atelectrauma: Damage from repetitive opening and closing of alveoli causing shear stress on lung tissue 1, 2
• Biotrauma: Inflammatory response triggered by mechanical injury that can lead to systemic inflammation and multi-organ failure 2
• Shear strain: Injury from uneven distribution of ventilation causing stress between different lung regions 3

Signs and Symptoms

VILI often overlaps with the underlying condition (e.g., ARDS) making diagnosis challenging, but key indicators include:

• Radiographic changes: New or worsening infiltrates on chest imaging 1, 4
• Deteriorating gas exchange: Worsening PaO2/FiO2 ratio despite stable or increasing ventilator support 1
• Decreased lung compliance: Stiffening of the lungs requiring higher pressures to deliver the same tidal volume 5
• Increased work of breathing: Patient-ventilator asynchrony or increased respiratory effort 6
• Inflammatory markers: Elevation in inflammatory mediators in bronchoalveolar lavage fluid and systemic circulation 2
• Hemodynamic instability: Can occur as biotrauma leads to systemic inflammatory response 2

Treatment Strategies

Prevention (Primary Treatment)

1. Low Tidal Volume Ventilation

   • Use 4-8 ml/kg predicted body weight 1
   • Maintain plateau pressure ≤30 cmH2O 1

2. Optimal PEEP Selection

   • Higher PEEP in moderate to severe ARDS 1
   • Base PEEP on gas exchange, hemodynamic status, and lung recruitability 1
   • Consider recruitment maneuvers before PEEP selection in moderate to severe ARDS 1

3. Prone Positioning

   • Implement for >12 hours/day in severe ARDS 1
   • Monitor for complications including pressure injuries and tube displacement 1

4. Patient Positioning

   • Maintain semi-recumbent position (30-45° head elevation) to reduce aspiration risk 4
   • Consider kinetic bed therapy in appropriate patients 1

5. Ventilator Circuit Management

   • Change ventilator circuits only for each new patient and when soiled 1
   • Use closed endotracheal suction systems 1
   • Consider endotracheal tubes with subglottic secretion drainage capability 4

Management of Established VILI

1. Reassessment of Ventilator Settings

   • Immediately reduce tidal volumes and plateau pressures if elevated 1
   • Optimize PEEP to prevent atelectrauma 1

2. Adjunctive Therapies

   • Consider neuromuscular blockade in severe cases to reduce ventilator asynchrony 1
   • Evaluate for extracorporeal membrane oxygenation (ECMO) in refractory cases 1

3. Anti-inflammatory Strategies

   • Consider corticosteroids in patients with evidence of fibroproliferation 1
   • Avoid excessive fluid administration 1

CVICU-Specific Tips

1. Post-Cardiac Surgery Considerations

   • Be vigilant for right ventricular dysfunction when increasing PEEP 5
   • Balance respiratory and hemodynamic goals, especially in patients with unstable cardiovascular status 1

2. Monitoring

   • Regularly assess plateau pressures, driving pressures, and mechanical power 2
   • Monitor for patient-ventilator asynchrony which can worsen VILI 6, 2
   • Track trends in compliance and resistance to detect early deterioration 5

3. Weaning Strategies

   • Implement standardized weaning protocols to minimize ventilation duration 4
   • Consider daily interruption of sedation when appropriate 4
   • Avoid reintubation whenever possible as it increases risk of complications 4

4. Common Pitfalls to Avoid

   • Don't use "one-size-fits-all" ventilation strategies; personalize based on patient physiology 5
   • Avoid excessive oxygen (target SaO2 >88% rather than 100%) to prevent oxidative injury 2
   • Don't delay implementing lung-protective strategies in at-risk patients 7
   • Avoid excessive sedation that may prolong mechanical ventilation 4

5. Special Considerations

   • Maintain glycemic control as hyperglycemia increases risk of complications 4
   • Consider the impact of blood transfusions on lung injury risk 4
   • Evaluate for and treat ventilator-associated pneumonia promptly 1

By implementing these evidence-based strategies, clinicians can significantly reduce the incidence and severity of VILI in CVICU patients, potentially improving outcomes and reducing mortality.