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REBEL Core Cast 147.0–Ventilators Part 5: Key Mechanical Ventilator Pressures & Definitions Made Simple

REBEL Core Cast 147.0–Ventilators Part 5: Key Mechanical Ventilator Pressures & Definitions Made Simple

REBEL Cast

December 22, 202514m 20s

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Show Notes

🧭 REBEL Rundown

🗝️ Key Points

  • 💨 Peak vs. Plateau Pressures: PIP reflects total airway resistance and compliance, while Pplat isolates alveolar compliance—elevations in both suggest decreased lung compliance (e.g., ARDS, pulmonary edema, pneumothorax).
  • 🧱 PEEP Protects Alveoli: Maintains alveolar recruitment and prevents collapse; typical range 5–8 cmH₂O, but higher levels may benefit moderate–severe ARDS.
  • ⚙️ Driving Pressure (ΔP = Pplat − PEEP): Lower ΔP reduces atelectrauma and improves outcomes; optimize by adjusting PEEP thoughtfully.
  • 💥 Prevent VILI: Keep Pplat < 30 cmH₂O, use low tidal volumes (6 mL/kg IBW), and monitor for barotrauma, volutrauma, atelectrauma, and biotrauma.
  • 📚 Evidence-Based Practice: ARDSNet and subsequent trials confirm that lung-protective ventilation—low Vt, limited pressures, and individualized PEEP—improves survival in ARDS.

📝 Introduction

This episode reviews essential ventilator pressures and how to interpret them during ICU rounds.

🚀 Under Pressure

  1. Peak Inspiratory Pressure (PIP)
    • Definition: Total pressure required to deliver a breath.
    • Reflects: Airway resistance + lung/chest wall compliance.
    • Common Causes of ↑ PIP:
      • Mucus plugging
      • Biting the endotracheal tube
      • Kinked tubing or bronchospasm
  2. Plateau Pressure (Pplat)
    • Definition: Alveolar pressure measured after an inspiratory hold.
    • Reflects: Lung compliance (stiffness of lung tissue).
    • When Both PIP & Pplat Are Elevated:
      → Indicates poor compliance (e.g., ARDS, pulmonary edema, pneumothorax).
  3. Positive End-Expiratory Pressure (PEEP)
    • Definition: Pressure remaining in airways at end-expiration to prevent alveolar collapse.
    • Typical Range: 5–8 cmH₂O but needs to titrated to meet patient requirements 
    • Notes:
      • Provides physiologic “glottic” PEEP in intubated patients.
      • Using high PEEP strategy shows mortality benefit only in moderate–severe ARDS in meta-analysis.
  4. Driving Pressure (ΔP)
    • Definition: ΔP = Pplat − PEEP.
    • Reflects: Pressure needed to keep alveoli open during the respiratory cycle.
    • Goal: Lower ΔP → less atelectrauma & improved outcomes.
    • Optimize: Increase PEEP to reduce ΔP and alveolar cycling.

📖 Interpreting High PIP/High Pplat

  • ↑ PIP & ↑ Pplat
    • Interpretation: ↓ Compliance
    • Common Causes: ARDS, pulmonary edema, pleural effusion, pneumothorax
  • ↑ PIP & Normal/Low Pplat
    • Interpretation: ↑ Airway Resistance
    • Common Causes: Mucus plug, bronchospasm, tube obstruction or biting

🤕 Ventilator-Associated Lung Injury (VILI)

  1. Barotrauma:
    • Mechanism: Excessive airway pressure damages alveoli.
    • Prevention: Keep Pplat < 30 cmH₂O.
  2. Volutrauma:
    • Mechanism: Overdistension from excessive tidal volumes.
    • Prevention: Use low tidal volume ventilation (6 mL/kg ideal body weight).
    • ARDSNet trial: 6 mL/kg → lower mortality compared to 12 mL/kg.
    • Ideal Body Weight: Based on height and sex, not actual weight.
    • Typical patient: Tidal Volume: 6–8 mL/kg IBW
    • ARDS: Tidal Volume: 4–6 mL/kg IBW
  3. Atelectrauma:
    • Mechanism: Repeated opening/collapse of unstable alveoli.
    • Prevention: Optimize PEEP to keep alveoli open and reduce driving pressure.
  4. Biotrauma:
    • Mechanism: Inflammatory cascade (↑ IL-6, TNF-α) from mechanical injury.
    • Effect: Can trigger systemic inflammation & multiorgan dysfunction.
    • Prevention: Minimize all other forms of VILI.

Post Peer Reviewed By: Marco Propersi, DO (Twitter/X: @Marco_propersi), and Mark Ramzy, DO (X: @MRamzyDO)

👤 Show Notes

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