• • 💨 Master the 3 Types of Breaths
    Control, Assist, and Spontaneous — know the difference before tackling ventilator modes.
  • 📦 Breath Delivery: Volume vs. Pressure
    Volume-Targeted = fixed volume → monitor pressure
    📈 Pressure-Targeted = fixed pressure → monitor volume
  • 🫁 Lung Compliance = Pressure-Volume Relationship
    Volume mode: ↑ pressure = ↓ compliance (stiff lungs)
    Pressure mode: ↓ tidal volume = ↓ compliance

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For many medical residents, the ICU can feel like stepping into a pressure cooker. At the heart of that stress often lies one intimidating machine: the ventilator. Rather than diving headfirst into complex ventilator modes, this episode lays a critical foundation by breaking down the basic building blocks of mechanical ventilation, something every clinician should master before moving on to more advanced concepts. Once you know the 3 types of breaths and how those breaths are delivered, you can more easily understand most of the mechanical ventilator modes. 

To simplify things, we use a pull-up analogy to explain the types of ventilator breaths:

• Once you know the type of breath, the next key concept is how it’s delivered:

  1. Volume-Targeted Delivery

  • The ventilator delivers a fixed tidal volume (e.g., 400 mL) with each control or assist breath.
  • What to monitor: Pressure. As lung compliance worsens, pressure increases.
  • Risk: Barotrauma if the pressure becomes too high.

  2. Pressure-Targeted Delivery

  • The ventilator delivers air to a preset pressure (e.g., 15 cm H₂O).
  • What to monitor: Tidal volume. As compliance drops, so does delivered volume.
  • Adjustment: Modify pressure to maintain appropriate ventilation.

• The relationship between pressure and volume is described by compliance:
  • 📐 Compliance = Δ Volume / Δ Pressure
• In volume mode:
  • Rising pressure to achieve the same volume = decreased compliance (stiff)
  • Decreasing pressure to achieve the same volume = increased compliance (loose)
• In pressure mode:
  • Dropping tidal volume at a constant pressure = decreased compliance (stiff)
  • Rising tidal volume at a constant pressure = increased compliance (loose)

Before tackling advanced ventilator modes, master these foundational concepts:

• The three breath types
• The two delivery methods
• The role of lung compliance

Once you’ve got these down, the rest of mechanical ventilation becomes far easier to understand.

Stay tuned for Part 2, where we’ll build on this foundation and unpack the most commonly used ventilator modes.

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

Show Notes By: Nicole Ebalo, DO

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The post REBEL Core Cast 141.0–Ventilators Part 1: Simplifying Mechanical Ventilation — Types of Breathes appeared first on REBEL EM - Emergency Medicine Blog.