• • ❌ Don’t chase perfect numbers: Adequate and safe is often better than “perfect but harmful.”
  • 💨 Oxygenation levers: Start with FiO₂ and PEEP, but remember MAP is the true driver.
  • 🫁 Ventilation levers: Adjust RR and TV, tailored to underlying physiology.
  • 🚫 Watch your obstructive patients: Sometimes less RR is more.

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When you take the airway, you take the wheel and you now control the patient’s oxygenation and ventilation. In this REBEL Crit episode, Dr. Lodeserto and Dr. Acker walk through the physiology, ventilator strategies, and clinical curveballs that separate calm control from chaos at the bedside.

1. Oxygenation — Getting O₂ In

• Primary levers: FiO₂ (fraction of inspired oxygen) and PEEP (positive end-expiratory pressure).
• Real driver: Mean Airway Pressure (MAP) :  the average pressure applied to the lungs across the entire respiratory cycle.
• Key physiology:
  • Oxygen enters blood by diffusion down a concentration gradient.
  • Adequate alveolar surface area is critical → PEEP keeps alveoli open, prevents collapse/reopen injury, and ensures FiO₂ delivery actually translates into effective oxygenation.
• MAP analogy: Just as mean arterial pressure drives perfusion, mean airway pressure drives oxygenation. Prolonged inspiratory time or sustained pressure (e.g., APRV, inverse I:E) can raise MAP.
• Risks: Excessive pressure/volume can cause barotrauma or volutrauma. 

2. Ventilation — Getting CO₂ Out

• Primary levers: Tidal Volume (TV) and Respiratory Rate (RR).
• Minute Ventilation = RR × TV.
• Mechanism: Ventilation removes CO₂ through bulk convection (movement of air in and out).

Disease-specific strategies:

• Obstructive Disease (COPD / Asthma)
  • RR ↓ to allow more time for exhalation.
  • Ensure expiratory flow = inspiratory flow → prevents air trapping.
  • If not equal → auto-PEEP → increased intrathoracic pressure → ↓ preload, risk of hypotension, cardiac arrest, or pneumothorax.
• Metabolic Acidosis
  • RR ↑ to blow off CO₂ and buffer acidosis.
• ARDS
  • Tidal volume limited to 4–6 mL/kg IBW to minimize ventilator-induced lung injury.
  • RR becomes the main adjustment knob.
  • Exception: in obstructive lung disease, patients need extra time to exhale (I:E may be 1:4–1:6).

Ventilator management is part science, part art. Understanding the physiology and knowing when to bend or break the rules  helps protect patients from ventilator-induced injury and improves outcomes.

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

Show Notes By: Rubén Tapia-Bucheli, M.D.

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The post REBEL Core Cast 143.0–Ventilators Part 3: Oxygenation & Ventilation — Mastering the Balance on the Ventilator appeared first on REBEL EM - Emergency Medicine Blog.