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Do you increase PEEP or FIO2 first?

Published in Ventilator Oxygenation Strategies 2 mins read

When treating hypoxia in a mechanically ventilated patient, increasing the Fraction of Inspired Oxygen (FiO2) is often the initial and most immediate adjustment.

Addressing hypoxia, which is assessed by evaluating the patient's PaO2 or SpO2 levels, typically involves two primary strategies: adjusting FiO2 or Positive End Expiratory Pressure (PEEP).

Strategies for Improving Oxygenation

  • Increasing FiO2: This is frequently the first step taken due to its direct and rapid impact on oxygen delivery. By increasing the percentage of oxygen in the inspired air, more oxygen becomes available for gas exchange in the lungs, leading to a quicker improvement in arterial oxygen saturation.

  • Adjusting PEEP: If increasing FiO2 alone does not adequately resolve the hypoxia, or if the underlying lung condition benefits from enhanced alveolar recruitment, PEEP becomes a critical intervention. PEEP maintains a positive pressure in the airways at the end of exhalation, preventing the collapse of small airways and alveoli. This helps to increase the functional residual capacity, improve lung compliance, and enhance the surface area available for gas exchange.

    PEEP Titration Guidelines

    The adjustment of PEEP is a deliberate process to optimize oxygenation while minimizing potential adverse effects.

    1. Initial PEEP Setting: PEEP is typically started at 5 cmH2O as a foundational setting on mechanical ventilation.
    2. Gradual Increments: If the patient remains hypoxic or if further lung recruitment is desired, PEEP can be carefully increased. Common increments involve raising PEEP from the initial 5 cmH2O to 8 cmH2O, and then to 10 cmH2O if needed.
    3. Observation Period: It is crucial to allow approximately 20 minutes between each PEEP adjustment. This waiting period is essential for the alveoli to recruit fully and for clinicians to assess the patient's physiological response, including oxygenation status and hemodynamics, before making further changes. This deliberate approach contrasts with the immediate effect of FiO2 adjustments.

Comparative Overview of Oxygenation Strategies

Parameter Primary Action for Hypoxia Key Benefit Titration Considerations
FiO2 Initial, rapid increase Immediate oxygen delivery Quick response, generally no significant lag time.
PEEP Subsequent titration (if needed) Alveolar recruitment, improved gas exchange Gradual increase (e.g., 5 → 8 → 10 cmH2O), requires a 20-minute waiting period between changes for alveolar recruitment.