Protective lung ventilation

General

Protective lung ventilation aims for low tidal volume ventilation. A large study has shown a decrease in mortality, when patients with acute lung injury/ARDS were ventilated with low tidal volumes. Today, the protective lung ventilation algorithm by the ARDS network provides a reasonable default approach for mechanically ventilated patients, especially those at risk for developing ARDS

Ventilation setup and adjustment

• Calculate the predicted body weight (men: 50 + 0.91 (length in cm - 152), women: 45 + 0.91 (length in cm - 152)). A calculator can be found in the ventilation calculators
• Initial tidal volume Vt = 8ml/kg predicted body weight
  • Reduce Vt by 1 ml/kg at intervals up to 2 hours until Vt = 6 ml/kg/PBW
• set RR (respiratory rate) to baseline ventilation, but not over 35/min
• adjust Vt and RR to achieve pH and plateau pressure goal

Oxygenation Goal

• Goal: paO₂ 55 – 88 mmHg or SpO₂ 88 – 95 %
• use PEEP minimum 5 cmH₂O
• consider using FiO2/PEEP table:

Plateau pressure

• Goal: plateau pressure ≤ 30 cmH₂O
• if pPlat > 30 cmH₂O
  • decrease Vt by 1 ml/kg until minimum Vt 4 ml/kg is reached
• if pPlat < 25 cmH₂O and Vt < 6 ml/kg
  • increase Vt by 1 ml/kg until pPlat > 25 cmH₂O or Vt = 6 ml/kg

pH

• Goal: pH 7.3 – 7.45
• Acidosis:
  • pH < 7.3: Increase RR until pH > 7.3 or PaCO₂ < 25 mmHg
    • maximum RR 35/min
  • pH < 7.15: Increase RR to 35/min
    • if pH remains < 7.15: increase Vt in 1 ml/kg steps until pH > 7.15 (target of 30 cmH₂O max be exceeded)
    • consider NaHCO₃
• Alkalosis
  • pH > 7.45: Decrease RR if possible

Permissive hypercapnia

Elevated PaCO₂ can be the result of low volumes and should be tolerated, as long as the pH is manageable. The articles I’ve come across so far suggest an pH > 7.1 or > 7.2 as tolerable.

Additional links

• ARDSnet Ventilator card

Pocket card

The gist of this page is available as pocket card. You can download it via the link below.

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