Obstructive Lung Strategy

Written on 10/10/2024
jombuatapp

When ventilating patients with obstructive lung diseases such as asthma and COPD, the primary goals are to prevent air trapping (auto-PEEP), avoid barotrauma, and ensure adequate gas exchange.

 

1. Set Initial Tidal Volume (TV)

  • TV: 7–8 mL/kg of Ideal Body Weight (IBW)

Rationale: Provides sufficient ventilation while minimizing the risk of overdistension.

 

2. Set Respiratory Rate (RR)

  • RR: 12–14 breaths per minute

Rationale: A moderate RR allows for longer exhalation time, reducing the risk of air trapping.

 

3. Set Inspiratory Flow Rate

  • Inspiratory Flow Rate: 80 L/min

Rationale: A higher flow rate shortens inspiratory time, allowing more time for exhalation.

 

4. Set Fraction of Inspired Oxygen (FiO₂)

  • FiO₂: Start at 1.0 (100%)
  • Titrate:
    • Aim for:
      • PaO₂: 55–80 mm Hg
      • SpO₂: 88–95%

Rationale: Begin with high FiO₂ to correct hypoxemia, then reduce to avoid oxygen toxicity.

 

5. Set Positive End-Expiratory Pressure (PEEP)

  • PEEP: 0–5 cm H₂O
    • Lower PEEP in Asthma: PEEP 0–2 cm H₂O
    • Optimal PEEP in COPD: PEEP 5 cm H₂O

Rationale: May counterbalance intrinsic PEEP and reduce the work of breathing.

 

6. Monitor for Auto-PEEP

Auto-PEEP: Intrinsic PEEP caused by incomplete exhalation.

  • To measure auto-PEEP: Perform an Expiratory Hold.

 

If auto-PEEP is present:

Adjust one at a time

  • Decrease RR.
  • Increase expiratory time.
  • Reduce tidal volume if necessary.
  • Set PEEP at 50-80% of the measured autoPEEP.
    • To counterbalance dynamic hyperinflation.

 

If Auto-PEEP causing hemodynamic instability:

  • Disconnect with the ventilator.
  • Perform manual chest decompression.

 

7. Set Inspiratory to Expiratory Ratio (I:E Ratio)

  • I:E Ratio: 1:3, 1:4

Rationale: Prolonged expiratory time reduces air trapping and allows for complete exhalation.

 

8. Check Plateau Pressure (Pplat)

  • Measure Pplat using an inspiratory pause.

 

Adjust According to Pplat:

If Pplat > 30 cm H₂O:

  • Reduce Tidal Volume (TV).
  • Decrease RR to lower mean airway pressure.

 

If Pplat ≤ 30 cm H₂O:

    Check Arterial pH:

        i) If pH > 7.20:

  • Continue current settings.

        ii) If pH < 7.20:

  • Increase RR gradually, monitoring Pplat to remain ≤ 30 cm H₂O.
  • If pH remains < 7.20 despite adjustments:
    • Consider administering sodium bicarbonate (NaHCO₃) to correct severe acidosis.

 

9. Do not forget to administer Bronchodilators!

  • Intubation does not resolve the bronchospasm.