From the Guidelines
To address respiratory acidosis in ARDS patients already in prone position, optimize ventilator settings by increasing minute ventilation through higher respiratory rates (20-35 breaths/minute) while maintaining protective lung strategies (tidal volumes 4-6 mL/kg ideal body weight) as recommended by the most recent guideline 1.
Key Considerations
- Consider permissive hypercapnia if pH remains >7.15-7.20, as some degree of respiratory acidosis may be acceptable to prevent ventilator-induced lung injury 1.
- Ensure adequate sedation with medications like propofol (starting at 5-50 mcg/kg/min), midazolam (1-2 mg/hr), or dexmedetomidine (0.2-1.5 mcg/kg/hr) to improve ventilator synchrony.
- For severe acidosis (pH <7.15), cautiously reduce dead space by optimizing PEEP (typically 10-15 cmH2O), using recruitment maneuvers, and ensuring proper endotracheal tube positioning 1.
- In refractory cases, consider extracorporeal CO2 removal (ECCO2R) or veno-venous ECMO if available.
- Avoid sodium bicarbonate for pure respiratory acidosis as it provides only temporary relief and may worsen intracellular acidosis.
Ongoing Management
- Maintain close monitoring of arterial blood gases every 2-4 hours initially, then as clinically indicated, to assess response to interventions while continuing prone positioning for 12-16 hours daily to optimize ventilation-perfusion matching 1.
- Prone positioning of 16 h daily for patients affected with acute respiratory distress syndrome (ARDS) with a duration of ventilation < 36 h and a PaO2/FiO2 < 150 mmHg2 showed a significant survival benefit for 28-day mortality 1.
From the Research
Addressing Respiratory Acidosis in ARDS Patients on Prone Position
To address respiratory acidosis in ARDS patients who are already on prone position, several considerations must be taken into account:
- The use of prone positioning has been shown to improve oxygenation in ARDS patients 2, 3.
- However, prone position ventilation (PPV) may also lead to an increase in arterial carbon dioxide partial pressure (PaCO2) and a decrease in pH, resulting in respiratory acidosis 4.
- Permissive hypercapnia, a strategy used to minimize lung injury, may impair pulmonary gas exchange and worsen respiratory acidosis 5.
- Alternative therapies for CO2 management, such as adjusting ventilator settings or using other interventions, may be necessary to mitigate the effects of permissive hypercapnia 6.
Management Strategies
Some potential management strategies for respiratory acidosis in ARDS patients on prone position include:
- Adjusting the fraction of inspired oxygen (FiO2) to minimize hyperoxia and reduce the risk of worsening respiratory acidosis 4.
- Using lung-protective ventilation strategies, such as low tidal volumes and neuromuscular blocking agents, to minimize lung injury and reduce the risk of respiratory acidosis 3.
- Monitoring arterial blood gas analysis and adjusting ventilator settings as needed to maintain optimal oxygenation and ventilation 4.
- Considering alternative therapies for CO2 management, such as extracorporeal CO2 removal, in patients with severe respiratory acidosis 6.