From the Guidelines
In COPD patients on BiPAP, the pressure support (PS) mode most effectively reduces CO2 levels. This is because PS mode provides a set pressure difference between inspiration and expiration, which helps unload respiratory muscles and improve alveolar ventilation, as suggested by the European Respiratory Journal guidelines 1. When using BiPAP for COPD exacerbations, typical settings include an inspiratory positive airway pressure (IPAP) of 12-20 cmH2O and expiratory positive airway pressure (EPAP) of 4-6 cmH2O, with the difference between these pressures (PS level) being crucial for CO2 removal.
The effectiveness of BiPAP in reducing CO2 levels can be attributed to its ability to overcome airway resistance and reduce the work of breathing, allowing patients to take deeper breaths with less effort, as noted in the official ERS/ATS clinical practice guidelines 1. This improved ventilation increases CO2 elimination from the bloodstream. Additionally, the respiratory rate can be adjusted in some BiPAP modes to ensure adequate minute ventilation if the patient's spontaneous rate is insufficient.
Key considerations for using BiPAP in COPD patients include:
- Monitoring arterial blood gases to assess the effectiveness of CO2 removal
- Adjusting pressure support levels to optimize ventilation
- Closely monitoring patients with severe acidosis and respiratory distress, as they may require invasive ventilation if their condition does not improve with BiPAP, as recommended by the European Respiratory Journal guidelines 1. The pressure support mode of BiPAP is particularly useful in COPD patients with hypercapnic respiratory failure, as it helps to reduce CO2 levels and improve alveolar ventilation, ultimately reducing the risk of respiratory acidosis and improving patient outcomes, as suggested by the official ERS/ATS clinical practice guidelines 1.
From the Research
Effects of BiPAP Modes on CO2 in COPD Patients
- The study 2 compared the effects of BiPAP, pressure support (PS), and continuous positive airway pressure (CPAP) on respiratory mechanics in COPD patients, but did not specifically focus on the effect of BiPAP modes on CO2 levels.
- However, the study 3 found that the Average Volume Assured Pressure Support (AVAPS) mode resulted in a more rapid and steady improvement in pH and pCO2 levels compared to the BiPAP spontaneous/timed (S/T) mode in patients with acute exacerbation of COPD with type 2 respiratory failure.
- Another study 4 compared the effects of auto-titrating and fixed expiratory positive airway pressure (EPAP) during intelligent volume-assured pressure support (iVAPS) ventilation in patients with COPD and hypercapnic respiratory failure, and found that auto-titrating EPAP resulted in a significant decrease in daytime PaCO2 levels.
- The study 5 found that BiPAP with a standard exhalation valve did not improve maximum exercise capacity in patients with COPD, and actually increased CO2 production (VCO2) and dyspnea, which reduced peak exercise workload.
Comparison of BiPAP Modes
- The study 3 suggests that the AVAPS mode may be more effective in improving CO2 levels compared to the BiPAP S/T mode in patients with acute exacerbation of COPD with type 2 respiratory failure.
- The study 4 found that auto-titrating EPAP during iVAPS ventilation resulted in a significant decrease in daytime PaCO2 levels, suggesting that this mode may be more effective in managing CO2 levels in patients with COPD and hypercapnic respiratory failure.
- However, the study 2 found that BiPAP resulted in a higher work of breathing and pressure-time product compared to PS, which may have implications for CO2 management in COPD patients.