From the Guidelines
No, if end-tidal carbon dioxide (EtCO2) remains elevated on Non-Invasive Ventilation (NIV), adjusting the Inspiratory Positive Airway Pressure (IPAP) should be prioritized over adjusting the Expiratory Positive Airway Pressure (EPAP). Elevated EtCO2 indicates carbon dioxide retention, which is primarily addressed by increasing ventilation. This is achieved by increasing the IPAP, which enhances tidal volume and minute ventilation, thereby improving CO2 clearance 1. The typical approach would be to increase IPAP by 2-4 cmH2O increments while monitoring patient response and comfort. EPAP adjustments are more appropriate for addressing oxygenation problems or upper airway obstruction rather than ventilation issues. EPAP helps maintain airway patency and improves oxygenation by preventing alveolar collapse, but has less direct effect on CO2 elimination.
When adjusting NIV settings for elevated EtCO2, it's also important to:
- Check for mask leaks
- Assess patient-ventilator synchrony
- Consider increasing respiratory rate settings if available on the ventilator The goal is to normalize EtCO2 while maintaining patient comfort and preventing complications like barotrauma. According to the BTS/ICS guideline for the ventilatory management of acute hypercapnic respiratory failure in adults, inadequate IPAP is often used in AECOPD, and IPAP should be progressively increased to reach an IPAP of 20–30 within 10–30 min 1.
In contrast, EPAP may need to be increased in the presence of persisting hypoxaemia, or if there is a degree of upper airway obstruction, but this is not the primary concern when addressing elevated EtCO2 1. The BTS guideline for oxygen use in adults in healthcare and emergency settings also emphasizes the importance of careful monitoring for hypercapnic respiratory failure with respiratory acidosis in patients with COPD, and avoiding excessive oxygen use 1. However, this guideline does not directly address the adjustment of NIV settings for elevated EtCO2.
Therefore, based on the most recent and highest quality evidence, adjusting IPAP is the recommended approach for managing elevated EtCO2 on NIV, rather than adjusting EPAP.
From the Research
Adjusting EPAP in NIV for Elevated EtCO2
- When end-tidal carbon dioxide (EtCO2) is still elevated on Non-Invasive Ventilation (NIV), adjusting the Expiratory Positive Airway Pressure (EPAP) may not be the first step, as the primary goal of NIV is to reduce CO2 levels by adjusting variables such as IPAP, backup respiratory rate, or using assisted pressure-controlled ventilation mode (APCV) 2.
- Studies have shown that automatically adjusting EPAP algorithms can be effective in patients with chronic respiratory failure, and may offer advantages over manually adjusted EPAP 3.
- However, the decision to adjust EPAP should be based on individual patient needs and response to treatment, as well as the underlying cause of hypercapnia.
- In patients with severe hypercapnia, NIV has been shown to be effective in reducing CO2 levels, and the measurement of EtCO2 can be a reliable method for monitoring the effectiveness of NIV 4.
- Auto-titrating EPAP has been shown to be effective in decreasing PaCO2 and improving patient comfort and satisfaction in patients with COPD and hypercapnic respiratory failure 5.
- However, measuring EtCO2 using a naso-buccal sensor may not be accurate for predicting PaCO2 levels or variations over time during NIV 6.