Initial CPAP Settings: FiO2 and Flow Rate
For hypoxemic respiratory failure requiring CPAP, start with a pressure of 10 cmH2O and FiO2 of 0.6 (60%), then titrate based on clinical response. 1
Initial Pressure Settings
- Begin CPAP at 10 cmH2O for patients who are oriented and can tolerate a well-fitted, non-vented face mask 1
- Alternative starting range is 5-7.5 cmH2O, titrated upward to 10 cmH2O based on clinical response 1
- For patients with lower oxygen requirements (FiO2 <0.4), low-flow CPAP systems are appropriate 1
Initial FiO2 Settings
- Start with FiO2 of 0.6 (60%) as the standard initial setting 1
- Alternative initial FiO2 of 0.4 (40%) can be used in less severe cases 1
- For severe hypoxemia, FiO2 may need to be set at 0.8 (80%) initially 2
Oxygen Flow Rate for Supplemental O2
When adding supplemental oxygen to CPAP:
- Start at 1 L/min for both pediatric and adult patients 1, 3
- Increase by 1 L/min increments at intervals no shorter than 15 minutes 1, 3
- Connect oxygen via T-connector at the PAP device outlet for optimal mixing 1, 3
- Maximum safe oxygen bleed is typically 10-15 L/min with most devices 3
Escalation Protocol
If initial settings are inadequate:
- Increase CPAP to 12-15 cmH2O with FiO2 0.6-1.0 (60-100%) 1
- CPAP pressures may be increased up to 15-20 cmH2O if needed 1
- Higher pressures reduce effective FiO2 delivery, requiring flow rate adjustments 3
Target Oxygen Saturation
- Maintain SpO2 between 90-96% in most patients 1
- For patients with strong respiratory drive (low PaCO2), target SpO2 ≥94% 1
- In type 2 respiratory failure, titrate to SpO2 88-92% 1
- Avoid SpO2 >96% to prevent hyperoxia 1
Critical Monitoring Parameters
Reassess within 1-2 hours of initiating CPAP to determine effectiveness 1:
- Reduction in respiratory rate to <25 breaths/min indicates positive response 2
- Improvement in PaO2/FiO2 ratio suggests efficacy 2
- Failure to improve or clinical deterioration mandates prompt intubation 1
Important Caveats
- Higher CPAP pressures decrease effective FiO2 for a given oxygen flow rate due to increased intentional leak 3
- Risk of pneumothorax increases with CPAP ≥8 cmH2O, especially when FiO2 >0.6 is required 4
- Effective FiO2 varies with pressure settings but not with respiratory rate or pressure support 3
- Pulse oximetry may overestimate actual arterial oxygen saturation, so a slightly higher SpO2 goal (90-94%) may be prudent 1, 3