When to Use BiPAP vs HFNC in Respiratory Distress
For patients with acute respiratory distress, HFNC is suggested over BiPAP for hypoxemic respiratory failure, while BiPAP is preferred for hypercapnic respiratory failure. 1, 2
Mechanisms of Action
- HFNC delivers high flow rates of heated and humidified oxygen-air mixture, creating a washout effect in the upper airways, reducing anatomical dead space, and provides modest positive end-expiratory pressure (PEEP) effect of approximately 2-5 cmH2O at 50-60 L/min 2, 3
- BiPAP delivers two different pressure levels: higher inspiratory positive airway pressure (IPAP) and lower expiratory positive airway pressure (EPAP), providing pressure support to augment tidal volume, and can deliver higher and more controlled PEEP levels, typically 4-12 cmH2O 2, 3
Clinical Decision Algorithm
Use HFNC for:
- Acute hypoxemic respiratory failure (primary indication) 1, 2
- Patients with moderate to severe acute hypoxemic respiratory failure (PaO2/FiO2 ≤200 mmHg) 1
- Post-operative patients at low risk of respiratory complications 1
- Patients who need respiratory support but require better comfort and tolerance 3
- Patients who need to eat, drink, or communicate while receiving therapy 3
Use BiPAP for:
- Hypercapnic respiratory failure (primary indication), such as COPD exacerbations 2, 3
- Neuromuscular diseases or ICU-associated muscle weakness 2
- Patients with high risk of extubation failure (BiPAP showed significantly higher successful extubation rates compared to HFNC) 4
- When higher levels of positive pressure support are needed than HFNC can provide 3
- When respiratory muscle fatigue is a concern (consider BiPAP in ST mode) 2
Comparative Effectiveness
- HFNC may reduce mortality compared to BiPAP in acute hypoxemic respiratory failure (risk ratio 0.77,95% CI 0.52 to 1.14) 1
- BiPAP typically achieves higher PaO2/FiO2 ratios compared to HFNC 2, 3
- HFNC is generally better tolerated with higher comfort levels due to the heated and humidified oxygen delivery system and less restrictive interface 3
- BiPAP masks can cause skin breakdown and discomfort, with studies showing significantly more prevalent skin breakdown with NIV than HFNC after 24 hours 3
Monitoring Response
- For HFNC, monitor response within 1-2 hours of initiation 2
- For BiPAP, improvement in gas exchange within 1 hour (PaO2/FiO2 <175 mmHg after 1 hour of NIV is associated with need for intubation) 1
- Monitor expired tidal volume in BiPAP patients (exceeding 9-9.5 mL/kg predicted body weight while on BiPAP can predict treatment failure) 1
Special Considerations
- In pediatric patients with bronchiolitis, evidence is mixed:
- Some studies suggest HFNC is non-inferior to BiPAP in infants with bronchiolitis 5
- Other meta-analyses indicate HFNC carries a significantly higher risk of treatment failure compared to CPAP/BiPAP (RR, 1.45; 95% CI, 1.06 to 1.99) 6
- HFNC had a higher failure rate compared to BiPAP or CPAP in the management of infants and children with acute bronchiolitis in the PICU 7
Potential Pitfalls and Caveats
- Delaying intubation when either HFNC or BiPAP is failing can lead to worse outcomes; close monitoring is essential 3
- NIV failure occurs more frequently in patients with more severe ARF: PaO2/FiO2 <200 mmHg before treatment and higher Simplified Acute Physiology Score II (>35) are associated with a two-fold risk of intubation 1
- Resource considerations may influence device selection, as BiPAP may require more intensive monitoring in some settings 3
- In low-income countries, HFNC may reduce health equity due to high oxygen consumption 1