Can High Flow Nasal Cannula (HFNC) with a Fraction of Inspired Oxygen (FIO2) of 60% be replaced by a Bilevel Positive Airway Pressure (BiPAP) machine in a patient?

Differences Between BiPAP and HFNC: Can HFNC at 60% FiO2 Be Replaced by BiPAP?

BiPAP can replace HFNC with 60% FiO2 in patients at high risk of extubation failure, as BiPAP therapy has been shown to be more effective in preventing reintubation in high-risk patients, though individual patient factors should guide this decision. 1

Key Differences Between BiPAP and HFNC

Mechanism of Action

• HFNC delivers high flow rates (up to 50-60 L/min) that exceed the patient's inspiratory flow demands, creating a washout effect in the upper airways, reducing anatomical dead space and improving ventilation 2
• BiPAP provides two levels of positive airway pressure: inspiratory positive airway pressure (IPAP) and expiratory positive airway pressure (EPAP), which actively assists both inspiration and expiration 3
• HFNC generates only modest positive end-expiratory pressure (PEEP) effect (approximately 2-5 cmH2O at 50-60 L/min), while BiPAP can deliver higher and more controlled PEEP levels (typically 4-12 cmH2O) 4, 3

Oxygen Delivery and FiO2

• HFNC can reliably deliver FiO2 up to 100% when flow rates are adequate (60 L/min), but at lower flow rates (20-40 L/min), the actual FiO2 delivered may vary based on the patient's tidal volume and inspiratory flow 5
• BiPAP can deliver precise FiO2 regardless of the patient's breathing pattern, making it more reliable for patients requiring exact oxygen concentrations 3
• At an FiO2 of 60%, HFNC requires flow rates of at least 50-60 L/min to ensure the set FiO2 is actually delivered to the patient 5

Patient Comfort and Tolerance

• HFNC is generally better tolerated with higher comfort levels due to the heated and humidified oxygen delivery system and less restrictive interface 4
• BiPAP masks can cause skin breakdown and discomfort, with studies showing significantly more prevalent skin breakdown with NIV than HFNC after 24 hours 4
• HFNC allows for eating, drinking, and communication while receiving therapy, which is more difficult with BiPAP masks 2

Clinical Efficacy Comparison

Oxygenation

• BiPAP typically achieves higher PaO2/FiO2 ratios compared to HFNC (studies show HFNC results in a slightly lower PaO2/FiO2 ratio, with MD -63,95% CI -80 to -46) 4
• When compared to NIV (including BiPAP), HFNC may result in higher PaO2 values (MD 6.2 mmHg, 95% CI 3.58 mmHg to 8.28 mmHg) 4

Ventilation and CO2 Removal

• BiPAP is more effective for CO2 removal in hypercapnic patients due to its ability to provide ventilatory support 3
• HFNC has little to no significant effect on PaCO2 values compared to conventional oxygen therapy (MD 0.01 mmHg, 95% CI -1.17 mmHg to 1.2 mmHg) 4
• BiPAP is preferred for patients with hypercapnic respiratory failure, while HFNC is primarily indicated for hypoxemic respiratory failure 2

Prevention of Intubation/Reintubation

• Recent evidence suggests BiPAP therapy is more efficient than HFNC in preventing tracheal reintubation among patients with a high risk of extubation failure 1
• For patients with moderate risk of extubation failure, HFNC and NIV (including BiPAP) show similar reintubation rates (risk ratio 1.02,95% CI 0.73 to 1.44) 4

Clinical Decision-Making Algorithm for Replacing HFNC with BiPAP

Consider BiPAP over HFNC when:

• Patient has hypercapnic respiratory failure (elevated PaCO2) in addition to hypoxemia 3
• Patient is at high risk for extubation failure with multiple risk factors 1
• Patient requires precise FiO2 delivery that may not be achieved with HFNC due to high inspiratory demands 5
• Patient needs higher levels of positive pressure support than HFNC can provide 4

Continue HFNC instead of switching to BiPAP when:

• Patient is comfortable and stable on HFNC with adequate oxygenation 4
• Patient has primarily hypoxemic respiratory failure without significant hypercapnia 4
• Patient has issues with mask tolerance, claustrophobia, or skin integrity concerns 4
• Patient has excessive secretions that require frequent clearance 2

Practical Considerations for Transition

When transitioning from HFNC at 60% FiO2 to BiPAP:

• Start BiPAP with similar FiO2 (60%) to maintain oxygenation 3
• Begin with moderate pressure settings (IPAP 8-12 cmH2O, EPAP 4-7 cmH2O) and titrate based on patient response 3
• Monitor arterial blood gases after 1-2 hours to assess effectiveness 2
• Watch for signs of respiratory distress, including increased respiratory rate, use of accessory muscles, and decreased oxygen saturation 1

Potential Pitfalls and Caveats

• Delaying intubation when either HFNC or BiPAP is failing can lead to worse outcomes; close monitoring is essential 4
• Skin breakdown is significantly more prevalent with NIV than HFNC after 24 hours of use 4
• Patient comfort and tolerance may affect compliance and effectiveness of either therapy 4
• Resource considerations may influence device selection, as BiPAP may require more intensive monitoring in some settings 4

In summary, while both HFNC and BiPAP have their place in respiratory support, BiPAP can replace HFNC at 60% FiO2 particularly in patients with hypercapnic respiratory failure or at high risk for extubation failure. However, the transition should be carefully monitored with attention to patient comfort, tolerance, and physiological response.