How to Report HFNC Settings in the Medical Record
Document HFNC settings by recording both the flow rate (in L/min) and the fraction of inspired oxygen (FiO2 as a percentage or decimal), as these are the two essential parameters that define the therapy and guide clinical decision-making.
Essential Parameters to Document
When recording HFNC in the medical record, you must include:
- Flow rate: Document in liters per minute (L/min), typically ranging from 30-60 L/min 1
- FiO2: Record as either a percentage (e.g., 60%) or decimal (e.g., 0.60) 2
Example Documentation Format
A complete HFNC order or progress note should read:
- "HFNC at 40 L/min, FiO2 60%"
- "High-flow nasal cannula: Flow 50 L/min, FiO2 0.50"
Additional Clinical Parameters to Track
Beyond the device settings, document these physiological responses to guide ongoing management:
- SpO2/FiO2 ratio: This helps assess oxygenation efficiency 2
- ROX index: Calculate as (SpO2/FiO2)/respiratory rate - a key predictor of HFNC success 2
- Respiratory rate: Essential for calculating ROX index and monitoring work of breathing 1
- Patient comfort level: HFNC improves comfort compared to conventional oxygen and NIV 1
Practical Flow Setting Guidance
The evidence suggests a pragmatic approach to initial settings 2:
- Start at 40 L/min for most patients with acute hypoxemic respiratory failure, as mean peak tidal inspiratory flow (PTIF) in these patients is typically 30-40 L/min
- Titrate flow upward based on ROX index improvement and patient tolerance
- The ROX index plateaus when HFNC flow reaches approximately 1.34-1.67 times the patient's individual PTIF
Common Pitfall to Avoid
Many clinicians set initial flows at 45-50 L/min based on convention 3, but starting at 40 L/min and titrating based on physiological response (ROX index) is more evidence-based 2. The key is that HFNC flow should exceed the patient's inspiratory demand to maximize benefit.
Monitoring and Adjustment Documentation
Record changes in settings along with the clinical rationale:
- Document why flows or FiO2 were adjusted (e.g., "Increased flow from 40 to 50 L/min due to persistent tachypnea and ROX index <4.88")
- Note patient response to changes within 5-10 minutes 2
- Track trends in SpO2, respiratory rate, and work of breathing
The standardized documentation of these parameters allows for consistent monitoring and facilitates timely escalation or de-escalation of respiratory support based on objective criteria rather than subjective assessment alone.