High-Flow Nasal Cannula (HFNC) Therapy

Algorithm Steps

1. ▶

   Start

   Acute Hypoxemic Respiratory Failure

   Hypoxia despite conventional O2 therapy

   1. ◆

      Decision

      HFNC Indicated?

      Assess suitability

      • INDICATIONS:
      • • Hypoxemia despite O2 15L/min NRB
      • • Type 1 respiratory failure
      • • Post-extubation support
      • • Immunocompromised with ARF
      • • Pre-oxygenation for intubation
      • • Palliative comfort
      1. ⚠

         Warning

         ⚠️ Consider NIV/Intubation Instead

         HFNC may not be appropriate

         • Hypercapnic respiratory failure (Type 2)
         • Severe acidosis (pH <7.25)
         • Hemodynamic instability
         • Decreased consciousness (GCS <12)
         • Unable to protect airway
         • Facial trauma/surgery
         1. ✓

            Outcome

            Intubation

            HFNC failure

            • Do not delay intubation if failing
            • HFNC can be used during apneic oxygenation
            • Experienced intubator preferred
            • Video laryngoscopy recommended
      2. ●

         Action

         Initiate HFNC

         Starting settings

         • Flow: Start at 30-40 L/min
         • FiO2: Start at 0.6-1.0 (titrate to SpO2)
         • Temperature: 37°C (or 34°C if not tolerated)
         • Nasal prongs sized appropriately
         • Ensure proper humidification
         1. ●

            Action

            Titrate Settings

            Optimize flow and FiO2

            • FLOW: Increase to 50-60 L/min if needed
            • Higher flow = more PEEP effect, CO2 washout
            • FiO2: Titrate to SpO2 92-96% (88-92% if COPD)
            • Reduce flow if discomfort/nasal dryness
            1. ●

               Action

               Close Monitoring

               Assess response hourly

               • Respiratory rate (target <25-30/min)
               • SpO2 on current settings
               • Work of breathing
               • Patient comfort
               • ROX index at 2, 6, 12 hours
               1. ◆

                  Decision

                  Calculate ROX Index

                  Predict HFNC success/failure

                  • ROX = (SpO2/FiO2) / Respiratory Rate
                  • At 2h: ROX ≥4.88 = likely success
                  • At 6h: ROX ≥4.88 = likely success
                  • At 12h: ROX <3.85 = likely failure
                  • Lower ROX = higher intubation risk
                  1. ●

                     Action

                     ROX ≥4.88 (Favorable)

                     Continue HFNC

                     • Low intubation risk
                     • Continue current settings
                     • Wean FiO2 if SpO2 above target
                     • Can consider flow reduction later
                     1. ●

                        Action

                        Weaning HFNC

                        When improving

                        • Reduce FiO2 first (to 0.4 or less)
                        • Then reduce flow (by 5-10 L/min steps)
                        • Monitor for rebound hypoxemia
                        • Consider trial on nasal cannula
                        1. ✓

                           Outcome

                           Transition to Conventional O2

                           Weaning successful

                           • If SpO2 maintained on low-flow HFNC
                           • Trial simple nasal cannula or mask
                           • Monitor closely after transition
                           • Can return to HFNC if needed
                  2. ●

                     Action

                     ROX 3.85-4.88 (Intermediate)

                     Heightened vigilance

                     • Increase monitoring frequency
                     • Optimize settings
                     • Prepare for escalation if declining
                     • Repeat ROX in 2 hours
                     1. ◆

                        Decision

                        Clinical Deterioration?

                        Signs of HFNC failure

                        • Worsening hypoxemia despite max settings
                        • RR increasing >35-40/min
                        • Accessory muscle use worsening
                        • Hemodynamic instability
                        • Altered mental status
                  3. ⚠

                     Warning

                     ⚠️ ROX <3.85 (Unfavorable)

                     High failure risk

                     • Consider early intubation
                     • Do not delay if deteriorating
                     • Trial of NIV may be considered
                     • Avoid prolonged HFNC failure