From the Guidelines
High flow nasal cannula (HFNC) therapy should be initiated in patients with respiratory distress who have hypoxemia but are not yet requiring intubation, with a preference for HFNC over conventional oxygen therapy (COT) and noninvasive ventilation (NIV) in hypoxaemic acute respiratory failure, as suggested by the European Respiratory Society guidelines 1. The guidelines recommend starting with flow rates of 30-60 L/min and FiO2 of 50-100% based on severity, titrating to maintain SpO2 ≥92-94% (or 88-92% in COPD patients) 1. Key considerations for HFNC therapy include:
- Temperature setting: 34-37°C for comfort
- Patient positioning: semi-recumbent or upright position
- Monitoring: vital signs, work of breathing, and oxygen saturation every 1-2 hours initially
- Mechanism of action: providing heated, humidified oxygen at high flows, which washes out anatomical dead space, provides positive airway pressure, reduces work of breathing, and improves oxygenation
- Assessment of response: within 1-2 hours, with consideration for escalation to non-invasive ventilation or intubation if no improvement occurs Common indications for HFNC therapy include:
- Hypoxemic respiratory failure
- COPD exacerbations
- Post-extubation support
- Pre-oxygenation before intubation Contraindications for HFNC therapy include:
- Respiratory arrest
- Severe hemodynamic instability
- Facial trauma
- Recent facial surgery Potential complications of HFNC therapy are minimal but include:
- Nasal discomfort
- Skin breakdown
- Potential delay in necessary intubation if patients are not closely monitored, as noted in the American College of Physicians guideline 1.
From the Research
Guidelines for Initiating and Managing High Flow Nasal Cannula (HFNC) Therapy
- The guidelines for initiating and managing HFNC therapy in patients with respiratory distress are not well-established, but several studies provide insight into its use 2, 3, 4, 5, 6.
- HFNC oxygen therapy comprises an air/oxygen blender, an active humidifier, a single heated circuit, and a nasal cannula, delivering adequately heated and humidified medical gas at up to 60 L/min of flow 2.
- The physiological effects of HFNC include reduction of anatomical dead space, PEEP effect, constant fraction of inspired oxygen, and good humidification 2.
Indications for HFNC Therapy
- HFNC therapy has been applied to a variety of patients with diverse underlying diseases, including hypoxemic respiratory failure, acute exacerbation of chronic obstructive pulmonary disease, post-extubation, pre-intubation oxygenation, sleep apnea, acute heart failure, and patients with do-not-intubate order 2.
- HFNC has been used as an alternative oxygen interface for adults who present with moderate hypoxemia that persists after receiving oxygen by reservoir-bag masks or similar therapy 3.
Management of HFNC Therapy
- The ROX index, defined as the ratio of oxygen saturation as measured by pulse oximetry/FiO2 to respiratory rate, can help identify patients with low and high risk for intubation 4.
- A ROX greater than or equal to 4.88 measured at 2,6, or 12 hours after HFNC initiation was consistently associated with a lower risk for intubation 4.
- HFNC, when set at 60 L/min, significantly reduces the indexes of respiratory effort in adult patients recovering from acute respiratory failure 5.
Outcomes of HFNC Therapy
- The early use of HFOT in patients admitted to an ED for acute respiratory failure did not reduce the need for mechanical ventilation as compared to COT, but decreased respiratory rate 6.
- HFNC therapy has been shown to decrease breathing frequency and work of breathing and reduce needs of escalation of respiratory support in patients with diverse underlying diseases 2, 5.