HFO — High-Flow Oxygen Therapy
A flow-controlled mode delivering a constant, warmed and humidified high flow through a high-flow nasal cannula. It does not control the breath cycle; it supports oxygenation, washes out dead-space CO₂ and improves comfort. An external O₂ source, heated humidifier and HFNC are required.
Physiological basis
Four mechanisms explain HFNC’s benefit. Dead-space washout: high flow continuously clears CO₂ from the upper airway and proximal airways, improving effective alveolar ventilation. Increased FRC / weak PEEP effect: at 20–60 L/min a small positive airway pressure forms, supporting alveolar patency (FRC up ~25%).
Reduced work of breathing: flow that meets or exceeds inspiratory demand lowers respiratory effort, while warmed, humidified gas preserves mucociliary clearance and eases dyspnea. Stable FiO₂: unlike conventional oxygen, HFNC delivers a reliable 21–100% FiO₂ at 20–70 L/min — critical in acute hypoxemic failure.
Adjustable parameters 1
Start at 20–30 L/min; increase per tolerance and SpO₂ target. Typical adult target 40–60 L/min; pediatric 2 L/kg/min.