High‑Flow Nasal Cannula (HFNC) for Pneumonia with Respiratory Distress

Indications and Patient Selection

HFNC is indicated when conventional oxygen delivery (standard nasal cannula or simple face mask) cannot maintain the target SpO₂ of 94–98 % in patients with pneumonia‑related respiratory distress, before escalating to a non‑rebreather mask or non‑invasive ventilation. 2
HFNC should be considered in acute hypoxemic respiratory failure without hypercapnia, even before a non‑rebreather mask, because it provides heated, humidified oxygen at high flow rates that improve oxygenation and reduce work of breathing. 4

Compared with standard oxygen therapy, HFNC reduces treatment failure (need to escalate to another respiratory support) with a relative risk 0.62 (95 % CI 0.45–0.86). 1
HFNC shows little or no effect on overall mortality (RR 0.96, 95 % CI 0.82–1.11) but is associated with a lower likelihood of requiring endotracheal intubation. 1
In patients with pneumonia complicated by hypoxemic respiratory failure, HFNC can lower the incidence of intubation and may improve short‑term outcomes, although the mortality benefit remains uncertain. 1

Step 1 – Venturi mask: If SpO₂ < 94 % on a Venturi mask, increase the FiO₂ sequentially (24 % → 28 % → 35 % → 40 % → 60 %). [2][4]
Step 2 – HFNC vs. non‑rebreather:
- If the Venturi mask at 60 % FiO₂ (≈12–15 L/min) is insufficient, HFNC is the preferred next step for patients without a high risk of hypercapnia. [5][6]
- Alternatively, a non‑rebreather mask at 15 L/min with immediate senior‑physician review may be used when HFNC is contraindicated. [2][4]
Step 3 – Early intubation: HFNC must not delay intubation if the patient shows clear clinical deterioration (e.g., rapidly falling SpO₂, worsening work of breathing). 1

Arterial blood‑gas assessment: Obtain an ABG within 30–60 minutes when any of the following occurs: persistent respiratory distress, increasing dyspnea, altered mental status, or respiratory rate > 30 breaths/min. 6
Frequent reassessment while on HFNC: Look for signs of impending failure such as severe organ dysfunction, thoraco‑abdominal asynchrony, markedly increased respiratory rate, inadequate oxygenation despite maximal HFNC settings, or persistent tachycardia. [6][2]
Adjustment interval: Maintain each oxygen‑delivery level for at least 5 minutes before making further changes, unless there is a sudden, large drop in SpO₂. 4

Inhaled bronchodilators are not recommended for pneumonia patients with tachypnea and shallow breathing when there is no evidence of bronchospasm; current British Thoracic Society (BTS) guidance advises oxygen therapy alone. 2
Tachypnea in this context is driven by hypoxemia and parenchymal infiltrates rather than airway obstruction. 2
Spacer‑based inhalers require coordinated inspiratory effort, which may be compromised in severe tachypnea; therefore, routine bronchodilator use is discouraged. 2
If clinical features suggest a bronchospastic component (wheezing, known asthma/COPD, prior positive response to bronchodilators), adjunct bronchodilator therapy may be considered. 2

HFNC should not be used as a means to postpone necessary intubation; delayed intubation in deteriorating patients increases the risk of ventilator‑induced lung injury. 1