High Flow Nasal Cannula (HFNC)

HFNC delivers heated, humidified oxygen through soft nasal prongs, the same type of cannula used for standard low-flow oxygen, just larger and more precisely engineered. Key differences from conventional oxygen therapy:

• Standard nasal oxygen delivers 2 to 5 litres per minute; HFNC can deliver up to 60 litres per minute
• Oxygen concentration is adjustable anywhere from 21% (room air) up to 100%
• Gas is warmed to approximately 37°C and humidified to prevent airway dryness and irritation

At these flow rates, several clinically useful things happen:

• Continuous high flow flushes out carbon dioxide accumulating in the nasopharynx between breaths, a dead space washout effect
• A small but meaningful positive airway pressure is generated, helping keep small airways and alveoli open
• The work of breathing decreases noticeably
• The patient remains comfortable enough to cooperate with therapy

HFNC is used primarily in patients with acute hypoxaemic respiratory failure, where oxygen levels fall significantly despite conventional therapy. Common clinical situations include:

• Severe pneumonia
• Acute exacerbations of interstitial lung disease
• COVID-related respiratory failure
• Post-extubation support during weaning off invasive ventilation
• Acute cardiogenic pulmonary oedema
• Patients who are not candidates for intubation but need more than a face mask can provide

It is not appropriate for every situation. HFNC may not be suitable for patients with:

• Very high carbon dioxide levels on blood gas analysis
• Severely impaired consciousness
• Haemodynamic instability requiring urgent intervention

The decision is always made carefully, based on blood gas values, observed work of breathing, and the patient's clinical trajectory.

The difference in comfort is often immediately apparent. Unlike tight mask-based therapies:

• Patients can speak in short sentences and communicate with family
• Sips of water and soft foods are possible in many cases
• The nasal prongs sit comfortably without the claustrophobic sensation of a sealed mask
• Patients appear more alert and settled, something families visiting the ICU frequently notice and find reassuring

Monitoring is continuous and vigilant throughout. Parameters tracked include:

• Oxygen saturation and respiratory rate
• Heart rate and blood pressure
• Blood gas analysis is repeated at regular intervals to ensure carbon dioxide is not rising

If a patient is not responding within the first one to two hours, breathing effort remains high, or oxygen levels don't improve, escalation to invasive ventilation is considered promptly. A delay in recognizing HFNC failure is a known risk, and our teams are trained to identify early warning signs.

HFNC is generally well tolerated, but a few considerations are worth noting:

• Nasal dryness or mild skin irritation around the prongs can occur, managed with appropriate humidification settings and skin care
• In patients with high respiratory drive, large effortful breaths may theoretically cause self-inflicted lung injury, which is why monitoring remains vigilant
• Reluctance to escalate to intubation when needed can occasionally delay necessary intervention; clear communication about goals of therapy helps avoid this

Most patients who respond well to HFNC improve gradually over 24 to 72 hours. Flow rates and oxygen concentration are weaned down progressively as the condition stabilizes. Compared to mask-based therapies:

• Oral intake is far less restricted
• Communication with family and the care team remains possible
• Mobility is better preserved

This matters enormously for patient morale and cooperation during what is often a frightening period of illness.

High-flow nasal cannula oxygen therapy in Navi Mumbai at our Department of Pulmonology helps patients with acute respiratory failure. Our critical care team monitors response closely, adjusts parameters in real time, and makes timely decisions about escalation or weaning, ensuring every patient receives the right level of support at the right moment.