Caution urged with high flow oxygen in acute respiratory failure

Nasal high flow oxygen has clear advantages for the patient – but don’t delay intubation, an expert has advised.

Exercise caution when considering nasal high flow oxygen therapy in a critically ill patient, as it may delay a definitive diagnosis and be associated with worse outcomes, a respiratory insights forum has heard.

Professor Andrew Bersten, Head of the Department of Critical Care Medicine at Flinders Medical Centre, told the forum held in Melbourne that despite mounting evidence that nasal high flow was beneficial in patients with acute hypoxemic respiratory failure (AHRF), it was important not to delay intubation or ventilation.

“When people aren’t responding, rather than push on with nasal high flow you should change over earlier rather than later,” he said.

AHRF is usually associated with high respiratory drive and high inspiratory flow rates. Simple oxygen delivery devices are inadequate, so oxygen is generally delivered via nasal high flow or via non-invasive positive pressure ventilation, Professor Bersten explained.

However, this method was contentious for some indications such as pneumonia, chest injury or for pre-oxygenation prior to intubation.

Nasal high flow better tolerated, clinically effective

Nasal high flow was usually better tolerated by patients, easy to implement and was clinically effective, Professor Bersten told delegates.

One recent trial in patients with acute respiratory failure after cardiothoracic surgery found nasal high flow did not result in a worse rate of treatment failure compared with intermittent Bilevel Positive Airway Pressure (BiPAP).

A French study comparing nasal high flow with a mask after extubation found nasal high flow decreased discomfort from airway dryness, with fewer patients experiencing oxygen desaturation or requiring reintubation.

This was confirmed in a recent Spanish randomised controlled trial, which found that among extubated patients at low risk for reintubation, the use of high-flow nasal oxygen compared with conventional oxygen therapy reduced the risk of reintubation within 72 hours.

Professor Bersten said it also appeared that nasal high flow increased comfort during sleep, reducing sleep disturbances and allowing patients to breathe less while they were at rest.
However, despite this generally favourable signal for the use of nasal high flow, research showed that its use might cause delayed intubation and worse clinical outcomes in patients with respiratory failure.

Professor Bersten said it was critical to know the appropriate diagnosis and whether more aggressive therapy was warranted.

Delayed decision-making allowed more time for disease progression, more rapid desaturation and more hemodynamic instability, he said.

“Many say these treatments are cosmetic and delay definitive investigation. If it’s inevitable you are going to intubate, then don’t delay,” Professor Bersten said.

“A lot of these therapies are simply buying time – if you’re missing a definitive diagnosis opportunity, while the oxygenation is better, you haven’t changed the underlying disease.”

He advised that investigations while using nasal high flow should include bronchoscopy, Bronchoalveolar lavage (BAL) and Computed Tomography (CT).

“We looked at 300 bronchoscopies and in over two thirds of the time it changed management,” he said.

It was also vital not to lose control of ventilation as it may lead to worse outcomes in the very sick patient through ventilation-induced injury, such as lung stretch.

“Poorly controlled mechanical ventilation can cause lung injury, but when you breathe spontaneously you also have the same lung stretch, so any technique like nasal high flow or non-invasive ventilation means less control,” he said.

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