High-flow nasal oxygen failure in hypoxaemic respiratory failure — FFICM MCQ

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ModerateVentilationHigh-flow nasal oxygen failure in hypoxaemic respiratory failureFFICM

A 73-year-old woman with severe community-acquired pneumonia is treated with high-flow nasal oxygen at 60 L/min and FiO2 0.85. After 2 hours her respiratory rate is 38/min, SpO2 is 90%, PaO2 is 7.5 kPa and lactate is 2.4 mmol/L. She is alert but tiring, and escalation to invasive ventilation is consistent with her treatment plan. What is the most appropriate ventilation strategy?

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Correct answer: E — Prepare for tracheal intubation and invasive ventilation

The correct answer is E, prepare for tracheal intubation and invasive ventilation. This patient has objective evidence of high-flow nasal oxygen (HFNO) failure: persistent tachypnoea (RR 38), hypoxaemia (SpO2 90%, PaO2 7.5 kPa) despite FiO2 0.85 and 60 L/min flow, rising lactate, and clinical tiring. Failure to improve oxygenation and work of breathing on maximal HFNO after an adequate trial is a recognised indication to escalate to invasive ventilation rather than persist with non-invasive support. Delaying intubation in a deteriorating, tiring patient risks an unplanned crash intubation with a much higher complication rate, so a planned, controlled approach is safer once escalation is deemed appropriate for the patient. This reflects standard UK critical care practice of using dynamic reassessment (respiratory rate, oxygenation trend, work of breathing) rather than fixed time points to decide on HFNO failure. Why the other options are wrong: D. Continue high-flow nasal oxygen overnight: this ignores objective markers of failure (worsening tachypnoea, hypoxaemia, rising lactate, tiring) and risks exhaustion, hypoxic arrest or crash intubation overnight without senior review. C. Switch to low-flow nasal cannulae: this is a step down in respiratory support and would worsen hypoxaemia in a patient already failing maximal HFNO. A. Start ward-based CPAP without ICU review: CPAP does not address the ventilatory failure component (rising RR and tiring) as effectively as invasive ventilation, and initiating it on a ward without ICU input in a deteriorating patient is unsafe. B. Give intravenous morphine to reduce respiratory rate: sedating a tiring, tachypnoeic hypoxaemic patient risks respiratory depression and precipitates arrest; it treats a symptom, not the underlying respiratory failure. Key point: Objective signs of HFNO failure (persistent hypoxaemia, tachypnoea, rising lactate, tiring) in a patient for whom escalation is appropriate mandate planned intubation rather than continued non-invasive support.

Reference: British Journal of Anaesthesia, High-flow nasal oxygen therapy in intensive care and anaesthesia, 2018, https://www.bjanaesthesia.org/article/S0007-0912(17)53999-9/fulltext