Oxygen, high-flow and non-invasive respiratory support — OSCE

Candidate instructions

You are the paediatric registrar in the emergency department. A 5-month-old infant has been brought by ambulance with a 2-day history of coryzal illness and worsening breathing. Standard low-flow nasal cannula oxygen at 2 L/min has been started by the triage nurse, but the infant remains in distress. [7]

You have 10 minutes to: assess the infant's respiratory status using a structured approach; decide on the appropriate level of respiratory support and state the starting parameters; explain your plan to the infant's parent, who is visibly anxious; and outline your reassessment and escalation plan. A buzzer will sound at 8 minutes. [7]

Marking domains

Domain 1 — Clinical assessment (3 marks)

Performs a structured assessment of work of breathing (respiratory rate against age norms, recession, grunting, nasal flaring) and assesses efficacy (air entry on auscultation, chest rise) and effect (SpO2, colour, conscious state). Clears the threat gate: confirms no apnoea, bradycardia, silent chest or altered conscious state that would mandate immediate intubation. [7]

Domain 2 — Decision-making and device selection (4 marks)

Identifies that the infant has moderate bronchiolitis failing standard low-flow oxygen and selects high-flow nasal cannula as the appropriate escalation, with correct rationale (dead-space washout, reduced work of breathing, PEEP effect, humidification). States the correct starting parameters: flow 2 L/kg/min, FiO2 titrated to target SpO2 92 to 95 per cent. Explains why BiPAP or CPAP are not the first escalation step here (no hypercapnia, no neuromuscular weakness). [1] [7]

Domain 3 — Escalation and failure criteria (2 marks)

States a clear reassessment plan: within 30 to 60 minutes of starting HFNC, and defines failure criteria: worsening hypoxaemia, rising PaCO2, exhaustion, haemodynamic instability, apnoea — that would trigger intubation without delay. [7]

Domain 4 — Communication with the parent (1 mark)

Explains the plan in clear, non-technical language, acknowledging the parent's anxiety and offering reassurance. Describes what HFNC is (warm, moist air through small prongs that helps the baby breathe), why it is needed, what to expect, and what will happen if it does not work. [4]

Examiner notes

This station tests the candidate's ability to make a real-time escalation decision and communicate it, not just recite facts. Look for structured assessment using work, efficacy and effect of breathing — not just "the baby looks sick." Candidates must state correct HFNC dosing at 2 L/kg/min — fixed flows without weight adjustment reveal a knowledge gap. [1] The cardinal error in this scenario is open-ended HFNC with no plan for failure; the strong candidate states upfront what would make them intubate. [7]