Bronchiolitis and viral lower respiratory tract infection — branching viva

Opening

Examiner: A 4-month-old arrives in winter with two days of a runny nose and cough, now breathing fast with recession, diffuse crackles and wheeze, feeding half normal and saturating 91 percent. How do you approach her? ^[1]

Candidate: I would make a clinical diagnosis of bronchiolitis — a first viral lower respiratory tract infection in an infant under twelve months — and grade its severity by observation before disturbing her, keeping her settled on her carer's lap. She has moderate work of breathing, feeding around half and saturations of 91 percent, which places her in the moderate band. My plan is supportive care: support feeding, give oxygen if saturations stay below target, and reassess serially, while deliberately not reaching for bronchodilators or steroids. ^{[1] [5]}

Branch 1 — supportive care and the drugs you withhold

Examiner: Why not give her a salbutamol trial for the wheeze? ^[2]

Candidate: Because the obstruction in bronchiolitis is mechanical — sloughed epithelium, oedema and mucus in the small airways — rather than reversible bronchospasm, and infant bronchioles have little smooth muscle to relax. The Cochrane review of bronchodilators found no meaningful benefit in oxygenation, admission or length of stay, so salbutamol is not part of routine care, and the same applies to adrenaline, corticosteroids, antibiotics and physiotherapy. ^{[2] [1]}

Examiner (probe): What oxygen saturation target would you use, and why? ^[4]

Candidate: I aim for a target of around 90 to 92 percent. The BIDS equivalence trial showed that a 90 percent target was as safe as a 94 percent target while reducing oxygen use and length of stay, so I titrate oxygen to that lower target rather than chasing normal saturations, and I interpret the number alongside her feeding and work of breathing. ^{[4] [1]}