Airway suction, oxygen devices and nebuliser technique: Viva

Branch 1: Clearing the airway — suction technique

The candidate should lead with the principle that an obligate nose-breather with bronchiolitis often obstructs behind nasal secretions, so gentle suction alone may transform the child. They suction what they can see first: mouth and oropharynx with a rigid Yankauer, and the nose gently, pre-oxygenating before and between passes and limiting each pass to about 5 to 10 seconds with continuous heart-rate and SpO2 monitoring. [3]

The examiner should probe the physiology and the complications. The candidate explains that suctioning provokes a vagal bradycardia and desaturation within seconds, which is why pre-oxygenation, short passes and monitoring are non-negotiable. They state that a suction catheter is sized to about half the airway lumen, advanced gently and never forced, and that deep, blind pharyngeal suction in infants has caused iatrogenic mediastinitis, so the safe rule is to suction only what can be seen. [4]

If the examiner pivots to the tracheostomy-dependent child, the candidate switches to sterile technique with an appropriately-sized catheter, follows the child's own airway plan, and involves the family, who are usually the most expert people at the bedside. [3]

Branch 2: Choosing and justifying the oxygen device

The candidate states a target SpO2 of 94 to 98 percent for this acutely ill infant, oxygen being a drug with a target and not a flow to be maximised. They explain why the infant is failing nasal cannula: it is a variable-performance device whose delivered FiO2 (24 to 40 percent) is diluted by entrained room air during the infant's rapid recessive breathing, and the nasal secretions block gas delivery. [1]

The examiner should test classification. The candidate distinguishes variable-performance devices (nasal cannula, simple and reservoir masks) from fixed-performance devices (heated humidified high-flow nasal cannula, tracheal tube), and justifies escalation to high-flow nasal cannula at 1 to 2 L/kg/min with blended oxygen, citing the PARIS trial that high flow reduces intubation in bronchiolitis. They note that high-flow oxygen must be heated and humidified to avoid mucosal damage, and that a simple mask must run at least 5 to 6 L/min to avoid carbon dioxide rebreathing. [1]

If pushed on oxygen harm, the candidate cites the Oxy-PICU finding that conservative targets are as safe as liberal ones, and notes that over-oxygenation harms preterm infants (retinopathy of prematurity), so oxygen is given to a target and weaned, not chased. They escalate to intensive care if the SpO2 stays below target despite correct therapy, recognising that a failing saturation signals a cause to fix, not simply more oxygen. [1]

Branch 3: Delivering an inhaled bronchodilator

The candidate states that, if wheeze suggests a reversible component, the first-line delivery tool for a child who can use one is a spacer with a salbutamol metered-dose inhaler, one puff at a time with tidal breathing, because the Cochrane evidence shows it is as effective as a nebuliser and faster. They reserve a jet nebuliser for the infant who cannot use a spacer or who needs high-flow oxygen at the same time. [2]

The examiner should test aerosol physics. The candidate explains that droplet size decides deposition: droplets larger than 5 micrometres deposit in the mouth, the respirable fraction of 1 to 5 micrometres reaches the lower airways, and droplets smaller than 1 micrometre are exhaled. A slow driving gas flow makes large useless droplets, so the jet nebuliser is driven at 6 to 8 L/min, and a crying infant wastes the dose by depositing it in the mouth, which is why calming the child and aiming for quiet tidal breathing improves delivery. [2]

If the examiner escalates to a severe asthma attack in an older child, the candidate gives salbutamol 5 mg nebulised for a child of 5 years and over (2.5 mg under 5), adds ipratropium 250 microgram for a severe attack, gives a systemic steroid within the first hour, and uses continuous nebulised salbutamol for a life-threatening attack with senior intensive care support. [2]