Inhaled therapies and device selection — branching viva

Opening — the eighteen-month-old with no spacer

Examiner: An eighteen-month-old with viral wheeze has been prescribed a salbutamol pressurised inhaler with no spacer. What is the correct device, and why is the spacer essential? [1] [8]

Candidate (model): The correct device for this age is a pressurised metered-dose inhaler seated in a small-volume valved holding chamber with a tightly-fitting face mask. The spacer is essential because a pressurised inhaler fires its aerosol cloud in under a tenth of a second at high velocity — far too fast for an infant to time to a single breath — so without a spacer most of the dose deposits in the oropharynx and almost nothing reaches the lung. The spacer intercepts the fast cloud, slows and suspends it, so the infant can clear it by slow tidal breathing over around six breaths, with the mask sealed firmly to the face. A dry-powder inhaler would not work at this age because the child cannot generate the inspiratory flow. [1] [8]

Branch 1 — teaching the family

Examiner: How do you teach the family to use it, and what is the commonest reason it fails at home? [3]

Candidate (model): I demonstrate, then have the parent return the demonstration. Shake the canister, seat the mask firmly against the child's face, fire one actuation into the chamber, and hold the mask in place for around six slow tidal breaths, watching the one-way valve move with each breath. I wait until that puff is cleared before the next. The commonest reason it fails is mask leak — the aerosol streams out around a loosely-held mask — so I emphasise a firm seal. I also prime a new plastic spacer with several wasted actuations and advise washing it in detergent without rinsing or wiping, to suppress the static charge that would otherwise attract the drug to the chamber wall. [3]

Branch 2 — the acute asthma device choice

Examiner: Now a six-year-old presents with a moderate acute asthma exacerbation. What is your first-line reliever device route, and on what evidence? [5]

Candidate (model): For most children with acute asthma, my first-line route is salbutamol by pressurised inhaler and spacer. The Cochrane review of holding chambers versus nebulisers for beta-agonist treatment of acute asthma found the spacer at least as effective as the nebuliser, with fewer side-effects such as tremor and tachycardia and a shorter emergency department stay. I give the dose one actuation at a time into the spacer, cleared by the breaths, and repeat it over the first hour per the local acute-asthma guideline. The exact age-stratified puff counts I would verify against the current Australian Asthma Handbook or local protocol. [5]

Branch 3 — when the nebuliser is right

Examiner: When would you reach for the oxygen-driven nebuliser instead? [5]

Candidate (model): I reserve the oxygen-driven nebuliser for the child who is hypoxic, exhausted, or unable to coordinate the spacer — because it both delivers the reliever and supplies oxygen, which a spacer cannot. It is not a more powerful version of the spacer, and I would never withhold oxygen or delay the reliever to wait for a nebuliser that a spacer could match now. For the child who can take a spacer, the spacer remains first-line. [5]

Branch 4 — the failing preventer

Examiner: Finally, a nine-year-old on a regular inhaled corticosteroid says it isn't working and her reliever use has risen; she admits she often uses the inhaler without the spacer. Walk me through your assessment before you change the dose. [1] [3]

Candidate (model): The commonest reason an inhaled corticosteroid appears to fail is poor delivery, not an inadequate dose — and using the inhaler without the spacer deposits most of the dose in the oropharynx. So first I watch her take the dose. I check the SEAL: the seal of the mouthpiece, the exhalation and effort (slow deep breaths with a breath-hold), the actuation (shake, one puff at a time into a seated chamber), and whether the lung dose is preserved (primed, static-free spacer, rinse and spit afterwards, dose counter checked). I also exclude non-adherence, the wrong diagnosis — a foreign body, airway malacia, protracted bacterial bronchitis — and genuine disease severity. My plan is to correct the technique and re-assess control over two to four weeks before I escalate the drug. [1] [3]

Closing — the principles examiners reward

Examiner: Give me the three principles you would want every registrar to remember. [1] [5]

Candidate (model): First, match the device to the child's age and inspiratory flow — a spacer with a mask under four, a spacer with a mouthpiece four to six, a dry-powder inhaler from school age. Second, a spacer is not an accessory; it is the device that makes a pressurised inhaler work in a child, by slowing and suspending the cloud so respirable particles reach the lung. Third, when an inhaled drug seems to fail, check the device and the technique before you escalate the dose — a loose mask, an unprimed spacer, or a technique that has drifted explains more poor control than inadequate prescribing. [1] [5]