You’re seeing a child with acute asthma in the emergency department. Their inhaler was not working… You prescribe ten puffs of salbutamol via a metered-dose inhaler and spacer.
The nurse returns after giving it and tells you that the home inhaler seems empty. Thinking this may be the reason the child needed to come to the hospital, they suggest you chat about making sure the child doesn’t run out of medication.
Looking at the inhaler, you can’t see a dose counter and wonder, “How do you know when the inhaler is empty?”
Why is the treatment of asthma a problem in the UK?
Asthma-related morbidity and mortality in children remain high in the UK. Despite national NICE quality standards, media drives, annual asthma reviews and post-exacerbation follow-up, there has been no sustained reduction in the rate of acute asthma exacerbations in children.
What does this have to do with Metered Dose Inhalers, and how should children and parents be advised on identifying an empty inhaler?
The NICE quality standards (2018) recommend assessment of adherence, medication review and inhaler technique at every asthma review. Metered-dose inhalers (MDIs), have been used to treat childhood and adult asthma for over six decades. They are reliable and easy to use.
One of the biggest disadvantages of metered dose inhalers is the inability to tell how much medication is left in an inhaler. This is due to the design feature of MDIs. They contain a propellant and the active drug to expel the labelled number of doses or accuations. Up to 86 actuations may be just the propellant, containing negligible active drug once all the medication has been used. Although the inhaler may appear to be delivering an audible ‘puff’, there may be little or no active drug component.
Some inhaler devices have an integrated dose counter, making identifying the number of actuations left easier. However, not all inhalers have them. Salbutamol (Ventolin®, Salamol®), the most prescribed inhaler, does not contain a dose counter in the UK.
Salbutamol is recommended as a rescue/reliever medication, and patients are advised to use up to 1-12 puffs four hourly during wheezy episodes. The manufacturer recommends noting when the new inhaler was opened and counting the total doses used. Alternatively, you could weigh the inhaler to determine when it is empty. Shaking the inhaler, simple ‘test’ actuations or floating the canister in a water bowl are not recommended.
Corticosteroid ’preventer’ inhalers contain Beclomethasone (Clenil Modulite®) or fluticasone (Flixotide®). Some, but not all, have a dose counter – Seretide® (Fluticasone+ Salmeterol), and Symbicort® (Budesonide+ Formoterol) do.
Disappointingly, the patient information leaflets accompanying the inhalers contain very little information. Ventolin and Salamol leaflets contain no warning that the inhaler will continue to produce a spray with little or no active drug.
West Midlands Severe Asthma Network QI Project
A QI project was undertaken by eight hospitals as part of the WMPSAN (West Midlands Paediatric Severe Asthma Network) to look at this issue. Prospective cross-sectional data was collected for children with asthma, preschool wheeze and other children with respiratory diagnoses who had been prescribed an inhaler. Data was collected from 157 children between October 2020 to September 2021.
Children and families were shown an empty MDI salbutamol inhaler that gave the recommended 200 doses and was asked how they knew that the inhaler had medicines left in them. Of 123 children and families, 90 (73.5%) said the inhaler was either full or partially full, and 33 (26.5%) said the inhaler was empty.
86 children (54.8%) said they could identify an empty inhaler, and 71 (45.2%) were unsure or unaware. 105 (69.9%) shook the inhaler to see if medication was left in it, and 27 (29.9%) looked for visible aerosol during actuation, neither of which are useful. Only three patients said they would look at the dose counter, and two kept count of actuations delivered.
What does this mean?
This raises a significant patient safety issue: children and families cannot consistently identify when inhalers are empty.
There is an urgent need for the pharmaceutical industry and national guidelines to produce educational information around the identification of empty inhalers as well as improving inhaler technology. Since August 2020, all salbutamol inhalers in Australia have a dose counter. New asthma guidelines should explicitly provide information on identifying an empty inhaler. This should also become a part of the standard asthma management and an educational package delivered to patients and parents. Dose counters should be made available with all salbutamol and preventer inhalers.
What does this mean for your patient?
You let them know that once all their medication has been given, the inhaler can still deliver several sprays that contain no active drug.
You remind them that the most effective way to ensure the inhaler isn’t empty is to keep a count of the doses puffed (perhaps on the cardboard box of the inhaler) or to weigh the inhaler with electronic kitchen scales.
A full Salamol® inhaler weighs 26g, and an empty one weighs 17g. A full Ventolin inhaler weighs 37g and 25g empty. You also ensure they have multiple inhalers in different places (school, living room, bedroom, aunties place) though this can make it tricky to track the number of doses left.
Fullwood I, Evans T, Davies B, et al. Do you know when the inhaler is empty? Archives of Disease in Childhood Published Online First: 12 May 2022. doi: 10.1136/archdischild-2022-324027
Rubin BK, Durotoye L. How do patients determine that their metered-dose inhaler is empty? Chest 2004;126:1134–7.