Jane Scullion looks at the increasing complexity of the multitude of MDI and DPI devices that are available and the therapeutic options they offer, in the second of two feature articles.
Read this article to learn more about:
- inhaler devices and therapeutic options available for the treatment of asthma and chronic obstructive pulmonary disease (COPD)
- selecting the most appropriate inhaler device and therapy for an individual patient.
After reading this article and the previous article in the series, ‘Test and reflect’ on your updated knowledge with our multiple-choice questions. Earn a total of 2 CPD credits for reading the articles and completing the MCQs.
Guidelines stress the importance of making sure that people can use their inhalers.1,2 Types of inhaler device include: pressurised metered-dose inhalers (pMDI); soft mist inhalers; or the less commonly prescribed dry-powder inhalers (DPI). In addition, there are multiple variations of each type of inhaler and the medications that they contain. Despite the wide range of inhalers that are available, the steps for using them are relatively similar (Box 1),1 however, they require different inspiratory flow rates. Inhalation should be slow and steady for the pMDI, and quick and deep for the DPI. Inhaler stickers can be placed on to the patient’s inhaler as a reminder of the correct inhaler technique (Figure 1, below).3 With aerosol devices, the ideal inspiratory flow rate is 30 litres/minute this equates to taking a slow and steady breath in for around 4 seconds.4 The newer devices have a softer plume and better valve technology, and some have a smaller particle size, which increases deposition. The Respimat® inhaler, although it is an aerosol, produces a soft mist, increasing deposition in the lung. A slow and steady breath in is required, although there will be adequate deposition if the inhalation is quicker and deeper.
Box 1: Seven basic steps1
- Prepare inhaler device
- Prepare (or load) dose
- Breathe out (not into the inhaler!)
- Put lips around mouthpiece
- Breathe in
- MDI: slow and steady
- DPI: quick and deep
- Remove inhaler from mouth and hold breath for up to 10 seconds
- Repeat as directed
DPIs require less coordination by the person using them, but they do require an adequate amount of inhalation, because it is inspiratory flow that releases the medication from the carrier agent. DPIs require a quick and deep inhalation which may be problematic in patients with little inspiratory effort, such as those with severely compromised lung function.4
With so many different devices available that have differing functionalities and techniques for use, it is useful to think about the questions in Box 2 when considering device suitability for patients. It is also important to consider which therapeutic and dose equivalents are compatible for delivery by each device when considering which one to use. This is especially important when considering the administration of inhaled corticosteroids (ICSs)—the therapeutic equivalent dose of different ICS varies depending on which device is used.5 The British National Formulary (BNF) provides information on inhaler devices, and the therapeutic options that can be delivered by these for asthma and COPD.6,7,8
Box 2: Considerations when choosing an inhaler device
- Is it easy to prepare/load?
- Does it need shaking?
- Is there a dose counter or can you tell easily when the device is empty?
- How many doses does it contain?
- Does the dose counter count down if the person fiddles with the inhaler or is it accurate in terms of doses taken?
- Is it breath-actuated or does it need coordination?
- Can you load multiple doses?
- Is there audible or visual feedback to show that the dose has been delivered?
- Is there a taste or cold freon effect?
- What inspiratory flow rate do you need?
Inhaler devices contain different doses of medication therefore, devices are not interchangeable if we want consistent dosing. Additionally, some of the generic medications have different equivalent doses to the original inhalers. If patients do not understand that the prescribed doses are equivalent, they may be reluctant to use their inhaler because they may feel that the dose is too high, or they may feel that they require more doses because the dose seems too low. The drugs will also have different durations of action, and some are taken as required, so dosing schedules vary from one to three times a day.
Evidently, all inhaler devices are not the same, although many ‘switch’ programmes are going on around the country. One inhaler is changed for another cheaper, generic device often without any review or guidance for patients. It is not always apparent that this issue is recognised by healthcare professionals.
A number of questions should be asked when selecting an inhaler device to administer a drug for the treatment of a respiratory disorder:
- does the device have a range of therapeutic options?
- what is the licensed dose for each of these for asthma?
- what is the licensed dose for each of these for COPD?
- what are the licensing indications for different age groups?
- does the person have the correct inspiratory flow rate to deliver the medication dose?
Many medications are available for the treatment of respiratory disorders, and not all of these are administered by inhalation. Those medications that are inhaled can be broadly divided into two classes—bronchodilators and anti-inflammatory drugs (see Figure 2, below). Some bronchodilators are short-acting and are not taken on a regular basis, whereas some are long-acting and are taken regularly. Inhaled corticosteroids are for prevention and need to be taken regularly to be effective.
When considering how to treat a patient, decisions should be made on an individual basis taking into account current guidelines and local formulary recommendations.4
Figure 3 illustrates the various therapeutic approaches that can be taken for the treatment of asthma and COPD. Similar to the number of devices there are to choose from, there are many different therapeutics, and combinations of therapeutics, that can be administered using these devices. For simplicity, Figure 3 does not detail the short-acting agents (short-acting muscarinic antagonists, SAMA; short-acting beta2 agonists; SABA)—but these are part of the therapeutic armoury. The drugs featured are indicated for asthma and/or COPD, but not all are licensed for both conditions, or for all age groups—the BNF will provide more detail of these, and also of the brand names available for each drug.6,7,8
There are also combination treatments in development combining both LABA and LAMA molecules into one dimer molecule, which is known as a muscarinic antagonist, beta2-agonist (MABA).9
Prescribing the right device and the right drug
Patients requiring inhaled therapies should receive education and training on the use of appropriate medication for their symptoms. The healthcare professional should be aware: of the availability of other drugs in the same device; device effectiveness; personal technique and experience with the device; inspiratory flow rate; cost; and local formularies.4 Some patients, including the elderly and children, may find it difficult to use certain inhaler devices and consideration should be given to this. In terms of prescribing, we should prescribe both the drug and the device. Given the growth of generic formulations and new devices, it is also recommended that we should prescribe by brand name;2,4 this prevents the dispensing of inhaler devices that the patient may not have seen before and may not be able to use.
As prescribers and those involved in patient teaching, we need to be capable of using and demonstrating effective use of inhalers. Prescribing inhaler devices and associated medications will be an expensive and ineffective option if patients are not taught how to use them correctly.10 The BTS/SIGN British guideline on the management of asthma states that inhalers should only be prescribed to patients once they have received training on the use of the device, and have demonstrated satisfactory technique.2 Furthermore, the NICE guideline, Chronic obstructive pulmonary disease in over 16s: diagnosis and management recommends that a patient’s ability to use an inhaler should be assessed at regular intervals by a competent healthcare professional, with the correct technique being re-taught as necessary.11 Asthma UK12 and Right Breathe13 provide useful patient information entitled Using your inhalers, which includes instructional videos on using different types of inhaler devices.
- Scullion J, Fletcher M. Inhaler standards and competency document. London: Respiratory Futures, 2016. Available at: www.respiratoryfutures.org.uk/media/69774/ukig-inhaler-standards-january-2017.pdf
- British Thoracic Society/Scottish Intercollegiate Guidelines Network. British guideline on the management of asthma. SIGN 153, updated 2016. Available at: www.sign.ac.uk/guidelines/fulltext/153 and www.brit-thoracic.org.uk/quality-improvement/guidelines/asthma/
- Usmani O, Capstick T, Chowan H et al. Choosing an appropriate inhaler device for the treatment of adults with asthma or COPD. Originally developed for Guidelines 2016; also published on Guidelines for Nurses 2016. Available at: www.GuidelinesforNurses.co.uk/WPG/inhaler-choice
- Scullion J, Holmes S. Maximising the benefits of inhaler therapy. Practice Nursing 2013;24 (12): 594–600.
- Barnes N. The properties of inhaled corticosteroids: similarities and differences. Prim Care Respir J 2007; 16 (3): 149–154.
- NICE, British National Formulary (BNF). Asthma, acute. Available at: bnfc.nice.org.uk/treatment-summary/asthma-acute.html (accessed 11 April 2019).
- NICE, British National Formulary (BNF). Asthma, chronic. Available at: bnfc.nice.org.uk/treatment-summary/asthma-chronic.html (accessed 11 April 2019).
- NICE, British National Formulary (BNF). Respiratory system, drug delivery. Available at: bnfc.nice.org.uk/treatment-summary/respiratory-system-drug-delivery.html (accessed 11 April 2019).
- Cazzola M, Lopez-Campos J et al. The MABA approach: a new option to improve bronchodilator therapy. Eur Respir J 2013; 42: 885–887.
- Chrystyn H, Price D. Not all asthma inhalers are the same: factors to consider when prescribing an inhaler. Prim Care Respir J 2009; 18 (4): 243–249.
- NICE. Chronic obstructive pulmonary disease in over 16s: diagnosis and management. NICE Guideline 115. NICE, 2018. Available at: www.nice.org.uk/ng115.
- Asthma UK. Using your inhalers. Available at: www.asthma.org.uk/advice/inhalers-medicines-treatments/using-inhalers/ (accessed 11 April 2019).
- RightBreathe.www.rightbreathe.com (accessed 11 April 2019).
Device selection in children and adults
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Striking a balance: device choice and therapeutic dosages