Consensus guideline on the use of inhaler devices in asthma continued

Different types of device

Pressurised metered-dose inhalers

• These were the first type of inhaler device to be introduced, and remain the most commonly prescribed delivery system for bronchodilators and inhaled corticosteroids (ICS) in the UK
• The devices rely on a propellant to expel the drug
  • traditionally, the propellants were CFCs but these have now mostly been phased out. They have been replaced with hydrofluoroalkane (HFA) based propellants
• The larger particle size typical of CFC-pMDIs results in a low level of lung deposition:
  • introduction of HFA propellants and molecules of smaller particle size has led to the development of some pMDI devices with improved lung deposition; e.g. extrafine beclometasone and ciclesonide
  • some HFA pMDI products have been re-formulated to mimic the lung deposition traditionally associated with CFC-pMDIs, whereas others have been formulated to contain a smaller particle size, and provide more distal lung delivery
• Patients often have poor technique with pMDIs
• Advantages:
  • consistent dose emission
  • wide range of available drugs
  • multi-dose
  • quick to use
  • small, portable, and discreet
  • familiar to HCPs and patients
  • typically less expensive than other inhaler devices if no spacer is prescribed
• Disadvantages:
  • complicated technique to master
  • high oropharyngeal deposition (lower with some CFC-free devices due to lower emission velocity with smaller particle size)
  • variable lung deposition
  • associated with the cold freon effect (reduced with HFA devices)
  • often difficult to know when empty or close to empty: only one device available has a dose counter
  • not easy for HCPs to teach to patients
  • test firing commonly wastes drug supply
• Technique issues:
  • reliant on high level of coordination between actuation and inhalation
  • a degree of manual dexterity needed
  • requires slow inhalation
  • some devices are more forgiving of poor technique (e.g. BAIs)
  • technique is lost over time

Pressurised metered-dose inhalers plus spacers

• Adding a spacer to a pMDI increases the level of lung deposition and lowers oropharyngeal deposition
• Spacers may be useful for younger patients, together with tight-fitting and age-appropriate masks
• Spacers should be replaced as per manufacturer’s recommendations (typically 6–12 months for plastic spacers), or if visibly damaged
• Advantages:
  • associated with a reduced cold freon effect
  • can be used to deliver high-dose bronchodilators in severe asthma
  • reduce the need for patient coordination with actuation and inhalation
• Disadvantages:
  • potential compatibility issues—although some spacers can accommodate all pMDI mouthpieces, others will only fit specific pMDIs
  • plastic spacers are susceptible to static-charge
  • they can be bulky and not easily portable
  • spacers are often unpopular with patients
• Technique issues:
  • each actuation should be inhaled separately
  • tidal breathing is effective in patients unable to take a large single breath
  • minimal delay between actuation and inhalation is required
• Spacer cleaning issues—patients should be advised of the following care instructions:
  • clean monthly
  • wash in warm soapy water
  • do not rinse
  • air dry
  • after washing, wipe mouthpiece clean of detergent before use

Breath-actuated pressurised metered-dose inhalers

• These more modern devices overcome some of the coordination problems associated with ‘press-and-breathe’ pMDIs since they automatically actuate on inspiration
• Devices are available for both bronchodilators and ICS
• Advantages:
  • overcome coordination problems between inhalation and actuation
  • few steps, easy to use
  • easy for HCPs to teach
  • popular with patients
  • small and portable
  • relatively inexpensive compared to other ICS pMDIs ± spacer
• Disadvantages:
  • require slow inhalation
  • limited range of drugs available
  • cold freon effect present, particularly with CFC formulations; reduced with HFA devices
  • cannot be used with a spacer
  • unsuitable for younger children (<5 years)
• • Technique issues:
  • Autohaler® device requires a moderate degree of manual dexterity
  • generation of inspiratory flow (optimum inspiratory flow range for BAIs: 20–60 l/min) is required to actuate the device

Dry powder inhalers

• These breath-actuated devices were developed to overcome usage problems associated with pMDIs
• Inspiratory flow of the patient deaggregates the drug and allows small particles to reach the bronchi, carried on the inspired air. The inhalation manoeuvre used should be ‘as deep and hard as possible’ and this has to occur immediately at the start of each inhalation
• Advantages:
  • no propellant
  • no cold freon effect
  • high level of lung deposition than traditional pMDIs
  • wide range of available drugs
  • most have a dose counter or indicator
  • few steps, easy to use
  • easy for HCPs to teach to patients
  • small, portable, and discreet
• Disadvantages:
  • powder inhalation can trigger cough
  • dependent on flow rate and acceleration of inspiration
  • may have storage restrictions: some are susceptible to humidity so must be kept dry
  • generally more expensive than pMDIs
• Technique issues:
  • patients with severe lung disease may not be able to generate the minimum effective inspiratory flow required
    • sufficient inspiratory flow required to activate (optimum inspiratory flow range for DPIs: 60–90 l/min; Accuhaler^®: 30–90 l/min; Clickhaler^®: 15–60 l/min
  • should not be exhaled into as this introduces humidity

Nebulisers

• Can deliver a high dose of medication without any inspiratory manoeuvre by the patient
• Rarely necessary in asthma and should only be prescribed after assessment by a specialist
• In acute mild to moderate asthma, a pMDI plus spacer is as least as effective as a nebuliser

Consensus guideline on the use of inhaler devices in asthma continued

Selected features of each type of inhaler device for asthma

pMDI=pressurised metered-dose inhalers; HFA=hydrofluoroalkane; BAI=breath-actuated pMDIs; DPI=dry powder inhalers.
* Guide cost can vary between formulations, strengths, and molecule selected

Selecting an appropriate inhaler device

• The algorithm has been developed to help guide selection of the most appropriate inhaler device for each asthma patient

Cost-effectiveness

• Cost-effectiveness must also be considered when choosing an inhaler device
  • costs of inhaler devices vary widely; generally, generic pMDIs have the cheapest unit cost and DPIs are the most expensive, although individual formulations vary
  • precise cost comparisons between inhaler devices are hampered because of differences in dosing schedules, potency, and formulations
  • pharmacy costs account for only a small proportion of the total cost of asthma and non-pharmacological costs tend to be underestimated; indeed, uncontrolled asthma presents a much larger strain on the National Health Service, accounting for 75% of total healthcare costs of asthma, particularly when hospital admission is required
  • when all costs are considered, the device with the cheapest unit cost is not necessarily the most cost-effective option; often the most cost-effective device is the one the patient can and will use

Consensus guideline on the use of inhaler devices in asthma continued

Algorithm for the selection of the most appropriate inhaler device for each patient

Special groups

• It is important to educate a patient’s parents and/or carers about asthma, how to use the inhaler device correctly and the importance of following the prescribed treatment regimen
• Children:
  • aged 0–5 years: use pMDI plus spacer (plus a mask for those aged <3 years) since this group cannot generate inspiratory flow for BAIs or DPIs, or coordinate breath and actuation as required with pMDIs alone
  • aged 5–12 years: as children get older they may express a preference for a device other than an pMDI plus spacer and they should be involved in the decision of which inhaler to use
• Elderly:
  • special attention should be paid to the ability of elderly patients to use inhalers effectively
    • cognitive impairment may prevent effective training
    • co-morbidities may impact ability to use a device
    • manual dexterity may be reduced and affect ability to use certain devices; there are several aids available for those with physical disability
• People with learning disabilitites:
  • cognitive impairment may prevent effective training
  • a pMDI plus spacer (with or without a mask) may be more appropriate in this situation
  • patient choice remains important