Inspiratory flow – breathing in too quickly or too slowly

The total lung deposition of an inhaled drug is strongly affected by the speed of inhalation and the required speed varies depending on the type of inhaler used. Aerosols such as MDIs need a slow and steady inhalation to increase lung deposition. DPIs require a quick and deep inhalation to generate a large internal turbulent force to break up the formulation and optimise the particle size and lung deposition. The inhalation should be forceful from the start of inhalation.

Not continuing to breathe in after pressing the canister

Inhaling deeply maximises the opportunity for the drug particles to reach the small airways. If no additional air is inhaled, the drug will remain in the larger airways, limiting its effect. Patients should therefore continue to breathe in after pressing the canister.

Not holding the breath after inhalation

Holding the breath increases lung deposition through the process of sedimentation, meaning the air is still enough for the drug particles to settle on the surface of the lungs. A 10 second breath is thought to be ideal, but if this is not possible, encourage the patient to hold for as long as is comfortable after inhaling.

Multiple actuations without waiting in between

Very rapid actuations can reduce the dose delivered per actuation, limiting the drug’s effectiveness. However, salbutamol MDIs can be actuated immediately after the required breath holding for 10 seconds without affecting the dose delivered. Patients should be advised according to the type of inhaler they use.

Using an empty inhaler

Patients frequently fail to detect when their inhaler is empty, particularly when using reliever MDIs. They should therefore be encouraged to regularly check their inhalers to ensure there is a sufficient amount of the drug remaining to be effective.

Poor maintenance of inhaler or spacer device

Spacers should be reviewed every six to 12 months to check that the structure is intact (e.g. no cracks), the outer casing is clean and the valve is functioning effectively.

Reflection exercise

Think about the last time you counselled a patient about their inhaler technique. How confident are you that you correctly assessed their inhaler technique? What went well and what could you improve?