3.1.5 Peak flow meters, inhaler devices and nebulisers
Peak Flow Meters
- Measurement of peak flow is helpful for patients who are unable to detect deterioration in their asthma and for those with moderate or severe asthma. Mini-Wright® and Vitalograph® peak flow meters are the most commonly prescribed.
- Inhaler devices include pressurised metered-dose inhalers, breath-actuated inhalers, soft mist inhalers and dry powder inhalers. Many patients can be taught to use a pressurised metered-dose inhaler effectively but some patients, particularly the elderly and children, find them difficult to use. Spacer devices can help such patients because they remove the need to coordinate actuation with inhalation. Dry powder inhalers may be useful in adults who are unwilling or unable to use a pressurised metered-dose inhaler. Alternatively, breath-actuated inhalers are suitable provided they can use the device effectively. Asthma UK have useful information for patients on ‘using your inhalers’.
- On changing from a pressurised metered-dose inhaler to a dry powder inhaler, patients may notice a lack of sensation in the mouth and throat previously associated with each actuation. Coughing may also occur.
- The patient should be instructed carefully on the use of the inhaler and it is important to check that the inhaler continues to be used correctly. Inadequate inhalation technique may be mistaken for a lack of response to the drug.
- Spacer devices remove the need for coordination between actuation of a pressurised metered-dose inhaler and inhalation. The spacer device reduces the velocity of the aerosol and subsequent impaction on the oropharynx and allows more time for evaporation of the propellant so that a larger proportion of the particles can be inhaled and deposited in the lungs. Spacer devices are particularly useful for patients with poor inhalation technique, for children, for patients requiring high doses of inhaled corticosteroids, for nocturnal asthma and for patients prone to candidiasis with inhaled corticosteroids. They should be prescribed for patients receiving high dose steroids.
- It is important to prescribe a spacer device that is compatible with the metered-dose inhaler. Spacer devices should not be regarded as interchangeable, patients should be advised not to switch between spacer devices. Refer to BNF Chapter 3.
- Patients should inhale from the spacer device as soon as possible after actuation because the drug aerosol is very short-lived; single-dose actuation is recommended. Tidal breathing is as effective as single breaths. The device should be cleaned once a month by washing in mild detergent and then allowed to dry in air without rinsing; the mouthpiece should be wiped clean of detergent before use. Some manufacturers recommend more frequent cleaning, but this should be avoided since any electrostatic charge may affect drug delivery. Spacer devices should be replaced every 6 to 12 months.
- Nebulisers are not currently prescribable in general practice (but they are free of VAT); patients should be appropriately assessed before nebulised therapy is deemed appropriate. A spacer should be tried before considering a nebuliser.