Optimising Inhaled Treatment through Assessment and Training
As the majority of asthma medication is delivered via inhalers, optimum inhaler technique is an important factor in the management of this disease. Other diseases such as COPD also rely heavily on the inhaled route of drug administration, and in future, it may be possible to deliver drugs this way for other diseases (e.g. insulin for diabetes). Patients need medication for both short-term relief and long-term prevention, and the delivery of these drugs to the lungs is affected significantly by changes in the speed of inhalation.
Assessing inspiratory flow is an opportunity to educate and review inhaler use. Determining whether or not a patient can obtain the optimum inspiratory flow rate for a device can be a significant step towards optimizing treatment. For some patients, it reveals their inability to use a particular device, alerting health professionals to a likely reason for poor response to treatment.
Patients that cannot achieve the optimum inspiratory flow for their inhaler may not gain maximum benefit from their prescribed medication, and healthcare professionals may wish to take this factor into account when selecting a particular design of inhaler.
Recognition of a sub-optimal inhalation is more difficult than many perceive, and experienced respiratory professionals now recognise that without an objective test, a visual observation of technique is no more accurate than a guess.
Another benefit of using a meter is that the patient can be shown how much they need to modify their technique. Encouraging someone to speed up or slow down becomes simple when there is a gauge to measure progress and provide feedback.
Inspiratory Flow and Optimum Inspiratory Flow Range
For each type of inhaler, the most effective delivery occurs when the patient achieves a flow within the Optimum Inspiratory Flow Range. This range of flows is associated with the most desirable, or most beneficial outcome for the patient, and can be identified by analysing the following parameters:
Clinical effects (how effective the treatment is)
Side-effects (undesirable changes in body functions)
Lung deposition (the amount of drug reaching the lungs)
Deposition outside the lungs (in the mouth and oropharynx)
Fine particle fraction (the size distribution of the particles inhaled)
Dose repeatability at different flows (the variation of dose in repeated use)
At flow rates outside this optimum range, certain devices may deliver an effective (rather than optimum) dose. However, inspiratory flow rates outside the optimum range may reduce pulmonary deposition significantly.
Inspiratory Flow Reference Data
Clement Clarke has identified the inspiratory flow rates that are associated with each inhaler device. Where possible, a minimum flow rate for efficacy is listed, as well as the range of flows required for optimum performance.
