There are various devices available in the market to deliver medication directly to the airways and lungs. They have three advantages. Firstly, they are helpful to deliver the medication directly into the windpipe and lungs. As the medication is delivered locally, (where the medication needs to act) maximal benefit could be achieved easily. Secondly, the amount of medication required to get adequate response is minimal. Thirdly, the side effects are minimal compared to oral medication.
Different types of devices:
Metered dose inhaler (aerosol inhalers or puffers):
It is a plastic case with a mouth piece which contains a canister. Inside the canister the required medicine is placed in a pressurised form whose exit is guarded by a valve. When the canister is pushed the valve opens and a measured (metered) dose of medication will be propelled (by a chemical propellant) in to the mouth piece. Metered dose inhalers are popular due to their simplicity and convenience to carry around. But the main drawback of these types of inhalers is, they need good co-ordination between activation of the canister and inhalation of the medication delivered to the mouth piece (hand- lung co-ordination). Most of the time, around 90% of the medication is deposited in the throat rather than going into the lungs. This problem can be minimised either by using these inhalers with a spacer or by breath actuated inhalers.
The common chemical propellant used in these inhalers was chlorofluorocarbon (CFC). But now, this has been replaced by hydrofluroalkane (HFA), due to an international agreement following the fear that Chlorofluorocarbon might damage the ozone layer of the atmosphere.
These devices have a holding chamber and one way valve fitted in the mouth piece. Also there is a provision for attaching the inhalers on the other side. When the canister (inhaler) is activated, the medication from the inhaler is delivered to the holding chamber. Patient will have sufficient time to inhale the medication through the mouth piece.
Spacers are helpful for those who have poor co-ordination while using metered dose inhalers or for children who won’t be able to use the inhaler directly. Spacers are also helpful in reducing the side effects like oral thrush, which is a common side effect of corticosteroid inhalers.
Dry powder inhalers (tube and disk inhalers):
In these inhalers, instead of a chemical propellant, medication is released in response to patient’s breathing effort. Some patients found it useful, as there is no need of hand-lung co-ordination. But the main drawback of these types of inhalers is, the patient has to breathe in more quickly compared to metered dose inhalers. Unfortunately, spacers cannot be used with theses type of inhalers. Due to this particular reason, children and some adults find it difficult to use them. They are available as tube and disk inhalers.
There are special devices that can combine the medication with air or oxygen and deliver as a mist (aerosol vapour). Nebulisers are normally used for severe asthma attacks, where the patient needs a large dose of inhaled medication without making much breathing effort.
This sixth part of “Walking with a Doc Series – Asthma”, describes about the assisted devices useful for the treatment of asthma.