Asthma is a chronic respiratory disease that affects approximately 300 million across the world, according to the World Health Organization. Asthma causes mucus build-up and inflammation of the airways that result in symptoms such as wheezing, shortness of breath, coughing and chest tightness. Those who suffer from asthma experience episodes when symptoms are exacerbated by triggers, such as cold air, allergens or air contaminants. There is no cure for asthma but symptoms can be actively managed through close monitoring and medications. Asthma inhalers, of which there are several types, provide an advantage because they deliver the medications directly to the airways where it is needed most.
Metered Dose Inhaler
A metered dose inhaler is a small pressurized canister that contains an aerosol form of medication. To release the medication the canister is pushed down into the plastic boot-shaped mouthpiece while the patient takes in a deep breath. Some metered dose inhalers are automatic and release the medication as the patient breathes. Automatic versions are especially useful for children who have a difficult time coordinating their breath with pushing the pump.
Some models of metered dose inhalers have a counter that keeps track of the number of doses. In models that lack a counter, the doses must be counted manually, which increases the risk of running out of medication.
When using metered dose inhalers it is OK to breathe out a little during the dosing. One disadvantage to this type of inhaler is that some of the medication can settle on the tongue or on the back of the throat, never reaching the airways, according to the Mayo Clinic.
Metered Dose Inhaler with Spacer
Another type of inhaler is a metered dose inhaler with a spacer. A spacer is a holding chamber, such as a small bag or tube, with a one-way valve. The spacer attaches to the metered dose inhaler. When the inhaler is pumped, the medication goes into the spacer. The user can then inhale the medication in more than one breath if needed.
Using a spacer allows more of the medication to reach the airways instead of settling on the tongue or throat. It also decreases the amount of medication that is swallowed, which decreases the incidence of side effects. The disadvantage of using a metered inhaler with a spacer is that the added bulkiness makes it not as convenient to carry.
Dry Powder Inhaler
Metered dose inhalers require a chemical propellant, such as chlorofluorocarbons or hydrofluoroalkanes to deliver the medication as an aerosol. Dry powder inhalers do not require a chemical propellant as they deliver the medication in powder form. This type of inhaler can be more difficult to use for some patients as they must breathe in a deep, fast breath to get the medication into the lungs. In addition, accidentally breathing out during dosing can result in lost medication.
The advantage of using dry powder inhalers is that it is very clear how much medication remains in the device. Also, some models are single dose inhalers which can be loaded with a single dose capsule. These features help to ensure that the user never runs out of medication unknowingly.
