Mechanical Function
Asthma inhalers, also known as measured-dose inhalers, are mechanically designed to deliver medication directly to the patient's lungs. This gives them an advantage over oral or intravenous injections, especially since there are little to no side effects with this method. Asthma inhalers primarily rely on a pumping system composed of two parts: a canister and an actuator. The patient would press on the canister, which pushes a liquid medication into the actuator. The actuator turns the medication into an aerosol spray so that it can be quickly absorbed by the lungs.
Propellant
For the medication to expel at the proper speed, the propellant must have specific properties and ratings. It must leave with enough force to turn the medicine into an aerosol cloud, as well as act as the medication medium. For example, the vapor pressure must be between 40 and 80 psig. It must also be non-flammable with a boiling point above 30 degrees Celsius, according to the Journal of Fluorine Chemistry. Propellants should also have no obvious toxicity to patients and should be able to fully dissolve active ingredients, as well as common additives.
Spacers
For some patients that do not have strong breathing power, such as small children, a direct reception from the asthma inhaler can be problematic. Spacers can help alleviate this issue. A spacer is a horizontal tube that sometimes comes with a collapsible bag inside of it and a plastic shield designed to fit over the patient's nose and mouth. It can be attached to the end of the actuator. Once the asthma inhaler canister is depressed, the medication goes into the spacer. The patient can then inhale the medication from the spacer versus directly from the actuator.
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