Asthma Lexicon: Metered Dose Inhaler

For most of us, having inhalers is an integral part of our lives. Personally, I’ve had inhalers since 1980. If you’re a nerd like me, you’ve taken one apart. You’ve dissected it and learned all the parts. No? Well, allow me to share what I’ve learned. Here are all terms associated with Metered Dose Inhalers along with a pithy definition.

Terms associated with Metered Dose Inhalers

  • Inhaler. A device that contains respiratory medicine. It allows you to inhale a respiratory medicine.
  • Puffer. Another term for an inhaler. You may hear it used interchangeably with an inhaler.
  • Pump. Yet another term for an inhaler.
  • Metered Dose Inhaler (MDI) .
    An inhaler that delivers a metered dose.
  • Solution. Liquid. Inhaler medicine is stored in a solution. This solution contains a propellant.
  • Propellant. It’s a chemical solution that creates the spray when you actuate the inhaler. Respiratory medicine is mixed in with a solution that contains the propellant.
  • Respiratory Medicine. It’s asthma medicine you want to inhale. Two common medicines used are rescue medicines and inhaled corticosteroids.
  • Metal Cannister. It’s a small canister to store a solution of medicine plus propellant. These contents are pressurized. The canister is narrowed at the top and contains an extension chamber.
  • Pressurized. This means the contents are kept at a pressure higher than atmospheric pressure. The pressure inside the canister is higher than the pressure of air in the room you are sitting in right now. This makes it so the medicine sprays out when you actuate it. This is why you will sometimes see inhalers referred to as Pressurized Metered Dose Inhalers.
  • Extension Chamber. This is the white thing on top of the inhaler. It allows the medicine plus propellant to spray out when you actuate the inhaler.
  • Plastic Actuator. It’s the plastic device that the metal canister sits in. The canister is inserted into it. 1
  • Actuator Nozzle. It’s a nozzle inside the bottom of the plastic actuator. It’s a small opening. When the canister is placed in the plastic actuator, the extension chamber fits snug into the actuator nozzle.
  • Metered Valve. It’s a valve inside the tip of the inhaler. It’s what assures you are getting a measured dose of the medicine when you acuate the inhaler. 1
  • Actuate. It’s when you cause the inhaler to spray the medicine plus propellant. To actuate asthma inhalers, you hold the device so your pointer finger is on top of the cannister. The thumb of the same hand is under the plastic actuator. You then squeeze. By doing this, you create a pressure that forces the extension chamber on the canister into the Actuator nozzle of the plastic actuator. This should produce a high-velocity spray.
  • Actuation. The process of actuating an inhaler.
  • High-Velocity Spray. It’s what is produced when you actuate the inhaler. It’s how you get the medicine to your airways. 1
  • Shake. Vigourously move up and down. This is necessary to make sure the medicine is adequately mixed with the propellant. This assures you will receive the desired dose of medicine when you actuate the inhaler.
  • Prime. Wasting a few sprays into the air to prime the valve. It assures you are getting the desired dose of medicine when the inhaler is actuated.

What to make of this?

Inhalers make it so we can live normally despite asthma. Now, you know as much about them. Some of this may be what some refer to as “useless wisdom.” Still, it’s neat to know how things work.

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This article represents the opinions, thoughts, and experiences of the author; none of this content has been paid for by any advertiser. The team does not recommend or endorse any products or treatments discussed herein. Learn more about how we maintain editorial integrity here.

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