Metered dose inhalers (MDI) are the most commonly prescribed. Like mini-aerosol cans, these devices push out a pre-measured spray of medicine. When the person squeezes the inhaler, a measured "puff" of medicine is released. Some MDIs have counters that indicate how many doses remain. If there's no counter, the number of doses already used should be tracked, so that the inhaler can be replaced on time.
Kids who use a metered dose inhaler also might use a spacer, which attaches to the inhaler and makes it easier to use. A spacer is a kind of holding chamber for the medicine, which eliminates the need to closely coordinate squeezing the inhaler and inhaling the medicine. With an inhaler and spacer, the medicine can be inhaled slowly when the user is ready. So, it's possible for very young kids and even babies to receive their medications using a metered dose inhaler with a spacer.
Spacers also make inhalers more effective. Sometimes with an MDI, the medicine will reach the back of the throat but not get down into the lower airways. A spacer helps to deliver the medicine into the lower airways, which is where it needs to go to work properly.
Babies and younger kids use a facemask (a plastic cup that covers the mouth and nose) to inhale the medication held in the spacer, whereas older kids can use a mouthpiece. It usually only takes a couple of minutes or less to give medication by metered dose inhaler with a spacer.
Dry powder inhalers deliver medicine in powder form, but they don't spray out. The user must do more of the work, inhaling the powdered medicine quickly and quite forcefully. At around 5 or 6 years of age, most kids are able to do this.
During an office visit, the doctor may ask your child to demonstrate using the inhaler and offer advice, if needed.