MDIs are convenient, portable, and highly reliable devices designed to deliver active medicine directly into the lungs by inhalation. MDIs are conceptually similar to DPIs.
Both MDIs and DPIs allow for the delivery of accurate, pre-determined doses of medicine directly to the respiratory passages. MDIs and DPIs also exhibit fundamental differences. All MDIs use a propellant to push the medicine out of its dosing canister. Except for the Maxair Autohaler, the MDIs on the market in the United States are manually activated rather than breath activated.
Manually activated means that the medicine is released from the MDI canister when you press down on (or actuate) the MDI. Breath activated means that the medicine is automatically released when you inhale deeply; the inward flow of air as you inhale triggers the medication release. Because most MDIs are manually activated, their proper use is technically more demanding and requires more coaching and more learning at the onset, as compared with DPIs.
The correct way to use your MDI is best demonstrated by your physician. There are two techniques for best use: the open-mouth and the closed-mouth technique. All MDIs come with directions. The directions on the manufacturer’s package insert describe the closed-mouth technique. Pulmonary specialists (such as me) generally prefer to teach their patients the open-mouth method of using the MDI.
Many pulmonary specialists believe that using the MDI with an open mouth enhances the delivery of medicine and favors the inhalation of the more desirable, smaller particles released by the MDI. You can read detailed information about each technique on the American College of Chest Physicians (ACCP) patient information pages, Using Inhaled Devices.
MDIs should be stored at room temperature, between 68F and 77F (20C–25C). Avoid subjecting any MDI to sustained temperatures below 59F or above 77F. MDIs should be stored in a vertical position (upright, not on its side) with the mouthpiece down when not in use.
If you notice that the plastic mouthpiece becomes coated with a whitish powder, pull the metal MDI canister out from the plastic mouthpiece and clean the mouthpiece.
Each MDI manufacturer has specific instructions on how to clean the mouthpiece, so be sure to check the correct method for the medicine you have been prescribed. All newer HFA MDI mouthpieces require once a week maintenance cleaning as per the manufacturer’s instructions. Always make sure the mouthpiece is completely dry before reinserting the metal canister. It is fine to let the plastic part air-dry.
All MDIs should be allowed to reach room temperature before use. If you carry your quick-relief MDI with you, and you are outdoors on an especially cold day, place it in an inner pocket close to your body rather than in a handbag or backpack. Never leave an MDI in the glove compartment or in the trunk of your car on a hot day; its contents are under pressure and can explode in very hot environments (120F or above). Several years ago, one of my patients didn’t seem to be faring as well as I had expected. She was an elderly widow and lived alone.
She and I spent an entire office visit carefully going over what had changed to explain her loss of asthma control. Imagine my consternation when she confided that she had hit on a great way to remember where she had put her MDIs: She stored them in her refrigerator’s vegetable drawer, at around 40F. She would take them from the vegetable bin, and go through the process of using the MDI, not realizing that they needed to be stored in a warmer environment, and certainly warmed to room temperature before use! After we decided that she should keep her medicines on the top of the chest of drawers in the bedroom, her asthma once again became controlled, to our mutual satisfaction.
The general concept in using an MDI is that you trigger the release of medicine from the MDI while simultaneously inhaling the medication into empty lungs. The basic technique consists of an initial exhalation to empty your lungs, release of a puff of medication to coincide with a full, steady, deep inhalation, followed by breath holding. To use your MDI, first remove the cap from the mouth-piece. Ideally, you should stand to use your inhaler. If you prefer to be seated, make sure that you sit upright. Hold the inhaler upright, with the mouthpiece at the bottom.
Many people find it most comfortable to hold the MDI with their thumb at the lowermost portion and their third finger on the topmost metal portion of the MDI canister. Next, shake the MDI canister to mix the medicine. After shaking the MDI, position the mouthpiece 2 to 3 finger widths (1 to 2 in.) in front of your open mouth. Tilt your head back slightly, and gently breathe out. When you have emptied your lungs, press on the
MDI and simultaneously take a slow, deep breath. Keep inhaling for at least 5 seconds. Once you have inhaled fully, hold your breath to allow the medicine to fully penetrate in your lungs and deposit there. Try to hold your breath for 10 seconds. Exhale and resume normal breathing. If your doctor has prescribed a second puff of medication, you may be instructed to wait a minute or more between doses.
The MDI-delivered medicine should be going straight into your lungs; consequently, it not should irritate your throat or cause you to cough, nor should it land on your tongue or have any taste. It is important that you learn to use your prescribed MDI correctly. Make sure you ask your physician any questions you may have about the way you are using your MDI .
I have found it very useful to watch my patients’ MDI technique during an office visit. A well-worded or carefully-timed pointer can make a world of difference. Remember that mastering good MDI technique involves a learning curve, and with proper instruction and supervision, even young children can use MDI-delivered asthma medication.
Metered Dose Inhalers: Common Errors in Technique
Forgetting to shake the MDI before use
Not priming the MDI before use, in accordance with the specific instructions of the manufacturer
Sitting in a hunched over position when inhaling from your MDI
Blocking the MDI opening with your tongue or teeth
Releasing the puff of medicine either before (“too soon”) or after (“too late”) you have initiated a deep breath (“poor coordination pattern”)
Taking in too shallow a breath
Not holding your breath for at least 10 seconds after inhaling your medicine
Neglecting to rinse your mouth (“rinse & spit”) after using your inhaled corticosteroid MDI
Forgetting to discard the MDI when no doses of medicine remain in the canister
Forgetting to learn for how many months you can use an MDI dispensed in a moisture-proof foil before it must be discarded (even if there is still medicine inside)