If you’re suffering from allergies or asthma, your physician may ask you to use a metered-dose inhaler (MDI) as a way to get medication into your lungs. An MDI uses a propellant gas to deliver a predetermined (metered) dose of medication as a fine spray or mist. Although the devices look simple, these inhalers are actually deceptively complex to use properly. Used incorrectly, the medicine won’t reach where it is needed to alleviate your asthma symptoms.

How It Works

In a typical inhaler, a solution with active ingredients is mixed with a liquefied gas propellant, or with a combination of water, ethanol, and propellant. These are packaged together in an aluminum canister or a plastic-coated glass container. To dispense a dose of the drug, one has to actuate a valve. An oral adapter, fitted snugly on the valve, allows for actuating the valve and directs the mist containing the medicine.

Common Usage Errors

Correct self-dosing with an MDI is fairly difficult. In one study, 100 people were first carefully trained to use MDIs. Upon later evaluation, only a small percentage always used the inhalers correctly.

The most common errors patients make include:

  • Failing to shake the canister prior to use
  • Failing to pause and exhale slowly
  • Not waiting 1-3 minutes between actuations
  • Poorly coordinating inhalation and actuation

The last-poor coordination-is by far the most frequent error and can result in nearly all of the drug being deposited in the mouth or throat rather than in the airways, where it could be effective. This misguided landing also can cause undesirable results such as hoarseness, mouth infections, or even systemic reactions.

Spacers Make a Difference

A spacer device can help with proper drug delivery. Some spacers resemble accordion-like bags; others are simple tube-like chambers. Although designs differ, all are basically a form of tubing that lengthens the distance from the inhaler’s opening to your mouth. This increased distance slows the speed of the fine particles and increases their chances of actually reaching your airways. Large slow-moving particles land inside the spacer rather than in your mouth, where they could cause problems.

Of course, not all spacers are alike. Your physician can help you select the inhaler and spacer that will best suit your needs.

Alternatives to MDIs

The Spinhaler is a device that delivers a powdered form of medication. The medication, contained in a capsule, is inserted into a cup set in a propeller-like rotor. The action of the Spinhaler propels (spins) the medication into the inhaled air is it is drawn into the airways. Medication is automatically released only when inhaling, so no coordination (between inhaling and actuating the medication) is necessary.

Based on the concept of the Spinhaler, a number of new devices using powdered medication have been developed. These devices (e.g., Rotohaler, Diskhaler and Nebuhaler) are very popular in Europe and Asia. However, they do not seem to enjoy the same success in the United States. You can expect to see more of them by 1997, when the federal ban on aerosol cans containing CFC propellants goes into effect in the United States. Recent studies with the asthma medication budesonide found that this type of device (Turbuhaler) is much more effective than the MDI and can be used without problems or coordination difficulties.

Young children, elderly patients, or any patient with poor coordination might want to try a nebulizer. This is a device that dissolves a liquid into a fine spray. Two drawbacks: doses delivered are much higher, and the device’s cost is higher.

Training Is Vital

Your physician or nursing staff should teach you how to properly use your inhaler. Have your technique reevaluated at each office visit. It is easy to become complacent and allow bad habits to inhibit the effectiveness of your inhaler. Ask your physician to check your skills with a peak flow meter as well. Accurate peak flow measurements are necessary for the best asthma control.

Nine Steps for Optimal MDI Use

  • Shake the inhaler to thoroughly mix the drug and propellant.
  • Remove the cap.
  • With your mouth open, hold the device upright and inverted about 3 to 4 cm (1 to 1 ½ inches) from your mouth. This increases the distance from the inhaler to the back of your mouth, thus minimizing the amount of drug deposited in your mouth and throat.
  • Tilt your head slightly back to further reduce drug deposit in your mouth.
  • At the start of a slow, deep inhalation, activate the inhaler and breathe in a full breath.
  • Hold the breath deep in your lungs for 10 seconds to allow all the drug particles to settle in your airways.
  • Exhale slowly.
  • After the last puff, gargle or rinse your mouth with water and a pinch of baking soda.
  • Repeat, if needed or prescribed, after 1 to 3 minutes.

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