Use of Metered Dose Inhalers, Spacers, and Nebulizers


Practice Essentials

Metered dose inhalers (MDIs), dry powder inhalers (DPIs), and nebulizers are modes of aerosol drug delivery that are used to treat respiratory disorders (eg, asthma, obstructive lung disorders, cystic fibrosispulmonary arterial hypertension, infectious pulmonary disease). [1A spacer is an external device that is attached to an MDI to allow for better drug delivery by enhanced actuation and inhalation coordination.

A diagram of an MDI is shown in the image below.

Cross-sectional diagram of metered dose inhaler (MCross-sectional diagram of metered dose inhaler (MDI).

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Metered dose inhalers (MDIs)

An MDI is a handheld aerosol device that uses a propellant to deliver the therapeutic agent.

Advantages of MDIs are as follows:

  • Portability

  • Multidose delivery capability

  • Lower risk of bacterial contamination [2]

Disadvantages of MDIs are as follows:

  • Need for correct actuation and inhalation coordination [34]

  • Oropharyngeal drug deposition [2]

Dry powder inhalers (DPIs)

A DPI is a breath-actuated device that delivers the drug in the form of particles contained in a capsule or blister that is punctured before use.

Advantages of DPIs include the following:

  • Breath-actuated

  • Spacer not necessary

  • No need to hold breath after inhalation

  • Portable

  • No propellant

Disadvantages of DPIs include the following:

  • Adequate inspiratory flow required for medication delivery

  • May result in high pharyngeal deposition

  • Humidity potentially causes powder clumping and reduced dispersal of fine particle mass

Inhalation accessory devices (IADs)

Inhalation accessory devices (IADs) generally fall into 2 categories: spacers and holding chambers. A spacer is an extension add-on device that permits the aerosol plume from the MDI to expand and slow down, turning it into a very fine mist instead of a high-pressure actuation spray. Valved holding chambers allow for a fine cloud of medication to stay in the spacer until the patient breathes it in through a one-way valve, drawing the dose of medication into the lungs.

Advantages of IADs are as follows:

  • Enhanced drug delivery

  • Compensation for poor technique/coordination with MDI

  • Reduced oropharyngeal deposition

Disadvantages of IADs are as follows:

  • Large size and volume of device

  • Bacterial contamination is possible; device needs to be cleaned periodically

  • Electrostatic charges may reduce drug delivery to the lungs

Nebulizers

Nebulizers are devices that transform solutions or suspensions of medications into aerosols that are optimal for deposition in the lower airway.

The following are advantages of nebulizers:

  • Provide therapy for patients who cannot use other inhalation modalities (eg, MDI, DPI)

  • Allow administration of large doses of medicine

  • Patient coordination not required

The following are disadvantages of nebulizers:

  • Decreased portability

  • Longer set-up and administration time

  • Higher cost

  • May need source of compressed air or oxygen (jet nebulizer)