What is the correct way to use a Metered-Dose Inhaler (MDI) device?

Correct Technique for Using a Metered-Dose Inhaler (MDI)

For patients ≥5 years old using a standard MDI, the optimal technique involves actuating the device during a slow, deep inhalation (30 L/min or 3-5 seconds) followed by a 10-second breath hold, and a spacer or valved holding chamber (VHC) must be used for patients who cannot coordinate actuation with inhalation. 1

Step-by-Step MDI Technique

For Standard MDI (Ages ≥5 years):

1. Shake the inhaler before use - This is one of the most commonly forgotten steps 2

2. Exhale to functional residual capacity (breathe out normally) before actuation - Failure to do this is the most common error, made by up to 56% of patients 3

3. Position the MDI correctly:

   • Insert mouthpiece between lips and teeth (closed-mouth technique) 1
   • The open-mouth technique (holding MDI 2 inches away) enhances lung delivery under laboratory conditions but has not consistently shown clinical benefit 1

4. Coordinate actuation with inhalation:

   • Begin a slow, deep inhalation (30 L/min or 3-5 seconds) 1
   • Actuate the canister at the start of inhalation, not before or after 3
   • This coordination problem is the second most common error, with many patients actuating too early 3

5. Continue inhaling slowly and deeply after actuation - Do not stop inhalation when the device is actuated 1

6. Hold breath for 10 seconds after completing inhalation 1

7. Rinse mouth and spit after using inhaled corticosteroids to reduce systemic absorption and local side effects like thrush 1

When to Use a Spacer or Valved Holding Chamber (VHC)

A spacer or VHC is strongly recommended for:

• All children <4 years old - Most cannot generate sufficient inspiratory flow or coordinate actuation 1
• Patients who cannot coordinate actuation with inhalation - This affects 77-89% of patients 3
• Elderly patients with weak fingers, poor coordination, or cognitive impairment 1, 4
• All patients using inhaled corticosteroids - Reduces oropharyngeal deposition and systemic side effects 1

Spacer/VHC Technique (Ages ≥4 years):

1. Shake the MDI 2
2. Actuate only once into the spacer/VHC per inhalation 1
3. Begin slow, deep inhalation (30 L/min or 3-5 seconds) immediately after actuation 1
4. Hold breath for 10 seconds 1

Face Mask Technique (Children <4 years):

1. Ensure tight fit of face mask 1
2. Allow 3-5 inhalations per actuation 1
3. Actuate only once into spacer/VHC 1
4. Note: Face mask reduces lung delivery by 50% compared to mouthpiece 1

Spacer/VHC Maintenance

Rinse plastic VHCs once monthly with low-concentration liquid household dishwashing detergent (1:5000 or drops per cup of water) and let drip dry - This reduces static charge and enhances drug delivery 1

Common Pitfalls to Avoid

• Failing to breathe out before actuation - Most common error 3
• Poor coordination of actuation timing - Second most common error, with most patients actuating too early 3
• Stopping inhalation at actuation - Patients often incorrectly stop breathing in when they press the canister 1
• Forgetting to shake the inhaler - Particularly common with spacer use 2
• Inhaling too rapidly - Should be slow (30 L/min), not fast 1
• Not holding breath after inhalation - 10-second breath hold is essential 1

Clinical Implications

Incorrect MDI technique directly correlates with poor asthma control - Patients unable to use pMDIs correctly have significantly worse asthma control and require more systemic steroid bursts 5. Since 77-89% of patients make at least one error with MDI technique 3, routine assessment of inhaler technique should be standard practice at every visit 3.

For patients who cannot master standard MDI technique despite instruction, consider breath-actuated MDIs or dry powder inhalers as alternatives 1, 4.