What is the correct technique for using a metered‑dose inhaler (MDI) with a spacer or a dry‑powder inhaler (DPI) for maintenance and rescue therapy?

Proper Inhaler Technique for MDI and DPI

Metered-Dose Inhaler (MDI) with Spacer Technique

For optimal drug delivery, patients using an MDI should actuate the device during a slow, deep inhalation (30 L/min or 3-5 seconds), hold their breath for 10 seconds after inhalation, and always use a spacer or valved holding chamber (VHC) for children under 4 years and patients who cannot coordinate actuation with inhalation. 1

Step-by-Step MDI Technique

• Preparation: Shake the inhaler before each use to ensure proper medication mixing, and prime the inhaler if it's new or hasn't been used recently per manufacturer instructions 1

• Positioning: Place the mouthpiece between the lips and teeth (closed-mouth technique), ensuring a tight seal 1

• Actuation and Inhalation: Begin a slow, deep inhalation (30 L/min or 3-5 seconds) and actuate the canister at the start of inhalation—not before or after 1

• Critical technique point: Continue inhaling slowly and deeply after actuation; do not stop inhaling at the moment of actuation 1

• Breath hold: Hold breath for 10 seconds after completing inhalation to allow medication deposition in the airways 1

• Multiple puffs: Wait 10-15 seconds between puffs if multiple puffs are prescribed 1

• Post-inhalation care: Rinse mouth and spit after using inhaled corticosteroids to reduce systemic absorption and prevent oral thrush 1

Spacer/VHC Technique

A spacer or VHC is mandatory for all children under 4 years old and strongly recommended for elderly patients with poor coordination, patients using inhaled corticosteroids, and anyone who cannot coordinate actuation with inhalation. 1

• Single actuation rule: Actuate only once into the spacer/VHC per inhalation 1

• Immediate inhalation: Begin slow, deep inhalation (30 L/min or 3-5 seconds) immediately after actuation—do not delay 1

• Breath hold: Hold breath for 10 seconds after completing inhalation 1

• Face mask for young children: Use a tight-fitting face mask over nose and mouth for children who cannot use a mouthpiece 1

• Spacer 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 to reduce static charge and enhance drug delivery 1

Dry Powder Inhaler (DPI) Technique

DPIs require a different technique than MDIs: patients must exhale to residual volume before placing the device in their mouth, then inhale forcefully and deeply to generate sufficient inspiratory flow for drug dispersion. 2, 3

Key DPI Technique Points

• Exhale first: Exhale to residual volume away from the device before inhalation—this is the most commonly missed step (51.9% of patients fail this) 3

• Forceful inhalation: Unlike MDIs, DPIs require a rapid, forceful inhalation to disperse the powder 2

• Breath hold: Hold breath for 10 seconds after inhalation 1

• No spacer compatibility: DPIs cannot be used with spacers, which may be a disadvantage for patients requiring high-dose inhaled corticosteroids 2

• Flow-dependent delivery: The majority of patients with severe acute asthma can achieve sufficient peak inspiratory flow to use a DPI effectively, but this should be verified 2

Common Errors and How to Avoid Them

MDI Errors

• Most common error: Not continuing to inhale slowly after activation of the canister (69.6% of patients make this mistake) 4

• Second most common: Failing to exhale before inhalation (65.8% of patients) 4

• Inhaling too rapidly: Patients should maintain a slow inhalation rate of 30 L/min, not a rapid breath 1

DPI Errors

• Most common error: Failing to exhale to residual volume before inhalation (51.9% of patients) 3

• Technique deterioration: Patients using DPIs have significantly more difficulty with correct technique than MDI users (only 34.6% of DPI users vs. 68.1% of MDI users demonstrate correct technique) 3

Training and Verification

Physicians must observe and regularly review patients' inhaler technique because 88.9% of patients make at least one mistake in inhalation technique. 4

• Repetitive training is essential: Patients trained 3 times have significantly higher rates of correct use compared to those trained fewer times 3

• First treatment under supervision: All patients should have their first treatment under supervision before domiciliary use 5

• Regular reassessment: Inhaler technique should be verified at every visit, as technique often deteriorates over time 1, 4

Device Selection Algorithm

For patients who cannot master standard MDI technique despite proper instruction, consider the following alternatives in order: 1

1. MDI with spacer and tight-fitting face mask (first choice for young children and those with coordination difficulties) 1
2. Breath-activated MDI (eliminates coordination requirement) 1
3. Dry powder inhaler (easier for some patients but requires adequate inspiratory flow) 1
4. Nebulizer as last resort (for patients unable to use any handheld device) 1

Special Populations

Children Under 4 Years

• Mandatory spacer use: All children under 4 years must use a spacer or VHC with face mask, as they cannot generate sufficient inspiratory flow or coordinate actuation 1

Elderly Patients

• Higher error rates: Older patients have more difficulty with correct inhaler technique than younger patients 4

• Spacer recommended: Use spacer/VHC for elderly patients with weak fingers, poor coordination, or cognitive impairment 1

Acute Exacerbations

For acute severe asthma, MDI with spacer is as effective and cheaper than nebulization and should be the preferred delivery method. 5

• Dosing for acute asthma: Salbutamol 100 mcg, one actuation then inhale, repeat up to 20 times via MDI with spacer 5

• Nebulizer indications: Reserve nebulizers for patients too breathless to use MDI with spacer, those requiring continuous bronchodilator therapy, or very young infants who cannot tolerate a face mask with spacer 5