What are the different types of inhalers and their uses in managing respiratory conditions like asthma and Chronic Obstructive Pulmonary Disease (COPD)?

Types of Respiratory Inhalers and Their Uses

For most patients with asthma and COPD, metered-dose inhalers (MDIs) with spacers should be the first-line choice, as they are equally effective as nebulizers while being more convenient, cost-effective, and efficient. 1, 2

Primary Inhaler Categories

Metered-Dose Inhalers (MDIs)

• Standard press-and-breathe MDIs deliver precise, reproducible doses and can be used in virtually all clinical situations, though they require proper hand-breath coordination 3
• MDIs with spacer devices eliminate coordination problems and are equally effective as nebulizers for bronchodilation in both acute exacerbations and stable disease 1
• Breath-actuated MDIs are available for patients who struggle with coordination between actuation and inhalation 2
• MDIs are small, portable, and the most cost-effective delivery method for most patients 2, 3

Dry Powder Inhalers (DPIs)

• DPIs eliminate the need for hand-breath coordination since they are breath-activated 3, 4
• These devices require adequate inspiratory flow to extract and disaggregate drug particles from lactose carriers 4
• DPIs are environmentally friendly, portable, and self-contained 3
• They may not be suitable for patients with severe airflow obstruction who cannot generate sufficient inspiratory flow 5

Nebulizers

• Nebulizers convert liquid medication into an aerosol mist and require minimal patient cooperation 3
• Primary indications include: patients requiring very high-dose bronchodilators (>1 mg salbutamol or >160 μg ipratropium), those unable to use hand-held devices despite proper instruction, and drugs that cannot be delivered by other means (such as rhDNase or antibiotics) 1, 2
• Nebulizers are particularly useful in acute severe asthma or COPD exacerbations when patients are too breathless to coordinate inhaler technique 1
• They require 5-10 minutes per treatment, need regular maintenance, and are less portable than other devices 1, 4

Soft Mist Inhalers (SMIs)

• SMIs dispense medication dissolved in aqueous solution as a slow aerosol cloud without propellant, using spring energy 4
• The slower aerosol velocity may improve lung deposition compared to traditional MDIs 4

Medication Classes Delivered by Inhalers

Short-Acting Bronchodilators

• β2-agonists: Salbutamol (albuterol) 200-400 μg or terbutaline 500-1000 μg up to four times daily via MDI 2
• Anticholinergics: Ipratropium bromide 40-80 μg up to four times daily via MDI 2
• For acute exacerbations via nebulizer: salbutamol 2.5-5 mg or terbutaline 5-10 mg, with ipratropium 500 μg added for asthma 1

Long-Acting Bronchodilators

• Long-acting β2-agonists (LABAs): Salmeterol 50 μg combined with inhaled corticosteroids for maintenance therapy 6
• LABAs should never be used as monotherapy in asthma due to increased risk of serious asthma-related events 6

Inhaled Corticosteroids

• Fluticasone propionate (100-500 μg) combined with salmeterol for asthma and COPD maintenance 6
• Patients should rinse mouth after use to reduce risk of oral candidiasis 6

Clinical Decision Algorithm for Device Selection

Step 1: Assess Clinical Urgency

• Acute severe exacerbation (cannot complete sentences, respiratory rate >25/min, heart rate >110/min, peak flow <50% best): Use nebulizer or MDI with spacer—both are equally effective 1
• Stable disease: Start with MDI with spacer 2

Step 2: Evaluate Patient Capability

• Good coordination and inspiratory effort: MDI with or without spacer 2
• Poor coordination but adequate inspiratory flow: DPI or breath-actuated MDI 2, 3
• Inadequate inspiratory flow or severe breathlessness: Nebulizer 1, 2
• Children under 4 years or elderly with multiple limitations: Nebulizer or MDI with spacer 1, 5

Step 3: Determine Dose Requirements

• Standard doses (salbutamol ≤1 mg or ipratropium ≤160 μg): MDI with spacer 1
• High doses (salbutamol >1 mg or ipratropium >160-240 μg): Nebulizer is more convenient 1, 2

Step 4: Consider Special Medications

• Drugs only available for nebulization (rhDNase, antibiotics): Nebulizer required 1
• Combination maintenance therapy: Use combination MDI or DPI devices when available 1, 6

Critical Safety Considerations

For COPD Patients

• Always drive nebulizers with air, not oxygen, in patients with CO2 retention to prevent worsening hypercapnia 1, 2, 7
• Provide supplemental oxygen via nasal cannulae at 4 L/min during air-driven nebulization if needed 1, 2
• Use mouthpiece rather than face mask when administering ipratropium to avoid ocular complications and potential glaucoma worsening 1

For Asthma Patients

• In hospital settings, drive nebulizers with oxygen for acutely ill patients or air for stable patients 1
• Add ipratropium 500 μg to β-agonist therapy in acute asthma for additional benefit 1
• Important distinction: Unlike acute asthma, adding anticholinergics to β-agonists provides no additional benefit in acute COPD exacerbations 1

Technique and Maintenance

• Proper inhaler technique must be demonstrated and checked periodically before modifying treatments 2
• Patients should be changed from nebulizers to hand-held inhalers as soon as condition stabilizes to permit earlier hospital discharge 1
• Disposable nebulizer components should be changed every 3-4 months, with annual compressor servicing 1

Common Pitfalls to Avoid

• Never use water for nebulization as it may cause bronchoconstriction 2
• Do not prescribe home nebulizer therapy without formal assessment by a respiratory specialist, including demonstration of at least 15% improvement in peak flow over baseline 1, 2
• Avoid combining LABA-containing inhalers with additional LABA medications due to overdose risk 6
• Do not assume nebulizers are superior to MDIs with spacers—they are equally effective when proper technique is used 1
• Patients requiring β-agonists should have first treatment supervised in elderly patients due to potential angina precipitation 1