Characteristics of inhaler devices3,7
| Device type | Mechanism of action |
|---|---|
| HFA pMDI | Pressurized suspension of micronized drug particles distributed in propellant; others are ethanolic solutions Precise amount (20–100 μL) dispensed with each press of canister Shaking not required as with CFC pMDIs Pressing canister releases drug |
| Breath-actuated pMDI | Pressurized canister with flow-triggered system driven by a spring Inhalation drives spring to trigger inhalation Requires higher PIF than HFA pMDIs, but lower than DPIs |
| DPI | Dry powder inside capsule (manual loading) or inside device Micronized drug particles (1–5 μm) blended with inactive excipient (40 μm) or used alone Inhalation deaggregates medication particles and disperses them within airways Minimum PIF rate required for deaggregation (varies by DPI device) Passive (breath-actuated) |
| SMI | Propellant-free Drug stored inside cartridge (loaded on first use) Spring releases dose into micropump; dose released when button is pressed "Uniblock" passes dose through minute channels releasing jet streams of drug solution |
| Breath-enhanced jet nebulizer | Air stream moves through jet causing drug solution to be aerosolized; powered by compressor Additional room air taken into nebulizer during inhalation drives aerosolization Nebulizer drug solution cools during nebulization Vents the expired air outside device Tabletop and portable models available |
| Breath-actuated jet nebulizer | Air stream moves through tube causing drug solution to be aerosolized; powered by compressor Patient inhalation drives aerosolization (does not occur unless patient inhales) Tabletop and portable models available |
| Ultrasonic nebulizer | Piezoelectric crystals vibrate causing aerosolization Nebulized drug solution gets heated during nebulization Portable |
| Vibrating mesh nebulizer | Piezoelectric crystals vibrate a mesh plate causing aerosolization Very fine droplets No significant change in temperature of the solution during nebulization Lower residual drug remaining in chamber compared with jet nebulizers Portable |
Abbreviations: CFC, chlorofluorocarbon; DPI, dry powder inhaler; HFA, hydrofluoroalkane; PIF, peak inspiratory flow; pMDI, pressurized metered-dose inhaler; SMI, soft mist inhaler.