Table 1.

Comparison of different types of devices that deliver drugs to the lungs

	Advantages	Limitations	Characteristic	Examples	References
Pressurized metered dose inhaler (pMDI)	Portable Small Cost-effective Rapid administration times Sterility and prevention of backflow Protection of the drug from light, oxygen and water Patient familiarity	Requiring coordination between actuation of the device and inhalation of the dose by the patient	Drug suspended or dissolved in propellant (with surfactant and cosolvent)	Easibreathe® (beclomethasone dipropionate, salbutamol)	[20–22]
Dry powder inhaler (DPI)	Small Portable Not require coordination of inhaler actuation with inhalation Deliver a relatively high dose	Sufficient inspiratory flow needed Require a pre-inhalation dose-loading step	Drug blend in lactose, drug alone, drug/excipient particles	Tobi® Podhaler (tobramycin) Colobreathe® (colistin)	[10, 20, 23]
Soft Mist Inhaler (SMI)	Portable Compact Multidose The relatively long generation time of the aerosol cloud facilitates coordination of inhalation and actuation. No propellants	The metered volume of 15 μl limits the dose-delivery capacity of the marketed design to drugs with the adequate solubility with respect to the required dose. The administration of tiotropium via Respimat® may not be used in patients with pre-existing cardiovascular comorbidities	Aqueous solution or suspension	Respimat® (ipratropium bromide, olodaterol, salbutamol, tiotropium bromide)	[20]
Air jet nebulizer		High amount of drug wastage Not all drug formulations may be appropriate	Generate aerosols from the liquid medicament using a source of compressed gas	Medix® Pari LC Plus®	[22, 24, 25]
Ultrasonic nebulizer	Large volume of solution can be aerosolized in a relatively short period of time	Oscillation of the piezoelectric crystal results in the production of heat	Aerosol creation is based on the vibrations of a piezoelectric crystal that generate high frequency sound waves	Aerosonic® Sonix 2000 systems®	[22, 25, 26]
Vibrating mesh nebulizer	Quiet Portable Easy to use Self-contained power source Particle size optimized for specific medications More efficient when compared to other nebulizers	Expensive Hard to clean Medication dosage requires adjustment Incompatible with viscous liquids or liquids that crystallize on drying	Use oscillation and a mesh membrane to induce droplet production through cavitation and wave formation in the liquid below the mesh	Pari eFlow®	[22, 27–29]