Table 3.
Main Characteristics of the Soft Mist Inhaler
| Formulation | Aqueous Solution or Suspension |
|---|---|
| Metering system | Reservoirs |
| Propellant | No |
| Dose counter | Yes |
| Priming | Actuate the inhaler toward the ground until an aerosol cloud is visible and then to repeat the process three more times |
| Temperature dependence | No |
| Humidity dependence | No |
| Actuator orifice | – |
| Lung deposition | 39.2%–67% |
| MMDA | ~ 3.7 μm |
| Aerosol exit velocity | 0.72–0.84 m/s |
| Lung distribution | Central and peripheral regions |
| Intrinsic resistance | Low/none |
| Inspiratory flow rate | Independent |
| Advantages | Portable and compact. Multi-dose device. Reusable. Compared with dry powder inhalers, a considerably smaller dose of a combination bronchodilator results in the same level of efficacy and safety |
| Disadvantages | Needs to be primed if not in use for over 21 days |
Abbreviations: SMI, soft mist inhaler; MMAD, mass median aerodynamic diameter; m/s, meter per second; μm, micrometer; L/min, liter per minute.