Aerosol delivery devices in the treatment of asthma

Nebulizers convert solutions or suspensions into aerosols with a particle size that can be inhaled into the lower respiratory tract. There are pneumatic jet nebulizers, ultrasonic nebulizers, and mesh nebulizers. Newer nebulizer designs are breath-enhanced, breath-actuated, or have aerosol-storage bags to minimize aerosol loss during exhalation. Nebulizers can be used with helium-oxygen mixture and can be used for continuous aerosol delivery. Increased attention has recently been paid to issues related to the use of a facemask with a nebulizer. The pressurized metered-dose inhaler (pMDI) is a very commonly used device for aerosol delivery. There are press-and-breathe and breath-actuated pMDI designs. Issues related to pMDIs that have received increasing attention are the conversion to hydrofluoroalkane propellant and the use of dose counters. Many patients have poor pMDI technique. Valved holding chambers and spacers are used to improve pMDI technique and to decrease aerosol deposition in the upper airway. In recent years increasing attention has been paid to the issues of electrostatic charge and facemasks related to valved holding chambers. Many newer formulations for inhalation have been released in dry-powder inhalers, which are either unit-dose or multi-dose inhalers. Systematic reviews and meta-analyses have suggested that each of these aerosol delivery devices can work equally well in patients who can use them correctly. However, many patients use these devices incorrectly, so proper patient education in their use is critical.