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Principles of Nebulizers

Nebulizers convert liquefied drugs into aerosols used most commonly to increase air flow to the lungs. Only particles small enough for lower respiratory absorption exit the nebulizer. The rest remain in the nebulizer reservoir for later use. Nebulizers are affordable and thus have changed little since their inception. Patient preference usually determines the type of nebulizer, including specialized, breath-enhanced and breath-actuated.

  1. Types of Nebulizers

    • Breath-enhanced nebulizers use a vented design to deposit greater amounts of liquefied medicine into a patient's lungs. Breath-actuated nebulizers either manually or electronically reduce aerosol waste caused by exhaling. When aerosols are inappropriate, small nebulizers are used. Ultrasonic nebulizers convert medicine to aerosol using ultrasonic waves. Using a T-piece, accessories are connected to nebulizers to increase performance. Infusion pumps cause continuous nebulization, which can more effectively treat asthma. Reservoir bags collect aerosol for reuse.

    Gas Stream

    • When a patient inhales on a nebulizer, compressed gas enters. This creates negative pressure. Relative humidity and other characteristics of this gas can be affected by the environment. The liquefied medicine mixes with this gas, forming droplets further refined following passage through a baffle. This mixture occurs either before or after it enters the nebulizer nozzle, indicating either an internal or external nebulizer. Both are equally effective, though patients usually have a preference.

    Volume

    • The volume of liquefied drug in a nebulizer is split between usable and unsable volume. Dead volume refers to the unusable portion that remains in the nebulizer reservoir. As a nebulizer is used, the water in the liquefied drug evaporates and cools, which increases droplet size. Droplet size ranges from one micrometer to five micrometers. Patients cycle through nebulizers depending on usage, even tapping them to increase output. Eventually, nebulizers sputter when they contain nearly no usable volume.

    Breathable Dose

    • Breathable or respirable dose refers to the mass of breathable-sized droplets produced by a nebulizer. The greater the mass, the greater the effectiveness of the nebulizer. This dosage is measured by the number of droplets produced, as well as the volume of each individual droplet. Two sizes of droplets allow for efficient absorption of the medicine. Airways absorb the larger size, and lungs absorb the smaller size.

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