Aerosol therapy is the delivery of medication during the inhalation phase of respiration. Medications such as bronchodilators, corticosteroids, mucolytic agents and antibiotics are commonly administered in this manner to treat asthma, cystic fibrosis, chronic obstructive pulmonary disease (COPD), emphysema and various other pulmonary conditions. Drugs are administered using aerosol therapy for the following reasons:
Patients may use aerosol therapy for a few days or a lifetime, depending on their illness or disease state. A patient with an acute respiratory illness may use a single drug with a single device for a short period of time, whereas a patient with chronic respiratory illness such as asthma may use multiple drugs and multiple devices over an extended period of time.
This article will provide a greater understanding of the options available to patients and clinicians to optimize the use of aerosol therapy in the home setting. Types of delivery devices, factors that increase drug delivery and patient education will be reviewed.
- The ability to use a smaller amount of drug in a greater concentration.
- The ability to deliver a drug to a specific site.
- The ability to reduce the potential for systemic side effects.
There are several factors that influence the delivery and effective deposition of aerosol medications.
The first factor to consider is the relationship between particle size and delivery. In order for an aerosol particle to be considered within respirable range - that amount of aerosolized medication that may actually reach the lungs and airways - the particle must be between one-half and five microns. Particle sizes outside that range are not considered to be effective in facilitating treatment. Drug particles less than one-half micron will be too "light" and will be expired prior to reaching the back of the throat. A drug particle larger than five microns will be too "heavy" to make the "turn" into the airways once it reaches the back of the throat. In addition, particles greater than five microns increase the risk for systemic side effects. The greater percentage of drug that is within the one to five micron range, the greater the potential for effective aerosol therapy.
A second factor influencing drug delivery is the design of the delivery device. Device design considerations include the material used to construct the device, the number of parts, the durability of the device, and cleaning requirements. Device design also influences particle size. The speed and flow rate of the delivery gas, and the ability to interchange spacers with metered dose inhalers also contributes to drug deposition.
Additionally, the patient's ability, both physically and mentally, to use and understand the various delivery devices is an important factor in drug deposition. It is critical for clinicians to ensure that patient assessments occur in the environment in which the aerosol therapy will be administered, and that patients receive quality education with ongoing monitoring.
The three most common types of delivery devices available for aerosol drug therapy include dry powder inhaler (DPI), Metered dose inhaler (MDI) and the small volume nebulizer (SVN).
Dry Powder Inhaler
Drugs administered as dry powder use a Dry Powder Inhaler (DPI). While this type of device is portable and free of chlorofluorocarbons (CFCs), and the treatment time is minimal, there are disadvantages to this method. Some DPI devices require high inspiratory flow rates for adequate delivery of the drug to the lungs. The required high inspiratory effort may prevent certain segments of the patient population from using this device (e.g., pediatric and geriatric patients).
Metered Dose Inhaler (MDI)
MDIs are hand held devices activated by the patient. The ability to apply pressure to the base of the canister while at the same time taking a deep inhalation is key to the effectiveness of this treatment.
Most patients requiring aerosol therapy use an MDI. While this device is portable, fast and easy to use, many patients have difficulty using an MDI properly. Incorrect use of this device can lead to overuse and create systemic side effects, as a majority of the medications may deposit in the mouth and stomach. Patients experiencing difficulty tend to use their device on a constant basis and often wonder why they feel anxious, shaky and experience unsatisfactory results.
Proper use of the device to achieve maximum drug delivery depends on the patient's ability to coordinate hand movement and inspiratory effort. If, due to arthritis or other upper extremity compromise, they cannot apply pressure to the base of the MDI, or if they are unable to take a slow deep breath, it is wise to consider other devices for aerosol therapy administration.
Inhalation Accessory Devices
Inhalation accessory devices (IADs) are used in conjunction with MDIs. IADs are often referred to as spacers and holding chambers and promote increased drug deposition when used with a MDI. When the speed of drug delivery from an MDI is greater than the patient's ability to inhale, the IAD increases the distance the drug travels before reaching the patient, thus slowing the speed and allowing for greater drug deposition in the lungs. Patients using MDIs should also use an IAD as part of each treatment. A prescription is required to obtain an IAD. While reimbursement is often available for the MDI, it is not always available for IADs. Using the MDI without a spacer may compromise the ultimate drug deposition. There are multiple IADs on the market, both with and without masks in sizes to fit all age groups.
Small Volume Nebulizer
The small volume nebulizer delivers drug via a fine spray or mist. The process requires high velocity airflow to break the liquid into small particles so that respirable particles are produced. The initiation of this process does not depend on the quality of the patient's inhalation efforts or manual dexterity. The process requires compressed gas - either a compressor nebulizer or an oxygen cylinder.
Multiple factors influence the nebulization rate and particle size distribution. These include nebulizer design; solution volume and viscosity; and flow rate of the delivery gas. Cleaning and changing the unit is also important. If protocols for the care of the nebulizer are not followed, particle size may become larger with each treatment. Drug delivery in the respirable particle range may be compromised, and even though the nebulizer appears to be operating well, effective treatment is not achieved.
Often nebulizers are viewed as generic devices; however, this is a misconception. There are many models of small volume nebulizers commercially available, each with different specifications. It is imperative that the nebulizer unit is appropriate for the application. Questions for clinicians to consider with regard to nebulizer specifications include:
Responses to these questions will promote maximum effectiveness and successful treatment outcomes for the patient and clinician.
- Is the nebulizer disposable or non-disposable?
- How much volume does the nebulizer hold?
- Can more than one medication be delivered at the same time?
- Can viscous medications, be delivered through the nebulizer?
- What percentage of medication is delivered in the respirable particle range size of 1 - 5 microns?
- What are the nebulizers cleaning instructions?
- What is the anticipated time for each treatment?
- Does the patient need a mask or mouthpiece?
- Is the patient able to appropriately manipulate the nebulizer?
- Does the nebulizer have to be upright, for patients who receive treatments while in bed?
- Is the compressed gas source suitable for the selected small volume nebulizer?
Patients in the home or other ambulatory settings will most likely use a compressor, versus an oxygen cylinder, as a power source for the nebulizer. Various models of compressors are available. The basic model is a stationary, plug in type that uses a standard AC outlet. Other types have an attachment that connects to a car cigarette lighter, while others can be carried and deliver treatments from a rechargeable battery.
In conclusion, quality patient education is the key to effective aerosol therapy. Patient education not only facilitates correct drug administration, but contributes to patient compliance. Aerosol therapy is a method of drug deposition. While aerosol therapy appears extremely easy to administer, there are significant issues that can compromise effective results.
For further information or assistance please contact Air Systems Medical Supplies.