Asthma Devices

Advantages and Disadvantages of Clinically AvailableInhalers Used in Asthma and Other Pulmonary

DiseasesAuthors: Anita SM, JA MalikThe use of inhaled aerosol medications for the treatment of pulmonary diseases, which became well-established in the last half of the 20th century, has advantages over oral and parenteral routes of delivery. The use of inhaled aerosols allows selective treatment of the lungs directly by achieving high drug concentrations in the airway while reducing systemic adverse effects by minimizing systemic drug levels.1 Inhaled beta 2 -agonist bronchodilators produce a more rapid onset of action than oral delivery. Some drugs are only active with aerosol delivery (eg, for asthma patients, cromolyn and ciclesonide; for cystic fibrosis patients). Aerosol drug delivery is painless and often convenient. For these reasons, the National Asthma Education and Prevention Pro- gram guidelines2 favor aerosol inhalation over theOral route or parenteral (ie, subcutaneous, IM, or IV) route. Similarly, the National Heart, Lung, and Blood Institute/World Health Organization Global Initiative for Chronic Obstructive Lung Disease recommended that bronchodilator medications are central to symptom management in COPD patients and that inhaled therapy is preferred.3There are also disadvantages to aerosol drug therapy. One of the most important disadvantages is that specific inhalation techniques are necessary for the proper use of each of the available types of inhaler device. A less than optimal technique can result in decreased drug delivery and potentially reduced efficacy.4,5 Improper inhaler technique is common among patients.6–8 The proliferation of inhalation devices that are available for patients has resulted in a confusing number of choices for the health-care provider and in confusion for both clinicians and patients trying to use these devices correctly. Several studies have demonstrated lack of physician, nurse, and respiratory therapist knowledge of device use.9–13 Inhaler devices are less convenient than oral drug administration insofar as the time required for drug administration may be longer and some patients may find the device less portable. This is particularly true for conventional compressed-air nebuliser, the oldest of the currently used types of aerosol delivery devices.Device manufacturers have long been aware of the importance of portability and ease of use with aerosol delivery devices. As a result, these devices have evolved over time. From the 19th century until 1956, compressed-air nebuliser (also called jet nebuliser) were the only devices that were in common clinical use for the administration of inhaled aerosol drugs. In 1955, the pressurized metered-dose inhaler (MDI) was developed.14 Ultrasonic nebuliser, which utilize high-frequency acoustical energy for the aerosolization of a liquid, were introduced in the 1960s.15,16 In 1971, Bell and col-leagues 17 introduced the first dry powder inhaler (DPI), known as the Spinhaler, for the inhalation of cromolyn sodium. This and subsequent DPIs have been “breath-actuated,” providing drug only when demanded by patient inhalation, thus avoiding acommon error with MDI use, the improper timing of inhaler actuation. Investigators developed open-tube spacer devices, intended for use with MDIs, in the late 1970s.18–20The addition of a one-way valve (holding chamber)18 or blind reservoir (ie, reverse-flow spacer)21,22 allowed the aerosol delivered by the MDI to be contained in the spacer for a finite period of time, thereby circumventing the need for the coordinated actuation of the MDI with inhalation. Other spacer/holding chamber designs followed, and today there are several devices that vary in design, shape, size, and assembly.The 1987 Montreal protocol mandated the phase out of the use of chlorofluorocarbons (CFCs) as propellants in all MDIs. This resulted in a redesign of MDIs in the 1990s, utilizing hydrofluoroalkane propellants.22Each type of aerosol device has its own advantages and disadvantages. Nebuliser/compressor systems require minimal patient cooperation and coordination, but are cumbersome and time-consuming to use. Matching nebulisers with associated air compressors is necessary to assure optimal efficiency of drug delivery. MDIs are quicker to use and highly portable, but require the most patient training to ensure coordination for proper use. Up to 70% of patients fail to use them properly. The improper timing of MDI actuation with breath initiation is a common problem.7 DPIs are easier to use than MDIs because they are breath-actuated, but require a relatively rapid rate of inhalation in order to provide the energy necessary for drug aerosolization.Advantages and disadvantages of various inhalers are summarized below:23Advantages of Small-volume jet nebuliser Patient coordination not requiredEffective with tidal breathingHigh dose possibleDose modification possibleNo CFC releaseCan be used with supplemental oxygenCan deliver combination therapies if compatibleDisadvantages of Small-volume jet nebuliserLack of portabilityPressurized gas source requiredLengthy treatment timeDevice cleaning requiredContamination possibleNot all medication available in solution formDoes not aerosolize suspensions wellDevice preparation requiredPerformance variabilityExpensive when compressor added inAdvantages of Ultrasonic nebuliserPatient coordination not requiredHigh dose possibleDose modification possibleNo CFC releaseSmall dead volumeQuietNewer designs small and portableFaster delivery than jet nebuliserNo drug loss during exhalation (breath-actuated devices)Disadvantages of Ultrasonic nebuliser ExpensiveNeed for electrical power source (wall outlet or batteries)Contamination possibleNot all medication available in solution formDevice preparation required before treatmentDoes not nebulise suspensions wellPossible drug degradationPotential for airway irritation with some drugsAdvantages of Pressurized MDI Portable and compactTreatment time is shortNo drug preparation requiredNo contamination of contentsDose-dose reproducibility highSome can be used with breath-actuated mouthpieceDisadvantages of Pressurized MDI Coordination of breathing and actuation neededDevice actuation requiredHigh pharyngeal depositionUpper limit to unit dose contentRemaining doses difficult to determinePotential for abuseNot all medications availableMany use CFC propellants Advantages of Holding chamber, reverse-flow spacer, or spacerReduces need for patient coordinationReduces pharyngeal deposition