March 2000 – Spacer Devices

March 2000

Spacer Devices

A guide to selecting the best spacer for use with metered dose inhalers

BY CATHY ALLISON, B.Sc.(Pharm)

Metered dose inhalers (MDIs) are a convenient and popular way to administer medication to patients with asthma andchronic obstructive pulmon-ary disease. However, up to 89 per cent of adults are unable to correctly use an MDI;¹ the most common problems are lack of “hand-lung” coordination, and involuntary cessation of inhalation once cold aerosol particles reach the throat (often referred to as the “cold freon” effect). Spacer devices facilitate MDI use, and at least 10 different spacer devices are currently available in Canada. Given the complexity of features that affect aerosol drug delivery, and the large array of spacer devices available, how can pharmacists decide which one to recommend to patients? This article provides the information needed to choose the most appropriate spacer to meet individual patient needs.

WHY USE A SPACER?

The use of a spacer device with an MDI provides several benefits. A spacer reduces the need to coordinate MDI actuation and inhalation (“hand-lung” coordination), allowing MDIs to be used in neonates, infants, children, adults, the elderly and in handicapped patients. A spacer improves drug delivery to the lower airways by decreasing the velocity of aerosol particles, and by facilitating the evaporation of propellant, producing “respirable” particles in the 1-5 micron range. The use of a spacer decreases local side effects such as medication taste, coughand the “cold freon” effect. Spacer use also reduces the risk of oral thrush and dysphonia caused by inhaled corticosteroids.² Systemic drug side effects are minimized by reducing oropharynx deposition of drug which is then swallowed; this is of particular significance with high doses of inhaled corticosteroids.³ The use of a spacer has also been shown to provide equal, if not superior, benefits to nebulized therapy at a greatly reduced cost.^3,4

DOES THE CHOICE
OF SPACER MATTER?

Despite a lack of clinical data, it is commonly assumed that most spacers can be used “generically” with MDIs that deliver any kind of medication.⁵ Several studies have determined that drug delivery of a beta-agonist (usually salbutamol) from an MDI with a spacer device is virtually the same as, if not better than, the MDI used alone.^5-7 However, more recent studies have shown a considerable variation in MDI corticosteroid delivery, ranging from a 29-67 per cent reduction,^5,8 to a 10-49 per cent increase⁹ with certain spacer devices. A dose reduction may occur with drugs that are formulated in solution, as opposed to suspension. This is of particular significance since some of the commercial products which are currently being reformulated to replace chlorofluorocarbon (CFC)-containing MDIs will be provided as solutions. There is a scarcity of basic research on how spacer devices influence the pulmonary deposition and efficacy of different types of existing MDI formulations. In addition, interaction of newly formulated MDIs with new and existing holding chambers may be problematic and must be studied.⁵ In addition to MDI formulation, other factors influence the performance of spacer devices, including valve resistance, electrostatic charge, chamber volume, the patient’s breathing pattern and “dead space.”

THE IDEAL SPACER DEVICE

In order for pharmacists to select the most appropriate spacer, it is necessary to define the elements of an ideal device.

Appropriate chamber volume: The chamber must allow production of sufficient aerosolized drug in the respirable range to reach the lower airways. Large, 750 mL cone-shaped chambers are more effective for older children¹⁰ and adults¹¹ than an MDI used alone, while small volume spacers (~ 145 mL) appear to be as effective as an optimally used MDI.¹² Small-volume spacers are more suitable for infants and small children, who have smaller tidal volumes and lower inspiratory flow rates.^3,13 The portability and convenience of small-volume devices also encourages compliance.

Low resistance inhalation and exhalation valves: A one-way inspiratory valve prevents the patient from exhaling into the device. This valve must operate at even very low inspiratory flow rates. An exhalation valve allows the patient to exhale comfortably without the need to remove the device from the face, and prevents re-breathing of exhaled air. Exhalation ports should be guarded by a valve or flap to prevent outside air from being drawn into the chamber during inhalation, which may decrease the delivered dose.¹⁴ Valves should be visible to the caregiver to confirm that they open and close during therapy, and they should be installed securely behind a tamper-resistant guard that prevents accidental choking or removal.

Appropriate, well-fitting mask: A snug fit is very important when using a spacer device with mask for infants, children or adults. Ideally, the mask should be transparent, have a comfortable soft cushion, conform to fit various facial shapes, and be available in several sizes. Another important feature is a valved exhalation port in the mask to allow humid air to exit without interfering with the next inspired breath. Some spacer devices allow different sizes of masks to be purchased separately, enabling removal of the mask once the patient is able to use the mouthpiece alone.

Minimal dead space: Dead space, often found in device masks, refers to the volume between both the inspiratory and expiratory valves and the patient’s face. As the dead space rises, higher inspiratory volumes must be generated to draw the aerosol out of the chamber, resulting in decreased drug delivery.¹³ Dead space also increases the re-breathing of exhaled gases. Unfortunately, healthcare providers will not find dead space volumes stated in product inserts. To assess dead space, the device should be physically examined while the mask is placed over the patient’s face; there should be minimal space between the patient’s face (which will partially fill the mask) and the exhalation valve.

Compatible with all MDIs: The spacer must have a flexible, universal inlet suitable for connection to all MDIs. The spacer device should not require removal of the MDI canister from the manufacturer’s plastic case (which serves as the actuator) for placement in a “generic” actuator. Although the plastic case appears to be just packaging, it is a crucial element in the delivery of the fine particle dose that will reach the patient’s lower respiratory tract.⁵ Furthermore, removal of the canister separates the pharmacy prescription label from the product and removes the colour-coding element which helps patients to differentiate bronchodilators from anti-inflammatory agents.

Durability: The spacer should be made from durable material that won’t crack when dropped, or deteriorate quickly with use. Devices should be inspected periodically, paying particular attention to the integrity of the inhalation valve. Some spacers have inhalation valves that may be replaced; otherwise the entire device must be replaced. With proper use and regular cleaning, a spacer device should last for one to two years. Some manufacturers offer a limited warranty, ranging from six months to one year.

Easily cleaned, able to withstand repeated washing: Spacer devices should be washed prior to first use to remove the static charge acquired during the manu-facturing process. Regular, proper cleaning is important for optimal performance and longevity of the spacer device, and reduces the risk of infection. While each manufacturer specifies guidelines for proper cleaning, it is most often recommended to wash the device in warm water containing a mild liquid dish soap, followed by air-drying without rinsing.¹⁵ A thin film of detergent may help to counteract static charge build-up that reduces the respirable dose by attracting aerosolized drug particles to the walls of the plastic chamber.^16,17 Note that while beta-agonists are water-soluble, corticosteroids are not and therefore a mild detergent and warm water are required to properly clean spacers used to administer cortico-steroids.¹⁸ Drying with paper towels or a cloth may cause a build-up of static inside the spacer device, so air-drying is recommended. Some spacer devices are dishwasher-safe, making cleaning more convenient.

Inexpensive: The ideal spacer device is one that the patient can afford. Some insurance companies and provincial formularies do not reimburse for spacer devices. This is unfortunate since certain patients must use a spacer device in order to benefit from MDI use. While home-made devices from toilet paper rolls or Styrofoam cups¹⁹ have been used, a long-term cost-benefit analysis may show that costs are actually higher due to excessive drug loss or treatment failure. If a spacer device is required, pharmacists should strongly encourage their patients to purchase a commercial device that will facilitate drug delivery in a consistent and reliable manner. Alternative sources of reimbursement for spacer devices may be available at the municipal level of social services. Regional offices of the Canadian Lung Association may sell spacer devices to the public at cost.

Safe, simple, foolproof operation: The spacer device should not require complicated assembly for use or disassembly for cleaning. It should not be constructed of small parts that may break free and become choking hazards.

Built-in flow rate monitor: The ideal spacer should have a whistle device to give immediate feedback if breathing is too fast. Most whistles are calibrated to sound at an inspiratory flow rate of 30 L/min. The whistle should not be heard during correct use.

SPACER DEVICES
AVAILABLE IN CANADA

The salient features of spacer devices currently available in Canada are summarized in Table 1. The advantages and disadvantages of each spacer are outlined in Table 2, based on the characteristics of the ideal spacer discussed above.

From this tabulation, pharmacists will realize that all MDI spacer devices are not the same, and the “ideal” device has yet to be developed and marketed. A hybrid design that combines the advantageous characteristics of several devices would be a welcome product.

It has been proposed that holding chambers and spacers should be marketed for use only with the specific drug(s)/MDIs with which they have been tested, and that this information be clearly indicated in the package inserts.⁵ To achieve this goal, more stringent regulations governing the licensing and marketing of spacer devices in Canada would be required.

THE PHARMACIST’S ROLE

Pharmacists should physically examine new and existing spacer devices, to verify that design features meet basic criteria for safety and good performance. Device manufacturers should be asked to provide clinical data which compares drug delivery using the MDI with spacer device to the MDI alone, for each inhaled drug in patients of all age groups. Only then can the best spacer device be selected to meet the specific needs of individual patients.

It has been consistently documented that medical personnel do not know how to appropriately use MDIs and spacer devices.^20-23 Never assume that someone else has adequately informed your patient about the proper use of an MDI with spacer device, including care and cleaning. These are complex devices that require repeated, ongoing education to reinforce good technique. The accepted method for using an MDI with a spacer device is reviewed in Table 3.

Pharmacists have a clear role in the initial selection of an appropriate spacer device, and an equally important role in the ongoing monitoring of device function and integrity. A note on the patient profile can serve as a reminder to ask patients to bring their devices in to be checked every six months, when MDIs are refilled. A brief inspection of the device, combined with a review of proper technique, is tangible pharmaceutical care.

CONCLUSION

Current Canadian regulations do not require manufacturers of spacer devices to provide evidence of efficacy or compatibility with specific MDI formulations. As a result, pharmacists must be aware of basic spacer design features to facilitate and optimize drug delivery to patients of various ages. The spacer selected must be easy to use, durable and affordable.

Cathy Allison, B.Sc.(Pharm), is a phar-macist in the pharmacy department at the Children’s Hospital of Eastern Ontario in Ottawa, ON.

REFERENCES

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2. Toogood JH, Jennings B, Greenway RW, et al. Candidiasis and dysphonia complicating beclomethasone treatments of asthma. J Allergy Clin Immunol 1980;65:145-53.

3. Newhouse MT. Pulmonary drug targeting with aerosols: principles and clinical applications in adults and children. Am J Asth Allergy Pediatr 1993;7:23-35.

4. Newman SP, Newhouse MT. Effect of add-on devices for aerosol drug delivery: deposition studies and clinical aspects. J Aerosol Med 1996;9:55-69.

5. Ahrens R, Lux C, Bahl T, et al. Choosing the metered-dose inhaler spacer or holding chamber that matches the patient’s need: evidence that the specific drug being delivered is an important consideration. J Allergy Clin Immunol 1995;96:288-94.

6. Dolovich M, Ruffin RE, Roberts R, et al. Optimal delivery of aerosols from metered dose inhalers. Chest 1983;84:36-41.

7. Fairshter RD. Evaluation of a metered-dose aerosol delivery system using partial flow volume curves. Am Rev Respir Dis 1987;135:741-3.

8. Barry PW, O’Callaghan C. Inhalational drug delivery from seven different spacer devices. Thorax 1996;51:835-40.

9. Finlay WH, Zuberbuhler P, Mandl M. Particle size measurements for the Space-chamber metered dose inhaler holding chamber compared with Aerochamber and metered dose inhaler alone. J Aerosol Med 1997;10:213-9.

10. Levison H, Reilly PA, Warsley GH. Spacing devices and metered dose inhalers in childhood asthma. J Pediatr 1985;107:662-8.

11. Cushley MJ, Lewis RA, Tattersfield AE. Comparison of three techniques of inhalation on the airway response to terbutaline. Thorax 1983;38:908-13.

12. Dolovich M, Duffin R, Carr D, et al. Clinical evaluation of a simple demand inhalation MDI aerosol delivery device. Chest 1983;84:36-40.

13. Everard ML, Clark AR, Milner AD. Drug delivery from holding chambers with attached facemask. Arch Dis Child 1992;67:580-5.

14. Bisgaard H. Demands on spacer devices for young children. Pediatr Pulmonol 1997;16(Suppl):188-9.

15. Boulet LP, Becker A, Berube D, et al. Canadian asthma consensus report 1999. Can Med Assoc J 1999;161(11 Suppl):S1-S62.

16. O’Callaghan CO, Lynch J, Cant M, et al. Improvement in sodium cromoglycate delivery from a spacer device by use of an anti-static lining, immediate inhalation and avoiding multiple actuations of drug. Thorax 1993;48:603-6.

17. Wildhaber JH, Devadason SG, Eber E, et al. Effect of electrostatic charge, flow, delay and multiple actuations on the in vitro delivery of salbutamol from different small volume spacers for infants. Thorax 1996;51:985-8.

18. Rau JL, Zhu Y. Reservoir design and dose availability with long-term metered dose inhaler cortico-steroid use. J Aerosol Med 1998;11:15-26.

19. Zar HJ, Liebenberg M, Weinberg EG, et al. The efficacy of alternative spacer devices for delivery of aerosol therapy to children with asthma. Ann Trop Paediatr 1998;18:75-9.

20. Hanania NA, Wittman R, Kesten S, et al. Medical personnel’s knowledge of and ability to use inhaling devices; metered-dose inhalers, spacing chambers and breath-actuated dry powder inhalers. Chest 1994;105:111-6.

21. Mas JC, Resnick DJ, Firschein DE, et al. Misuse of metered dose inhalers by house staff members (letter). Am J Dis Child 1992:146:783-5.

22. Amirav I, Goren A, Pawlowski NA. What do pediatricians in training know about the correct use of inhalers and spacer devices? J Allergy Clin Immunol 1994;94:669-75.

23. Self TH, Kelso TM, Arheart KL, et al. Nurses’ performance of inhalation technique with metered-dose inhaler plus spacer device. Ann Pharmacother 1993;27:185-7.