21 May 2003
SPACER DEVICES
(Prepared by Soren Pedersen for the GINA Science Committee)
The three main advantages of spacer devices with a valve system are:
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They are easy to use. A spacer reduces the need for patients to coordinate inhalation
with actuation of the metered dose inhaler and hence reduces the problems of poor
inhaler technique seen in many patients using a metered dose inhaler. The aerosol
cloud is available for inhalation for a prolonged period of time. This is particularly
important in young children with shallow, irregular breathing patterns.
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They improve drug targeting by retaining the large particles that would normally be
deposited in the oropharynx. As a result a larger proportion of the drug that reaches
the patient is deposited in the intra-pulmonary airways and less in the oropharynx.
Therefore, spacers reduce oral and gastrointestinal absorption of the inhaled drug.
This is advantageous, particularly for inhaled glucocorticosteroids which have a low
first-pass metabolism (BDP, Flunisolide and Triamcinolone). Moreover, use of a
spacer reduces the risk of oropharyngeal side effects.
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They can be used with a face mask. This is mainly advantageous in very young
children, who cannot fit their lips tightly around the mouthpiece of the spacer. A valve
system and a face mask with a low dead space are preferable.
These advantages are achieved at the expense of some inconvenience. Spacer devices are
more inconvenient to carry around than a dry powder inhaler or a pMDI. It is not known how
that affects compliance. However, spacers are more convenient than nebulizers, which they
can replace in the majority of patients - also in patients with severe acute asthma.
The proportion of the dose drug that the patient inhales may vary greatly with different
spacers. Data about a spacer derived from studies with one drug and pMDI may not apply to
other drugs. Changing from one spacer to another may be unimportant with some drugs but be
critical for others.
The way a spacer is used can markedly affect the amount of drug delivered.
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Multiple actuations of the metered dose inhaler into the spacer before inhalation may
markedly reduce the proportion of the drug inhaled.
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Delay between actuating the metered dose into the spacer and inhalation may also
reduce the amount of drug available to the patient. The extent to which this occurs
varies from spacer to spacer, but to maximise drug delivery, inhalation should start as
soon as possible after actuation of the inhaler. If a health professional or a carer is
actuating the inhaler for the patient this should be done only when the patient is ready
and the spacer in place.
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If a face mask is used it must be fitted tightly around the child’s mouth and nose,
otherwise the amount of drug inhaled is reduced.
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Static electricity accumulates on many polycarbonate and plastic spacers, attracting
drug particles. Highly charged spacers deliver less drug than those with an antistatic
lining. A simple way of reducing any charge on a spacer is to wash it with detergent,
which has a similar effect on drug delivery as antistatic paint, but the charge may reaccumulate. Spacers made of antistatic materials or metals reduce this problem. If a
patient or general practitioner carries a new plastic spacer for occasional use, it should
be regularly washed to reduce the charge. The spacer should drip dry after the
washing. Drying it with a piece of cloth may increase static electricity.
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Spacer size may affect the amount of drug available for inhalation, but this will vary
with the drug prescribed and the pMDI used. This is quite complex and to avoid
unpleasant surprises it is recommended to use a spacer which has been formally tested
with a given drug and pMDI. Young children can use spacers of all sizes, but
theoretically a lower volume spacer (<350 mL) is advantageous in very young
children.
The majority of the available information about spacers has come from laboratory studies in
which the drug was collected in particle sizing cascade impactors or on filters. The relatively
few pharmacokinetic studies in children have largely supported the laboratory findings.
However, little information exists about the clinical importance of the in-vitro differences
found between the various spacer devices..
When should spacers be used?
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Preferred choice in the majority of pre-school children.
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Delivery of inhaled glucocorticosteroids with a low first pass metabolism in all age
groups.
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Patients, who cannot use pMDIs or DPIs
REFERENCES
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2002;4(2):85-93.
3. O'Callaghan C, Barry P. Spacer devices in the treatment of asthma. BMJ. 1997 Apr
12;314(7087):1061-2
4. Pedersen S & O=Callaghan C. Aerosols and other devices. In: Silverman M, ed.
Childhood asthma and other wheezing disorders. London: Arnold Publishers, 2002:290-306.
5. Pedersen S. Inhalers and Nebulizers, which to Choose and Why. Respir Med. 1996;90:6977
6. Bisgaard H. Drug delivery from inhaler devices. BMJ. 1996;Oct 12;313(7062):895-6