Send letter to journal:
Re: Should use of home-made spacers be incorporated into guidelines for asthma management?

Dear Editor

Zar et al[1] found that lung deposition of aerolised technetium-99DTPA inhaled via modified 500 ml plastic bottle was higher compared to a Babyhaler in both young and other children. There was no difference in lung deposition when a mask was used. Though other workers[2] have recommended the attachment of facemasks to treat patients of all ages.

In another study[3] children aged 5 to 13 years with acute asthma were studied and it was concluded that a conventional spacer and sealed 500 ml plastic bottle produced similar bronchodilatation, an unsealed bottle gave intermediate improvement in lung function, and a polystyrene cup was least effective as a spacer for children with moderate to severe airways obstruction.

A metered-dose inhaler (MDI) with spacer is the best way to deliver inhalation therapy for the treatment of acute asthma. In India, commercially produced spacers are available but most of the patients find it too costly and are thus unable to purchase. These patients, then take the prescribed inhalers directly without any attachment. We know that inhalers if taken directly are generally ineffective as medicine fails to reach the lungs. Thus, use of bottle spacers should be incorporated into the guidelines for asthma management in developing countries. However, owing to their size, the bottle spacers are inconvenient to carry and in these patients dry powder inhalers should be recommended as the next best thing.

Children with asthma can lead relatively normal lives, just like their non-asthmatic friends. Diligent monitoring and adherence to a management plan can make all the difference.

References

1. Zar HJ, Weinberg EG, Binns HJ, Gallie F, Mann MD. Lung deposition of aerosol - a comparison of different spacers. Arch Dis Child 2000;82:495-8.

2. O’Callighan C, Milner AD, Swarbrick. Spacer device with facemask attachment for giving bronchodilators to infants with asthma. BMJ 1989;298:160-1.

Send letter to journal:
Re: Spacers and holding chambers: Not the last word, we hope

Dear Editor:

Zar and colleagues[1] compared home-made spacers and two commercially available valved holding chambers (VHCs) for the treatment of children with acute asthma. We acknowledge that the practice of using empty drink bottles is common in some countries (by either necessity or choice). We, as a manufacturer of one of the VHCs that was evaluated, are highly concerned about the support to the hypothesis that coffee-cup or drink bottle spacers are as effective as properly designed add-on devices, given by implication in the Editor's comments on this article (Archives this Month June 2000),

In Zar et al's paper[1] the production technique did not simulate the release of medication from a pressurized metered dose inhaler (pMDI). Instead, the technique created a radiolabelled aerosol by pneumatic nebulization into a bag (which would have acted as a particle pre-selector). This set-up would not have reproduced accurately the ballistic component (polydispersed particles) that is inevitably released at actuation of a pMDI. It has already been demonstrated that these particles are more effectively separated by a VHC than a spacer (with no valve). Had a pMDI containing the radiolabelled aerosol been used (as is the normal practice in gamma-scintigraphic studies evaluating pMDI systems), we believe that the dynamic aerosol behavior (inertial impaction of the ballistic component, turbulent deposition, etc) following actuation into the chamber would have been quite different to that observed by having patients drawing in the already formed aerosol from an anesthesia bag. Simply put, the protocol more closely simulated a continuous jet nebulizer releasing a liquid phase aerosol into a bag, which was then connected to a chamber/spacer device, and may therefore have little relevance to what actually occurs inside a VHC used with a pMDI.

A well designed holding chamber (with a valve) will retain a significant portion of the coarse component of the emitted dose (particles greater than about 5 microns aerodynamic diameter) from the pMDI. A spacer (home-made or otherwise) will not perform this function effectively. Rather it will momentarily contain the aerosol and then deliver particles of all sizes to the well-coordinated patient who is able to time inhalation with actuation of the pMDI. In the case of corticosteroid, the emitted coarser particles can promote local topical infections, such as oral candidiasis as well as increases in overall systemic absorption.

The inhalation valve, that distinguishes a VHC from a spacer, needs to be a carefully designed component whose function is to retain the aerosol once created following actuation of the pMDI, then release it during the inspiratory cycle. Many children, particularly those suffering an acute exacerbation of asthmatic symptoms, have poor coordination, and are therefore likely to mistime inhalation with pMDI actuation. Such patients, who are at greatest risk, are therefore likely to derive least benefit from the use of home-made spacers.

While we have other observations of a technical nature, the information given here should be sufficient to provide you with the message that this study should not be taken as the final word but rather as a finding concerning the debate about the efficacy of home-made versus manufactured add-on delivery devices for use in pMDI-based therapy. Having said this, if a VHC is unavailable for whatever reason, an empty drinking bottle may be better than nothing at all.

Jolyon P Mitchell PhD, FRSC(UK), CChem
Scientific Director
Medical Aerosol Research Laboratory
Trudell Medical International

Reference

Send letter to journal:
Re: Re: Spacers and holding chambers: Not the last word, we hope

Dear Editor

Dr Mitchell is concerned that the methodology used in our study does not simulate the release of aerosol from a metered dose inhaler (MDI). As discussed in the article, the method of aerosol delivery in our study differs from that of a MDI but as the delivery system was kept constant and the particular spacer varied, a valid comparison of the efficacy of different spacers could be made.[1] This delivery system has been previously developed and tested in older children.[2] In these studies aerosol lung deposition was equivalent from a conventional spacer or sealed modified bottle spacer but a cup performed poorly delivering significantly less aerosol to the lungs than did the other spacers.

The validity of these findings was borne out by the results of a clinical study in which a similar response to bronchodilator was obtained when children with acute asthma were given a beta-2 agonist via an MDI- bottle or conventional spacer but a poor response occurred in those using a cup.[3]

We agree with Dr Mitchell that the presence of an inhalation valve may affect pulmonary deposition of aerosol. However, valveless spacers may also function efficiently as spacers. When compared to an MDI alone, increased lung deposition has been reported with a valved Cone Spacer and a valveless Tube Spacer.[4] These two spacers have also been found to produce similar increases in bronchodilation compared to a MDI alone.[3] Moreover, oropharyngeal deposition may be reduced by up to 60% with a valveless spacer.[4] Recently, valveless spacers have been reported to enhance the delivery of aerosol to the lungs in infants with chronic lung disease compared to the same spacer with a valve.[5] The results of our clinical study suggest that a valveless bottle spacer provided effective drug delivery to the lungs resulting in similar bronchodilation compared to that obtained with a valved conventional spacer.[6]

The availability of a spacer device is essential in order to provide care to children with asthma. For many children particularly those in developing countries, a low cost spacer is not available. We believe that our studies have shown that a modified 500ml plastic bottle functions effectively as a spacer providing equivalent or superior aerosol deposition to a conventional spacer and producing similar clinical improvement. Such a bottle-spacer is a first step in providing asthma care to many children throughout the world.

Heather J Zar
Michael Mann
Eugene Weinberg

Department of Paediatrics and Child Health
Red Cross Children's Hospital
University of Cape Town, South Africa

References

(1) Zar HJ, Weinberg EG, Binns HJ, Gallie F, Mann MD. Lung deposition of aerosol - a comparison of different spacers. Arch Dis Child 2000;82:495-8

(2) Zar HJ, Liebenberg M, Weinberg E, Binns HJ, Mann MD. The efficacy of alternative spacer devices for delivery of aerosol therapy to children with asthma. Ann Trop Paed 1998:18;75-9

(3) Rivlin J, Mindorff C, Reilly PA, Levison H. Pulmonary response to a bronchodilator delivered from three inhalation devices. J Pediatr 1984;104:470-3

(4) Newman SP, Moren F, Pavia D, et al. Deposition of pressurized suspension aerosols inhaled through extension devices. Am Rev Respir Dis 1981;124:317-20

(5) Fok TF, Lam K, Chan CK et al. Aerosol delivery to non-ventilated infants by metered dose inhaler: Should a valved spacer be used? Pediatr Pulmonol 1997:24;204-212