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London, UK
Correspondence to: Peter J. Barnes, DM, National Heart & Lung Institute, Imperial College, Dovehouse St, London SW3 6LY, UK; e-mail: p.j.barnes{at}imperial.ac.uk
To the Editor:
The conclusions reached by Dolovich and colleagues1 in a special report of meta-analyses of randomized controlled clinical trials of aerosol delivery devices and inhaled therapy for patients with asthma and COPD are concise and show that devices used for the delivery of bronchodilators and steroids can be equally efficacious. However, we believe that when selecting a delivery device, much more prominence should be given to a patient’s ability to use the selected device correctly. The conclusion that all devices can be equally efficacious was obviously obtained from analyses of randomized controlled clinical trials in which patient participation required the ability of patients to use the devices being studied correctly. That there were no differences in drug efficacy between different delivery systems is therefore expected.
There is now clear evidence that misuse of corticosteroid metered-dose inhalers is associated with decreased asthma control,2 and previous studies34 have reported a decreased bronchodilator response in patients not using the pressurized metered-dose inhaler correctly. Incorrect use of inhalation devices has been reported frequently in the past; in the literature search reported by Cochrane et al,5 the frequency of efficient inhalation technique ranged from 46 to 59%. These findings support our view that the most important recommendation to clinicians about the prescription of an inhaler is the confirmation by observation that the device can be used efficiently. The conclusions of the meta-analyses reported by Dolovich et al1 do not emphasize the importance of checking inhaler technique in all patients prior to the prescription of any inhalation device for the first time, and the need to check technique regularly thereafter especially if there is poor symptom control.
References
Hamilton, ON, Canada
Correspondence to: Myrna B. Dolovich, PEng, Faculty of Health Sciences, McMaster University, 1200 Main St West, HSC 1V16, Hamilton, ON, Canada L8N 3Z5; e-mail: mdolovic{at}mcmaster.ca
To the Editor:
Teaching patients correct inhaler technique and reinforcing this technique with each subsequent office visit are indeed key steps to the successful implementation of aerosol therapy, as aptly stated by Drs. Barnes and Crompton. In 1982, Crompton1 identified the difficulties patients had when using their metered-dose inhalers; and this article, along with eight others, were discussed in the introduction to our meta-analysis.2 In addition, the take-home message from the meta-analysis was that for patients unable to master the required inhalation technique for a specific delivery device, other choices for inhalers delivering equivalent drug doses and providing the same clinical efficacy were often available. The importance of correct inhaler technique to successful therapy was stressed throughout the body of the text, with the points made in the Abstract re-emphasized in the concluding paragraphs, in which we restated that competence in the use of an inhaler needed to be confirmed by the physician or health-care worker when choosing an aerosol delivery device for their patient.
The selection criteria for studies included in the meta-analysis2 were randomized controlled trials (RCTs) in which responses to the same drug were tested using different delivery devices, thus eliminating the influence of device/drug combinations. In the descriptions of the methods and subject inclusion criteria for the many studies we reviewed, patient ability to use the various devices was one of the variables frequently mentioned. One can only assume that an inability to use a device correctly excluded a subject from a trial, but also that correct inhaler technique was taught prior to study entry. The studies selected for analysis included trials in which devices were tested under conditions of actual clinical use (type 1 studies) or in a laboratory setting with well-trained subjects (type 2 studies). In the former, inhaler technique may have been reinforced on clinic visits but not monitored otherwise. Barnes and Crompton have stated that the use of correct inhaler technique in all studies analyzed resulted in our not discerning differences in efficacy between devices, and this may be true. However, the purpose of the meta-analysis was to test whether device performance influenced response, independent of drug, and with patients able to use the devices correctly. ß2-Agonists were the test drugs for the majority of the RCTs, with doses sufficient to achieve the plateau of the dose-response curve. Only four studies of corticosteroids met the selection criteria for inclusion in the analysis; these RCTs compared metered-dose inhaler plus spacer to dry powder inhaler use in well-controlled adult asthmatics and showed no differences in response using either delivery device. It is possible that these results were only a consequence of patients using the correct inhaler technique. We do agree that poor inhaler technique is a contributing factor to loss of asthma control and would welcome RCTs comparing delivery devices in this population. We fully agree with Drs. Barnes and Crompton that a patient’s ability to use an aerosol delivery device correctly is an exceedingly important aspect when choosing an inhaler, and thank them for underscoring this point in their review of the guidelines.
References
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