Editor—We did not include spirometry data for patients, although they are available. The only source of patients with the diagnosis of chronic obstructive pulmonary disease in this study was a specialist respiratory clinic in a tertiary hospital and the diagnosis was not reconfirmed on entry to the study. Spirometry is a diagnostic criterion for the disease, but indicators of severity of disease include degree of dyspnoea.1-3 In severe, late stage disease, with an already established diagnosis, spirometry may cause great discomfort to the patient, have questionable accuracy, and correlate poorly with the subjective sensation of dyspnoea.4
Our study was an efficacy study powered to detect a change in the subjective sensation of breathlessness. A study is currently in the final stages of planning, which is powered primarily on safety, including respiratory depression. Given our current data informing power calculations, this will be a much larger study. Ensuring non-inferiority of opioids over placebo will be the primary end point, with dose ranging and effectiveness over time assessed. We welcome Berrill and Linnane's remarks about carbon dioxide monitoring in this context.
We agree that any drug treatment needs to be introduced after careful consideration of potential adverse effects and benefits. The patient's clinical course should be carefully monitored. Unfortunately, the concerns about opioids in patients with chronic obstructive pulmonary disease are not from systematic studies, nor are they using low dose sustained release morphine with its inherently lower peak concentrations.
Additional authors are Belinda S Fazekas, research manager, and Annie McHugh, research nurse, both Southern Adelaide Palliative Services, Repatriation General Hospital, Daw Park, SA 5042; Chuong Bui, consultant, Department of Nuclear Medicine, Nepean Hospital, Kingswood, NSW 2747, Australia.
Competing interests: Placebo capsules of identical appearance were provided by the company that manufactures sustained release morphine sulphate (Kapanol, Glaxo Wellcome Australia); no direct funds were provided by the drug company.
References
- 1.McKenzie DK, Frith PA, Burdon JG, Town GI. The CPODX plan: Australian and New Zealand guidelines for the management of chronic obstructive pulmonary disease 2003. Med J Aust 2003;178(suppl): S7-39. [DOI] [PubMed] [Google Scholar]
- 2.Canadian Thoracic Society. Executive summary. Canadian Thoracic Society recommendations for management of chronic obstructive pulmonary disease—2003. Can Respir J 2003;10(suppl): SA. [DOI] [PubMed] [Google Scholar]
- 3.Global Initiative for Chronic Obstructive Lung Disease. Global strategy for the diagnosis, management, and prevention of COPD. Updated 2003. www.goldcopd.com (accessed 16 Nov 2003).
- 4.Heyse-Moore L, Beynon T, Ross V. Does spirometry predict dyspnoea in advanced cancer? Pall Med 2000;14: 189-95. [DOI] [PubMed] [Google Scholar]