van Dijk, W. DScheepers, P. T. JCremers, RLenders, J. W. MKlerx, WSchermer, T. R. JHeijdra, Yvonnevan Weel, Chris2016-01-042016-01-041745-6215http://hdl.handle.net/1885/95209BACKGROUND Chronic obstructive pulmonary disease (COPD) is a common disease, associated with cardiovascular disease. Many patients use (long-acting) bronchodilators, whilst they continue smoking alongside. We hypothesised an interaction between bronchodilators and smoking that enhances smoke exposure, and hence cardiovascular disease. In this paper, we report our study protocol that explores the fundamental interaction, i.e. smoke retention. METHOD The design consists of a double-blinded, placebo-controlled, randomised crossover trial, in which 40 COPD patients smoke cigarettes during both undilated and maximal bronchodilated conditions. Our primary outcome is the retention of cigarette smoke, expressed as tar and nicotine weight. The inhaled tar weights are calculated from the correlated extracted nicotine weights in cigarette filters, whereas the exhaled weights are collected on Cambridge filters. We established the inhaled weight calculations by a pilot study, that included paired measurements from several smoking regimes. Our study protocol is approved by the local accredited medical review ethics committee. DISCUSSION Our study is currently in progress. The pilot study revealed valid equations for inhaled tar and nicotine, with an R2 of 0.82 and 0.74 (p < 0.01), respectively. We developed a method to study pulmonary smoke retentions in COPD patients under the influence of bronchodilation which may affect smoking-related disease. This trial will provide fundamental knowledge about the (cardiovascular) safety of bronchodilators in patients with COPD who persist in their habit of cigarette smoking. TRIAL REGISTRATION ClinicalTrials.gov: NCT00981851.© 2011 van Dijk et al; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.administration, inhalationbreath testsbronchodilator agentscardiovascular diseasescross-over studiesdouble-blind methodhumansinhalation exposurelungnetherlandspulmonary disease, chronic obstructivequestionnairesrespiratory function testsrisk assessmentrisk factorssmokingresearch design2011-02-1010.1186/1745-6215-12-372016-02-24