title: Evaluation of the exhaled carbon monoxide levels in smokers with COPD.
abstract: OBJECTIVE
  To measure exhaled carbon monoxide (COex) levels in smokers with and without COPD.
  
  
  METHODS
  Smokers treated at outpatient clinics of São Lucas Hospital in the city of Porto Alegre, Brazil, between September of 2007 and March of 2009 were invited to participate in this study. The participants completed a questionnaire regarding demographic and epidemiologic characteristics and were submitted to spirometry, as well as to determination of COex and urinary cotinine levels. The participants were divided into two groups: those with COPD and those without COPD.
  
  
  RESULTS
  The study involved 294 smokers, of whom 174 (59.18%) had been diagnosed with COPD. All of the participants presented with urinary cotinine levels > 50 ng/mL. Smokers with COPD presented significantly higher median values for age and pack-years than did those without COPD (p < 0.001 and p = 0.026, respectively). No other statistically significant differences were found. When adjusted for gender, age at smoking onset, number of cigarettes/day and urinary cotinine level, the mean values of COex were higher, but not statistically so, in the COPD group than in the non-COPD group (17.8 +/- 0.6 ppm and 16.6 +/- 0.7 ppm, respectively; p = 0.200). The differences remained nonsignificant when plotted logarithmically. A wide dispersion of COex values was found when the participants were classified by FEV1 level (r = -0.06; p = 0.53) or by Global Initiative for Chronic Obstructive Lung Disease classification (r = 0.08; p = 0.34). The proportions of false-negative results for smoking were 18.4% and 6.7%, respectively, in the COPD and non-COPD groups (p = 0.007).
  
  
  CONCLUSIONS
  Since COex values did not differ significantly between smokers with COPD and those without, there seem to be no major contraindications to their use in smokers with COPD.
authors.affiliation: Department of Pulmonology, Pontifícia Universidade Católica do Rio Grande do Sul - PUCRS, Pontifical Catholic University of Rio Grande do Sul - São Lucas Hospital, Porto Alegre, Brazil. jmchatkin@pucrs.br
authors.forename: Gustavo
authors.initials: G
authors.lastname: Chatkin
authors.forename: José Miguel
authors.initials: JM
authors.lastname: Chatkin
authors.forename: Gabriel
authors.initials: G
authors.lastname: Aued
authors.forename: Guilherme Oliveira
authors.initials: GO
authors.lastname: Petersen
authors.forename: Edna Thais
authors.initials: ET
authors.lastname: Jeremias
authors.forename: Flávia Valladão
authors.initials: FV
authors.lastname: Thiesen
mesh_terms: D000368:Aged; D015415:Biomarkers / Q000032:analysis / Q000652:urine; D001944:Breath Tests; D002248:Carbon Monoxide / Q000032:analysis*; D016022:Case-Control Studies; D003367:Cotinine / Q000652:urine; D003430:Cross-Sectional Studies; D005188:False Negative Reactions; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D029424:Pulmonary Disease, Chronic Obstructive / Q000652:urine*; D012907:Smoking / Q000652:urine; D016540:Smoking Cessation
chemical_list: D015415:Biomarkers; D002248:Carbon Monoxide; D003367:Cotinine