The Relation between Exhaled Carbon Monoxide Level and Smoking Cessation Outcome

Smoking is the first preventable cause of mortality in the world. Smoking cessation is affected by various factors like nicotine dependence rate, individual issues and social factors. Measuring the level of exhaled carbon monoxide is a simple noninvasive diagnostic method for determination of smoking status and nicotine dependence; and this study evaluated its correlation with the outcome of smoking cessation. In this cross-sectional study, all individuals who had attended the smoking cessation programs in Tehran smoking cessation clinic for 6-sessions during a one- year period were questioned using a questionnaire designed according to the WHO and NRITLD questionnaires. At first, level of exhaled carbon monoxide was measured in all cases and those who quit smoking (no smoking even one puff) after the third treatment session were followed by phone in 1, 3, 6, 12 and 24 month intervals respectively. Three hundred forty- seven cases were questioned in this study out of which, 292 (84.1%) cases were males. At the end of the treatment course, 237 cases (68.3%) successfully quit smoking, 27 cases (7.8%) cut down smoking and 83 cases (23.9%) were excluded from the study due to the exceeded absence from the course. After disregarding the excluded group, the success rate of smoking cessation was calculated to be 89.8%. Measurement of the level of expired carbon monoxide (CO) showed that the exhaled CO level was < 10 parts per million (ppm) in 98 cases (28.2%), between11-20 ppm in 149 cases (42.9%) and > 20 ppm in 100 (28.8%) cases. The highest rate of success in quitting smoking was observed among those with expired CO level < 11-20 ppm and cigarette consumption less than 30 cigarettes per day (p=0.00). Since cases with high concentration of exhaled carbon monoxide showed lower success rates in quitting smoking, more specific treatment courses along with more precise consultation and follow up are recommended for such cases.