Breath carbon monoxide as an indication of smoking habit in the military setting

ECT Low, MCC Ong, M Tan
Correspondence: Dr Mark Tan, minglong@cyberway.com.sg

ABSTRACT
Introduction The breath carbon monoxide (CO) monitor has been shown to be an effective tool in predicting smoking habits. This study aims to assess whether the breath CO level can be employed to determine a person's smoking habit in the military setting and to analyse various factors that can influence the breath CO levels.
Methods 155 navy personnel were questioned on their smoking habits in phase one of the study. The subjects were explained the objective of the study and instructed to provide two breaths into the CO monitor (EC-50 Smokerlyser, Bedford Instruments, Kent, UK). In a subsequent single blind study, 40 trainees were not told of the purpose of the study and were assessed via a questionnaire and smokerlyser estimation. Descriptive statistics were used to examine the data and assess distribution. Depending on the distribution, a two-sample t test or Mann-Whitney U test were used to test for a significant difference between CO levels among smokers and non-smokers.
Results In phase one, the mean breath CO levels were 11.6 (plus or minus 6.2) ppm for smokers and (1.9 plus or minus 0.9) ppm for non-smokers (p-value less than 0.0001). A cut-off level of 5 ppm gave a sensitivity of 96 percent and a specificity of 98 percent. The high CO levels were clustered within five hours of the last cigarette smoked. Therefore, this value may not reliably predict smoking habits if an individual smoked more than five hours before the test. Of the 40 subjects in phase two, five smokers who stated that their last cigarette smoked was 48 hours before the breath test had a mean CO level greater than 5 ppm. (range of 5.5 to 18.0 ppm). On further questioning, all admitted to having smoked on the day of the test.
Conclusion The breath CO monitor has good potential for use as an adjunct in future smoking control assessments and a reading greater than 5 ppm strongly suggests that the military outpatient is a smoker.

Keywords: breath carbon monoxide, carbon monoxide, military, smoking, smoking control
Singapore Med J 2004; 45(12): 578-582