A repeatable method for determination of carboxyhemoglobin levels in smokers.

Fourteen male smokers participated in ten afternoon test sessions to determine the daily variation in expired breath carbon monoxide (CO), and whole blood percent carboxyhemoglobin (%COHb), hemoglobin and hematocrit levels. Each individual's test session was conducted at approximately the same time of day to estimate CO-related measures under relatively stable conditions. Subjects smoked ad libitum prior to testing. The 'usual brand' cigarette was smoked during the first measurement week (sessions 1-5 held on Monday through Friday) and a research cigarette prototype which primarily heats rather than burns tobacco (TOB-HT) was smoked by 12 of the 14 subjects for 3 weeks prior to and during the second measurement week (sessions 6-9 held on Tuesday through Friday). Following the last 'usual brand' measurement session, subjects completed 21 days of ad libitum smoking of the TOB-HT cigarette before starting sessions 6-9 to allow acclimation to the TOB-HT research cigarette. Following session 9, 11 of the 14 subjects continued to smoke the TOB-HT cigarette for an additional 3 weeks and then participated in an additional test session (session 10). The data indicate that daily measurements of afternoon %COHb and expired breath CO values for an individual are reproducible when using this protocol. Carboxyhemoglobin and expired breath CO levels were elevated by 24.4 and 30.6%, respectively, after switching to the TOB-HT cigarette. This increase was not due to an increase in the number of cigarettes consumed since the subjects smoked an average of 21 cigarettes prior to the measurement session when smoking either their 'usual brand' or the TOB-HT cigarette.