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Carboxyhemoglobin Levels in Primary and Secondary Cigar and Pipe Smokers*
Carboxyhemoglobin Levels in Primary and Secondary Cigar and Pipe Smokers* Allan L. Goldman, M.D., F.C.C.P. o o
This study of 130 subjects was performed to obtain more data about the smoking habits and levels of carboxyhemoglobin in various types of pipe and cigar smokers. These smokers may be divided by history into primary or secondary smokers and also into current inhalers and noninhalers. Prior studies of carboxyhemoglobin levels have yielded conflicting results, presumably due to differences in current habits of inhalation, which were often not taken into account. Cigarette, primary pipe, and secondary pipe inhalers ·had simUar carboxyhemoglobin
levels that were significantly higher than nonsmokers (5.6, 5.0, 5.4, and 1.0 percent, respectively). Cigar inhalers had markedly elevated concentratious of carboxyhemoglobin (13.8 and 11.8 percent in primary and secondary inhalers, respectively). Most secondary cigar and pipe smokers inhaled, whereas most primary smokers did not. Intentional inhalation, rather than p.t smoking history, is the most important factor in determining the carboxyhemoglobin level for each type of smoker.
There are many hazards associated with smoking. 1 Some, including atherosclerosis and reversible secondary polycythemia, have been related to levels of carboxyhemoglobin in the blood. 2•3 Carboxyhemoglobin levels in the blood are linearly related to alveolar levels of carbon monoxide and, thus, reflect inhalation of tobacco smoke. Although there is ample data concerning habits of inhalation and consequent carboxyhemoglobin levels for cigarette smokers, there are few data available for different types of cigar and pipe smokers. 4 A recent study from our institution revealed that ex-cigarette smokers who switched to cigars frequently inhaled. Inhaling cigar smokers had much higher carboxyhemoglobin levels than inhaling cigarette smokers.5 Pipe and cigar smokers can be subdivided into groups in several ways. They can be subdivided by past smoking history into primary smokers (those who have never inhaled cigarettes) and secondary smokers (those who have discontinued inhaling cigarettes and changed to pipes or cigars) . Pipe and cigar smokers can also be subdivided according to habits of inhalation, as determined by a questionnaire. Because alveolar levels of carbon
monoxide and blood levels of carboxyhemoglobin are linearly related, the concentration of carboxyhemoglobin can also be used as an objective measure of inhalation. Prior studies have brought conflicting results regarding the carboxyhemoglobin levels in cigar and pipe smokers, presumably due to the differences in the groups studied, as well as lack of data regarding past smoking history and inhalation.4-7 In an attempt to get more data on inhaling and subsequent carboxyhemoglobin levels in different types of cigar and pipe smokers, the following study was performed.
°From the Veterans Administration Hospital and the Pulmonary Disease Section, Department of Internal Medicine, College of Medicine, University of South Florida, Tampa. Read in part at the annual meeting of the American Thoracic Society, New Orleans, May 17, 1976. 0 0 Associate Professor of Medicine and Chief, Pulmonary Disease Section. Manuscript received August 30; revision accepted October 12. Reprint requests: Dr. Goldman, 13()()() North 30th Street, Tampa33612
CHEST, 72: 1, JUlY, 1977
MATERIALS AND METIIODS
A total of 130 subjects were studied and grouped by smoking habits, as determined by a questionnaire administered by pulmonary technicians. All subjects were studied in the Tampa ( Fla) Veterans Administration Hospital's Pulmonary Function Laboratory. Subjects had been referred for an analysis of arterial blood gas levels, which was performed on a blood gas analyzer (Radiometer PHM-72). Arterial oxygen saturation ( Sa02) was calculated from the arterial oxygen pressure ( Pa0 2) and pH. A portion of the sample of arterial blood was analyzed by spectrophotometric oximeter ( Instrumentation Laboratory CO-Oximeter (model 182) for levels of carboxyhemoglobin, oxyhemoglobin, and total hemoglobin, as well as actual Sa02. The samples of arterial blood for the measurements were obtained throughout the day. In smokers, these were obtained after 10 AM. The technique of calibration has been published previously. II It should be pointed out that the oxygen desaturation caused by carboxyhemoglobin will not be picked up by calculating the Sa02 from Pa02 and pH or by Van Slyke's
CARBOXYHEMOGLOBIN LEVELS IN CIGAR AND PIPE SMOKERS 33
technique for determining oxygen saturation, in which oxyhemoglobin is divided by the sum of the oxyhemoglobin and reduced hemoglobin. To pick up the defect in Sa0 2 caused by carboxyhemoglobin, the measurement of Sa02 was done by the spectrophotometric oximeter ( CO-Oximeter), which takes carboxyhemoglobin into account, or a measurement of oxygen content must be performed. REsULTS
Table 1 gives the mean carboxyhemoglobin level and mean measured Sa02 of the groups studied. There was no apparent difference in the amount of tobacco smoked, the frequency of smoking, or the time since last exposure in the different groups of particular types of smokers. From Table 1, it can be seen that noninhaling (whether primary or secondary) cigar or pipe smokers had similar carboxyhemoglobin levels that were only slightly higher than nonsmokers. The mean values for Sa02 in the noninhaling groups were not significantly different from the nonsmokers ( P > 0.4) . Cigarette and pipe inhalers had similar values for carboxyhemoglobin level and for Sa02 ( P > 0.5) that were, as expected, different from nonsmokers (P < 0.001). Cigar inhalers, whether primary or secondary smokers, had higher carboxyhemoglobin levels and lower values for Sa02 than cigarette or pipe inhalers ( P < 0.005). There was no difference in carboxyhemoglobin level or Sa02 between primary and secondary cigar inhalers ( P > 0.5). Intentional inhalation, rather than past smoking history, was the most important single factor in determining carboxyhemoglobin levels. Although most secondary cigar smokers ( 34/38) and secondary pipe smokers ( 12/18) admitted to inhaling, some did not and had low carboxyhemoglobin levels consistent with noninhalation. Conversely, although most primary cigar smokers ( 8/11) and primary pipe smokers (5/6} said they did not inhale and Table I--Carbo%Yhemo.lobin Le.lel and Sa02 in 130 Subjee" Grouped by Smolci~ Habit*
Group
Carboxyhemoglobin No. of Level, percent Subjects
Nonsmokers Cigarette inhalers Primary cigar inhalers Secondary cigar inhalers Primary cigar noninhalers Secondary cigar noninhalers Primary pipe inhalers Secondary pipe inhalers Primary pipe noninhalers Secondary pipe noninhalers *Table values are means ± SE.
34 ALLAN L GOLDMAN
16 41 3 34 8 4 12 5 6
1.0±0.1 5.6±0.5 13.8±1.2 11.8 ± 1.1 2.1 ±0.3 1.9±0.3 5.0 5.4±0.5 1.3±0.2 2.5±0.5
Sa02, percent 96.7±0.7 91.8±0.7 85.7 ± 1.2 85.7 ± 1.2 95.6±0.4 96.4±0.3 94.6 92.4 ±0.7 96.3±0.7 96.3±0.5
had low carboxyhemoglobin levels, some did inhale, as evidenced by their history and high carboxyhemoglobin levels. Habitual unintentional inhalation did not seem to be a common occurrence. DISCUSSION
The present study has examined different categories of cigar and pipe smokers in regard to their past and present smoking habits and present carboxyhemoglobin levels. Previous studies have yielded conflicting results on carboxyhemoglobin levels in cigar and pipe smokers, probably due to differences in the groups under study, as well as insufficient data on past smoking history and inhalation. Goldsmith and Landaw4 in 1968 reported that pipe and cigar smokers had estimated carboxyhemoglobin levels of 1.7 percent, which was only slightly higher than the level of 1.2 percent in nonsmokers. These investigators• attributed this to minimal inhalation; however, they did not specify whether these subjects were primary or secondary smokers or whether they inhaled. Cowie et al6 studied seven cigarette smokers before and after changing to cigars. These researchers6 found the carboxyhemoglobin levels to be similar and, thus, believed that the subjects continued to inhale, although this was not specifically investigated. Castleden and Cole7 in 1973 studied 50 cigar and pipe smokers. Most participants were medical staH. These investigators7 found the secondary smokers to have higher carboxyhemoglobin levels than primary smokers ( 5.2 vs 2.3 percent) but found no significant difference between secondary cigar and pipe smokers. In their study,7 no primary smoker admitted to inhaling. Nine secondary pipe smokers who said they were noninhalers had elevated carboxyhemoglobin levels, suggesting unintentional inhalation. Inhalation by the cigar smokers was not mentioned. A previous study from our laboratory revealed that secondary cigar smokers who intentionally inhaled had very high carboxyhemoglobin levels. 5 The current study extends these findings and reveals that cigar inhalers in general, whether primary or secondary, have very high carboxyhemoglobin levels, while pipe inhalers have carboxyhemoglobin levels similar to cigarette inhalers. It appears that the habit of inhalation and what is smoked, rather than the past smoking history, are the most important determinants of carboxyhemoglobin levels. The differences seen in our study when compared to prior studies may be partly attributable to the populations studied. We studied outpatients and not volunteers or medical personnel. In any event, our experience would seem to be
CHEST, 72: 1, JULY, 1977
more representative of the general population of patients. From this study, it can be seen that patients should refrain from all forms of smoking. Cigar and pipe smokers should be questioned regarding inhalation, and this should particularly be discouraged because of the known consequences of elevated concentrations of carboxyhemoglobin, including reversible secondary polycythemia and an increased incidence of atherosclerosis. 1.s It is also known that cigar and pipe smokers in general have an increased incidence of cancer of the oral cavity, larynx, lung, and esophagus when compared to nonsmokers. 1 Whether some of these malignant neoplasms occur more commonly in a subgroup of patients who inhale remains to be determined.
CHEST, 72: 1, JUlY, 1977
REFERENCES 1 The Health Consequences of Smoking: A Report of the Surgeon General (publication HSM 72-7516). US Department of Health, Education, and Welfare, 1972 2 Wald N, HowardS, Smith PG, et al: Association between atherosclerotic diseases and carboxyhaemoglobin levels in tobacco smokers. Br Med J 1:761-765, 1973 3 Sagone AL, Balcerzak SP: Smoking as a cause of erythrocytosis. Ann Intern Med 82:512-515, 1975 4 Goldsmith JR, Landaw SA: Carbon monoxide and human health. Science 162:1352-1359, 1968 5 Goldman AL : Cigar inhaling. Am Rev Respir Dis 113:8789, 1976 6 Cowie J, Sillett RW, Ball K : Carbon-monoxide absorption by cigarette smokers who change to smoking cigars. Lancet 1:1033-1035, 1973 7 Castleden CM, Cole PV: Inhalation of tobacco smoke by pipe and cigar smokers. Lancet 2:21-22, 1973
CARBOXYHEMOGLOBIN LEVELS IN CIGAR AND PIPE SMOKERS 35
This study of 130 subjects was performed to obtain more data about the smoking habits and levels of carboxyhemoglobin in various types of pipe and cigar smokers. These smokers may be divided by history into primary or secondary smokers and also into current inhalers and noninhalers. Prior studies of carboxyhemoglobin levels have yielded conflicting results, presumably due to differences in current habits of inhalation, which were often not taken into account. Cigarette, primary pipe, and secondary pipe inhalers ·had simUar carboxyhemoglobin
levels that were significantly higher than nonsmokers (5.6, 5.0, 5.4, and 1.0 percent, respectively). Cigar inhalers had markedly elevated concentratious of carboxyhemoglobin (13.8 and 11.8 percent in primary and secondary inhalers, respectively). Most secondary cigar and pipe smokers inhaled, whereas most primary smokers did not. Intentional inhalation, rather than p.t smoking history, is the most important factor in determining the carboxyhemoglobin level for each type of smoker.
There are many hazards associated with smoking. 1 Some, including atherosclerosis and reversible secondary polycythemia, have been related to levels of carboxyhemoglobin in the blood. 2•3 Carboxyhemoglobin levels in the blood are linearly related to alveolar levels of carbon monoxide and, thus, reflect inhalation of tobacco smoke. Although there is ample data concerning habits of inhalation and consequent carboxyhemoglobin levels for cigarette smokers, there are few data available for different types of cigar and pipe smokers. 4 A recent study from our institution revealed that ex-cigarette smokers who switched to cigars frequently inhaled. Inhaling cigar smokers had much higher carboxyhemoglobin levels than inhaling cigarette smokers.5 Pipe and cigar smokers can be subdivided into groups in several ways. They can be subdivided by past smoking history into primary smokers (those who have never inhaled cigarettes) and secondary smokers (those who have discontinued inhaling cigarettes and changed to pipes or cigars) . Pipe and cigar smokers can also be subdivided according to habits of inhalation, as determined by a questionnaire. Because alveolar levels of carbon
monoxide and blood levels of carboxyhemoglobin are linearly related, the concentration of carboxyhemoglobin can also be used as an objective measure of inhalation. Prior studies have brought conflicting results regarding the carboxyhemoglobin levels in cigar and pipe smokers, presumably due to the differences in the groups studied, as well as lack of data regarding past smoking history and inhalation.4-7 In an attempt to get more data on inhaling and subsequent carboxyhemoglobin levels in different types of cigar and pipe smokers, the following study was performed.
°From the Veterans Administration Hospital and the Pulmonary Disease Section, Department of Internal Medicine, College of Medicine, University of South Florida, Tampa. Read in part at the annual meeting of the American Thoracic Society, New Orleans, May 17, 1976. 0 0 Associate Professor of Medicine and Chief, Pulmonary Disease Section. Manuscript received August 30; revision accepted October 12. Reprint requests: Dr. Goldman, 13()()() North 30th Street, Tampa33612
CHEST, 72: 1, JUlY, 1977
MATERIALS AND METIIODS
A total of 130 subjects were studied and grouped by smoking habits, as determined by a questionnaire administered by pulmonary technicians. All subjects were studied in the Tampa ( Fla) Veterans Administration Hospital's Pulmonary Function Laboratory. Subjects had been referred for an analysis of arterial blood gas levels, which was performed on a blood gas analyzer (Radiometer PHM-72). Arterial oxygen saturation ( Sa02) was calculated from the arterial oxygen pressure ( Pa0 2) and pH. A portion of the sample of arterial blood was analyzed by spectrophotometric oximeter ( Instrumentation Laboratory CO-Oximeter (model 182) for levels of carboxyhemoglobin, oxyhemoglobin, and total hemoglobin, as well as actual Sa02. The samples of arterial blood for the measurements were obtained throughout the day. In smokers, these were obtained after 10 AM. The technique of calibration has been published previously. II It should be pointed out that the oxygen desaturation caused by carboxyhemoglobin will not be picked up by calculating the Sa02 from Pa02 and pH or by Van Slyke's
CARBOXYHEMOGLOBIN LEVELS IN CIGAR AND PIPE SMOKERS 33
technique for determining oxygen saturation, in which oxyhemoglobin is divided by the sum of the oxyhemoglobin and reduced hemoglobin. To pick up the defect in Sa0 2 caused by carboxyhemoglobin, the measurement of Sa02 was done by the spectrophotometric oximeter ( CO-Oximeter), which takes carboxyhemoglobin into account, or a measurement of oxygen content must be performed. REsULTS
Table 1 gives the mean carboxyhemoglobin level and mean measured Sa02 of the groups studied. There was no apparent difference in the amount of tobacco smoked, the frequency of smoking, or the time since last exposure in the different groups of particular types of smokers. From Table 1, it can be seen that noninhaling (whether primary or secondary) cigar or pipe smokers had similar carboxyhemoglobin levels that were only slightly higher than nonsmokers. The mean values for Sa02 in the noninhaling groups were not significantly different from the nonsmokers ( P > 0.4) . Cigarette and pipe inhalers had similar values for carboxyhemoglobin level and for Sa02 ( P > 0.5) that were, as expected, different from nonsmokers (P < 0.001). Cigar inhalers, whether primary or secondary smokers, had higher carboxyhemoglobin levels and lower values for Sa02 than cigarette or pipe inhalers ( P < 0.005). There was no difference in carboxyhemoglobin level or Sa02 between primary and secondary cigar inhalers ( P > 0.5). Intentional inhalation, rather than past smoking history, was the most important single factor in determining carboxyhemoglobin levels. Although most secondary cigar smokers ( 34/38) and secondary pipe smokers ( 12/18) admitted to inhaling, some did not and had low carboxyhemoglobin levels consistent with noninhalation. Conversely, although most primary cigar smokers ( 8/11) and primary pipe smokers (5/6} said they did not inhale and Table I--Carbo%Yhemo.lobin Le.lel and Sa02 in 130 Subjee" Grouped by Smolci~ Habit*
Group
Carboxyhemoglobin No. of Level, percent Subjects
Nonsmokers Cigarette inhalers Primary cigar inhalers Secondary cigar inhalers Primary cigar noninhalers Secondary cigar noninhalers Primary pipe inhalers Secondary pipe inhalers Primary pipe noninhalers Secondary pipe noninhalers *Table values are means ± SE.
34 ALLAN L GOLDMAN
16 41 3 34 8 4 12 5 6
1.0±0.1 5.6±0.5 13.8±1.2 11.8 ± 1.1 2.1 ±0.3 1.9±0.3 5.0 5.4±0.5 1.3±0.2 2.5±0.5
Sa02, percent 96.7±0.7 91.8±0.7 85.7 ± 1.2 85.7 ± 1.2 95.6±0.4 96.4±0.3 94.6 92.4 ±0.7 96.3±0.7 96.3±0.5
had low carboxyhemoglobin levels, some did inhale, as evidenced by their history and high carboxyhemoglobin levels. Habitual unintentional inhalation did not seem to be a common occurrence. DISCUSSION
The present study has examined different categories of cigar and pipe smokers in regard to their past and present smoking habits and present carboxyhemoglobin levels. Previous studies have yielded conflicting results on carboxyhemoglobin levels in cigar and pipe smokers, probably due to differences in the groups under study, as well as insufficient data on past smoking history and inhalation. Goldsmith and Landaw4 in 1968 reported that pipe and cigar smokers had estimated carboxyhemoglobin levels of 1.7 percent, which was only slightly higher than the level of 1.2 percent in nonsmokers. These investigators• attributed this to minimal inhalation; however, they did not specify whether these subjects were primary or secondary smokers or whether they inhaled. Cowie et al6 studied seven cigarette smokers before and after changing to cigars. These researchers6 found the carboxyhemoglobin levels to be similar and, thus, believed that the subjects continued to inhale, although this was not specifically investigated. Castleden and Cole7 in 1973 studied 50 cigar and pipe smokers. Most participants were medical staH. These investigators7 found the secondary smokers to have higher carboxyhemoglobin levels than primary smokers ( 5.2 vs 2.3 percent) but found no significant difference between secondary cigar and pipe smokers. In their study,7 no primary smoker admitted to inhaling. Nine secondary pipe smokers who said they were noninhalers had elevated carboxyhemoglobin levels, suggesting unintentional inhalation. Inhalation by the cigar smokers was not mentioned. A previous study from our laboratory revealed that secondary cigar smokers who intentionally inhaled had very high carboxyhemoglobin levels. 5 The current study extends these findings and reveals that cigar inhalers in general, whether primary or secondary, have very high carboxyhemoglobin levels, while pipe inhalers have carboxyhemoglobin levels similar to cigarette inhalers. It appears that the habit of inhalation and what is smoked, rather than the past smoking history, are the most important determinants of carboxyhemoglobin levels. The differences seen in our study when compared to prior studies may be partly attributable to the populations studied. We studied outpatients and not volunteers or medical personnel. In any event, our experience would seem to be
CHEST, 72: 1, JULY, 1977
more representative of the general population of patients. From this study, it can be seen that patients should refrain from all forms of smoking. Cigar and pipe smokers should be questioned regarding inhalation, and this should particularly be discouraged because of the known consequences of elevated concentrations of carboxyhemoglobin, including reversible secondary polycythemia and an increased incidence of atherosclerosis. 1.s It is also known that cigar and pipe smokers in general have an increased incidence of cancer of the oral cavity, larynx, lung, and esophagus when compared to nonsmokers. 1 Whether some of these malignant neoplasms occur more commonly in a subgroup of patients who inhale remains to be determined.
CHEST, 72: 1, JUlY, 1977
REFERENCES 1 The Health Consequences of Smoking: A Report of the Surgeon General (publication HSM 72-7516). US Department of Health, Education, and Welfare, 1972 2 Wald N, HowardS, Smith PG, et al: Association between atherosclerotic diseases and carboxyhaemoglobin levels in tobacco smokers. Br Med J 1:761-765, 1973 3 Sagone AL, Balcerzak SP: Smoking as a cause of erythrocytosis. Ann Intern Med 82:512-515, 1975 4 Goldsmith JR, Landaw SA: Carbon monoxide and human health. Science 162:1352-1359, 1968 5 Goldman AL : Cigar inhaling. Am Rev Respir Dis 113:8789, 1976 6 Cowie J, Sillett RW, Ball K : Carbon-monoxide absorption by cigarette smokers who change to smoking cigars. Lancet 1:1033-1035, 1973 7 Castleden CM, Cole PV: Inhalation of tobacco smoke by pipe and cigar smokers. Lancet 2:21-22, 1973
CARBOXYHEMOGLOBIN LEVELS IN CIGAR AND PIPE SMOKERS 35