Carbon monoxide and human health

Low-cost apparatus for cigarette smoke exposure in rats

BACKGROUND

The effects of tobacco smoke on the central nervous system are usually studied with isolated nicotine, ignoring other compounds present in cigarette smoke. The few studies that use in vivo whole-body cigarette smoke exposure are usually performed in expensive commercial apparatus.

NEW METHOD

We presented a feasible, safe, and low-cost apparatus for cigarette smoke exposure in rodents.

RESULTS

Rats exposed to cigarette smoke in this apparatus showed cotinine levels similar to human active smokers. Additional results showed that cigarette smoke exposure increased glutamate and aspartic acid levels and decreased leucine, isoleucine, ornithine, phenylalanine, and tryptophan levels in the cerebrospinal fluid of rats.

COMPARISON WITH EXISTING METHOD(S)

Our apparatus is feasible, safe, and costs 67-fold less than a commercial automatized smoking machine. Beyond the low cost, it does not require specialized knowledge for building or maintenance.

CONCLUSIONS

We concluded that our low-cost apparatus is reliable and reproduces cigarette smoke use in humans.

Microcirculation After Trochanteric Femur Fractures: A Prospective Cohort Study Using Non-invasive Laser-Doppler Spectrophotometry

Proximal femur fractures represent a major healthcare problem in the aging society. High rates of post-operative infections are linked to risk factors that seem to affect local microcirculation. Patterns and time courses of alterations in microcirculation have, however, not been previously investigated. The aim of this prospective cohort study was to evaluate perioperative changes in microcirculation after trochanteric femur fractures using non-invasive laser-Doppler spectrophotometry to analyze how oxygen saturation (SO₂), hemoglobin content (Hb) and blood flow changed before and after surgery, and how these parameters were altered by implant type, gender, smoking, diabetes and age. Measurements were separately recorded for nine locations around the greater trochanter in 2, 8, and 15 mm depths, before surgery and 8, 24, 48 h, 4, 7, and 12 days after surgery in 48 patients. Three implants were compared: Dynamic Hip Screw, Gamma3 Nail, and Percutaneous Compression Plate. Surgery resulted in significant differences between the healthy and injured leg in SO₂, Hb and flow. Each parameter showed comparable values for both legs prior to surgery. Significantly higher values in SO₂ and flow were registered in women compared to men before and after surgery. Smoking caused significant increases in SO₂, Hb, and flow only in the superficial layer of the skin after surgery. Diabetes decreased blood flow at 2 and 8 mm depth and increased SO₂ at 8 and 15 mm depth after surgery. Age revealed a significant negative correlation with flow. The ability to increase the flow rate after surgery decreased with age. Comparison of implants indicated the minimally invasive implant PCCP altered microcirculation less than the DHS or the Gamma3 nail. Overall, the proximal femur fracture alone did not alter local skin microcirculation significantly in a way comparable to the effect caused by surgery. In conclusion, microcirculation after proximal femur fractures is highly affected by surgery, gender, smoking, diabetes, age and implant in ways specified in this study.

The Influence of Smoking on the Variations in Carboxyhemoglobin and Methemoglobin During Urologic Surgery

Introduction:

Surgery is supposed to modulate the production of carbon monoxide by the reduction of heme oxygenase activity or transcriptional regulation of inducible heme oxygenase. On the other hand, the inhalation of tobacco smoke can substantially raise the level of carboxyhemoglobin in the blood. Furthermore, methemoglobin is maintained at a constant level. However, excessive production of methemoglobin relative to total methemoglobin reductase activity results in methemoglobin increase.

Aim:

The aim of our study was to investigate the perioperative variations of carboxyhemoglobin and methemoglobin during urologic surgeries, and at the same time to evaluate the changes in methemoglobin as a possible indicator of nitric oxide generation. Our second aim was to evaluate the effect of preoxygenation on the level of carboxyhemoglobin and methemoglobin and the influence of blood transfusion on their changes.

Material and methods:

The study included 30 patients scheduled for urologic surgery under general endotracheal anesthesia, aged 18–60 years without any history of respiratory disease, divided into two groups. The study group comprised patients who were smoking cigarettes or tobacco pipe, while the control group included non-smokers. In both groups carboxyhemoglobin (COHb) and methemoglobin (MetHb) levels were determined preoperatively, after preoxygenation, and postoperatively.

Results:

COHb levels were decreased postoperatively in both groups. The average values of COHb between the two groups were statistically significantly different (p=0.00). MetHb levels increased postoperatively in the group of smokers and decreased in the group of non-smokers. There were no statistically significant differences in the average postoperative MetHb levels between the two groups.

Conclusion:

Changes in carboxyhemoglobin and methemoglobin concentrations in arterial blood occur during urologic surgery, although these amplitudes are small when compared with carbon monoxide intoxication and methemoglobinemia. It is likely that organ perfusion and functions are affected by these monoxide gas mediators during urologic surgery.

Active Smoking and Hematocrit and Fasting Circulating Erythropoietin Concentrations in the General Population

Cigarette smoking continues to be one of the major risk factors for increased morbidity and mortality worldwide. Among many adverse health effects, smoking can induce erythrocytosis, which is commonly believed to result from elevated serum erythropoietin (EPO) levels. Currently, however, this notion is only alleged, without data available to substantiate it. Hence, we analyzed data from the Prevention of Renal and Vascular End-Stage Disease study, a prospective population-based cohort study. Smoking behavior was quantified as number of cigarettes smoked per day and as 24-hour urinary cotinine excretion levels, an objective and quantitative measure of nicotine exposure. In 6808 community-dwelling participants, the prevalence of nonsmokers, former smokers, and current smokers were 29%, 43%, and 28%, respectively. Hematocrit levels were higher in current smokers (41.4%±3.6%) than in nonsmokers (40.3%±3.6%) (P<.001). In contrast, median EPO levels were lower in current smokers (7.5 IU/L; interquartile range [IQR], 5.7-9.6 IU/L) than in nonsmokers (7.9 IU/L; IQR, 6.0-10.7 IU/L) (P<.001). In multivariate linear regression analysis, current smoking, compared with nonsmoking, was independently positively associated with hematocrit levels (β=.12; P<.001) and hemoglobin levels (β=.11; P<.001), but inversely associated with EPO levels (β=-.09; P<.001). In sensitivity analyses, we observed a dose-dependent inverse association of smoking exposure reflected by 24-hour urinary cotinine excretion levels with EPO levels. Contrary to common belief, we identified that in the general population, smoking is inversely associated with EPO levels. Future mechanistic insight is needed to unravel the currently identified association, and if reproduced in other studies, guidelines for diagnosis of secondary erythrocytosis may need to be revisited.

Progress in the reduction of carbon monoxide levels in major urban areas in Korea

Long-term trends in observed carbon monoxide (CO) concentrations were analyzed in seven major South Korean cities from 1989 to 2013. Temporal trends were evident on seasonal and annual timescales, as were spatial gradients between the cities. As CO levels in the most polluted cities decreased significantly until the early 2000s, the data were arbitrarily divided into two time periods (I: 1989-2000 and II: 2001-2013) for analysis. The mean CO concentration of period II was about 50% lower than that of period I. Long-term trends of annual mean CO concentrations, examined using the Mann-Kendall (MK) method, confirm a consistent reduction in CO levels from 1989 to 2000 (period I). The abrupt reduction in CO levels was attributed to a combination of technological improvements and government administrative/regulatory initiatives (e.g., emission mitigation strategies and a gradual shift in the fuel/energy consumption mix away from coal and oil to natural gas and nuclear power).

Relation between workplace accidents and the levels of carboxyhemoglobin in motorcycle taxi drivers

OBJECTIVE: to investigate the relation between workplace accidents and the levels of carboxyhemoglobin found in motorcycle taxi drivers. METHOD: correlational, quantitative study involving 111 workers and data obtained in July 2012 through a questionnaire to characterize the participants and blood collection to measure carboxyhemoglobin levels. RESULT: 28.8% had suffered workplace accidents; 27.6% had fractured the lower limbs and significant symptoms of carbon monoxide exposure were verified in smokers. The carboxyhemoglobin levels were higher among smokers and victims of workplace accidents. CONCLUSION: motorcycle taxi drivers had increased levels of carboxyhemoglobin, possibly due to the exposure to carbon monoxide; these levels are also increased among smokers and victims of workplace accidents. The study provides advances in the knowledge about occupational health and environmental science, and also shows that carboxyhemoglobin can be an indicator of exposure to environmental pollutants for those working outdoors, which can be related to workplace accidents.

Effect of smoking on age at the time of coronary artery bypass graft surgery; baseline data results from the ROSETTA-CABG registry

BACKGROUND

Coronary artery disease (CAD) is a leading cause of death. The aetiology of this disease is not known, but many important risk factors have been recognised.

OBJECTIVE

To evaluate the effect of smoking on age at the time of coronary artery bypass graft surgery (CABG), and to examine this finding in the light of medical literature.

METHODS

The authors recruited patients immediately after CABG in a prospective, study in 16 centres and enrolled 408 patients, of which 395 were ultimately analysed.

RESULTS

Among the 395 patients analysed, there were 60 smokers and 335 non-smokers. The smokers were 8.4 years younger than non-smokers at the time of index CABG. The average age of smokers was 55.79.0 years, and that of non-smokers was 64.1±9.9 years (p<0.001). Hyperlipidaemia was present in 76.7% of smokers and 74.6% of non-smokers (p-NS). Hypertension was present in 58.3% of smokers and 63.9% of non-smokers (p-NS). Diabetes mellitus was present in 21.3% of smokers and 29.3% of non smokers (p-NS). Left ventricular ejection fraction was 53.0±10.5% in smokers and 53.3 ±13.8% in non-smokers (p-NS). Myocardial infarction had occurred in 41.7% of smokers and 35.5% of non-smokers (p-NS).

CONCLUSION

Smoking accelerates atherosclerosis and coronary thrombosis resulting in severe form of CAD that cannot be managed by medications or PCI, and requires coronary artery bypass graft surgery (CABG) 8.4 years earlier than non-smokers.

The Wisconsin Epidemiologic Study of Diabetic Retinopathy XXIII: the twenty-five-year incidence of macular edema in persons with type 1 diabetes

OBJECTIVE

To examine the 25-year cumulative incidence of macular edema (ME) and its relation to various risk factors.

DESIGN

Population-based study.

PARTICIPANTS

A total of 955 insulin-taking persons living in an 11-county area in southern Wisconsin with type 1 diabetes diagnosed before age 30 years who participated in baseline examinations (1980-1982) and at least 1 of 4 follow-up (4-, 10-, 14-, and 25-year) examinations (n=891) or died before the first follow-up examination (n=64).

METHODS

Stereoscopic color fundus photographs were graded using the modified Airlie House classification and the Early Treatment Diabetic Retinopathy Study retinopathy severity scheme. Competing risk of death was included in statistical models.

MAIN OUTCOME MEASURES

Incidence of ME and clinically significant ME (CSME).

RESULTS

The 25-year cumulative incidence was 29% for ME and 17% for CSME. Annualized incidences of ME were 2.3%, 2.1%, 2.3%, and 0.9% in the first, second, third, and fourth follow-up periods of the study, respectively. In univariate analyses, the incidence of ME was associated with male sex, more severe diabetic retinopathy, higher glycosylated hemoglobin, proteinuria, higher systolic and diastolic blood pressure, and more pack-years of smoking. Multivariate analyses showed that the incidence of ME was related to higher baseline glycosylated hemoglobin (hazard ratio [HR] per 1% 1.17; 95% confidence interval [CI], 1.10-1.25; P<0.001) and higher systolic blood pressure (HR per 10 mmHg 1.15; 95% CI, 1.04-1.26; P=0.004) and marginally to proteinuria (HR 1.43; 95% CI, 0.99-2.08; P=0.06).

CONCLUSIONS

These data show that relatively high 25-year cumulative rates of incidence of ME were related to glycemia and blood pressure. The lower risk of incident ME in the last period of the study may reflect recent improvement in care.

Zinc Protoporphyrin: A Metabolite with a Mission

Zinc protoporphyrin (ZnPP) is a normal metabolite that is formed in trace amounts during heme biosynthesis. The final reaction in the biosynthetic pathway of heme is the chelation of iron with protoporphyrin. During periods of iron insufficiency or impaired iron utilization, zinc becomes an alternative metal substrate for ferrochelatase, leading to increased ZnPP formation. Evidence suggests that this metal substitution is one of the first biochemical responses to iron depletion, causing increased ZnPP to appear in circulating erythrocytes. Because this zinc-for-iron substitution occurs predominantly within the bone marrow, the ZnPP/heme ratio in erythrocytes reflects iron status in the bone marrow. In addition, ZnPP may regulate heme catabolism through competitive inhibition of heme oxygenase, the rate-limiting enzyme in the heme degradation pathway that produces bilirubin and carbon monoxide. Physiological roles, especially relating to carbon monoxide and possibly nitric oxide production, have been suggested for ZnPP. Clinically, ZnPP quantification is valuable as a sensitive and specific tool for evaluating iron nutrition and metabolism. Diagnostic determinations are applicable in a variety of clinical settings, including pediatrics, obstetrics, and blood banking. ZnPP analytical methodologies for clinical studies are discussed. In addition to diagnostic tests and metabolic studies, ZnPP has a potential therapeutic application in controlling bilirubin formation in neonates as a preventive measure for hyperbilirubinemia. Biochemical research techniques, both in vivo and in vitro, are described for further studies into the role of ZnPP in metabolism and physiology.

Low-level carbon-monoxide poisoning: inability of neuropsychological testing to identify patients who benefit from hyperbaric oxygen therapy

INTRODUCTION

Although major sequelae of carbon-monoxide (CO) poisoning and its treatment with hyperbaric oxygen (HBO) are well-documented, a syndrome of low-level CO poisoning has received relatively little attention. Subtle symptoms of poor concentration, language difficulty, problems with calculations, and memory loss were noted after an acute exposure of 131 dormitory residents to low levels of CO. The CO Neuropsychological Screening Battery (CONSB), a series of tests reported by others as useful to identify victims of CO poisoning, was performed on a subset of 46 victims. It was hypothesized that their test scores would improve after treatment with HBO.

METHODS

Testing was performed both before and after HBO on 35 CO-exposed victims. A control group of 20 students residing on the same college campus, but not involved with the CO incident, also were tested on two separate occasions to assess the ability of the test to identify selectively victims of low-level CO poisoning, as well as to evaluate its validity when administered serially.

RESULTS

Both CO-exposed and control subjects demonstrated significant performance improvement when completing the testing for the second time. In addition, the baseline test scores were not significantly different for either the CO-exposed or the control groups. Nonetheless, all CO-exposed victims reported immediate subjective improvement of their symptoms after HBO therapy.

CONCLUSION

These observations and a review of the literature suggest that there might exist a syndrome of subtle neurological disturbances in victims of low-level CO poisoning. Whether this is permanent or might regress spontaneously over time is unknown. As a diagnostic adjunct, the CONSB does not appear to be as useful in low-level CO poisoning.

Effects of carbon monoxide exposure in patients with documented cardiac arrhythmias

OBJECTIVE

This study was designed to determine whether carbon monoxide has proarrhythmic effects at rest and during upright exercise in patients with myocardial ischemia and moderate baseline ectopic activity.

BACKGROUND

Exposure of patients with documented myocardial ischemia to low levels of carboxyhemoglobin (COHb) alters the myocardial response to exercise. Anecdotal reports from patients with myocardial ischemia have noted the development of arrhythmias related to carbon monoxide exposure. Increased frequency of arrhythmias related to carbon monoxide exposure in patients performing supine bicycle exercise has been recently reported.

METHODS

Twenty-eight nonsmoking men and five nonsmoking women with documented coronary artery disease and a minimum of 30 ventricular ectopic beats/h over a 20-h period were studied. Subjects were exposed in a randomized double-blind fashion to either room air or sufficient carbon monoxide to elevate their COHb concentration to 3% or 5% in 1 h, followed by a maintenance exposure to carbon monoxide. The subjects then left the laboratory and resumed their normal daily activity to determine changes in ventricular ectopic beats after carbon monoxide exposure.

RESULTS

There was no significant change in the frequency of single ventricular ectopic beats at rest from 115 +/- 28 (in room air) to 121 +/- 31 at 3% COHb to 94 +/- 23 at 5% COHb. Exercise itself increased the frequency of ventricular ectopic beats, but there was no additional effect of carbon monoxide exposure on the exercise-induced increase in isolated ectopic beats or complex ectopic waveforms. Analysis of the data based on grouping of the subjects by the severity of disease (ventricular ectopic beat frequency, ejection fraction, presence of exercise-induced ischemia) indicated no proarrhythmic effect of carbon monoxide.

CONCLUSIONS

In patients with frequent ventricular ectopic activity (> or = 30 ectopic beats/h), exposure to carbon monoxide producing either 3% or 5% COHb does not increase arrhythmia frequency of single or multiple beats during rest or exercise.

Population characteristics and cigarette yield as determinants of smoke exposure

Relationships of population characteristics, smoking history, and cigarette yield with smoke exposure as measured by peripheral blood concentrations of thiocyanate, carboxyhemoglobin, nicotine and cotinine were sought in 170 male smokers. This population of smokers had significant elevations of serum thiocyanate, blood carboxyhemoglobin and plasma nicotine and cotinine concentrations as compared with an equal number of age- and sex-matched nonsmokers and these concentrations correlated significantly with past 24-hour cigarette consumption. Although the nicotine yield of the cigarette correlated significantly with plasma cotinine and marginally with plasma nicotine, the reduction in plasma nicotine and cotinine was not proportionate to the reduced yield of the cigarettes, suggesting that smokers partially compensate for the lower yields of their cigarettes. Blood levels of carboxyhemoglobin, nicotine and cotinine were also significantly associated with the weight of the subjects, presumably due to the relationship between weight and the volume of distribution. Univariate and multiple regression analyses provided evidence that coffee and alcohol consumption and years smoked also may be important determinants of smoke exposure.

Carbon monoxide, carbon disulfide, lead and cadmium--four examples of occupational toxic agents linked to cardiovascular disease

A variety of industrial agents to which large segments of the population are exposed have been linked to the development of cardiovascular disease. These toxic agents, which include carbon monoxide, carbon disulphide, lead, and cadmium, are produced by a wide variety of industrial processes and so are ubiquitous in the modern industrial environment. Although the mechanisms by which such toxins may contribute to cardiovascular disease are not well defined, there are at least four possible theories that have received clinical and experimental support. The postulated mechanisms by which such toxins may play a role in vascular disease are: (1) an increase in blood pressure; (2) an increase in the levels of blood cholesterol and/or an induction of lipid accumulation in vessel walls; (3) an induction of a lipid peroxidation process thereby increasing the tendency of blood clotting; and (4) a promotion of a mutation in the arterial cell wall.

The effects of low-level carbon monoxide exposure upon evoked cortical potentials in young and elderly men

The neurophysiological effects of acute, low-level carbon monoxide (CO) exposure are not well known. This experiment investigated the effects of a 5% carboxyhemoglobin level upon two indices of neurophysiological function, reaction time and the late positive component of the visual evoked potential in young and elderly men. Results indicated (1) no effects of CO upon any of the neurophysiological indices and (2) greater absorption of CO by young than by elderly men. These results, along with those of other studies, indicate that acute, low-level CO exposure is probably not neurotoxic, in normal, healthy men.

Neurological manifestation of carbon monoxide poisoning

The clinical signs and post-mortem findings in a case of carbon monoxide poisoning are described, and correlated with the computer tomographic (CT) scan appearances. The value of serial CT scanning as a diagnostic tool is highlighted.

Acute effects of routine firefighting on lung function

We undertook a study to determine the acute effects of routine firefighting on lung function and the relationship between these acute effects and nonspecific airway responsiveness. For 29 firefighters from a single fire station, we calculated the concentration of methacholine aerosol that caused a 100% increase in specific airway resistance (Pc100). Over an 8-week period we than measured FEV1 and FVC in each firefighter before and after each 24-hr workshift and after every fire. From 199 individual workshifts without fires, we calculated the mean +/- 2 SD across-workshift change in FEV1 and FVC for each firefighter. Eighteen of 76 measurements obtained within 2 hr after a fire (24%) showed a greater than 2 SD fall in FEV1 and/or FVC compared to two of 199 obtained after routine workshifts without fires (1%; p less than .001). On 13 of 18 occasions when spirometry decreased significantly, we obtained repeat spirometry (postshift) 3-18.5 hr after fires, and on four of these occasions FEV1 and/or FVC were still more than 2 SD below baseline. Decrements in spirometry occurred as often in firefighters with high Pc100s as in those with low Pc100s. In two firefighters in whom FEV1 and FVC fell by more than 10% after fires, we repeated measurements of methacholine sensitivity, and it was increased over the prestudy baseline. These findings suggest that routine firefighting is associated with a high incidence of acute decrements in lung function.(ABSTRACT TRUNCATED AT 250 WORDS)

Marijuana smoking: effect on expired air carbon monoxide levels

A group of regular marijuana smokers was given expired air carbon monoxide (CO) tests before and after smoking low-dose, high-dose, and placebo marijuana cigarettes. Expired air CO doubled following smoking. There were no significant differences in CO levels in the different dose categories. Studies of the effects of marijuana on the body should attempt to separate effects of the drug from the effects that are secondary to the method of intake.

Exacerbation of coronary artery disease by occupational carbon monoxide exposure: a report to two fatalities and a review of the literature

The recent deaths of two workers with coronary artery disease (CAD) following exposure to carbon monoxide (CO) at work reinforced our appreciation of the hazard of this exposure to individuals with preexisting heart disease. Carbon monoxide acts to precipitate ischemia by reducing oxygen delivery to the myocardium. Animal and in vitro experiments suggest that CO may accelerate the development of atherosclerosis, particularly if exposure is in association with other risk factors. Thus, persons with known CAD who are exposed to CO at work are at risk for both the acceleration of the course of the underlying disease and for precipitation of acute ischemia or infarction following excessive exposure. Particular attention should be given to control of CO exposures in light of this hazard. For various reasons, preplacement evaluations or other job selection procedures do not adequately address his hazard. In view of the high prevalence of CAD in the U.S. and the high frequency of workplace exposure to CO, particular attention should be given to control of CO exposure through industrial hygiene measures.

Geographical patterns of heart disease in the Northeastern United States

A 49-county region surrounding the urban corridor from New York through New Jersey to Philadelphia was the focus of an investigation of the spatial patterns of mortality from four types of heart disease: major cardiovascular, acute ischemic, chronic ischemic and cerebrovascular. The data used were age-adjusted mortality rates for white males and white females for the period 1968-1972. Central to the research was interest in the existence of county clusters with similar rates, high and low risk areas and possible associations of mortality rates with environmental and socioeconomic conditions. The tasks completed in this first phase of a projected multi-phase project led to the identification of four country clusters within the region. High major cardiovascular rates appear to make the Southern New Jersey cluster a high risk zone. In contrast, a Central Corridor cluster has relatively low rates for all the diseases. No clear pattern was in evidence for the Northwestern Periphery cluster. Finally, a stark contrast between acute and chronic ischemic rates appeared in the Urban Spur. The next step in this research will be to search for either consistency or deviation from these patterns in the 1973-1976 period. A risk factor data set will be created to analyze the patterns in greater detail.

Haptoglobin concentrations in children aged 9-10 years and its correlation to indirect parameters of erythrocyte turnover

Low serum haptoglobin values are often found in children. Nine different parameters were studied in 125 healthy children aged 9-10 years to get indirect information on erythrocyte turnover and its possible relation to the low mean plasma haptoglobin level in childhood. The mean LD activity was higher than in adults. The mean carboxyhaemoglobin per cent saturation (COHb %) and the mean serum haptoglobin concentrations were lower than in adults. No significant correlation was found between serum haptoglobin and serum iron, serum bilirubin and COHb %. Significant correlation at low r-values was found between serum iron, serum bilirubin and COHb %. The low serum haptoglobin levels often seen in children seemed not to be caused by an increase in erythrocyte turnover.

A study of carboxyhaemoglobin levels of cigarette and sheesha smokers in Saudi Arabia

A single carboxyhaemoglobin (COHb) estimation of late evening blood sample among non-smokers, cigarette smokers, and sheesha smokers was evaluated among Saudis. The COHb level in smokers of 15 to 40 cigarettes a day ranged between 0.7 and 10.3 with a mean value of 6.1 +/- 2.58 COHb. Values among sheesha smokers ranged between 6.5 and 13.9 with a mean value of 8.8 +/- 1.83, significantly higher than those of cigarette smokers (P less than 0.001) for a given degree of exposure to tobacco smoke.

Diurnal levels of immunoreactive erythropoietin in normal subjects and subjects with chronic lung disease

Serum levels of immunoreactive erythropoietin (Ep) were measured in 48 normal male and female volunteers, ages 20-60 years, to establish a control value for Ep of 18.5 +/- 5.0 (mean +/- SD) mU/ml. Levels of the hormone were also measured sequentially over a 24 h period of time in an additional 17 'normal' volunteers with no diurnal variation. Diurnal levels of immunoreactive Ep were also measured in 30 subjects, with chronic lung disease. These patients, in contrast to normal subjects exhibited a diurnal variation in the level of immunoreactive Ep with peak levels occurring at midnight. The only variable measured which correlated with the serum immunoreactive Ep level in subjects with chronic lung disease was the level of carboxyhaemoglobin (P less than 0.02).

Carbon monoxide in breath in relation to smoking and carboxyhaemoglobin levels

Carboxyhaemoglobin (COHb) levels were studied in 11 249 men. The distribution among the 2613 men who smoked cigarettes was well separated from that in 6641 non-smokers (including ex-smokers). The distribution for 2005 cigar and pipe smokers was intermediate, though some of the highest COHb levels occurred in cigar smokers. Using a COHb cut-off level of 2%, 81% of cigarette smokers, 35% of cigar and pipe smokers, and 1.0% of non-smokers had raised COHb levels. In a subsidiary experiment alveolar air samples were collected from 162 smokers and 25 non-smokers using a simple breath sampling technique. Carbon monoxide concentrations in alveolar breath were highly correlated with COHb levels (r = 0.97) indicating that COHb levels can be estimated reliably by measuring the concentration of carbon monoxide in breath. Alveolar carbon monoxide measurement is thus a simple method of estimating whether a person is likely to be a smoker.

Augmentation of myocardial ischemia by low level carbon monoxide exposure in dogs

This study was conducted to determine whether low level exposure to carbon monoxide would increase myocardial ischemia associated with acute myocardial infarction. An hour after coronary artery ligation, eleven anesthetized dogs underwent five sequential respiratory exposures to 5,000 ppm carbon monoxide, producing mean blood carboxyhemoglobin levels of 4.9% to 17.0%. Ischemia, as indicated by the amount of S-T segment elevation in epicardial electrocardiograms, increased significantly at the lowest carboxyhemoglobin level and increased further with increasing carbon monoxide exposure. These changes occurred in the absence of altered heart rate, blood pressure, left atrial pressure, cardiac output, or blood flow to ischemic myocardium. Flow to non-ischemic myocardium increased with carbon monoxide exposure, the percentage increase being approximately double the increase in carboxyhemoglobin level. Thus, low level exposure to carbon monoxide can significantly augment ischemia in acute myocardial infarction, apparently through a reduction in oxygen supplied to ischemic tissue. The data suggest that hypoxia induced by carbon monoxide exposure is more severe than can be accounted for by a simple reduction in oxygenated hemoglobin.

Brake reaction time--effects of age, sex, and carbon monoxide

Simulated braking responses have been tested in relation to blood carboxyhemoglobin (HbCO) levels. The main determinants of percentage of HbCO in 352 subjects attending a fall fair were daily cigarette consumption and minutes since the last cigarette. In women the brake response time deteriorated from age 16 yr, but in the men there was an improvement from age 16 to the early 20s. Times at all ages were better for men than for women. Average response times and the rate of aging of the braking response were very similar in smokers and in nonsmokers. In the nonsmokers, however, response time with step function CO increments of as much as 7% HbCO. There was a suggestion of a small increase of reaction time, with an opposing decrease of leg movement time, during the first few minutes after CO exposure; nevertheless, these trends were statistically insignificant.

Smokers' polycythemia

Twenty-two smokers with elevated hematocrits (mean, 54 per cent) had elevated blood carboxyhemoglobin (mean, 11.6 per cent; normal, less than 1 per cent) and a "left-shifted" oxygen-hemoglobin dissociation curve (mean P50, 21.6 +/- 2.3 [+/- S.D.] torr; normal, 26.7 +/- 1.1). Red-cell volume was increased in 14 of 18, and plasma volume reduced in 14 of 18. Fatigue and headache were common, and syncopal attacks occurred in four patients. Symptoms disappeared and the elevated red-cell volume decreased markedly in all five patients who were able to reduce severely their smoking habit; low plasma volume increased in three of four patients studied. We conclude that carbon monoxide exposure from cigar and cigarette smoke is a frequent cause of an elevated red-cell volume or a reduced plasma volume (or both). Measurement of carboxyhemoglobin should be a routine part of the evaluation of all polycythemic subjects.

Carboxyhemoglobin levels in primary and secondary cigar and pipe smokers

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 similar carboxyhemoglobin levels that were significantly higher than nonsmokers (5.6, 5.0, 5.4, and 1.0 percent, respectively). Cigar inhalers had markedly elevated concentrations 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 past smoking history, is the most important factor in determining the carboxyhemoglobin level for each type of smoke.

Secondary polycythaemia in chronic respiratory insufficiency

The relationship between polycythaemia, P50 and SaCO (saturation in carboxyhaemoglobin) has been studied in 50 patients who were hypoxaemic due to chronic respiratory insufficiency. These patients were divided into two groups according to their haemoglobin concentration and haematocrit: 21 polycythaemic patients with haemoglobin greater than or equal to 16 g/dl and haematocrit greater than or equal to 50% and 29 patients without polycythaemia. PaO2, PaCO2, plasma and erythrocyte pH, haemoglobin, haematocrit, and carbon monoxide saturation and intraerythrocytic 2-3 diphosphoglycerate concentration were measured during steady-state ventilation. All polycythaemic patients were smokers and their carbon level was significantly higher than that observed in patients without polycythaemia. Additionally, their P50 and 2-3 DPG concentration were significantly lower than in patients without polycythaemia. The correlations between P50 and HbCO and between Hb and HbCO were significant (r=--0-672; r=0-552 respectively: P less than 0-001). Eleven non-polycythaemic patients who were smokers had a high level of HbCO but normal P50. A group of 29 normoxic subjects was also studied, 14 non-smokers and 15 smokers with a high HbCO level. The mean value of P50 was lower in smokers and their haematocrit was higher although the difference was not significant for the latter. The HbCO increase by tobacco seems to be a factor in the occurrence of polycythaemia in patients with chronic respiratory insufficiency. The level of increase of HbCO and/or its duration and perhaps other individual factors and explain why all patients with high HbCO level and hypoxaemia were not polycythaemic.

Expired air carbon monoxide and serum thiocyanate as objective measures of cigarette exposure

Expired air carbon monoxide (CO) and serum thiocyanate (SCN) were used to asses exposure to cigarettes in 139 middle-aged men. Subjects who reported smoking cigarettes generally had CO levels exceeding 8ppm and SCN levels exceeding 100umol/L; non-smokers had lower levels. For both tests the mean concentration among men smoking more than one pack daily was three times that of non-smokers. The is a high correlation between the two tests (r=.571 for smokers), an association that was largely independent of the smaller correlations between either test and reported smoking frequency (r=.476 for CO; r=.479 for SCN). The ability to distinguish between individuals who reported "typical" smoking habits and non-smokers was best when the CO and SCN analyses were used together to take advantage of their separate sources of variance; it was 99 per cent when the two tests were mutually concordant (91 per cent of cases). The CO and SCN measurements allowed 16 individuals who reported light smoking habits to be categorized into high and low presumptive tobacco exposure groups. The two tests are inexpensive and suitable for use in epidemiologic and health care delivery programs.