Relationship of respiratory symptoms and pulmonary function to tar, nicotine, and carbon monoxide yield of cigarettes

Acute changes in left ventricular diastolic function: cigarette smoking versus nicotine gum

BACKGROUND

Echocardiographic evidence of diastolic dysfunction has been demonstrated during acute cigarette smoking in patients with coronary artery disease. Similar studies in healthy patients have shown conflicting results. Furthermore, it is unclear whether nicotine or some other cigarette-related substance is responsible for these observations.

HYPOTHESIS

The purpose of the study was to confirm or refute acute effects of cigarette smoking on diastolic function in healthy patients and to compare diastolic effects of a cigarette to smokeless nicotine delivery (nicotine gum).

METHODS

In all, 27 healthy volunteers were self-assigned into one of two cohorts. A baseline echocardiogram was performed in all patients. The first cohort proceeded to smoke a cigarette and the second to chew a piece of nicotine gum. Within minutes after exposure, another echocardiogram was performed. Traditional measures of diastolic function were compared before and after substance exposure by paired t-tests.

RESULTS

The cigarette cohort showed echocardiographic evidence of diastolic dysfunction after smoking. The E:A ratio (time integral) decreased from 2.95 to 2.22 (p < 0.002). Atrial reversal pulmonary velocity, atrial reversal duration, and color flow propagation all showed statistically significant alterations (p < 0.05). The nicotine gum cohort showed no change in traditional diastolic parameters.

CONCLUSIONS

Diastolic function is impaired during acute exposure to cigarette smoke but unchanged after exposure to nicotine gum. It is therefore unlikely that nicotine alone is responsible for cigarette-induced acute diastolic dysfunction.

Mechanisms of chronic airway obstruction in smokers

Studies over the past few decades have showed a clear association between cigarette smoking and the development of chronic airway obstruction. Yet, only a minority of smokers is affected so that in many, even heavy, smokers, pulmonary function remains within normal limits. While carcinogens have been well characterized, there is only limited information about the constituents of cigarette smoke responsible for inducing chronic airway obstruction. In addition, the associated risks factors for airway obstruction in smokers have not been totally identified. The present paper is a review of the recently accumulated facts concerning the intimate action of cigarette smoke at the level of large and small airways and lung parenchyma. The role of classical inflammatory cells such as neutrophils and alveolar macrophages is reviewed, but emphasis is put on recent evidence indicating the involvement of CD8 + T-lymphocytes and possibly eosinophils in the genesis of the structural changes leading to airways obstruction. The mechanisms by which airway inflammation and remodelling cause airway narrowing and airflow limitation are discussed, along with the associated loss of lung elasticity secondary to destructive emphysema. Other biological, epidemiological, physiopathological, and clinical aspects are analyzed, stressing such fundamental aspects as the defence mechanisms, the morpho-functional correlations, the identification of susceptible smokers, and the early detection of airway obstruction, both in specialized laboratories and in primary care.

Cigarette smoking and dyspnea perception

Cigarette smoking has been implicated as an important risk factor for the development of respiratory symptoms in adults. The relationship of dyspnea with cigarette smoking has been examined in smokers and ex-smokers and the beneficial effects of smoking cessation have been demonstrated. Recent studies reported that in subjects who smoke cigarettes the risk of developing respiratory symptoms is higher in a dose-dependent way. Environmental tobacco smoke heavily influences the incidence of respiratory symptoms in both adults and in children. Up to the present time, the mechanisms whereby cigarette smoking causes dyspnea perception remain to be defined. Abnormalities in sensory nerves might diminish the perception of bronchoconstriction in smokers. In this regard, it has been postulated that prolonged exposure to cigarette smoke may lead to chronic depletion of sensory nerve neurotransmitters. Eosinophil airway inflammation has been proposed as a determinant of breathlessness via mechanisms affecting either the mechanical pathways that control breathlessness or the afferent nerves involved in perception of dyspnea. An increased number of eosinophils in some smokers implies the possibility that smoking may trigger immunological or other reactions associated with eosinophilia. In conclusion, cigarette smoking is by far one of the greatest risk factors for most respiratory symptoms, including dyspnea. Smoking is associated with the development of symptoms in a dose-dependent way and eosinophilia and airway hyperresponsiveness (AHR) increase the risk of developing dyspnea.

Effects of cigarette smoke with different tar contents on hepatic and pulmonary xenobiotic metabolizing enzymes in rats

The effects of smoke from cigarettes with two different tar contents (32 mg/cigarette, high tar, and 15 mg/cigarette, low tar) on hepatic and pulmonary monooxygenase (MO) activities (aniline 4-hydroxylase [AH]; aminopyrine N-demethylase [AMND]; 7-ethoxyresorufin O-deethylase [EROD]; p-nitroanisole O-demethylase [p-NAOD]), lipid peroxidation (LP) and reduced glutathione (GSH) levels and glutathione S-transferase (GST) activities toward several substrates (1-chloro-2,4-dinitrobenzene [CDNBI; 1,2-dichloro-4-nitrobenzene [DCNB]; ethacrynic acid [EAA]; 1,2-epoxy-3-(p-nitrophenoxy)-propane [ENPP]) were determined in adult male rats. Adult male rats were exposed to smoke of high- or low-tar cigarettes five times a day, with 1-hour intervals, for 3 days in a chamber where smoke and fresh air lead alternatively and were killed 16 hours after the last treatment. Smoke of both high- and low-tar cigarettes (SHTCC and SLTCC) significantly increased hepatic and pulmonary EROD and p-NAOD activities compared to controls. However, the increase noted by SHTCC on pulmonary EROD activity was higher than that of SLTCC. Hepatic AMND and pulmonary AH activities were significantly increased only by SHTCC. LP level was significantly decreased and increased by SHTCC in liver and lung, respectively, whereas it remained unaltered by SLTCC. Only SHTCC significantly increased GSH level in liver. In the lungs, both SHTCC and SLTCC significantly increased GSH level to the same extent. Hepatic GST activity toward EAA was significantly increased by SHTCC but was significantly decreased by SLTCC. ENPP GST activity was significantly decreased by SHTCC and SLTCC in the livers. In the lungs, all the GST activities examined were significantly depressed by SHTCC whereas only GST activity toward DCNB was reduced significantly by SLTCC. These results reveal that the hepatic and pulmonary MOs and GSTs are differentially influenced by SHTCC and SLTCC in rats.

Health impact of "reduced yield" cigarettes: a critical assessment of the epidemiological evidence

Cigarettes with lower machine measured "tar" and nicotine yields have been marketed as "safer" than high tar products over the last four decades, but there is conflicting evidence about the impact of these products on the disease burden caused by smoking. This paper critically examines the epidemiological evidence relevant to the health consequences of "reduced yield" cigarettes. Some epidemiological studies have found attenuated risk of lung cancer but not other diseases, among people who smoke "reduced yield" cigarettes compared to smokers of unfiltered, high yield products. These studies probably overestimate the magnitude of any association with lung cancer by over adjusting for the number of cigarettes smoked per day (one aspect of compensatory smoking), and by not fully considering other differences between smokers of "high yield" and "low yield" cigarettes. Selected cohort studies in the USA and UK show that lung cancer risk continued to increase among older smokers from the 1950s to the 1980s, despite the widespread adoption of lower yield cigarettes. The change to filter tip products did not prevent a progressive increase in lung cancer risk among male smokers who began smoking during and after the second world war compared to the first world war era smokers. National trends in vital statistics data show declining lung cancer death rates in young adults, especially males, in many countries, but the extent to which this is attributable to "reduced yield" cigarettes remains unclear. No studies have adequately assessed whether health claims used to market "reduced yield" cigarettes delay cessation among smokers who might otherwise quit, or increase initiation among non-smokers. There is no convincing evidence that past changes in cigarette design have resulted in an important health benefit to either smokers or the whole population. Tobacco control policies should not allow changes in cigarette design to subvert or distract from interventions proven to reduce the prevalence, intensity, and duration of smoking.

Smoking and chronic obstructive pulmonary disease

Smoking is overwhelmingly the major cause of chronic bronchitis and emphysema worldwide. Additional risk factors for developing COPD are presented, along with the variables that govern cigarette smoke deposition in the lung. Major paradigms for the pathogenesis of COPD, including the protease-antiprotease and oxidant-antioxidant theories are described, and evidence for impaired reparative mechanisms in the causation of emphysema is noted. A description of the natural history of declining lung function in smokers and in the susceptible subset of smokers that ultimately develop smoking-induced COPD is accompanied by a discussion of the effects of smoking cessation on preservation of lung health. The disordered ventilation and gas-exchange physiology in the cigarette smoke-damaged lung is explained on the basis of the observed morphological changes.