Effects Of Tobacco Smoking On+Gz Tolerance In Pilots And Its Mechanism

BackgroundThe world health organization indicates that global of widespread death anddisease popularity is highly correlated to tobacco overuse. The population ofsmokers is up to 3.5 billion in China, and smoking leads to 100 million deathsannually. Due to irregular life and long-term mental stress, the problem ofsmoking in pilots is much more serious. With the emergence of highperformance fighter, persistent high G acceleration, high G growth and highcognitive load, the requirements for pilots' body almost reach the physiologicallimits. Tobacco and its burning smoke contain lots of substance which harmfulto human body. The greatest influence on people-airplane is acceleration (Gz),when pilots steer airplanes in high speed. +Gz tolerance is one of the routineexaminations in selection of fighter pilots, which also determines whether pilotscan fly or not. +Gz is comprehensive results of physiological regulation andreaction of constitutional or physical factors, and the function of cardiovascularsystem plays an important role in +Gz tolerance. If pilots fail to make theappropriate adjustments under the condition of +Gz, dizziness, blurred vision, oreven G-induced loss of consciousness (G-LOC) will happen, which seriouslythreaten flight safety. It is suggesting that changes of cardiovascular structure and function by cigarette smoking may influence the cardiovascular regulationunder the condition of +Gz, though effects of tobacco smoking on +Gz tolerancehave not been reported at domestic and abroad.This research will focus on +Gz tolerance in pilots to determine thecharacteristic of +Gz tolerance in smoking pilots, then chronic smoking ratsmodel will be established to explore the effects of tobacco smoking oncardiovascular system and its mechanism.Objective1. To investigate the effects of smoking on +Gz tolerance in pilots.2. To explore the changes of vasoconstriction and vasodilatation,pathological changes and the corresponding response to NOS blocker andpotassium channel blockers of thoracic aorta in rats.MethodsPartâ… : Effect of smoking on +Gz tolerance in pilots1. 170 male pilots were administered to questionnaire of epidemiology onsmoking habit, and then divided into 4 groups (0, 1, 2, 3 group) according toquantity of smoking.2. +Gz tolerance, aorthostatic tolerance and treadmill exercise were testedand contrastively analysized.Partâ…¡: Effects of cigarette smoking on vasoconstriction and vasodilatationof thoracic aorta in rats1. 32 rats in 3 weeks old were randomly divided into 4 groups(n=8), control(CON) group, short-term heavy smoking(SS) group, medium-term heavysmoking (MS) group and long-term heavy smoking(LS) group. Rats were ininhalation of smoke based on smoking time.2. Rats models of smoking were established, and isolated rat thoracic aorticperfusion apparatus were used. Effects of SS, MS and LS on vasoconstrictioninduced by KCl, phenephrine(PE) were observed, as well as aceylcholine (Ach)relaxation on vessel rings which enduthium were not scraped. The roles of preconditioning with NG-Nitro-L-Arginine Methyl Ester(L-NAME) constrictionby PE were also evaluated. Nitric oxide (NO) content in vessel rings ofintervention group was measured with Griess method.3. The effects of KCl, norepinephrine (NE), sodium nitroprusside(SNP),tetraethylammonium (TEA), and 4-aminopyridine (4-AP) on thoracic aorta withendothelium scraped were observed in four groups.4. The pathologic changes of vessel were observed after HE staining in fourgroups.ResultResults1. Smoking rate in pilots was 61.74 percent.2. Dysfunction rate of cardiovascular system in smoking level 2 group andsmoking level 3 group was significantly higher than it in smoking level 0 group(P<0.05).3. Compared with smoking level 0 group, +Gz tolerance decreasedsignificantly in smoking level 2 group and smoking level 3 group (P<0.05).4. Compared with control(CON) group, the contractile response of thoracicaortas which endothelium was not scraped increased significantly(P<0.05) in LSgroup and MS group induced by KCl or PE, in addition, the relative relaxationresponse induced by Ach and serum NO content in LS group and MS groupdecreased significantly (P<0.05), vasoconstriction induced by KCl and maximalconcentration of PE had significant negative correlation with NO content inblood vessel (P<0.05), furthermore, its intensity was proportional to the durationof smoking.5. The contractile response of thoracic aorta with endothelium scrapedinduced by KCl or PE increased significantly (P<0.05), while the relativecontractile response induced by TEA (TEA/KCl) or 4-AP (4-AP/KCl) decreasedsignificantly (P<0.05), and the vasodilatation response induced by sodiumnitroprusside (SNP) decreased significantly in MS group and LS group,compared with CON group (P<0.05), furthermore, its intensity was proportional to the duration of smoking.6. The structure of vascular endothelium was damaged in MS group and LSgroup, with intima building up and inflammatory cell infiltrating, as well assmooth muscle cell of media was proliferated. The intimal structure wascompleted and smooth, and vascular smooth muscle cells also distributedhomogenyeously in CON group and SS group.Conclusion1. Smoking rate in pilots was high.2. Poor +Gz tolerance in pilots was induced by smoking to some extent.3. Cardiovascular function in pilots was reduced by smoking to some extent.4. The vasoconstriction response of arteries in smoking rats was increased,while the vasodilatation function and NO content in blood vessels was decreased,NO and potassium channel may play an important role in the changes of arterialfunction in cigarette smoking rats.5. The structure of thoracic aorta in smoking rats was damaged.