Isolated heart responsiveness to beta-simulation after exercise training in obesity

PURPOSE: Exercise training results in many health benefits, but few studies have focused on whether exercise training might attenuate the adverse effects of obesity on heart function. Therefore, the purpose of this study was to determine whether exercise training attenuated obesity-related decreases in systolic contractile function in response to beta-adrenergic stimulation, using the rabbit model of obesity. METHODS: Female New Zealand white rabbits were divided into four groups: lean sedentary, lean exercise-trained, obese sedentary, and obese exercise-trained. Obese rabbits were fed an ad libitum high-fat diet. Exercise-trained rabbits underwent a 12-wk progressive treadmill exercise training protocol. After 12 wk, the Langendorff isolated heart method was used to study developed pressure, +dP/dt, and -dP/dt responses to increasing concentrations of isoproterenol (10(-9)--3 x 10(-7) M). Log concentration-response data were fit to a sigmoidal function, using a four-parameter (minimum, maximum, EC(50), slope) logistic equation. Groups were compared using a 2 x 2 analysis of variance. RESULTS: Although obesity shifted the concentration-response curves for developed pressure, +dP/dt, and -dP/dt to the right as indicated by an increase in the EC(50) (P < or = 0.05), there was no effect of exercise training on any of the logistic regression parameters. EC(50) (log M) values for combined lean versus combined obese were -8.50 +/- 0.7 vs -8.20 +/- 0.09 (developed pressure), -8.04 +/- 0.06 vs -7.68 +/- 0.07 (+dP/dt), and -8.17 +/- 0.07 vs -7.91 +/- 0.09 (-dP/dt). CONCLUSION: These results confirm the negative effect of obesity on responsiveness of the isolated heart to beta-adrenergic stimulation but indicate that exercise training does not significantly attenuate obesity-related changes.     

Effects of repeated brain ischemia induced by rapid lower body negative pressure on brain water and Na+,K+-ATPase activity in rats

BACKGROUND: It has been demonstrated that during +Gz exposure cerebral blood flow is significantly reduced resulting in brain ischemia. Animal centrifuge models are commonly used to investigate the mechanisms of +Gz-induced loss of consciousness (G-LOC) and their pathophysiological effects on the brain. These dynamic models are limited because we currently are unable to obtain accurate measures of membrane ion flux or single cell electrophysiological responses from animals under centrifugation. HYPOTHESIS: The aim of the present study was to develop a non-centrifuge animal model of short-term, repeatable and complete brain ischemia using a rodent lower body negative pressure (LBNP), and to investigate the effects of repeated complete brain ischemia induced by LBNP on brain Na+,K+-ATPase activity, Na+, K+ and water contents in rats. METHODS: Eight anesthetized rats were exposed randomly to LBNP of -2.67 kPa, -4.00 kPa, and -5.33 kPa, respectively, at the rate of -0.67 kPa x s(-1). The pressure rapidly returned to control level when EEG became isoelectric (flat). The mean arterial BP (MAP), EEG and ECG were recorded. Twenty-one rats were divided randomly into control, single LBNP exposure, and three LBNP exposures groups (n = 7 in each group). Brain samples were analyzed for Na+,K+-ATPase activity, Na+, K+ and water contents 1 h after single and three 2-min LBNP exposures (-4.00 kPa at a rate of 0.67 kPa x s(-1)), respectively. RESULTS: MAP decreased rapidly during LBNP exposure. The mean time to isoelectric EEG was 41.33 +/- 11.48, 30.67 +/- 3.88 and 25.67 +/- 3.45 s during -2.67, -4.00 and -5.33 kPa LBNP, respectively. Heart rate (HR) significantly decreased when EEG became isoelectric. MAP, HR and EEG rapidly returned after releasing LBNP. The brain Na+,K-ATPase activity decreased significantly after single LBNP exposure and decreased further after three LBNP exposures. The brain K+, Na+ and water contents increased significantly after three LBNP exposures. CONCLUSIONS: A rat model of short-term, repeatable brain ischemia was developed using rapid LBNP. Three -4.00 kPa LBNP exposures (2 min each) cause a significant reduction in brain Na+,K+-ATPase activity and brain edema in rats.     

Systemic Pulsatile Pressure in Type II Endoleaks After Stent Grafting of Experimental Abdominal Aortic Aneurysms

Purpose: To investigate pressure and maximum rate of rise of systolic pressure (peak dP/dt) in completely excluded aneurysms and endoleaks to determine the hemodynamic impact of endoleaks. Methods: In mongrel dogs (n = 36) experimental aneurysms were created by insertion of a patch (portion of rectus abdominis muscle sheath) into the infrarenal aorta. In group I (n = 18), all aortic branches of the aneurysm were ligated and all aneurysms were completely excluded by stent grafts. Group II (n = 18) consisted of aneurysms with patent aortic side branches that represented sources of endoleaks. One week (n = 12), six weeks (n = 12), and six months (n = 12) after stent grafting, hemodynamic measurements were obtained in thrombosed aneurysms and proved endoleaks. Systemic blood pressure and intraaneurysmal pressure were simultaneously measured and the respective peak dP/dt were computed. Results: At the six-month follow-up, the systolic-pressure ratio (intraaneurysmatic pressure: systemic pressure) was significantly increased in endoleaks compared to non-perfused areas (0.879 ± 0.042 versus 0.438 ± 0.176, p < 0.01, group II) or completely excluded aneurysms (0.385 ± 0.221, group I). Peak dP/dt ratio (intraaneurysmal peak dP/dt: systemic peak dP/dt) was 0.922 ± 0.154 in endoleaks, compared to 0.084 ± 0.080 in non-perfused areas (group II, p < 0.01), and was 0.146 ± 0.121 in completely excluded aneurysms (group I). The diastolic-pressure ratio was also increased in endoleaks compared to non-perfused areas (0.929 ± 0.088 versus 0.655 ± 0.231, p < 0.01, group II) or completely excluded aneurysms (0.641 ± 0.278, group I). In excluded aneurysms, pressure exposure declined as the length of the follow-up period increased. Conclusion: Type II endoleaks transmit pulsatile pressure of near systemic level and indicate insufficient treatment result. In contrast, complete endovascular exclusion of aneurysms results in significantly reduced pressure exposure.     

Myocardial flow and function after regional beta-blockade in exercising dogs

This study was designed to examine the contribution of beta 1- and beta 2-adrenergic receptors in modulating coronary blood flow and cardiac function in exercising dogs. Dogs were chronically instrumented to measure left circumflex flow velocity (CFV), heart rate, regional left ventricular function [systolic shortening, (%S) and maximum velocity of shortening (dL/dt(s)max)], and global left ventricular function [left ventricular pressure (LVP and dP/dtmax)]. Exercise significantly increased LVP (31 +/- 4%), dP/dtmax (130 +/- 17%), heart rate (116 +/- 20%), %S (28 +/- 6%), dL/dt(s)max (89 +/- 23%), and CFV (91 +/- 25%). Regional injection of the non-selective beta-blocker propranolol (1.0 mg) into the circumflex artery during exercise was associated with decreases in LVP (-8 +/- 3%), dP/dtmax (-17 +/- 3%), %S (-15 +/- 4), dL/dt(s)max (-13 +/- 4%), and CFV (-22 +/- 4%). Selective beta 1-receptor blockade with atenolol (1.0 mg, i.c.) was associated with similar decreases in LVP (-7 +/- 3%), dP/dtmax (-33 +/- 4%), %S (-12 +/- 3%), dL/dt(s)max (-17 +/- 2%), and CFV (-18 +/- 3%) during exercise. In contrast, selective beta 2-receptor blockade with ICI 118551 (250 micrograms, i.c.) produced significant decreases in only CFV (-11 +/- 2%) during exercise. Thus, the data suggest that the reductions in myocardial contractile function and flow after regional beta-blockade are primarily due to a decrease in myocardial beta 1-receptor stimulation. In addition, there apparently is a small involvement of either coronary vascular or pre-synaptic beta 2-receptors in mediating the coronary vascular flow response during exercise.     

自噬在X射线照射所致心肌线粒体损伤中的作用

目的观察X射线照射对大鼠心肌线粒体功能的影响以及自噬在线粒体功能损伤中的作用。方法将135只实验大鼠分成假照射组（10只）、照射组（80只）和照射＋3．甲基腺嘌呤（3-MA）组（45只）,假照射组接受0GyX射线照射,照射组给予20Gyx射线照射,照射＋3-MA组接受20Gvx射线照射前30min腹腔注射2μl 3-MA。采用蛋白免疫印迹法和实时定量PCR法检测心肌细胞的LC3II及Beclin1蛋白表达及其mRNA水平变化,检测左心室舒张压及＋-dP／dtmax（左心室压力上升及下降的最大速率）等离体心功能指标。结果与假照射组相比,照射组大鼠经20GyX射线照射后离体心功能在21d时出现降低;而在1d时心肌组织线粒体功能便出现了损伤;同时,心肌细胞自噬水平在3h、6h、12h、1d、2d、4d及7d时出现明显上升,与假照射组之间的差异显著,且在6h达到最高值。与照射组相比,照射＋3一MA组大鼠心肌LC3II及Beclin1表达水平明显下降,且心功能出现异常的时间提前至14d。结论x射线照射损伤大鼠心肌线粒体功能并诱导自噬发生,可能是心肌保护的重要因素。     

缺血预适应对失血性休克大鼠的保护作用研究

目的目的观察缺血预适应对失血性休克大鼠的保护作用。方法采用失血性休克复苏大鼠,观察缺血预适应对大鼠存活、血管收缩反应、血流动力学[平均动脉压（MAP）、左室收缩压（LVSP）、左室舒张末压（LVEDP）、左室压最大上升/下降速率（±dp/dtmax）、心率（HR）]、肝肾灌注和线粒体功能的影响。结果缺血预适应可延长失血性休克复苏大鼠存活时间,恢复血管对去甲肾上腺素（NE）和Ca2＋的反应性,恢复MAP、LVSP、LVEDP、±dp/dtmax、HR、NE升压效应,增加肝肾血流量、线粒体呼吸控制率和Na＋-K＋-三磷酸腺苷（ATP）酶活性（P〈0.01）。结论缺血预适应恢复血管收缩反应,改善血流动力学、血流灌注和线粒体功能,从而延长失血性休克复苏大鼠存活时间。     

Exercise tolerance and compensatory sympathetic tone during beta-blockade after myocardial infarction

Using chronically instrumented dogs with a healed anterior wall myocardial infarction, we have assessed the effect of acute beta-adrenergic blockade on exercise tolerance, left ventricular (LV) performance, and myocardial VO2. Mongrel dogs were instrumented with Doppler flow probes around the left circumflex coronary artery, LV pressure cells, epicardial ECG electrodes, and left atrial and coronary sinus catheters. Myocardial infarction was produced by ligation of the left anterior descending coronary artery at time of instrumentation (approximately 20% LV mass). After a 1-month recovery period, dogs were subjected to two identical submaximal graded exercise tests on a treadmill on separate days, once without (control) and once with (propranolol, 1 mg X kg-1, i.v.) acute beta-adrenergic blockade. Heart rate, LV pressure, dP/dt max, left circumflex blood flow velocity, and myocardial VO2 index were measured at each stage of the graded exercise test. All variables were significantly reduced from control during beta-block in exercise. beta-Adrenergic blockade in the presence of a 1-month-old anterior wall myocardial infarction did not compromise exercise capacity during submaximal exercise.     

浮动胸壁对犬心肺功能的损害及机械通气和肋骨牵引的治疗效果

目的 观察浮动胸壁对心肺功能的影响以及机械通气和肋骨牵引的疗效。方法 杂种1犬16只建立小面积（10cm^2/kg）和大面积（20cm^2/kg）浮动胸壁动物模型，每组8只，用胸腔置管、Swan-Ganz导管、血气分析等观察心排量（CO）、中心静脉压（CVP）、平均动脉压（MAP）、肺动脉压（PAP）、动脉氧分压（PaO2），肺动脉静脉分流分数（Qs.／Qt）及胸膜腔内压等的变化和机械通气、肋骨牵引固定的治疗效果。结果 浮动胸壁模型完成后，均出现反常呼吸，胸腔内压力为负值，未出现软化部分膨出；小面积组动脉血氧饱和度（SaO2）下降（P＜0．05），Qs/Qt下降（P＜0．05）。与治疗前比较，机械通气治疗后小面积组Qs/Qt下降（P＜0．05），CO和SaO2则升高（P＜0．05）；而大面积组SaO2、PaO2明显升同（P＜0．01），Qs/Qt和PaCO2下降（P＜0．05）。结论 浮动胸壁的病理胸腔容积减少为基础，机械通气和肋骨牵引固定是有效的治疗手段，机械通气对大面积浮动胸壁呼吸功能障碍的疗效更好。     

Evaluation of a videodensitometric method for monitoring the left ventricular contractile state.

Videodensitometry of the margins of the fluoroscopic image of the left ventricle (LV) was used to evaluate LV wall motion. Differentiation of the wall motion signal reflected the velocity of LV contraction (dv/dt) during various inotropic interventions in 6 anesthetized dogs. Alterations in dv/dt were similar to changes in simultaneously measured LV peak dP/dt and the quotient of dP/dt and developed LV pressure, two widely accepted parameters of LV contractile state.     

Estimation of coronary flow reserve with the use of dynamic planar and SPECT images of Tc-99m tetrofosmin

BACKGROUND: We developed a noninvasive method to examine coronary flow reserve with technetium 99m tetrofosmin based on the microsphere model. According to the microsphere model, myocardial blood flow (MBF) can be calculated by MBF = q / integral C(t)dt, where q is myocardial activity and C(t) is tracer concentration in blood. Because the ratio of integral C(t)dt at stress to rest is equal to the ratio of the first transit count in the pulmonary artery (PA) and attenuation factors were canceled out, we calculated the increase ratio of MBF (MBF(IR)). METHODS AND RESULTS: After injection of dipyridamole, tetrofosmin was injected as a bolus and serial dynamic planar images were obtained to measure the first transit count in PA (PAC). Myocardial single photon emission computed tomography was performed to measure the regional myocardial count (RMC). MBF(IR) was calculated as [(RMCs x PACr)/(RMCr x PACs) - 1] x 100, where r and s denote resting and stress conditions, respectively. In contrast, the increase in the myocardial uptake ratio (MUR(IR)) was defined as (RMCs x SCr/RMCr x SCs - 1) x 100, where SC is syringe count of tracer. The results were as follows: (1) The mean MBF of healthy subjects was 46.9% +/- 22.8%. (2) MBF(IR) of the infarcted region and ischemic region was significantly decreased (8.3% +/- 12.2% and 11.2% +/- 11.9%, respectively; P <.001). (3) MUR(IR) was significantly lower than MBF(IR) (14.1% +/- 21.2%; P <.001). (4) MBF(IR) decreased according to the heart rate at rest (r = 0.47; P <.05). CONCLUSIONS: MBF(IR) is a potential parameter with which to evaluate coronary flow reserve when the changes of arterial input function during stress are considered.     

异搏定(verapamil)对急性低压缺氧复合失血性休克狗的心血管功能和氧运送的影响

本文观察了Ca~(2+)通道阻断剂-异搏定(verapamil)对急性低压缺氧复合失血性休克狗的心血管功能和氧运送的影响。13只健康雄性家犬,在模拟4 000m(61.2kPa)高原低压舱内,复制失血性休克,低血压(5.33kPa)维持90min,然后把失血全部输回,比较异搏定对mAP、CI、LVWI、TPR、HR、LVSP及±dp/dt max以及DO_2、VO_2和MVO_2的影响。实验结果表明,急性低压缺氧复合失血性休克,异搏定对心血管功能的改善没有明显作用,但可提高全身和心肌耗氧量改善细胞代谢和减轻酸中毒,这可能与异搏定能减轻细胞线粒体内Ca~(2+)过负荷有关。     

生脉液对大冠状动脉临界狭窄心脏血流动力学影响

在１２条麻醉开胸犬上，用微米狭窄器造成冠状动脉前降支临界狭窄。以平均动脉压（ＭＡＰ）、左心室收缩压（ＬＶＳＰ）、左心室舒张压（ＬＶＤＰ）、室内压最大上升速率（ｄｐ／ｄｔｍａｘ）。室内压最大下降速率（－ｄｐ／ｄｔｍａｘ）及心输出量（ＣＯ）等血流动力学指标，观察生脉液在冠脉临界狭窄基础上用药前后心脏功能的改变。结果表明：冠脉临界狭窄时，ＬＶＤＰ明显升高（Ｐ＜０．０５），ＬＶＳＰ、ｄｐ／ｄｔｍａｘ、－ｄｐ／ｄｔｍａｘ及ＣＯ明显降低（Ｐ＜０．０５），提示心功能减弱。而给药后，可使心肌缺血心脏功能的损害减轻，上述指标明显好转     

Is there a disassociation of maximal oxygen consumption and maximal cardiac output?

PURPOSE: The purpose of the present study was to determine whether maximal cardiac output (Q) is affected by the duration of the maximal exercise test. METHODS: Nine healthy men (N = 6) and women (N = 3) performed three separate maximal treadmill exercise tests, separated by at least 24 h, and underwent a body composition assessment by hydrostatic weighing, all within a 2-wk period. A baseline maximal exercise test was performed to establish VO(2max). The second and third tests, assigned randomly, were designed to elicit the subjects' predetermined VO(2max) in either 6 or 12 min. Heart rate (HR), blood pressure (BP), minutes of ventilation, and oxygen consumption (VO(2)) were measured during all tests. At the end of the 6- and 12-min tests, Q was measured using an acetylene rebreathing technique. Stroke volume (SV), mean arterial pressure (MAP), total peripheral resistance (TPR), and arteriovenous O(2) difference were calculated using standard equations. RESULTS: Repeated-measures ANOVA indicated that there were no significant differences in HR and VO(2max) between the baseline, 6-min, and 12-min tests. Paired t-tests revealed significantly greater Q (25.1 +/- 5.6 vs 23.7 +/- 5.2 L.min-1) and SV (138.3 +/- 31.5 vs 130.5 +/- 31.2 mL) in the 6- versus 12-min tests, respectively. There were no significant differences in systolic BP, diastolic BP, MAP, TPR, or arteriovenous O(2) difference. CONCLUSIONS: Despite there being no difference in VO(2max) between the two tests, the 6-min maximal exercise test resulted in a significantly greater Q than the 12-min test, because of a significantly greater SV. Thus, there was a disassociation between VO(2) and Q during maximal exercise.     

Cardiovascular changes during and following 1-min exposure to +Gz stress.

Magnitude and duration of cardiovascular responses following anesthetized dogs. During lower G forces (+1 to +3GZ), responses were variable. In most dogs during higher G forces (+4 or +5GZ), aortic pressure, cardiac output, left ventricular pressure, and dp/dt were dramatically compromised. These changes were observed whether the onset of the gravitational inertial force was slow (0.1 G/s) or rapid (1.0 G/s). Cardiovascular changes after acceleration were consistent. Left atrial pressure and arterial pressure rose and a transient rise in dp/dt was often observed. Cardiac output rose briefly, then fell; hence, peripheral resistance increased. Magitude and duration of these changes were directly related to G forces during acceleration. Our results confirm that +GZ stress produces major cardiovascular changes. Our experiments also demonstrate that responses following +GZ stress may be dramatic and prolonged. Increased peripheral resistance elevates perfusion pressure and, concurrently, the increased preload may cause acute cardiopulmonary congestion.     

Cardiovascular responses to facial cooling are age and fitness dependent.

PURPOSE: Aging of the cardiovascular system may be altered by differences in physical fitness. We investigated the cardiovascular responses to brief periods of facial cooling (5 degrees C) in 20 healthy men differing in age and aerobic fitness (VO2max). METHODS: Facial cooling was administered at rest in the supine position during 60-s quiet breathing to 6 fit young (FY; VO2max = 75.8 +/- 18 mL x kg(-1) x min(-1); 29 +/- 7 yr), 6 sedentary young (SY; VO2max = 36.0 +/- 2.2 mL x kg(-1) x min(-1); 27 +/- 3 yr), 6 fit old (FO; VO2max = 56.1 +/- 4.0 mL x kg(-1) x min(-1); 54 +/- 5 yr), and 6 sedentary old (SO; VO2max = 29.6 +/- 5.0 mL x kg(-1) x min(-1); 62 +/- 2 yr) volunteers. The following were measured before and after facial cooling: heart rate (HR), mean arterial blood pressure (MAP), pressure-rate product (PRP), and M-mode echocardiographically determined left ventricular internal dimensions, peak circumferential shortening (peak V(CF)), and ejection fraction (EF). RESULTS: Facial cooling produced a statistically significant bradycardia in all groups except for the SO whereas MAP was increased in the young groups but unchanged in the older groups. Pressure-rate product was significantly reduced in the FY, unchanged in the SY and FO, and significantly increased in the SO group. None of the groups showed a change in left ventricular dimensions, whereas only the SO group showed an increase in peak V(CF) (P < 0.05). CONCLUSIONS: These data suggest that endurance training and fitness level do not significantly alter cardiovascular responses to facial cooling in young men or physically fit older men. However, in older subjects, a sedentary lifestyle appears to be associated with an absent facial cooling reflex bradycardia, an increased PRP, and contractility (peak V(CF)).     

In vivo assessment of myocardial blood flow in rat heart using magnetic resonance imaging: effect of anesthesia

PURPOSE: To assess the influence of isoflurane and pentobarbital anesthesia and the carrier gases on myocardial blood flow (MBF) in the rat heart in vivo. MATERIALS AND METHODS: MBF was quantified in vivo using arterial spin-labeling (ASL) magnetic resonance imaging (MRI). Left ventricular (LV) function was estimated during the same experiment using cine-MRI. Thirty-four male Wistar-Kyoto rats were divided in four groups, one anesthetized with isoflurane in oxygen:nitrous oxide mix (ISO), the three others with intraperitoneal pentobarbital, and breathing either room air (PB), oxygen:nitrous oxide (PB + N(2)O), or oxygen:nitrogen (PB + N(2)). RESULTS: MBF was significantly higher in the ISO and PB + N(2)O groups vs. PB and in ISO vs. PB + N(2), with the following respective MBF values: ISO, 5.9 +/- 1.1; PB, 4.0 +/- 0.8; PB + N(2)O, 5.1 +/- 1.4; and PB + N(2), 4.6 +/- 0.8 mL/g/minute, mean +/- SD. Ejection fractions were reduced by 10% in PB and PB + N(2)O rats vs. ISO rats. Cardiac output (CO) and index (CI) were 25 to 30% lower in all rats anesthetized with pentobarbital than with isoflurane. CONCLUSION: Isoflurane and nitrous oxide induce a higher MBF than pentobarbital. Isoflurane also induces a higher ejection fraction in healthy rats.     

胸部枪伤瞬时及早期心血管效应的实验研究

目的　探讨胸部枪伤瞬时及早期心血管效应及其机制。　方法　 30只家兔随机平均分为A :胸部贯穿伤组 (模型组 )、B :预扎肋间动脉致伤组、C :人工气胸后致伤组、D :预扎肋间动脉 人工气胸后致伤组、E :胸壁切线伤组。分别用 5 .5 6mm小口径步枪致伤 ,连续监测动脉压、心率、静脉压、心电图、左室内压等。　结果　A组伤前血压峰值为 ( 14.80± 1.2 9)kPa ( 1kPa =7.5mmHg) ,枪伤瞬间血压即刻呈单波峰升高 ,达伤前的 ( 1.5 8± 0 .0 8)倍 ,而后迅速降低至伤前水平以下 ,10s下降到最低点 ,30s开始回升 ,1min后回升至伤前的 ( 0 .80± 0 .0 7)倍 ,并逐渐稳定。静脉压瞬时升高后随即下降 ,左室内压和心率出现瞬时下降、而后逐渐恢复 ,B组和C组变化幅度较小。D组和E组仅枪击瞬间有短暂变化。　结论　胸部枪伤瞬间动、静脉压升高 ,而左室内压无变化 ,为枪弹冲击波直接引起。伤后数秒内血压下降 ,心动过缓 ,心肌受抑制和左室内压下降 ,而中心静脉压尚正常 ,提示与迷走反射有关。模型组于伤后 2h血压再度下降 ,则可能与胸内失血和肺损伤有关 ,缺氧也造成了心肌收缩力下降。预扎肋间动脉及临时造成人工气胸防止肺实质损伤 ,可减轻枪伤早期的心血管功能障碍。     

单腔气管插管二氧化碳人工气胸法应用于胸腹腔镜食管癌根治术的安全性研究

目的观察单腔气管插管、二氧化碳(CO2)持续吹入人工气胸在胸腹腔镜食管癌切除术中对呼吸、循环的影响,评价其安全性及可行性。方法对40例ASAⅡ～Ⅲ级拟行胸腹腔镜联合食管癌根治术患者的临床资料进行前瞻性分析。采用单腔气管插管,在中速充气(6～8 L/min)维持胸内压6～8 mmHg﹙1 mmHg=0.133kPa)的条件下,监测心率、平均动脉压(MAP)、中心静脉压(CVP)、脉搏血氧饱合度(SpO2)、气道压(Paw)及呼气末CO2分压(PETCO2)等呼吸、循环指标和血气指标,观察其在CO2充气前、后的变化,采集在4个时间节点的参数,分别为气管插管后20 min(T1)、人工气胸后20 min(T2)、人工气胸后60 min(T3)、人工气胸结束10 min(T4),同时采集动脉血气标本检测。结果 CO2吹入造成人工气胸后,CVP、Paw、PETCO2及PaCO2明显升高,动脉氧分压(PaO2)和血气pH值明显下降,MAP、HR和SpO2无明显变化。手术结束停止充气后,大多数指标恢复至基础值水平。所有病例均顺利完成胸腔镜手术,无严重并发症发生。结论单腔气管插管CO2吹入人工气胸时血流动力学基本稳定,生理指标在可接受的范围内,可应用于食管癌根治等复杂且耗时的胸腔镜手术。     

Leg blood flow and VO2 during peak cycle exercise in younger and older women

PURPOSE: To test the hypothesis that leg blood flow and leg O2 extraction during peak exercise are reduced with age in healthy normally active women. METHODS: Thirteen younger (20-27 yr) and 12 older (60-71 yr) nonendurance trained women performed graded upright leg cycling to maximum exertion (VO2peak), while leg blood flow (femoral vein thermodilution), cardiac output (acetylene rebreathing), mean arterial pressure (MAP, radial artery), and blood O2 contents were measured. RESULTS: Peak leg VO2 was 32% lower in the older versus younger women (0.81 +/- 0.06 vs 1.18 +/- 0.10 L x min(-1)) and was correlated with peak systemic VO2 (1.33 +/- 0.1 vs 1.78 +/- 0.1 L x min(-1)) in both groups. Peak leg blood flow and estimated leg vascular conductance were 29% and 38% lower, respectively, in the older women (both P < 0.001). Peak leg blood flow and peak estimated cardiac output were correlated in the older (r2 = 0.51, P = 0.02), but not younger (r2 = 0.10, P = 0.35), group. Estimates of peak systemic and leg arterial-venous O2 difference did not differ between groups (both P > 0.28). CONCLUSIONS: Reduced leg blood flow is a major contributor to the reduced peak systemic VO2 observed in older nonendurance trained women. Diminished leg blood flow during peak exercise in older women, in turn, is due to both central (reduced cardiac output) and peripheral (reduced leg vascular conductance) limitations.     

Walking trials in postmenopausal women: effect of low doses of exercise and exercise fractionization on coronary risk factors

We studied the fractionization of walking training and searched for the minimum dose to affect coronary risk factors in two randomized controlled trials. Altogether 134 (Study I) and 121 (Study II) healthy, sedentary postmenopausal women started the trials, and 130 (Study I) and 116 (Study II) completed them. In Study I the exercise intensity was 65% of the maximal aerobic power (VO2max) and a total of 300 kcal was expended in one (Group W1) or two (Group W2) daily walking bouts. In Study II the exercise was continuous, and the exercise intensity (% of VO2max) and energy expenditure (kcal session(-1)) were 55% and 300 kcal (Group W3), 45% and 300 kcal (Group W4), 55% and 200 kcal (Group W5) and 45% and 200 kcal (Group W6). All the subjects walked 5 days a week. The outcome measures were blood pressure, serum lipoproteins and blood glucose and plasma insulin in fasting state and also during 2-h oral glucose tolerance test in Study I. There was no change in diastolic pressure in the original study groups, but in the combined exercise group (W1+W2) in Study I, the mean diastolic pressure declined by -3.0 mmHg (95% con-fidence interval (CI) -5.5 to -0.4) (P=0.025) in comparison with that of the controls. The mean blood glucose declined by -0.21 mmol L(-1) (CI -0.33 to -0.09) in Group W1 and -0.13 mmol L(-1) (CI -0.25 to -0.01) in Group W2 compared to controls (P=0.03). Also the 2-h glucose concentration decreased in Groups W1 and W2 compared to controls. Systolic blood pressure, serum lipoproteins and insulin levels did not change in Study I or Study II. We conclude that our training program with the greatest exercise dose, exercise intensity 65% of VO2max and weekly expenditure of 1500 kcal had a minimal, positive effect on diastolic pressure and blood glucose, and the effect was similar in one or two daily exercise session groups. This exercise dose is probably close to the minimum to affect coronary risk factors in healthy postmenopausal women. To get a more pronounced and clinically relevant effect, a greater exercise dose is needed.