Disequilibrium Between Alveolar and End-Pulmonary-Capillary O<Subscript>2</Subscript> Tension in Altitude Hypoxia and Respiratory Disease: An Update of a Mathematical Model of Human Respiration at Altitude

We have previously formulated and validated a mathematical model specifically designed to describe human respiratory behavior at altitude. In that model, we assumed equality of alveolar and end-pulmonary-capillary oxygen tensions. However, this equality may not hold true during rapid and prolonged changes to high altitudes producing severe hypoxia as can occur in aircraft cabin decompressions and in some respiratory diseases. We currently investigate this possibility by modifying our previous model to include the dynamics of oxygen exchange across the pulmonary capillary. The updated model was validated against limited experimental data on ventilation and gas tensions in various altitude-decompression scenarios. The updated model predicts that during rapid and sustained decompressions to high altitudes the disequilibrium of gas tensions between alveolar gas and capillary blood could be 10 Torr, or larger. Neglecting this effect underestimates the severity of a decompression and its potential to produce unconsciousness and subsequent brain damage. In light of these results, we also examined the effect of this disequilibrium on the diminished oxygen diffusion capacity that can occur in some respiratory diseases. We found that decreases in diffusion capacity which would have minimal effects at sea level produced significant disequilibrium of gas tensions and a large fall in hemoglobin oxygen saturation at a cabin altitude of 4000–8000 ft. As demonstrated, this new model could serve as an important tool to examine the important physiological consequences of decompression scenarios in aircraft and the pathophysiological situations in which the equilibrium of gas tensions along the pulmonary capillary are particularly critical.     

Modeling the effect of time-dependent exposure on intensive care unit mortality

Purpose  To illustrate modern survival models with focus on the temporal dynamics of intensive care data. A typical situation is given in which time-dependent exposures and competing events are present. Methods  We briefly review the following established statistical methods: logistic regression, regression models for event-specific hazards and the subdistribution hazard. These approaches are compared by showing advantages as well as disadvantages. All methods are applied to real data from a study of day-by-day ICU surveillance. Results  Standard logistic regression ignores the time-dependent nature of the data and is only a crude approach. Cumulative hazards and probability plots add important information and provide a deep insight into the temporal dynamics. Conclusion  This paper might help to encourage researchers working in hospital epidemiology to apply adequate statistical models to complex medical questions. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

1989～1999年我院烧伤病原菌和细菌耐药性变迁

目的:通过对我院1989～1999年烧伤感染病原菌及耐药性的调查,分析烧伤感染病原菌和细菌耐药性变迁。方法:对1989年6月～1994年5月及1994年6月～1999年6月两个时期的烧伤病人,分别进行血培养和创面培养细菌检出的情况及药敏调。结果:血培养结果表明,铜绿假单胞菌上升至第1位;占24.2％;金黄色葡萄球菌退居第3位,其中,G~4球菌占56.5％,G杆菌占30.1％。创面培养,绿脓杆菌居首,占19.4％;阴沟杆菌居第2位,占14.1％,其中G杆菌占58.4％,G~4球菌占35.3％。阴沟杆菌,嗜麦芽黄单胞菌,粪肠球菌,以及白色念珠菌有明显上升。结论:烧伤感染病原菌和细菌耐药性变迁与头孢他啶,亚胺培南等广谱抗生素广泛应用有一定关系。     

人工关节置换术后感染的治疗

目的探讨人工关节置换术后感染的原因，处理方法和临床效果。方法白1992年1月～2004年2月年共收治7例人工关节置换术后感染患者，6例髋关节，1例膝关节。男性4例，女性3例；年龄43～74岁，平均58岁。术后感染发生在2个月内3例，1年内1例，2年以上3例（3、8、10年）。2例扩创，取出钢丝和捆绑带，置管持续冲洗，静点、口服抗菌素。1例取出假体，关节旷置。1例一期关节置换。3例二期关节置换。结果随访2～14年，平均随访8年，6例患者无感染复发迹象，疼痛消失，独立行走，关节功能满意。1例因拒绝取出假体，窦道反复破溃。结论应严格掌握关节置换适应证，预防感染重于治疗。术中病理切片检查对诊断感染，决定翻修手术的时机具有指导意义。     

Cadmium, lead, and thallium in smoke particulate from counterfeit cigarettes compared to authentic US brands.

Smoking remains the leading cause of preventable disease in the United States. Exposure to tobacco smoke leads to cancer, heart and lung disease, and addiction. The origin of the tobacco and cigarette manufacturing practices of counterfeit cigarettes are unknown. Because toxic metals are incorporated into the tobacco lamina during cultivation, the ambient metal content of the soil could produce significant differences in metal levels in both the tobacco and smoke of counterfeit cigarettes. We compared mainstream smoke cadmium, thallium, and lead deliveries from counterfeit and authentic brands. Mainstream smoke levels of all three metals were far greater for counterfeit than the authentic brands, in some cases by an order of magnitude. Significant differences still existed even after normalizing mainstream smoke metal levels with nicotine delivery; the counterfeits typically delivered much higher levels of all three analytes. Our findings, based on 21 different counterfeit samples, suggest that counterfeit cigarettes potentially result in a markedly greater exposure to toxic heavy metals than authentic brands, even after correcting for differences in nicotine intake. In view of the unknown health risks associated with inhaling higher levels of toxic metals, it is prudent to minimize exposure to toxic substances whenever possible.     

医院评审应用中的发展

社会的发展和医疗技术的进步,对医院的质量管理提出更高的要求。卫生行政部门借鉴国内外优秀质量管理标准和经验,建立了一系列医院评审标准,从1989年开始对医院进行强制认证,合理、有效地评价医院的医疗质量,使医院以病人为中心,促进了医院管理、决策、服务的水平。但由于医院内部管理、工作人员对评审标准的认识不一致,导致在评审应用过程中消极、浮夸等现象均有发生。因此,医院质量管理应从强制评审向以自我评估为主,独立评估为辅的方式转变,促进医疗质量的持续改进。     

居民区控制登革热媒介蚊虫的方法与效果探索

目的对居民区采用孳生地管理和文化防制相结合的方法来评价控制登革热媒介白纹伊蚊的效果，探索这种控制措施的成本以及推广的可行性。方法于2007年5—10月，选择普陀区师大三村和杨浦区的长恒苑为实验区，选择与实验区条件相似的小区为对照区，实验区采取专业人员每周2次检查清除各种小容器积水，每10天检查处理下水道、雨水井、明沟，同时宣传蚊虫的防治知识，上门动员和督促居民及时清除天井、阳台等处的各类容器积水，对照区则采取常规控制措施（突击灭蚊）。采用容器指数、孳生地阳性率、叮人法和人工小时法成蚊密度等指标评价实验区的控制效果。结果（1）6—9月居民户室内积水容器阳性率得到有效控制，实验区月平均阳性率5．56％，明显低于对照区16．81％；（2）6—9月实验区居民外环境积水阳性率平均4．74％，对照区为14．85％，二者间阳性率差异有统计学意义（u=4．503，P〈0．01）；（3）7—9月人诱法白纹伊蚊成蚊密度实验区分别为0．60、1．33和0．50只／30min，对照区分别为7．83、7．67和5．00只／30min；（4）6—9月人工小时法白纹伊蚊成蚊密度实验区为1．80只／h，对照区为5．80只／h；（5）防治成本按照控制面积计算，实验区每月支出人工和药物费用约为0．08元／m^2，对照区每月支出约为0.05元／m^2。结论社区采用上述孳生地管理和文化防治相结合的措施，能有效地将社区内白纹伊蚊幼虫孳生率和成蚊密度控制在较低水平，控制成本（0．08元／m^2）处于居委会和物业部门可接受范围内，有利于推广应用。     

河北省肾综合征出血热国家级监测点自然疫源地监测研究

目的了解河北省肾综合征出血热（HFRS）国家级监测点疫源地宿主动物的构成、分布及汉坦病毒携带状况。方法在全省4个国家级监测点，分别于春季、秋季开展宿主动物调查，采用夹夜法调查鼠密度，间接免疫荧光法检测汉坦病毒抗原携带情况。结果2005—2007年监测点居民区鼠密度波动在0．50％～3．19％之间，野外鼠密度波动在0．13％-0．94％之间。居民区鼠密度高于野外（χ^2=45．022，P〈0．01）。宿主动物构成以褐家鼠占绝对优势（77．57％），其次为大仓鼠（13．63％）和小家鼠（8．81％）。居民区汉坦病毒抗原阳性6只，鼠带病毒率1．91％，野外汉坦病毒抗原阳性2只，鼠带病毒率1．23％。8只阳性鼠中，褐家鼠7只，大仓鼠1只。结论河北省是以褐家鼠为主要宿主动物的混合型疫源地，应采取以消灭住宅区褐家鼠为主的综合性防制措施。同时应进一步加强北部地区的疫源地监测工作，从而有效地控制河北省HFRS的发生和流行。     

降钙素原在新生儿感染性疾病中的临床价值

目的:探讨降钙素原(PCT)在新生儿感染性疾病中的临床价值。方法:对104例住院新生儿进行PCT测定,将其分为重症感染、一般感染、非感染3组进行分析,并与C反应蛋白(CRP)、血培养进行比较。结果:PCT阳性率重症感染组为89.47%,一般感染组为42.58%,非感染组为19.23%,重症感染组PCT阳性率明显高于其他两组,三组比较差异有显著性(P=0.000)。以>2ng/L为临界值,诊断重症感染的敏感度为71.05%,特异度为93.94%。与CRP比较,PCT诊断重症感染的敏感度、特异度更高;与血培养比较,其阳性率更高。结论:PCT在新生儿细菌感染时会升高,重症感染时升高更明显,可作为新生儿感染的早期检测指标,与CRP相比,其优越性更明显,对新生儿重症感染如败血症等的诊断更有价值。