混合效应模型在研究接触-效应关系中的应用

目的 用混合效应模型研究工人接苯水平与白细胞水平的关系及其影响因素,并确定最适接触剂量指标.方法 在21个体检年度分别对每个研究对象的每次体检时估算区域浓度、8 h时间加权平均浓度(TWA8)、年度接触水平和累积接触水平.将接触水平定义为协变量,白细胞计数定义为效应变量,用混合效应模型分析剂量效应关系.结果 共观察接苯对象147名26 292人月,白细胞计数样本1 147份、对照组66名14112人月白细胞计数样本396份.接触组、对照组白细胞计数平均水平分别为5.36×109,6.13×109/L.平均区域浓度、TWA8、年度接触水平和累积接触水平分别为5.10 mg/m3,4.69 mg/m3,72.90 mg/m3·月,783.70 mg/m3·月.4个混合效应模型均能收敛,其中以TWA8信息标准值最低.工人接苯水平增加、接触时间增长,白细胞水平下降.性别、吸烟与否对白细胞水平无明显影响.结论 工人接苯水平和时间明显影响工人白细胞水平,TWA8可能是最适接触剂量指标.     

工作场所空气中奥克托今高效液相色谱测定方法研究

目的：建立工作场所空气中奥克托今的高效液相色谱测定方法。方法：按照《工作场所空气中毒物检测方法的研制规范》的要求，进行实验室试验和验证试验及现场应用试验。结果：方法的检测限为0．81μg／ml（进样10μl洗脱液），最低检出浓度为0．017mg／m^3（以采集240L空气样品计）。当HMX含量为0—200．0μg／ml时，标准曲线线性关系良好。相关系数r=0．9999．高、中、低3个浓度的样品，6次重复测定，相对标准偏差为0．12％，1．30％，洗脱效率为94．88％～104．75％，方法的回收率为94．27％～102．05％，样品在室温至少可保存14d，奥克托今浓度为0．12，39，82mg／m^3，采样效率为91．20％～100．00％，工作场所空气中与奥克托今共存的三硝基甲苯、黑索今、二硝基甲苯，对奥克托今测定无干扰。结论：本方法各项指标达到《工作场所空气中毒物检测方法的研制规范》的要求，适用于工作场所空气中奥克托今的现场监测及样品纯度的检测。     

Maternal sensitivity and infant autonomic and endocrine stress responses

Background

Early environmental exposures may help shape the development of the autonomic nervous system (ANS) and hypothalamic–pituitary–adrenal (HPA) axis, influencing vulnerability for health problems across the lifespan. Little is known about the role of maternal sensitivity in influencing the development of the ANS in early life.

Aims

To examine associations among maternal sensitivity and infant behavioral distress and ANS and HPA axis reactivity to the Repeated Still-Face Paradigm (SFP-R), a dyadic stress task.

Study design

Observational repeated measures study.

Subjects

Thirty-five urban, sociodemographically diverse mothers and their 6-month-old infants.

Outcome measures

Changes in infant affective distress, heart rate, respiratory sinus arrhythmia (RSA), and T-wave amplitude (TWA) across episodes of the SFP-R were assessed. A measure of cortisol output (area under the curve) in the hour following cessation of the SFP-R was also obtained.

Results

Greater maternal insensitivity was associated with greater infant sympathetic activation (TWA) during periods of stress and tended to be associated with greater cortisol output following the SFP-R. There was also evidence for greater affective distress and less parasympathetic activation (RSA) during the SFP-R among infants of predominantly insensitive mothers.

Conclusions

Caregiving quality in early life may influence the responsiveness of the sympathetic and parasympathetic branches of the ANS as well as the HPA axis. Consideration of the ANS and HPA axis systems together provides a fuller representation of adaptive versus maladaptive stress responses. The findings highlight the importance of supporting high quality caregiving in the early years of life, which is likely to promote later health.     

Comparison of capillary earlobe and venous blood monitoring for occupational lead surveillance

Biological monitoring for occupational lead exposure involves routine venous blood draws from exposed employees. This uncomfortable procedure normally yields more blood than what is needed for analysis. Capillary blood sampling is less invasive but introduces the possibility of surface contamination. The objective of this study was to compare venous and capillary (earlobe) blood lead samples obtained from occupationally exposed individuals. Phlebotomists trained specifically in the collection of blood samples for lead determination collected 2 venous blood samples and 2 capillary earlobe samples from each participating employee. Before the capillary draw, the employee's earlobe was cleansed with an alcohol wipe in an effort to remove potential lead contamination. A second alcohol wipe was then used to sanitize the lancing area and was retained for lead analysis. Both the venous and capillary samples were subsequently analyzed with the use of graphite furnace atomic absorption spectrometry (GFAAS). GFAAS of venous blood specimens was considered the reference method of sampling and analysis. We collected and analyzed 126 paired earlobe and venous samples. Earlobe sampling was preferred to venous sampling by 54% of the employees surveyed. The mean difference between the capillary and venous results was 38.8 +/- 48.1 microg/dL. Lead concentrations in earlobe blood were more than twice those found in venous samples in more than half of the samples (64 of 126). Despite simple cleansing with an alcohol wipe and no visible skin contamination, 94% of the wipe samples from earlobes contained more than 1 microg of lead. Even low concentrations of contamination can significantly alter the concentration of lead in the blood; for example, sample contamination of 0.3 microg lead in a 200-microL blood sample would yield an increase of 150 microg/dL in the measured lead concentration. The findings of this study suggest that until satisfactory skin cleansing and decontamination techniques are identified and evaluated, earlobe sampling should be avoided in the surveillance of occupational blood lead levels.     

定点采样法估测TWA值探讨

[目的 ]　探索一种从最高容许浓度 (MAC)过渡到 8小时时间加权平均浓度 (TWA)检测的定点采样 (GrabSample)方法。　[方法 ]　利用电子计算机技术对含一氧化碳的环境进行不同方式的模拟采样 ,分析采样结果与总体的符合情况 ,以确定合适的采样方法。　 [结果 ]　用采样频率将工作时间等分 ,在每一等分时间段内随机确定采样时机 ,或在第一等分时间段内随机 ,以后加上相等时间间隔确定采样时机 ,当采样频率适当时 ,可以得到与全程采样相近的TWA值 ;采样频率 (It)可根据采样时间 (Ts)用方程式It=36 .61 8Ts- 0 .50 4 5计算。　 [结论 ]　沿用MAC的标准采样方法 ,增加采样频率并用推荐方法确定采样时机 ,可以获得较为准确的TWA值     

车间空气中氯化锌（烟）卫生标准研究

飘扬较系统的动物试验结果和职业人群的流行病不调查，参考国外标准，结合我国实际，为使对职业接触氯化锌（烟）工人的呼吸道刺激和对肺的毒性减少到最小为依据，推荐时间国权平均容许浓度１ｍｇ／ｍ＾３，最高容许浓度２ｍｇ／ｍ＾３。     

基于时频分析的T波交替检测算法的研究

心电的T波交替现象与室性心律失常有关,已成为预测心脏猝死的一个无创的临床指标.当前T波交替分析常用谱分析方法,为弥补其不具备时间分辨率的不足,本研究提出一种鲁棒的基于时频分析的微伏级T波交替检测算法:通过心电信号的短时傅里叶变换,提取时域T波序列,计算其在选定时频区域的能量谱；然后运用Wilcoxon秩和检验统计分析方法,检测微伏级T波交替现象.经仿真实验、欧洲ST-T数据及临床检测实验,本算法对T波交替检测的平均灵敏性达90.4％,正确预测率达92.0％,在30 dB及以上信噪比情况下,实现了100％的正确检测.仿真实验还表明本算法也支持短时心电数据的TWA准确检测.     

T波电交替及其临床意义

T波电交替（T wave alternans,TWA）是指在规整的心律时,体表心电图上T波形态、极性和振幅的逐搏交替变化。目前大量研究认为T波电交替是人类及动物缺血心肌发生室速、室颤的标志,是预测发生恶性室性心律失常及猝死的有力预测指标。现就T波电交替的溯源与发展、发生机制、影响因素及临床意义等进行综述。     

基于T波最大值的T波电交替分析法

提出了一种基于T波最大值T波电交替(T-wave alternans,TWA)的快速傅氏变换(Fast fouriertransform,FFT)分析法。该方法能在减少抽样频率的条件下,保证计算精度。基于T波最大值的方法还解决了固定T波的取样点随着心率的变化而变化问题。该方法对连续128个正常心跳周期的ST-T结构中的T波最大值进行FFT变换,进而可以得到其功率谱曲线图。该功率谱图可反映TWA。