汽车驾驶员模拟精神负荷与心率变异性的相关性分析

汽车驾驶员精神负荷状态下的心率变异性分析对于揭示驾驶员职业应激特点,预防驾驶员职业疾病,保护驾驶员身体健康及提高行驶安全性有重要意义.本文在实验室条件下采用警惕任务代替驾驶员实际精神负荷,应用功率谱分析研究了模拟应激状态下心率变异性(TP,LF,HF,LF/HF)的变化趋势.本实验中,心率变异性频域主要指标如LF、HF、LF/HF表现出显著的线性趋势.结果表明,健康人在持续应激状态下,交感神经张力显著增加,迷走神经张力显著降低.实验结果表明HRV与精神疲劳具有较好的相关性.     

Effects of Behavioral Control and Type A Behavior on Cardiovascular Responses

The purpose of this study was twofold: (a) to examine the relationship between degree of behavioral control and cardiovascular changes in 60 adult males performing an anagram solution task, and (b) to assess the interaction between behavioral control and type of subject (A vs. B). Three conditions were used, differing from each other in the percentage of solvable anagrams (100, 50, and 30%). Systolic blood pressure (SBP), diastolic blood pressure (DBP), and heart rate (HR) were measured before, during, and after the anagram task. In all conditions, during-task SBP, DBP, and HR were significantly elevated above baseline. Blood pressure (BP) elevations appeared to be curvilinearly related to degree of behavioral control, i.e., more elevated in the 50% than in the 100% and 30% conditions. HR changes did not differ among conditions. Concerning the Type A behavior pattern, the results revealed significantly greater BP elevations for Type A than for Type B subjects, especially in the 50% condition, thereby confirming that the physiologic correlates of Type A behavior are predominantly evoked in challenging circumstances. Findings were discussed in the light of results of cardiovascular and endocrinological research. Consideration was given to the possible role of disengagement in the 30% condition and to differences in the pattern of responding between As and Bs.     

模拟腰椎前路、后路间盘摘除术T12-L5腰段脊柱应力松弛蠕变实验研究

研究了18例新鲜尸体T12－L5腰段脊柱应力松弛，蠕变特性。测定了完整脊柱（正常组）及模拟前路（对照1组），后路手术（对照2组）腰段脊柱的应力松弛和蠕变效应，得出了在恒应变，应力条件下应力－时间曲线及数据，用回归分析的方法处理实验数据，得出了归一化应务松弛，蠕变函数及曲线，对前路间盘摘除术与后路间盘摘除术对脊柱粘弹性的影响进行分析讨论。     

Microfilament system in the microvascular endothelium of the palmar fascia affected by mechanical stress applied from outside

The effect of externally applied mechanical stress was investigated by thin section electron microscopy of the microvessels in the unaffected palmar fascia in the carpal tunnel syndrome and in patients with Dupuytren's contracture before and after application of a continuous elongation device. In the unaffected palmar fascia the microfilaments of the endothelial cells were connected to a few adherens junctions and focal contacts; stress fibres were absent. In the cord of Dupuytren's disease the microfilaments were increased in quantity. The length ratios of the connections with the lateral and basal cell membrane were significantly higher than in the control group and increased to an even greater extent in the continuously extended fascia. Stress fibres appeared in the endothelial cells of postcapillary venules in the nonextended cord and in the endothelium of both arterioles and venules after extension elongation. The numerous intermediate filaments and the rare microtubules remained unchanged in the endothelial cells of all palmar fasciae analysed. In the endothelial cells of the microvessels the mechanical stress applied from outside mainly affected the contractile component of the cytoskeleton.     

Fluid and solid mechanical implications of vascular stenting

Vascular stents have emerged as an effective treatment for occlusive vascular disease. Despite their success and widespread use, outcomes for patients receiving stents are still hampered by thrombosis and restensosis. As arteries attempt to adapt to the mechanical changes created by stents, they may in fact create a new flow-limiting situation similar to that which they were intended to correct. In vitro fluid mechanics and solid mechanics studies of stented vessels have revealed important information about how stents alter the mechanical environment in the arteries into which they are placed. Adverse nonlaminar flow patterns have been demonstrated as well as remarkably high stress concentrations in the vessel wall. In vivo studies of stented vessels have also shown a strong relationship between stent design and their dynamic performance within arteries. Alterations in pressure and flow pulses distal to the stent have been observed, as well as regional changes in vascular compliance. Considering the influence of flow and stress on the vascular response and the suboptimal clinical outcomes associated with stenting, knowledge gained from stent/artery mechanics studies should play an increasingly important role in improving the long-term patency of these devices. © 2002 Biomedical Engineering Society. PAC2002: 8719Rr, 8780-y, 8719Uv     

Local cerebral blood flow in gently restrained rats: effects of propranolol and diazepam

Summary The cerebrovascular consequences of the gentle restraint commonly used for the measurement of local cerebral blood flow (LCBF) in conscious rats has been tested by using two drugs, propranolol and diazepam. Propranolol induced small LCBF decreases in 7 structures suggesting that the cerebral circulation was partially controlled by the activation of intra or extracerebral aminergic pathways in this protocol. Sedative doses of diazepam reduced LCBF in most of the structures but anxiolytic doses increased it in 4 structures. This effect may be due to a regionally differentiated modification of activity in the brain due to the selective inhibition of limbic structures by diazepam. Since propranolol and diazepam induced only small changes, the LCBF of gently restrained rats appeared to be minimally affected by the stressful situation imposed by the protocol.     

Humoral indices of stress in rats

Rats, bearing chronic venous cannulas, were subjected to 30 sec of constant current grid shock at 1 of 6 intensities (0, 0.25, 0.5, 1, 2, 4 mA), after being allowed to acclimate to the test chamber overnight. Blood, sampled before and after shock, was assayed for epinephrine, norepinephrine and corticosterone. Peak levels of both catecholamines increased in a stepwise fashion (i.e., monotonically) with increasing magnitude of stress, as reflected by current intensity of foot shock. Plasma corticosterone did not increase monotonically but instead showed similar increases in the 5 groups of rats that actually received shock. These data support earlier work which indicate that plasma corticosterone is not a sensitive index of stress; this is probably the case because of the relatively narrow range of responsiveness of the adrenal cortex to ACTH. In contrast, both plasma catecholamines appear to satisfy some of the requisites for a sensitive visceral index of stress.     

Objective stress monitoring based on wearable sensors in everyday settings

Abstract

Monitoring people’s stress levels has become an essential part of behavioural studies for physical and mental illnesses conducted within the biopsychosocial framework. There have been several stress assessment studies in laboratory-based controlled settings. However, the results of these studies do not always translate effectively to an everyday context. The current state of wearable sensor technology allows us to develop systems measuring the physiological signals reflecting stress 24/7 while capturing the context. In this paper, we present a stress monitoring system that provides objective daily stress measurements in everyday settings based on three physiological signals: electrocardiogram (ECG), photoplethysmogram (PPG), and galvanic skin response (GSR) using Shimmer3 ECG, Shimmer3 GSR+, and Empatica E4 wearable sensors. We perform controlled stress assessment experiments on 17 participants in which we successfully detect stress with a 94.55% accuracy for 10-fold cross-validation and an 85.71% accuracy for subject-wise cross-validation. In everyday settings, the system assesses stress with an 81.82% accuracy. We also examine whether motion artefacts affect stress assessment and filter the low-confidence readings to minimise false alarms.