Physiological workload reactions to increasing levels of task difficulty

The sensitivity of physiological measures to mental workload was investigated in a flight simulator. Twelve pilots had to fly through a tunnel with varying levels of difficulty. Additionally, they had to perform a memory task with four levels of difficulty. The easiest memory task was combined with the easiest tunnel task and the most difficult memory task with the most difficult tunnel task. Between the tunnel tasks, subjects had to fly a pursuit task in which a target jet had to be followed. Rest periods before and after the experiment were used as a baseline for the physiological measures. Mental workload was measured with heart period, continuous blood pressure, respiration and eye blinks. Several respiratory parameters, heart rate variability, blood pressure variability and the gain between systolic blood pressure and heart period (modulus) were scored. All measures showed differences between rest and flight, and between the pursuit and the tunnel task. Only heart period was sensitive to difficulty levels in the tunnel task. Heart rate variability increased when respiratory activity around 0.10 Hz increased, which occurred often. The modulus was hardly influenced by respiration and therefore appears to be a better measure than heart rate variability. Among the respiratory parameters, the duration of a respiratory cycle was the most sensitive to changes in workload. The time in between two successive eye blinks (blink interval) increased and the blink duration decreased as more visual information had to be processed. Increasing the difficulty of the memory task led to a decrement in blink interval, probably caused by subvocal activity during rehearsal of target letters. The data show that physiological measures are sensitive to mental effort, whereas rating scales are sensitive to both mental effort and task difficulty.     

Understanding the human performance envelope using electrophysiological measures from wearable technology

In this article, we capture electrophysiological measures from a new wearable technology to understand the human performance envelope. Using the NASA Multi-Attribute Task Battery (MATB II), participants completed tasks associated with flight control which included communication, tracking and system and resource monitoring. Electrophysiological measures relating to cardiac activity and respiration were taken using the new wearable technology. Our results show significant differences in both heart rate and respiration rate in response to different taskloads and that higher taskloads were associated with higher mental workload. Frequency measures of heart rate variability discriminated different task types but not taskloads. This finding may be related to differences in task complexity being more important than the number events which we have used to manipulate taskload. We suggest that this new generation of wearable sensors could be used to inform operator locus in a human performance envelope, indicating when assistance by the aircraft or another crew member may be necessary to maintain safe and efficient performance.     

Heart period variability and respiratory changes associated with physical and mental load: non-linear analysis

In the investigation of heart rate and heart rate variability, the discrimination between mental workload, physical activity and respiration is known to be methodologically difficult. At most, heart rate variability measures are more likely to be coarse-grained measures with variability confounded by heart rate. Moreover, the spectral analysis of heart rate variability shows broad-band frequency characteristics, pointing towards non-stationarity or non-linearity. From this it is suggested to focus on non-linear dynamic analyses that are variance-insensitive. The experimental section of the paper focuses on the estimation of two non-linear measures for both heartbeat dynamics and respiration, the correlation dimension indicating complexity and the Lyapunov exponents indicating predictability. The results indicate that the complexity of heart dynamics is related to the type of task and that the predictability of heart dynamics is related to the amount of load.     

Physiological and subjective responses to breathing resistance of N95 filtering facepiece respirators in still-sitting and walking

The objective of this study was to assess the impact of breathing resistance on physiological and subjective responses to N95 filtering facepiece respirators (N95 FFRs) during still-sitting and walking. Fifteen subjects sat for 5 min and walked for 5 min while wearing 2 different models of N95 FFRs, 1 model of which was equipped with exhalation valves (N95 FFR/EV). The subjects were monitored by a modified monitoring garment for respiratory signals (RSP) and surface electromyography (sEMG). Subjects also were asked to complete subjective ratings of overall breathing resistance. The results of the physiological measurements in this study have shown that compared with no respirator, wearing N95 FFR had a direct effect on increasing respiratory amplitude, muscle activity and fatigue of abdominal, and fatigue of scalene; The use of N95 FFR/EV conferred limited physiological benefit over N95 FFR in walking; Compared with sitting still, walking significantly decreased respiratory amplitude, but increased respiratory rate, the muscle activity of sternomastoid, scalene, diaphragm and abdominal, the fatigue of scalene and intercostal. The subjective survey showed that wearing respirators and walking had a direct effect on improving the subjective overall breathing resistance. Significantly low to moderate correlation coefficients were shown between physiological values (respiratory amplitude, the muscle activity of diaphragm, the muscle activity and fatigue of scalene and abdominal), and the subjective breathing resistance. This is the first reported study that combines RSP, sEMG and subjective overall breathing resistance to evaluate breathing resistance on the use of N95 FFR in sitting still and walking. The physiological responses to breathing resistance of wearing a N95 FFR for 5 min in still-sitting and walking are relatively small and should generally be well tolerated by healthy persons.Relevance to industryThis paper's findings can be readily employed by respirator manufactures and administrations for evaluating the respiratory muscle function (activity, fatigue) and breathing parameters of wearing N95 FFRs. Observations of present study are in support of issuing new regulations to raise the limit for breathing resistance over short periods at low-moderate exertion tasks. Thus, the manufacturers could easily fulfill the requirements for collection efficiency by adding more filter media while still meeting the requirements for air resistance.     

Mental workload measurement for emergency operating procedures in digital nuclear power plants

Mental workload is a major consideration for the design of emergency operation procedures (EOPs) in nuclear power plants. Continuous and objective measures are desired. This paper compares seven mental workload measurement methods (pupil size, blink rate, blink duration, heart rate variability, parasympathetic/sympathetic ratio, total power and (Goals, Operations, Methods, and Section Rules)-(Keystroke Level Model) GOMS-KLM-based workload index) with regard to sensitivity, validity and intrusiveness. Eighteen participants performed two computerised EOPs of different complexity levels, and mental workload measures were collected during the experiment. The results show that the blink rate is sensitive to both the difference in the overall task complexity and changes in peak complexity within EOPs, that the error rate is sensitive to the level of arousal and correlate to the step error rate and that blink duration increases over the task period in both low and high complexity EOPs. Cardiac measures were able to distinguish tasks with different overall complexity. The intrusiveness of the physiological instruments is acceptable. Finally, the six physiological measures were integrated using group method of data handling to predict perceived overall mental workload.

Practitioner Summary: The study compared seven measures for evaluating the mental workload with emergency operation procedure in nuclear power plants. An experiment with simulated procedures was carried out, and the results show that eye response measures are useful for assessing temporal changes of workload whereas cardiac measures are useful for evaluating the overall workload.     

核动力装置无线传感器抗辐照屏蔽设计和验证

无线传感器网络作为一种分布式无线网络系统,应用于核环境中,可以减少监测系统电缆布线工作量、降低核环境中装置使用和维护中电缆老化和端接故障带来的影响,有助于核环境中装置自动化、信息化水平的提升和设备的集成化、小型化.但其应用也面临强射线及中子辐照、射频和电磁干扰严重等特殊复杂核环境的制约.针对核环境中的γ辐射,通过屏蔽材...     

Monitoring of mental workload levels during an everyday life office-work scenario

Personal and ubiquitous healthcare applications offer new opportunities to prevent long-term health damage due to increased mental workload by continuously monitoring physiological signs related to prolonged high workload and providing just-in-time feedback. In order to achieve a quantification of mental load, different load levels that occur during a workday have to be discriminated. In this work, we present how mental workload levels in everyday life scenarios can be discriminated with data from a mobile ECG logger by incorporating individual calibration measures. We present an experiment design to induce three different levels of mental workload in calibration sessions and to monitor mental workload levels in everyday life scenarios of seven healthy male subjects. Besides the recording of ECG data, we collect subjective ratings of the perceived workload with the NASA Task Load Index (TLX), whereas objective measures are assessed by collecting salivary cortisol. According to the subjective ratings, we show that all participants perceived the induced load levels as intended from the experiment design. The heart rate variability (HRV) features under investigation can be classified into two distinct groups. Features in the first group, representing markers associated with parasympathetic nervous system activity, show a decrease in their values with increased workload. Features in the second group, representing markers associated with sympathetic nervous system activity or predominance, show an increase in their values with increased workload. We employ multiple regression analysis to model the relationship between relevant HRV features and the subjective ratings of NASA-TLX in order to predict the mental workload levels during office-work. The resulting predictions were correct for six out of the seven subjects. In addition, we compare the performance of three classification methods to identify the mental workload level during office-work. The best results were obtained with linear discriminant analysis (LDA) that yielded a correct classification for six out of the seven subjects. The k-nearest neighbor algorithm (k-NN) and the support vector machine (SVM) resulted in a correct classification of the mental workload level during office-work for five out of the seven subjects.     

Physical,mental, emotional,and subjective workload components in train drivers

This study, using 12 train drivers on a high speed track and 11 drivers on a mountain track, tried to differentiate between the physical, emotional, mental, and subjective workload components imposed on the drivers during work. With the simultaneous recording and on-line analysis of heart rate and physical activity, the emotional component in terms of the so-called additional heart rate was separated from the physical component. Mental workload was calculated by the heart rate variability and by shifts in the T-wave amplitude of the ECG. Speed of the train, mode of driving, and stress of the situation were rated by two observers who accompanied the drivers in the cabin. During speeds up to l00km/h as compared to standstills no heart rate changes occurred, but with speeds from l00km/h up to 200 km/h heart rate decreased indicating a monotony effect. However, heart rate variability, and T-wave amplitude indicated higher mental load during driving in most speed categories. Starting the train and coming to a halt showed greater emotional workload as compared to moving. Observer ratings of stress and subjective ratings of stress by the drivers revealed several discrepancies. Discrepancies were also seen between workload as indicated by the physiological parameters, and corresponding stress ratings by the observers or by the drivers.     

Enhancing cardiac parasympathetic nervous activity using a posture respiration ambient biofeedback system: a pilot study

A respiration–posture feedback system was developed to control breathing involuntarily. A small air chamber placed under a subject’s back deflates and inflates to make a subject’s upper body move vertically while lying on a bed. By regulating the deflation/inflation of the air chamber in synchronization with actual respiration, the subject’s respiration was successfully lengthened and deepened. The modulation of the respiration acted as a physiological sedative for the subject as the heart rate variability index suggested that the subject’s parasympathetic nervous system activity was enhanced.     

Mining Wi-Fi Channel State Information for breathing and heart rate classification

Current vital signs monitoring systems require that the subject wears sensing devices. An alternative approach is using device-free technologies such as the Channel State Information (CSI) of a Wi-Fi signal. However, recent works using CSI for vital signs monitoring rely on complex signal processing techniques to improve its reliability. Considering that breathing and heart rate provide relevant information about the current health status of a subject, in this paper we develop an experimental system that combines signal processing techniques, such as filters and time and frequency domain analysis, with Data Mining techniques for breathing and heart rate monitoring. We also provide a thorough analysis for understanding CSI data as a technology for vital signs monitoring. Using K-Nearest Neighbors, Support Vector Machines, and Quadratic Discriminant Classifier models, our system achieves an accuracy of 99.18% for breathing rate classification while identifying heart rate monitoring challenges that are also stated in this paper.     

A review of: “Human Motor Actions: Bernstein Reassessed.” Edited by H. T. A. WHITING. (Oxford: North-Holland, 1984.) [Pp. xxxv + 633.] ISBN 0-444-86813-5.

The physical work performance of eight fit fire fighters wearing fire brigade uniforms and wearing breathing apparatus was assessed. They were tested in a climatic chamber set at temperatures of 15 and 45°C respectively. The test was performed with and without fire fighting equipment. The subjects walked on a treadmill at a speed of 3.5km/h, which produce a workload equivalent of 20% of the subjects' maximal oxygen uptake without equipment, and 30% with equipment. The test lasted for 60 min. Heart rate, oxygen uptake, skin and deep body temperatures were measured during the test. The subjects estimated perceived physical exertion and perceived temperature. Wearing fire fighting equipment increased the oxygen uptake by 0.4 1min^-1. Heart rate at the end of the experiments reached near-maximum levels when the temperature was 45°C with equipment, and deep body temperature increased to an average of 38.7°C. The subjects' ratings of perceived exertion were highly correlated to heart rate. The loading induced by heat and protective equipment reduced the ability to perform strenuous work. The combination of thick clothing and heavy breathing apparatus was found to have a significant limiting effect on the endurance of fire fighters.     

钢厂步进梁加热炉监控系统的设计与实现

随着钢铁工业企业生产规模的不断扩展,对现场设备工作状况的实时监控提出了更高的要求。本文介绍了基于西门子上位组态软件WinCC的某钢厂步进梁式加热炉监控系统的设计与实现。     

Effect of varying levels of mental workload on startle eyeblink modulation

Previous research using punctuate reaction time and counting tasks has found that the startle eyeblink reflex is sensitive to attentional demands. The present experiment explored whether startle eyeblink is also modulated during a complex continuous task and is sensitive to different levels of mental workload. Participants (N = 14) performed a visual horizontal tracking task either alone (single-task condition) or in combination with a visual gauge monitoring task (multiple-task condition) for three minutes. On some task trials, the startle eyeblink reflex was elicited by a noise burst. Results showed that startle eyeblink was attenuated during both tasks and that the attenuation was greater during the multiple-task condition than during the single-task condition. Subjective ratings, endogenous eyeblink rate, heart period, and heart period variability provided convergent validity of the workload manipulations. The findings suggest that the startle eyeblink is sensitive to the workload demands associated with a continuous visual task. The application of startle eyeblink modulation as a workload metric and the possibility that it may be diagnostic of workload demands in different stimulus modalities is discussed.     

Effect of varying levels of mental workload on startle eyeblink modulation

Previous research using punctuate reaction time and counting tasks has found that the startle eyeblink reflex is sensitive to attentional demands. The present experiment explored whether startle eyeblink is also modulated during a complex continuous task and is sensitive to different levels of mental workload. Participants (N = 14) performed a visual horizontal tracking task either alone (single-task condition) or in combination with a visual gauge monitoring task (multiple-task condition) for three minutes. On some task trials, the startle eyeblink reflex was elicited by a noise burst. Results showed that startle eyeblink was attenuated during both tasks and that the attenuation was greater during the multiple-task condition than during the single-task condition. Subjective ratings, endogenous eyeblink rate, heart period, and heart period variability provided convergent validity of the workload manipulations. The findings suggest that the startle eyeblink is sensitive to the workload demands associated with a continuous visual task. The application of startle eyeblink modulation as a workload metric and the possibility that it may be diagnostic of workload demands in different stimulus modalities is discussed.     

Team performance in process control: influences of interface design and staffing levels

A study performed at the OECD Halden Reactor Project compared the effects of interface design and staffing levels on various aspects of team performance. Teams of nuclear power plant operators participated in challenging simulator scenarios, working in either a simulated conventional plant, with a hard-control interface, or in a simulated advanced plant, with a computerized interface. Two-team staffing levels, normal and minimum, were evaluated in each plant condition. All teams participated in the same five study conditions, lasting 1-3 h each. Several measures assessed team performance: situation awareness, workload, rated team interactions, rated overall performance and objective performance. The findings revealed that combinations of interface design and staffing levels supported different aspects of performance. Larger crews consistently performed better than smaller crews in the conventional plant. In the advanced plant, both crew types performed equally well; however, smaller crews had better situation awareness than larger crews. In general, performance was better for crews using the advanced plant interface, but workload was higher. Workload also was consistently higher in the smaller crews than in the larger crews, regardless of interface type. Links between the performance measures were also noted.     

Team performance in process control: influences of interface design and staffing levels

A study performed at the OECD Halden Reactor Project compared the effects of interface design and staffing levels on various aspects of team performance. Teams of nuclear power plant operators participated in challenging simulator scenarios, working in either a simulated conventional plant, with a hard-control interface, or in a simulated advanced plant, with a computerized interface. Twoteam staffing levels, normal and minimum, were evaluated in each plant condition. All teams participated in the same five study conditions, lasting 1– 3 h each. Several measures assessed team performance: situation awareness, workload, rated team interactions, rated overall performance and objective performance. The findings revealed that combinations of interface design and staffing levels supported different aspects of performance. Larger crews consistently performed better than smaller crews in the conventional plant. In the advanced plant, both crew types performed equally well; however, smaller crews had better situation awareness than larger crews. In general, performance was better for crews using the advanced plant interface, but workload was higher. Workload also was consistently higher in the smaller crews than in the larger crews, regardless of interface type. Links between the performance measures were also noted.     

组合机理知识的污水生化处理过程在线监视策略研究

本文把呼吸量估计知识组合到多变量主模型中，提出了一种新的污水生化处理过程（WWTP）在线监视策略.呼吸量是活性污泥(微生物)呼吸能力的一种表示,与微生物消耗的氧直接有关，其估计仅需要测量活性污泥反应器中溶解氧浓度和有关物料流量信号.由于溶解氧和流量计在工业污水处理现场安装普遍，响应快速，运行稳定且易维护，因此构造基于微生物呼吸量估计的过程监视方法，在故障检测与诊断速率、经济性等方面有显著的优势.把新方法应用到国际水协会发布的Benchmark问题，在监视暴风雨事件和毒素脉冲等典型的WWTP异常状态时，统计指标变化灵敏，诊断及时.     

Tracking workload in the emergency department

OBJECTIVE: The primary objective of this study was to create a methodology for measuring transient levels of physician workload in a live emergency department (ED) environment. BACKGROUND: Characterizing, defining, and measuring aspects of this interrupt-driven work environment represent the preliminary steps in addressing impending issues concerning ED overcrowding, efficiency, and patient and provider safety. METHODS: A time-motion task analysis was conducted. Twenty emergency medicine (EM) physicians were observed for 180-min intervals in an ED of an academic medical center. Near continuous workload measures were developed and used to track changing workload levels in time. These measures were taken from subjective, objective, and physiological perspectives. The NASA-Task Load Index was administered to each physician after observational sessions to measure subjective workload. Physiological measurements were taken throughout the duration of the observation to measure stress response. Additional information concerning physicians' patient quantity and patient complexity was extracted from the ED information system. RESULTS: Graphical workload profiles were created by combining observational and subjective data with system state data. Methodologies behind the creation of workload profiles are discussed, the workload profiles are compared, and quantitative and qualitative analyses are conducted. CONCLUSION: Using human factors methods to measure workload in a setting such as the ED proves to be challenging but has relevant application in improving the efficiency and safety of EM. APPLICATION: Techniques implemented in this research are applicable in managing ED staff and real-time monitoring of physician workload.     

Selection of input features across subjects for classifying crewmember workload using artificial neural networks

The issue of crewmember workload is important in complex system operation because operator overload leads to decreased mission effectiveness. Psychophysiological research on mental workload uses measures such as electroencephalogram (EEG), cardiac, eye-blink, and respiration measures to identify mental workload levels. This paper reports a research effort whose primary objective was to determine if one parsimonious set of salient psychophysiological features can be identified to accurately classify mental workload levels across multiple test subjects performing a multiple task battery. To accomplish this objective, a stepwise multivariate discriminant analysis heuristic and artificial neural network feature selection with a signal-to-noise ratio (SNR) are used. In general, EEG power in the 31-40-Hz frequency range and ocular input features appeared highly salient. The second objective was to assess the feasibility of a single model to classify mental workload across different subjects. A classification accuracy of 87% was obtained for seven independent validation subjects using neural network models trained with data from other subjects. This result provides initial evidence for the potential use of generalized classification models in multitask workload assessment.     

Evaluation of two instruments for recording sitting and standing postures and number of foot steps

The study evaluates two simple instruments that may be used to describe aspects of physical workload in almost any occupation: a pedometer, which measures the number of steps taken by the subject wearing it, and a posimeter, which quantifies the time spent sitting and the number of changes between sitting and a The present data showed that the pedometer registers the correct number of steps at 'ordinary' walking speed independent of type of floor (plastic carpet and stone floor), shoes (wooden shoes and sneakers) and gender. At 'slow' walking (2.4 km/h) a reduced number of steps was recorded. In a field study the median difference between pedometer registration and observation was 6% (range 1-27) of the observed obtained for the five investigated pedometers was 0-15%. The posimeter was found to give a good estimate of the percentage time spent sitting (mean deviation 3%, range 0-15%). The number of changes between sitting and standing was overestimated by the posimeter (median deviation 63% of the observed). Some extreme working postures can be misread by the posimeter.