Objective evaluation of stress with the blind by the monitoring of autonomic nervous system activity.

Accessibility for the blind in an urban space must be studied under real conditions in their daily environment. A new approach for evaluating the impact of environmental conditions on blind pedestrians is the objective measure of stress by the monitoring of the autonomic nervous system (ANS) activity. Original techniques of data analysis and spatial representation are proposed for the detection of the ANS activity through the assessment of the electrodermal activity. Skin resistance was recorded with an EmoSense system on 10 blind subjects who followed a charted course independently. The course was 1065 meters long and consisted of various environmental conditions in an urban space. The spatial frequency of the non-specific skin resistance responses was used to provide a more relevant representation of geographic hotspots. Results of statistical analysis based on this new parameter are discussed to conclude on phenomena causing mental stress with the blind moving in an urban space.

Introducing knowledge of wearing compression stockings on the skin blood flow by using microHematron device.

The aim of this preliminary study was to review the actual state of knowledge concerning the mechanisms underlying compression medical stockings action on the skin blood flow (SBF) in capillaries. SBF was assessed by measuring the thermal conductivity of living-tissues using microHematron ambulatory device. The investigation was performed for different postures using three standard French classes (10-15 mmHg, 15-20 mmHg and 20-36 mmHg) of Medical compression stockings (MCS) on six healthy subjects without chronic venous insufficiency. The experiment was divided into four stages (supine, sitting, standing and walking) and was repeated for each class of compression stockings and without MCS. The results showed a significant improvement of SBF depending on the class of MCS used. Best results were obtained for the Class III, which exerts to the highest level of pressure exerted around the ankle. Due to the low number of subjects, which therefore reduces the statistical relevance of results, a non-significant difference in SBF due to the subject's posture was observed. Nonetheless, a positive action by all the classes of MCS on SBF was measured for the supine position. This is a very important result; with patients with chronic venous insufficiency have often some mobility reduction, MCS may enhance their microcirculation even at rest.

Design and validation of an ambulatory system for the measurement of the microcirculation in the capillaries: microHematron device.

The non-invasive Hematron sensor is an active sensor used in studying skin blood flow (SBF) by measuring thermal conductivity of living tissues. Up to now, the Hematron device was composed of the Hematron probe and a heavy analog conditioning electronics. This paper presents the design, realization and validation of an ambulatory device (microHematron) associated with the original Hematron probe. The electronic architecture is based on a Programmable System on Chip (PSoC), which contributes in reducing the number of discrete components, and consequently, the electronic conditioning circuit of Hematron. The microHematron device can be worn on the wrist of the patient thanks to its size (4x3x1cm3) compared to the non-ambulatory conditioning electronics sized 20x30x20cm3. In addition, data can be stored in a microSD card or transmitted using a ZigBee module. The validation of the microHematron device was performed using the analog conditioning electronics as a reference. Experiments were performed first on a physical model reproducing microcirculation in order to characterize the linearity of the thermal conductivity as a function of water flow. Then, two experiments were hold in-vivo conditions highlighting the performances of this new device. In a first experiment, effects of mental calculation on effective tissue perfusion were measured and in a second one, effects of an anti-cellulite cream on micro-vascularisation and skin temperature were studied.

A wearable, low-power, health-monitoring instrumentation based on a Programmable System-on-Chip.

Improvement in quality and efficiency of health and medicine, at home and in hospital, has become of paramount importance. The solution of this problem would require the continuous monitoring of several key patient parameters, including the assessment of autonomic nervous system (ANS) activity using non-invasive sensors, providing information for emotional, sensorial, cognitive and physiological analysis of the patient. Recent advances in embedded systems, microelectronics, sensors and wireless networking enable the design of wearable systems capable of such advanced health monitoring. The subject of this article is an ambulatory system comprising a small wrist device connected to several sensors for the detection of the autonomic nervous system activity. It affords monitoring of skin resistance, skin temperature and heart activity. It is also capable of recording the data on a removable media or sending it to computer via a wireless communication. The wrist device is based on a Programmable System-on-Chip (PSoC) from Cypress: PSoCs are mixed-signal arrays, with dynamic, configurable digital and analogical blocks and an 8-bit Microcontroller unit (MCU) core on a single chip. In this paper we present first of all the hardware and software architecture of the device, and then results obtained from initial experiments.

Evaluation of the autonomic nervous system for fall detection.

Studies show that the proportion of elderly will reach 30% of the total population by 2050 in developed countries, such as France. The elderly live generally alone, thus many health problems related to age are under reported. Falling is one of these problems and several devices have been developed recently, based on accelerometers, in order to detect it and alert carers. In order to improve the detection success of these devices, we propose quantifying autonomic nervous system activity (ANS) using a wearable ambulatory device developed for this purpose. We studied the A.N.S's response on 7 adult subjects during simulated falls and standing-lying transitions. We implemented a classification method using the Support Vector Machine in order to classify these two situations using measured heart rate variability and electrodermal response. Good results (sensibility = 70.37%, specificity = 80%, positive predictor = 73.8%) were obtained using a Polynomial kernel (p = 5) for the support vector machine implementation.

An integrated device to evaluate a driver's functional state.

In the field of cognitive ergonomics, research on car drivers requires multimodal in-vehicle systems for recording not only driving-related behavior, but also contextual information from their surroundings. In addition, reliable information concerning a driver's functional state should be obtained. In this article, we describe an integrated device simultaneously recording specific physiological data, video recordings of the driver and environment, parameters from the vehicle, and contextual data. Physiological signals from the autonomic nervous system provide objective and quantitative information on the driver's alertness and his/her ability to process specific driving-related stimuli or other nonspecific information. Consequently, recorded physiological responses can be related to individual driving events. Electrodermal and cardiac activities are sensitive to time-dependent variations in arousal level and to certain external stimuli, so there is great interest in studying drivers' behavior via measured physiological signals that have been established as suitable behavioral indicators. The present integrated device is capable of processing the relevant indices from raw measured data in real time.

Cerebral temperature varies across circadian phases in humans.

The 24-hour rhythm of core body temperature (CBT) is commonly used in humans as a tool to assess the oscillation of the central endogenous circadian pacemaker. The invasive nature of the rectal sensor used to collect CBT makes it difficult to use in ambulatory conditions. Here we validate the use of a newly developed brain temperature (BT) sensor against that of a standard rectal temperature sensor using a 72-hour ultra-rapid sleep-wake (URSW) cycle procedure. A significant circadian variation of both body temperature recordings was observed from which a phase and amplitude was reliably determined. These results indicate that BT can be refined as a non-invasive alternative to CBT measurements in the evaluation of circadian phase in field conditions.

3D ultrasound elastography for early detection of lesions. evaluation on a pressure ulcer mimicking phantom.

A pressure ulcer is a damaged tissue area induced by an unrelieved pressure compressing the tissue during a prolonged period of immobility. The lack of information and studies on the development of this pathology makes its prevention difficult. However, it is both acknowledged that lesions initiate in the deep muscular tissues before they expand to the skin, and that lesions are harder than healthy tissues. Elastography is therefore an interesting tool for an early detection of the pathology. A 3D strain estimation algorithm is presented and evaluated on a PVA-cryogel phantom, mimicking a pressure ulcer at an early stage.

Infrared imaging analysis for thermal comfort assessment.

Skin temperature is a relevant and effective indicator for objective evaluation of human sensations and thermal states according to the surrounding thermal stresses. Managed by skin blood flow, sympathetic nervous system (constriction and sweating), subcutaneous thermal structure and facial vein patterns, facial coetaneous temperature variability can give information non-invasively on many physiological functions. These informations are deduced from thermal images obtained by far infrared imaging (7 - 14 microm). The work presented here deals with facial thermographic image analysis. Thermal regions of interest are extracted, such as left and right front, left and right cheek, left and right periobital region. Each region is analyzed by the FFT power spectrum calculation regarding to specific spectral band.

Autonomic-nervous-system activity during the preparation phase for the snatch in Olympic weight lifting.

PURPOSE: To examine the preparation phase for the snatch lift in Olympic weight lifting. Two behavioral periods were studied, each corresponding to specific mental processes: a stance in front of the bar and placement of hands on the bar. Each period was hypothesized to elicit different responses of autonomic-nervous-system activity. METHODS: Twelve elite male subjects completed 12 lifts at 90% to 95% of their best grade after warm-up (80% of their best grade). Because peripheral autonomic-nervous-system activity is related to arousal and activation variation, 6 variables were continuously recorded: electrodermal (skin resistance and potential), thermovascular (skin temperature and skin blood flow), and cardiorespiratory (heart rate and respiratory frequency). RESULTS: Responses (ie, phasic activities) were evident during the first behavioral period. Decrease in heart rate (mean = 19 beats/min) or in respiratory frequency (mean = 8.6 beats/min) was related to attention processes. These responses were weaker (-0.16 degrees C vs -0.25 degrees C in skin temperature) and shorter (2.7 seconds vs 4.3 seconds in skin resistance) than those recorded during execution. The second phase showed variations in basal levels (mean increase in heart rate of 25%), related to increase in activation, thus attesting the muscle system's process of preparation for effort. CONCLUSION: Weight lifters separated the preparation phase into 2 stages that were closely matched by different physiological activities. Weight lifting requires participants to share their mental resources among the 2 demanding concentration phases by first focusing their attention on the execution and then mobilizing energizing resources.

Observation of action and autonomic nervous system responses.

Observing somebody performing an action has been shown to elicit neuronal activity in the premotor cortex. This paper investigated physiological effect of observing an effortful action at the peripheral level. As Autonomic Nervous System responses reflect central nervous system processes such as movement planning and programming, it was expected that observing an action would elicit a pattern of ANS responses matching those recorded during actual movement. 12 male subjects, ages 23 to 28 years (M = 25.5, SD = 1.9), were selected as they were experienced in weight lifting. They were asked to observe a squat movement followed by returning to the upright position under 3 different conditions: (i) observation of actual movement performed by somebody else, (ii) observation of a video of the subject himself (first-person video), and (iii) observation of a video of somebody else performing the same movement (third-person video). Moreover, each movement was observed when performed at 50% and 90% of each participant's personal best mark (% of the highest weight which could be lifted). Three ANS parameters were continuously recorded: skin resistance, temperature and heart rate. ANS responses varied as a function of movement intensity: autonomic responses recorded during movement observation at 90% were significantly higher and longer than those recorded during movement observation at 50%. Thus, autonomic responses were linked to the amount of observed effort. Conversely, no difference was found among the three conditions of observation. ANS responses from observation of actual movement were shown to resemble those recorded under the two conditions of video observation.

Flexible technologies and smart clothing for citizen medicine, home healthcare, and disease prevention.

Improvement of the quality and efficiency of healthcare in medicine, both at home and in hospital, is becoming more and more important for patients and society at large. As many technologies (micro technologies, telecommunication, low-power design, new textiles, and flexible sensors) are now available, new user-friendly devices can be developed to enhance the comfort and security of the patient. As clothes and textiles are in direct contact with about 90% of the skin surface, smart sensors and smart clothes with noninvasive sensors are an attractive solution for home-based and ambulatory health monitoring. Moreover, wearable devices or smart homes with exosensors are also potential solutions. All these systems can provide a safe and comfortable environment for home healthcare, illness prevention, and citizen medicine.

Effect of a fatiguing protocol on motor imagery accuracy.

This study was devised to evaluate the influence of muscle fatigue on athletes' ability to perform motor imagery. Performance impairment is a consequence of fatigue, but alterations on perception and mental activity may also occur. To test whether peripheral fatigue affects mental processes, ten sports students imagined three consecutive countermovement jumps before and after a fatiguing protocol, through repetition of upright movements, at 70% of maximal voluntary contraction, until exhaustion. Autonomic nervous system responses and imagined movement durations were considered the dependent variables. Actual duration was systematically overestimated during both visual and kinesthetic imagery, but motor imagery duration and autonomic responses were similar without and under fatigue. Results suggest that muscle fatigue, unlike fatigue induced by prolonged exercise, does not elicit mental fatigue and therefore does not alter motor imagery accuracy.

Stroop color-word test, arousal, electrodermal activity and performance in a critical driving situation.

The aim of this experiment was to study drivers' performance when confronted with a critical crash avoidance situation. Subjects were asked to cover three laps of a private circuit (4 min per lap), respecting speed limits. During the last lap, an inflated dummy car, placed at an intersection, was pulled onto the traffic lane. The synchronization signal releasing the obstacle was triggered to make the braking distance too short, thus requiring subjects to brake and turn the driving wheel simultaneously. Before driving, subjects completed the Stroop color-word test. Skin conductance (SC) was recorded continuously, before and during driving. Subjects who performed the least well also performed the least well to Stroop test. The SC level showed that subjects avoiding the obstacle were more aroused than those who crashed into the dummy car. Performance to Stroop test and physiological arousal were thus shown to be determining factors in management of a critical driving situation.

Birth simulator: reliability of transvaginal assessment of fetal head station as defined by the American College of Obstetricians and Gynecologists classification.

OBJECTIVE: This study was undertaken to investigate the reliability of transvaginal assessment of fetal head station by using a newly designed birth simulator. STUDY DESIGN: This prospective study involved 32 residents and 25 attending physicians. Each operator was given all 11 possible fetal stations in random order. A fetal head mannequin was placed in 1 of the 11 American College of Obstetricians and Gynecologists (ACOG) stations (-5 to +5) in a birth simulator equipped with real-time miniaturized sensor. The operator then determined head position clinically using the ACOG classification. Head position was described as: (1) "engaged" or "nonengaged" (engagement code); (2) "high," "mid," "low," or "outlet" (group code); and (3) according to the 11 ACOG ischial spine stations (numerical code). Errors were defined as differences between the stations given by the sensor and by the operator. We determined the error rates for the 3 codes. RESULTS: "Numerical" errors occurred in 50% to 88% of cases for residents and in 36% to 80% of cases for attending physicians, depending on the position. The mean "group" error was 30% (95% CI 25%-35%) for residents and 34% (95% CI 27%-41%) for attending physicians. In most cases (87.5% for residents and 66.8% for attending physicians) of misdiagnosis of "high" station, the "mid" station was retained. Residents and attending physicians made an average of 12% of "engagement" errors, equally distributed between false diagnosis of engagement and nonengagement. CONCLUSION: Our results show that transvaginal assessment of fetal head station is poorly reliable, meaning clinical training should be promoted. The choice not to perform vaginal delivery when the fetus is in the "mid" position strongly decreases the risk of applying instruments on an undiagnosed "high" station. Conversely, obstetricians who perform only "low" operative vaginal deliveries also deliver unrecognized "mid" station fetuses. Therefore, residency programs should offer training in "mid" pelvic operative vaginal deliveries. Birth simulators could be used in training programs.

Comparison of "instrument-associated" and "spontaneous" obstetric depressed skull fractures in a cohort of 68 neonates.

OBJECTIVE: A depressed skull fracture is an inward buckling of the calvarial bones and is referred to as a "ping-pong" fracture. This study aimed to look at differences between "spontaneous" and "instrument-associated" depressed skull fractures. STUDY DESIGN: This retrospective, case-control analysis included every neonate who was admitted with a depressed skull fracture between 1990 and 2000. Cases after a spontaneous vaginal delivery, elective cesarean delivery, or cesarean delivery that was performed during labor without previous instrument use were classified as "spontaneous" (n = 18 cases). Cases after a delivery in which forceps or a vacuum cup had been used either successfully or unsuccessfully were classified as "instrument-associated" (n = 50 cases). Continuous data were analyzed with 2-tailed unpaired t tests; chi 2 analysis was used for nominal data. A probability value of <.05 was considered statistically significant. RESULTS: Fifty depressed skull fractures were associated with an instrument delivery, and 18 depressed skull fractures were classified as "spontaneous." The only obstetric parameter that differed significantly between the 2 groups was the length of the active phase. Among the 68 neonates, 15 neonates underwent prolonged second stage, forceps or manual head rotation, or forceps use during elective cesarean delivery. All "instrument-associated" cases were caused by forceps application or sequential instrument use; depressed skull fractures never occurred after isolated vacuum extraction. Every type of forceps was involved. Intracranial lesions were significantly more frequent in the instrument-associated group (30% vs 0%; P = .02). Two infants sustained persistent severe motor disabilities. CONCLUSION: Depressed skull fractures occur in the setting of spontaneous and operative deliveries, although the incidence is higher in the latter case. Depressed skull fractures that are associated with instrumental deliveries are significantly more likely to be associated with intracranial lesions. Persistent disabilities are rare.

Wearable medical devices using textile and flexible technologies for ambulatory monitoring.

Health smart clothes are in contact with almost all the surface of the skin offer large possibilities for the location of sensors for non invasive measurements. Head band, collar, tee-shirt, socks, shoes, belts for chest, arm, wrist, legs ... provide localization with specific purpose taking into account their proximity of an organ or a source of biosignal, and also its ergonomic possibility (user friendly) to fix a sensor, and the associated instrumentations (batteries, amplifiers, signal processing, telecom, alarm, display ...). Progress in science and technology offers, for the first time, intelligence, speed, miniaturization, sophistication and new materials at low cost. In this new landscape, microtechnologies, information technologies and telecommunications are a key factor. Microsensors : Microtechnologies offer the possibility of small size, but also intelligent, active device, working with low energy, wireless and non invasive or mini invasive. These sensors have to be thin, flexible and compatible with textile, or made using textile technologies, new fibers with specific properties: mechanical, electrical, optical ... The field of applications is very large, e.g. continuous monitoring on elderly population, professional and military activities, athlete's performance and condition, and people with disabilities. The research are oriented toward two complementary directions: Improving the relevancy of each sensor and increasing the number of sensors for having a more global synthetic and robust information.

Expertise and peripheral autonomic activity during the preparation phase in shooting events.

This study compared effectiveness of the concentration period in two groups of shooters to evaluate the influence of their expertise while concentrating on the target. Marksmen (pistol shooters, 10 men and 5 women) and pentathletes (6 men and 7 women) took part in a shooting competition in keeping with the rules of each event. Participants were then asked to imagine themselves shooting, at the laboratory. Five variables representing the activity of the autonomic nervous system were continuously recorded (skin resistance and potential, skin blood flow, skin temperature, instantaneous heart rate). Autonomic responses recorded during concentration, actual shooting, and mental imagery were compared by calculating the ratios concentration/ shooting and imagery/shooting. The resultant mean ratio was used to characterize each participant. The same autonomic nervous system pattern was observed during concentrating on the target, mental imagery, and actual shooting. However, marksmen showed ratios closer to 1.0 than pentathletes, absolute mean differences being .06 and .3, respectively. Shorter duration and weakest amplitude responses were recorded during the concentration phase in the Pentathlete group, suggesting that they have more difficulty in using mental imagery during competition than marksmen. When subjects performed well, a specific response pattern was observed in the Marksman group, but not in the Pentathlete group, except in skin potential. In both Marksman and Pentathlete groups, a majority of negative skin potential responses were found in the concentration and shooting phases for the best shots.

Mental workload in air traffic control: an index constructed from field tests.

BACKGROUND: Mental workload assessment is a recurrent issue in air traffic control (ATC). Studies of ATC have used either objective aspects, i.e., numbers and distribution of aircraft, or subjective factors, such as self-imposed performance and stress levels, with mixed results. This is partly due to the difficulty in bringing together comparable data pertaining to both air traffic, with its ever-changing distribution, and judgement or quickly fluctuating psychophysiological variables. METHODS: We propose a method of mental load estimation devised to take into account both objective traffic variables and the additional load imposed by subjective effects, including the seriousness of conflicts and the time-pressure for their resolution. First, we developed a traffic load index (TLI) to identify time boundaries during which additional load may occur. Then we quantified the additional load according to the air traffic situation. RESULTS: TLI was developed from analysis of 25 h of recordings of radar control sessions involving 25 professional air traffic controllers at a major airport. Results were then compared with a simple objective index (number of aircraft) and subjective workload ratings (NASA-TLX test). The whole population (intersubjects analysis) showed a better correlation between the TLI and the self-rated workload than for the number of aircraft alone. Among the controllers who rated more than one level of workload through the TLX-test, 77.8% showed better correlation between TLI and TLX than between N and TLX (intrasubjects analysis). CONCLUSION: Workload estimation should integrate both objective task variables and subjective evaluations associated with them.