This paper discusses the digital hardware and software that is required for data acquisition in a portable electronic nose (e‐nose) system. A review of current e‐nose systems is presented highlighting the methods employed by these systems to acquire the data from the sensor head.

The development of a sensor microsystems containing all the components of data acquisition system, such as sensors, signal-conditioning circuits, analog-digital converter, interface circuits and embedded microcontroller (MCU), has become the focus of attention in many biomedical applications. A review of the microsystems technology is presented in this paper, along with a discussion of the recent trends and challenges associated with its developments. A basic description of each subsystem is also given. This includes the different front end, mixed analog-digital, power management, and radio transmitter-receiver circuits. These sub-system designs are presented and discussed in a comparative study and final remarks are made. The performance of each sub-system is assessed regarding many aspects related to the overall system performance.

Objectives. To compare mobility in patients with venous leg ulcers to matched controls and determine the influence of mobility, age and ulcer size on ulcer healing.Methods. 25 leg ulcer patients, and 25 matched controls wore a mobility monitor (ActivPAL (TM), PAL Technologies Ltd, Glasgow, Scotland)) which recorded the number of steps and amount of time spent walking, standing, sitting or lying for a one-week period. A walking index was calculated. The ulcer group were treated with compression bandaging and ulcer healing recorded over 12 weeks.Results. There were 13 female subjects in each group. The median age was 70.5 (range 30-89) years. There was no difference in the amount of time either group spent standing, walking and resting. There was a significant reduction in the number of steps taken and in the walking index in the ulcer group compared to controls (ulcer group, median 6,685 steps/day, range 2074-17,999; control group median 8750, range 4917-16,043, p < 0.05, Mann Whitney a test). Smaller ulcers and ulcers of recent onset were most likely to heal within 12 weeks (p = 0.005 and p = 0.011 respectively, Chi squared test). The percentage of time spent mobilising and resting did not influence ulcer healing (r(s) = -0.125; p = 0.55).Conclusions. Mobility patterns among patients with leg ulcers are not significantly different to age matched controls. Ulcer patients take fewer steps per week compared to controls indicating they have reduced calf muscle pump function. Further studies are required to determine whether therapies which increase calf muscle activity have a role in ulcer treatment.

A threshold-based algorithm, to distinguish between Activities of Daily Living (ADL) and falls is described. A gyroscope based fall-detection sensor array is used. Using simulated-falls performed by young volunteers under supervised conditions onto crash mats and ADL performed by elderly subjects, the ability to discriminate between falls and ADL was achieved using a bi-axial gyroscope sensor mounted on the trunk, measuring pitch and roll angular velocities, and a threshold-based algorithm. Data analysis was performed using Matlab® to determine the angular accelerations, angular velocities and changes in trunk angle recorded, during eight different fall and ADL types. Three thresholds were identified so that a fall could be distinguished from an ADL: if the resultant angular velocity is greater than 3.1rads/s (Fall Threshold 1), the resultant angular acceleration is greater than 0.05rads/s2 (Fall Threshold 2), and the resultant change in trunk-angle is greater than 0.59rad (Fall Threshold 3), a fall is detected. Results show that falls can be distinguished from ADL with 100% accuracy, for a total data set of 480 movements.

Functional electrical stimulation may be used to correct hemiplegic drop foot. An optimised stimulation envelope to reproduce the EMG pattern observed in the tibialis anterior (TA) during healthy gait has been proposed by O'Keeffe et al. [O'Keeffe, D.T., Donnelly, A.E., Lyons, G.M., 2003. The development of a potential optimised stimulation intensity envelope for drop foot applications. IEEE Transactions on Neural Systems and Rehabilitation Engineering]. However this envelope did not attempt to account for changes in TA activity with walking speed. The objective of this paper was to provide data to enable the specification of an algorithm to control the adaptation of an envelope with walking speed. Ten young healthy subjects walked on a treadmill at 11 different walking speeds while TA EMG was recorded. The results showed that TA EMG recorded around initial contact and at toe off changed with walking speed. At the slowest velocities, equivalent to hemiplegic walking, the toe-off burst (TOB) of EMG activity had larger peak amplitude than that of the heel-strike burst (HSB). The peak amplitude ratio of TOB:HSB was 1:0.69 at the slowest speed compared to, 1:1.18 and 1:1.5 for the self-selected and fastest speed, respectively. These results suggest that an FES envelope, which produces larger EMG amplitude for the TOB than the HSB, would be more appropriate at walking speeds typical of hemiplegic patients.

The aim of this study was to assess the accuracy of the ‘activPAL™ Professional’ physical activity logger by comparing its output to that of a proven discrete accelerometer-based activity monitor during extended measurements on healthy subjects while performing activities of daily living (ADL). Ten healthy adults, with unrestricted mobility, wore both the activPAL™ and the discrete dual accelerometer (Analog Devices ADXL202)-based activity monitor that recorded in synchronization with each other. The accelerometer derived data were then compared to that generated by the activPAL™ and a complete statistical and error analysis was performed using a Matlab® program. This program determined trunk and thigh inclination angles to distinguish between sitting/lying, standing and stepping for the discrete accelerometer device and amount of time spent on each activity. Analysis was performed on a second-by-second basis and then categorized at 15 s intervals in direct comparison with the activPAL™ generated data. Of the total time monitored (approximately 60 h) the detection accuracies for static and dynamic activities were approximately 98%. In a population of healthy adults, the data obtained from the activPAL™ Professional physical activity logger for both static and dynamic activities showed a close match to a proven discrete accelerometer data with an offset of approximately 2% between the two systems.

Objectives: The calf muscle pump is recognized as an integral component of effective venous return from the lower limbs. The aim of this study was to determine if there is a correlation between calf muscle volume and venous blood flow among patients with venous leg ulcers. Methods: Nine patients with venous leg ulceration were recruited for this study. These patients underwent haemodynamic testing using duplex ultrasound to measure peak venous velocities in response to voluntary maximum plantar flexion, with and without compression bandaging. Each patient then had magnetic resonance imaging (MRI) of the lower limbs. Calf muscle volume was calculated from the MRI images using a specially designed Matlab computer program to identify and count muscle pixels. Analyses applied Pearson's correlation coefficient to determine correlation between calf muscle volume and mean peak venous velocities in response to voluntary contraction. Results: No correlation was seen between calf muscle volume and haemodynamic venous return in response to voluntary contraction, with or without compression bandaging. Conclusion: The volume of calf muscle available for promoting venous return alone may not be an accurate indicator of muscle functioning capability.

Using simulated falls performed under supervised conditions and activities of daily living (ADL) performed by elderly subjects, the ability to discriminate between falls and ADL was investigated using tri-axial accelerometer sensors, mounted on the trunk and thigh. Data analysis was performed using MATLAB to determine the peak accelerations recorded during eight different types of falls. These included; forward falls, backward falls and lateral falls left and right, performed with legs straight and flexed. Falls detection algorithms were devised using thresholding techniques. Falls could be distinguished from ADL for a total data set from 480 movements. This was accomplished using a single threshold determined by the fall-event data-set, applied to the resultant-magnitude acceleration signal from a tri-axial accelerometer located at the trunk.

This paper describes the design and evaluation of a miniature kinematic sensor based three dimensional (3D) joint angle measurement technique. The technique uses a combination of rate gyroscope, accelerometer and magnetometer sensor signals. The technique enables 3D inter-segment joint angle measurement and could be of benefit in a variety of applications which require monitoring of joint angles. The technique is not dependent on a fixed reference coordinate system and thus may be suitable for use in a dynamic system such as a moving vehicle. The technique was evaluated by applying it to joint angle measurement of the ankle joint. Experimental results show that accurate measurement of ankle joint angles is achieved by the technique during a variety of lower leg exercises including walking.

Long-term monitoring of mobility is beneficial in quantifying a person's functional health status. An SMS-based (Short Message Service) telemonitoring system has been redeveloped to remotely monitor the long-term mobility trends of elderly people in their living environment. Mobility is measured by an accelerometer-based portable unit, which is worn by each monitored subject. Mobility level summaries are transmitted hourly, as SMS messages, directly from the redeveloped portable unit to a remote server for long-term analysis. Each subject's mobility levels are monitored at the remote server using custom-designed mobility alert software and the appropriate medical personnel are alerted, by SMS, if deterioration in the subject's mobility levels is detected. This paper describes the process used to calibrate accelerometers for the wearable element of this telemonitoring system.

An upper limb electrical stimulation technique has been developed which features a novel self-configuration approach, to obtain an ideal wrist response from the patient. The system uses an analogue de-multiplexer in conjunction with an electrode matrix so that different electrode sites can be tested using only one channel of stimulation. A twin axis goniometer is attached to the patient's wrist and flex sensors are attached to the patient's fingers so that the control algorithm can assess the wrist response. A data acquisition unit logs the data for further analysis. A clinical investigation on healthy subjects was conducted to test the proposed system. The results show a high variation in hand response across different subjects. In addition, for all subjects tested an ideal response was found which shows some justification for the use of the proposed technique.

Rapid technological advances have prompted the development of a wide range of telemonitoring systems to enable the prevention, early diagnosis and management, of chronic conditions. Remote monitoring can reduce the amount of recurring admissions to hospital, facilitate more efficient clinical visits with objective results, and may reduce the length of a hospital stay for individuals who are living at home. Telemonitoring can also be applied on a long-term basis to elderly persons to detect gradual deterioration in their health status, which may imply a reduction in their ability to live independently. Mobility is a good indicator of health status and thus by monitoring mobility, clinicians may assess the health status of elderly persons. This article reviews the architecture of health smart home, wearable, and combination systems for the remote monitoring of the mobility of elderly persons as a mechanism of assessing the health status of elderly persons while in their own living environment.

Active voluntary contraction of the calf muscle is an essential factor in the circulatory system. Failure to exercise the calf muscles for prolonged periods may result in limited or poor blood circulation in the lower leg and increase the risk of deep vein thrombosis (DVT). An association between long distance travel and increased risk of DVT has been established. Most airlines recommend a number of lower leg exercises as a DVT preventative measure. Not all lower leg exercises induce calf muscle pump activity and therefore may not be beneficial in the prevention of DVT. A study was devised to investigate the exercises recommended to passengers for DVT prevention on long distance flights to determine a potential benefit to the health and safety of the passenger. The technique used for the evaluation of recommended airline exercises for optimal calf muscle pump activity is described.

This paper describes the development of an accurate, accelerometer based fall detection system capable of distinguish between Activities of Daily Living (ADL) and fall-events. Using simulated fall-events onto crash mats (under supervised conditions) and ADL performed by elderly subjects, distinguishing between falls and ADL is achieved using an accelerometer-based sensor, mounted on the trunk and thigh of the person. Data analysis was performed using MATLAB® to determine the peak accelerations recorded during eight different types of falls. A fall detection algorithm was proposed using simple thresholding techniques. Results from an evaluation of the detection algorithm show that a fall-event can be distinguished from an ADL with 100% accuracy using a single threshold applied to the resultant acceleration signal from a tri-axial accelerometer located at the chest. Thresholding was thus demonstrated to be capable of discriminating between an ADL and a fall-event, when those falls were simulated falls.

Present methods for investigation of the GI tract are invasive, distressing for the patient, and give a low diagnostic yield. Wireless, radio telemetry capsules, capable of monitoring physiological changes or visualizing the GI tract are noninvasive and could realize a faster time to diagnoses along with improved treatment of both organic diseases and functional disorders. Consequently, the patient's quality of life would improve. In this paper, early radiotelemetry capsules and the motivating factors for their development are discussed. Following this, prototype and commercially available digestible microsystems making use of microelectronics and microelectromechanical systems are presented. It is shown that these capsules have the potential to combine the functions of their predecessors and furthermore can be used for visualizing the gastrointestinal tract. These systems have the potential to improve diagnostic yield and, in the future, treatment of disease using these capsules should become a reality.

Long-term monitoring of mobility is beneficial in quantifying a person's functional health status. Deterioration in the health status of an elderly person living alone can indicate the onset of an illness or a reduction in their ability to care for themselves. A telemonitoring system, based on SMS (Short Message Service), has been redeveloped to remotely monitor the long-term mobility levels of elderly people in their living environment. Mobility is measured by an accelerometer-based portable unit, worn by each monitored subject. Mobility level summaries are transmitted hourly, as SMS messages, directly from the portable unit to a remote server for long-term analysis. Each subject's mobility levels are monitored at the remote server using custom-designed mobility alert software and the appropriate medical personnel are alerted, by SMS, if deterioration in the subject's mobility levels is detected. This paper describes the redevelopment of the portable unit and the results from a preliminary evaluation of this unit in a smart home setting. The system was tested on 4 young subjects, for a total of 24.25 hours, and was shown to have an average posture detection accuracy of 98.59%. It is expected that this system would reduce the financial burden on healthcare providers, by enabling more efficient allocation of healthcare resources, and would thus allow elderly persons to remain in their preferred environment, their home, for as long as possible.

This paper describes the use of a use case/task based method in the development of a portable neuromuscular stimulator device. The developed unit allows a variety of stimulus delivery algorithms to be incorporated dependent on the patient's requirements. The developed system consists of a stimulator unit, stimulator firmware, external sensors, a programmer unit, two stimulation channels and electrodes. A clinician specifies a suitable algorithm for a particular patient and then selects the relevant stimulus parameters for that algorithm using the programmer unit. The stimulator unit's architecture supports the addition of future algorithms. The device was developed in accordance with the European Medical Devices Directive 93/42/EEC resulting in the need for a well-defined development lifecycle during the design and development of the neuromuscular stimulator. This development lifecycle must place emphasis on the need to identify potential hazards. Therefore, the adoption of a use case/task driven approach as one of the strategies in eliciting the requirements, both functional and non-functional and specification stages of the development lifecycle resulted in a more rigid hazard/risk analysis leading ultimately to a more robust final system. A comprehensive review of the literature has revealed that use cases have been in use in other contexts but not so in a biomedical context. Therefore, this is a novel strategy to the development of a device in this field. A brief background on the historical development of drop foot stimulators shall be presented thereby displaying the benefits of the programmability feature of our stimulator.

A preliminary study to investigate which of the recommended airline exercises for DVT prevention produce optimal calf muscle pump activity. Four subjects were instructed to carry out ten lower leg exercises based on those recommended by airlines for DVT prevention. An EMG sensor was used to record calf muscle activity and a motion analysis system was used to ensure the exercise was conducted correctly. Statistical analysis showed significant differences in the level of calf muscle pump activity induced by the different exercises. Heel rise foot pumps were shown to induce highest levels of activity while many exercises did not induce any significant calf muscle activity at all. These findings indicate that a further, more detailed examination of the exercises recommended to passengers for DVT prevention on long distance flights should be conducted to determine the potential benefit to the health and safety of the passenger.