Performance of a condensed electrode patch compared to a diffuse electrode array for transabdominal fetal heart rate and uterine contraction monitoring: a preliminary report

Objective: Intrapartum monitoring of the fetal heart rate (FHR), maternal heart rate (MHR) and uterine activity (UA) can be done noninvasively via adhesive electrodes on the parturient’s abdominal surface. This approach, requiring multiple electrodes placed at specific positions on the abdomen, performs at least as well as ultrasound and tocodynamometry-based monitoring. We tested whether a single adhesive electrode template (a “patch”), which would simplify use and obviate errors in electrode placement, would function as well as diffusely arrayed single electrodes. Methods: Seventeen healthy term parturients were monitored simultaneously with a diffuse electrode array and a condensed array patch, each connected to an identical electronic processor. Equivalence of the two electrode systems was determined by comparing their success rate, percent agreement and percent equivalence for FHR and MHR detection. UA monitoring was assessed by comparing the percent agreement and sensitivity of the systems. Results: The success rates of the multiple electrode array and the patch for FHR and MHR detection were above 96%. The reliability of the patch was statistically equivalent to the standard electrode array. The percent agreement for FHR was 94.7 ± 4.0% and for MHR was 92.8 ± 5.3%. These were not affected by maternal body mass index or whether it was early or late labor. The percent equivalence for both FHR and MHR was above 98% indicating equivalence of the patch with the diffuse electrode array in the accuracy of heart rate detection. The percent agreement of UA detection between the patch and the electrode array averaged 98% and was not influenced by whether it was early or late labor. The sensitivity of the patch for detecting individual contractions was 86.1%, equivalent to the standard electrode array. However, the sensitivity was lower in early compared to late labor (82.1 ± 13.9 vs. 90.3 ± 9.3%; P=0.052). The lower 95% confidence limit in early labor (74.9%) fell below the 80% limit necessary for equivalence. Conclusion: The performance of an electrode patch template for intrapartum monitoring of fetal and maternal heart rate and uterine contractions was equivalent to that of a more diffuse electrode array in almost all respects

Monica Healthcare: From the research laboratory to commercial reality—A real‐life case study

The desire of many engineers is to see their work end up as a final product offering a real benefit to society—for a lecturer/professor at a university, this is a dream often out of reach of the majority. However, the university academic is a changed species from the early days of the binary line between Universities and Polytechnics and when a lecturer meant just that—teaching to future engineers. This article describes the process and experience gained by a university engineer to spin out their research from the university sector and achieve the goal of a product reaching a global audience

Cuff-less continuous blood pressure monitoring system using pulse transit time techniques

This paper describes the development of a continuous cuff-less blood pressure system based on the pulse transit time (PTT) technique. In this study, PTT is defined by two different approaches denoted as PTT1 and PTT2. PTT1 is the time difference between the R-wave peak of the Electrocardiogram (ECG) and the peak of the Photoplethysmogram (PPG). PTT2 is the time difference between two peak PPG signals on same cardiac cycle at different positions on the body. The ECG is acquired on the chest using 3 lead electrodes and a reflection mode optical sensor is deployed on brachial artery and fingertip to monitor the PPGs. These data were synchronized using a National Instruments data acquisition card along with Matlab software for subsequent analysis. A wrist-type cuff-based blood pressure device was used to measure blood pressure on the right hand. Brachial blood pressure was measured on the upper left arm using oscillometric blood pressure monitor. Experiments were conducted by elevating the right hand at different position to investigate variability of PTT under the effects of hydrostatic pressure. Next the variability of PTT due to blood pressure changes during a Valsalva maneuver was investigated. The result shows that the PTT1 is inversely proportional to blood pressure in both experiments. Meanwhile, there is weak correlation between PTT2 and blood pressure measurement which suggests that by excluding the pre-ejection period (PEP) time in PTT calculation may reduce the accuracy of PTT for blood pressure measurement. In conclusion, PTT measurement between ECG and PPG signals has potential to be a reliable technique for cuff-less blood pressure measurement

Development of tubular cardiovascular phantom system for pulse transit time simulation

This paper presents on the development of a tubular cardiovascular phantom system to simulate pulse transit time (PTT). The PTT defined as the delay time between two pulses in one cardiac cycle has been shown to be promising method for cuffless continuous blood pressure (BP) measurement. However most of the PTT measurement was performed on human subjects, thus giving a difficulty in validating sensor performance due to variability of BP. Therefore, a cardiovascular phantom system was proposed for simulate the PTT measurement. An electronic controlled module was developed to control pump operation for pulse generation. Plastic optical fibre (POF) sensors were used to measure the pulse signal on the flexible tube and the results were compared with an in-line pressure sensor. In this experiment, the delay time between two pulses were calculated offline using Matlab software and correlated with pulse pressure. The result demonstrate that the pulse delay time recorded by both sensors decreased with increase of pulse rate and pulse pressure. These results on the phantom study showed similar pattern to the human model, thus indicating that the system is able to simulate PTT for sensor validation purposes

Multiple channel crosstalk removal using limited connectivity neural networks

Limited connectivity neural network architectures are investigated for the removal of crosstalk in systems using mutually overlapping sub-channels for the communication of multiple signals, either analogue or digital. The crosstalk error is modelled such that a fixed proportion of the signals in adjacent channels is added to the main signal. Different types of neural networks, trained using gradient descent algorithms, are tested as to their suitability for reducing the errors caused by a combination of crosstalk and additional gaussian noise. In particular we propose a single layer limited connectivity neural network since it promises to be the most easily implemented in hardware. A variable gain neuron structure is described which can be used for both analogue and digital data

The development of a clinical interface for a novel newborn resuscitation device: a Human Factors approach to understand cognitive user requirements

BackgroundA novel medical device has been developed to address an unmet need in standardising and facilitating heart rate recording during neonatal resuscitation. In a time critical emergency resuscitation, where failure can mean death of an infant, it is vital that clinicians are provided with information in a timely, precise and clear manner to capacitate appropriate decision making. This new technology provides a hands free, wireless heart rate monitoring solution that easily fits the clinical pathway and procedure for neonatal resuscutation.To understand the requirements of the interface design for this new device, a human factors approach was implemented. This combined a traditional user-centred design approach with an Applied Cognititive Task Analysis (ACTA) to understand the tasks involved, the cognitive requirements and the potential for error during a neonatal resusciation scenario.MethodFourteen clinical staff were involved in producing the final design requirements. Two paediatric doctors supported the development of a visual representation of the activities associated with neonatal resucitation. This was used to develop a scenario based workshop. Two workshops were carried out in parallel and involved three paediatric doctors, three neonatal nurses, two advance neonatal practitioners and four midwives. Both groups came together at the end to reflect on the findings which emerged during the separate sessions.ResultsThe outputs of this study have provided a comprehensive description of information requirements during neonatal resuscitation, and enabled product developers to understand the preferred requirements of the user interface design for the device. The study raised three key areas for the designers to consider, which had not previously been highlighted. These related to: 1) interface layout and information priority - heart rate should be central and occupy two thirds of the screen, device, 2) size and portability – to enable positioning local to baby’s head and allow visibility from all angles and 3) auditory feedback - to support visual information on heart rate rhythm and reliability of the trace with an early alert for intervention, whilst avoiding parental distress.ConclusionThis study demonstrates the application of human factors and the ACTA method, which identified user requirements previously not identified. This methodology provides a useful approach to aid development of the clinical interface for medical devices

A hybrid neural network/rule-based technique for on-line gesture and hand-written character recognition

A technique is presented which combines rule-based and neural network pattern recognition methods in an integrated system in order to perform learning and recognition of hand-written characters and gestures in realtime. The GesRec system is introduced which provides a framework for data acquisition, training, recognition, and gesture-to-speech transcription in a Windows environment. A recognition accuracy of 92.5% was obtained for the hybrid system, compared to 89.6% for the neural network only and 82.7% for rules only. Training and recognition times are given for an able-bodied and a disabled user

Multi-exposure laser speckle contrast imaging using a high frame rate CMOS sensor with a field programmable gate array

A system has been developed in which multi-exposure Laser Speckle Contrast Imaging (LSCI) is implemented using a high frame rate CMOS imaging sensor chip. Processing is performed using a Field Programmable Gate Array (FPGA). The system allows different exposure times to be simulated by accumulating a number of short exposures. This has the advantage that the image acquisition time is limited by the maximum exposure time and that regulation of the illuminating light level is not required. This high frame rate camera has also been deployed to implement laser Doppler blood flow processing enabling direct comparison of multi-exposure laser speckle contrast imaging and Laser Doppler Imaging (LDI) to be carried out using the same experimental data. Results from a rotating diffuser indicate that both multi-exposure LSCI and LDI provide a linear response to changes in velocity. This cannot be obtained using single-exposure LSCI unless an appropriate model is used for correcting the response

Polymeric optical fibre sensor coated by SiO2 nanoparticles for humidity sensing in the skin microenvironment

The sensitivity of a low-cost polymeric optical fibre humidity sensor based on transmittance changes due to evanescent wave absorption is reported using test measurements in an environmental chamber and of the skin. The layer-by-layer method was used to coat 30mm of the central unclad section of a multimode polymeric optical fibre with 7 layers of a hydrophilic film consisting of bilayers of poly(allylamine hydrochloride) and SiO2 mesoporous nanoparticles. Sensor characterisation shows a decrease in light transmission as relative humidity increases as a result of refractive index changes of the coating deposited onto the optical fibre which correlates with a commercial capacitive humidity sensor. The sensitivity obtained for the sensor coated with an optimum 7 layers was approximately -3.87x10-3 and -9.61x10-3 in transmittance percentage per RH percentage for the range of ~10% to ~75% RH and 90% to 97% RH, respectively. In addition, a response time of 1.5s can be seen for breath monitoring with the polymeric optical fibre humidity sensor. The proof of concept measurements made on the skin indicate that this sensor has the potential to be used to monitor humidity of the skin microenvironment within a wound dressing which can be used to provide better prognosis of healing