Oxford BioHorizons Ltd.

Maidstone, United Kingdom

Oxford BioHorizons Ltd.

Maidstone, United Kingdom
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Matsumura K.,Hokkaido University | Yamakoshi T.,Fukuoka Institute of Technology | Rolfe P.,Harbin Institute of Technology | Rolfe P.,Oxford BioHorizons Ltd. | Yamakoshi K.-I.,Kanazawa University
IEEE Transactions on Biomedical Engineering | Year: 2017

Objective: The so-called volume-compensation method (VCM) allows noninvasive instantaneous arterial blood pressure (BP) measurement in human fingers. The VCM is mostly carried out with photoplethysmography (PPG) to detect arterial volume pulsations. However, measurement errors may occur due to movement of the PPG sensors relative to skin and underlying vasculature. We report here the effectiveness of a new technique, 'advanced VCM' (AVCM), developed by us to resolve this significant problem. Methods: The AVCM described uses a control system with procedures for adjusting system parameters derived from the pulsatile PPG signal and the finger cuff pressure. In open loop pre-operation, mean BP is estimated from a finger using the volume-oscillometric method. The control system reference is then adjusted to yield approximately equal values in mean BP and this gives optimum performance for instantaneous BP measurement. Systolic and diastolic BP values (SBP, DBP) from the instantaneous BP by the VCM and the AVCM were compared with the conventional brachial SBP/DBP measured simultaneously during 5-min baseline. SBP/DBP from the AVCM were also compared with brachial SBP/DBP during 36-min bicycle ergometer exercise. Results: Measurement errors that occurred when the BP measurement was run using the previous VCM essentially disappeared in the AVCM. Bland-Altman analysis revealed negligible fixed and proportional bias between finger SBP/DBP and brachial SBP/DBP. Conclusion: These findings suggest that the AVCM could be an effective technique to resolve the problem of measurement errors occurring with standard VCM. Significance: The newly proposed AVCM is potentially useful for all research and clinical situations where noninvasive continuous BP measurement is needed. © 1964-2012 IEEE.

Takehiro Y.,Kanazawa University | Matsumura K.,National Institute of Mental Health | Yamakoshi Y.,Chiba University | Hirose H.,Kinjo College | Rolfe P.,Oxford BioHorizons Ltd.
European Journal of Sport Science | Year: 2010

The aims of this study were to assess methods for performing physiological measurements in motor sports, and to carry out a preliminary study in athletes participating in kart racing. The measurement of physiological variables in motor sports is practically challenging, largely due to the restricted space available for sensors and instrumentation and to movement artefacts from driver's operations and car vibration, hence the paucity of publications. We performed a preliminary study of amateur racing kart athletes to assess the performance of basic measurement apparatus and to collect preliminary data on the possible influences of gravity on cardiovascular activity. We measured the vector magnitude of acceleration (G), instantaneous heart rate using electrocardiography, blood pressure with a wrist sphygmomanometer, eardrum temperature (taken as a measure of core body temperature) with a radiation thermometer, and lap time. The instrumentation functioned satisfactorily during karting on a racing circuit. In all participants during driving, heart rate was maintained at approximately 150 beats min 1. Time-frequency analysis of all heart rate data was performed to evaluate cardiac control mechanisms and this suggested that the observed rise in heart rate could be due to sympathetic acceleration. Furthermore, while we do not have sufficient data to draw firm conclusions, it is suggested that the rise in heart rate could be related to the G stresses to which the drivers were subjected. Cross-correlation analysis of the G and heart rate signals was performed in one participant and this showed a statistically significant correlation. We also found a statistically significant decrease in blood pressure (P<0.01) and a rise in eardrum temperature (P<0.01) immediately after the driving period. We conclude that although current sensors and instrumentation can allow basic monitoring of physiological variables in motor sport athletes, further developments are needed to allow more detailed investigations to be performed. Cardiovascular activity in response to G stresses warrants particular detailed investigation. © 2010 European College of Sport Science.

Yamakoshi T.,Kanazawa University | Matsumura K.,Kanazawa University | Rolfe P.,Oxford BioHorizons Ltd. | Hanaki S.,Kanazawa University | And 5 more authors.
IEEE Journal of Biomedical and Health Informatics | Year: 2014

We explored the potential of health screening based on the long-term measurement of cardiovascular parameters using the finger volume-oscillometric technique. An automated instrument made simultaneous measurements of key cardiovascular parameters, including blood pressure, pulse pressure, heart rate, normalized pulse volume as an index of α-adrenalin-mediated sympathetic activity, and finger arterial elasticity. These were derived from finger photo-plethysmographic signals during application of cuff pressure. To assess the feasibility of achieving a screening function, measurements were made in ten healthy volunteers during 10 days of day-to-day living (normal condition), and carried out several times at a fixed time every day. During successive 10-day measurements, a 30-hour period of total sleep deprivation was introduced as a physiological challenge (abnormal condition). A linear discriminant analysis of the data was conducted to determine whether these two conditions could be discriminated. Periodic data collection was performed rapidly and easily, and the %-correct classifications of normal and abnormal conditions were 78.2% and 77.5%, respectively. This ability of the method to discriminate between regular and sleep-deprived activities demonstrates its potential for healthcare screening during day-to-day living. Further investigations using larger age and gender groups of subjects including patients with cardiovascular diseases under real-life situations are required. © 2013 IEEE.

Yamakoshi T.,Kanazawa University | Matsumura K.,Kanazawa University | Rolfe P.,Harbin Institute of Technology | Rolfe P.,Oxford BioHorizons Ltd.
Transportation Research Part C: Emerging Technologies | Year: 2014

Vehicle-related countermeasures to sustain driver's alertness might improve traffic safety. The purpose of this study was to investigate the effects of somatosensory 20. Hz mechanical vibration, applied to driver's right heel during prolonged, simulated, monotonous driving, on their cardiovascular hemodynamic behavior. In 12 healthy young male volunteers, during 90-min periods of simulated monotonous driving, we compared cardiovascular variables during application of 20. Hz mechanical vibration with 1.5. Hz as a control and with no vibration. The parameters recorded were indices of key cardiovascular hemodynamic phenomena, i.e., blood pressure as an indicator of stress, cardiac output, and total peripheral-vascular resistance. The principle results were that all conditions increased the mean blood pressure, and elicited a vascular-dominant reaction pattern typically observed in monotonous driving tasks. However, mean blood pressure and total peripheral-vascular resistance during the monotonous task were significantly decreased in those receiving the 20. Hz vibration as compared with 1.5. Hz and with no vibration. The observed differences indicate the cardiovascular system being more relieved from monotonous driving stress with the 20. Hz vibration. The major conclusion is that applying 20. Hz mechanical vibration to the right heel during long-distance driving in non-sleepy drivers could facilitate more physiologically appropriate status for vehicle operation and could be a potential vehicular countermeasure technology. © 2013 Elsevier Ltd.

Yamakoshi T.,Kanazawa University | Matsumura K.,Kanazawa University | Rolfe P.,Harbin Institute of Technology | Rolfe P.,Oxford BioHorizons Ltd. | And 3 more authors.
Aviation Space and Environmental Medicine | Year: 2013

Introduction: We report a new methodology for detecting heat illness based on continuous tympanic temperature monitoring. This is relevant to industrial workers, astronauts, and pilots, as well as athletes. Here we evaluate the method in Grand Touring (GT) car racers in the closedcockpit category who can face life-threatening hyperthermia. Methods: The system comprises an earpiece containing an infrared-radiation-type tympanic thermometer and a microspeaker. In 10 healthy subjects, using a temperature-controlled water bath in the laboratory, we determined the differences in measurements taken from an infrared thermometer in one ear canal and from a thermistor probe in the other ear canal for direct tympanic temperature measurement. We employed an ingestible telemetry pill for gastrointestinal temperature measurement as a reference of core temperature. Then we assessed the usefulness of the system under real racing conditions with two professional drivers in the 2010 Super GT International Series held at the Twin Ring Motegi in Japan. Results: The results showed a good correlation between the infrared tympanic temperature and both the direct one ( r = 0.985) and the gastrointestinal temperature ( r = 0.932). The mean difference between these temperatures was 1 0.01°C and 1 0.27°C, with 95% confidence intervals (equal to 1.96 SD) of 0.30°C and 0.58°C, respectively. As for the field test, the system functioned well during real competitive and extremely severe race conditions on the racing circuit. Conclusions: The new method was found to perform well in an extreme car racing setting. It has the potential to be used in other applications, including the industrial and aerospace sectors. © by the Aerospace Medical Association, Alexandria, VA.

Liu Z.,Harbin Institute of Technology | Sun J.,Harbin Institute of Technology | Zhang Y.,Harbin Institute of Technology | Rolfe P.,Harbin Institute of Technology | Rolfe P.,Oxford BioHorizons Ltd
Biomedical Signal Processing and Control | Year: 2016

The analysis of the electroencephalogram (EEG) can yield much useful information about brain function, including indications of sleep stage. During the process of EEG analysis, feature extraction is one of the most critical technical aspect. Traditional EEG feature extraction methods are mainly based on single domain analysis. However, due to the highly non-stationary and nonlinear characteristics of the EEG, it is difficult to extract comprehensive information only from single domain analysis. In the present study, a novel feature extraction method was proposed based on the multi-domain analysis of the EEG. Fifteen characteristic parameters were extracted based on the multifractal detrended fluctuation analysis (MF-DFA), visibility graph algorithm (VGA), frequency analysis and nonlinear analysis. Ten optimal parameters of the fifteen parameters were selected by the genetic algorithm (GA). Then the Least Squares-Support Vector Machines (LS-SVM) were used to classify the sleep states. The cross validation results demonstrated that multi-domain feature extraction method can obtain more useful information in the EEG signal. Compared to the frequency domain parameters, nonlinear parameters and time domain parameters, the predictive accuracy of sleep staging classification with optimal multi-domain parameters improved 11.08%, 10.76% and 6.40% respectively. © 2016 Elsevier Ltd

Rolfe P.,Oxford BioHorizons Ltd. | Rolfe P.,Harbin Institute of Technology
Sensors and Materials | Year: 2012

Micro- and nanosensors have evolved rapidly in the last few decades and they have expanding roles within biology and medicine, where measurement science and technology is of key importance. The targets for measurement include a huge number of simple and complex molecules, physical quantities such as pressure, force, displacement and flow, and electrical and magnetic phenomena arising from the heart, brain, muscles and nerves. Routine clinical care of patients currently benefits from the use of macro- and microscale sensors based on electrical, electrochemical, acoustic, piezoelectric and optical principles. Disposable electrodes for recording biopotentials, such as the electrocardiogram and electroencephalogram, are common, whereas invasive electrochemical and optical fibre sensors for pressure, blood gases and pH are useful in intensive care. Microscale immobilised enzyme glucose sensors are largely confined to the analysis of small blood samples, their invasive use still facing technical challenges. Sensors constructed to the nanoscale using quantum dots and carbon nanotubes are now rapidly emerging, being aimed at more complex biomolecules such as DNA. Nanoparticles in general and surface-enhanced Raman spectroscopy also play important roles in these developments. The impact of micro- and nanosensors on the fundamental understanding of major biomedical challenges and on clinical diagnosis and care are highlighted here.

Lee J.,Kanazawa University | Matsumura K.,Kanazawa University | Yamakoshi T.,Kanazawa University | Rolfe P.,Harbin Institute of Technology | And 4 more authors.
Physiological Measurement | Year: 2013

Normalized pulse volume (NPV) derived from the ear has the potential to be a practical index for monitoring daily life stress. However, ear NPV has not yet been validated. Therefore, we compared NPV derived from an index finger using transmission photoplethysmography as a reference, with NPV derived from a middle finger and four sites of the ear using reflection photoplethysmography during baseline and while performing cold and warm water immersion in ten young and six middle-aged subjects. The results showed that logarithmically-transformed NPV (lnNPV) during cold water immersion as compared with baseline values was significantly lower, only at the index finger, the middle finger and the bottom of the ear-canal. Furthermore, lnNPV reactivities (ΔlnNPV; the difference between baseline and test values) from an index finger were significantly related to ΔlnNPV from the middle finger and the bottom of the ear-canal (young: r = 0.90 and 0.62, middle-aged: r = 0.80 and 0.58, respectively). In conclusion, these findings show that reflection and transmission photoplethysmography are comparable methods to derive NPV in accordance with our theoretical prediction. NPV derived from the bottom of the ear-canal is a valid approach, which could be useful for evaluating daily life stress. © 2013 Institute of Physics and Engineering in Medicine.

Matsumura K.,Kanazawa University | Rolfe P.,Harbin Institute of Technology | Rolfe P.,Oxford BioHorizons Ltd. | Lee J.,Kanazawa University | Yamakoshi T.,Kanazawa University
PLoS ONE | Year: 2014

Recent progress in information and communication technologies has made it possible to measure heart rate (HR) and normalized pulse volume (NPV), which are important physiological indices, using only a smartphone. This has been achieved with reflection mode photoplethysmography (PPG), by using a smartphone's embedded flash as a light source and the camera as a light sensor. Despite its widespread use, the method of PPG is susceptible to motion artifacts as physical displacements influence photon propagation phenomena and, thereby, the effective optical path length. Further, it is known that the wavelength of light used for PPG influences the photon penetration depth and we therefore hypothesized that influences of motion artifact could be wavelength-dependant. To test this hypothesis, we made measurements in 12 healthy volunteers of HR and NPV derived from reflection mode plethysmograms recorded simultaneously at three different spectral regions (red, green and blue) at the same physical location with a smartphone. We then assessed the accuracy of the HR and NPV measurements under the influence of motion artifacts. The analyses revealed that the accuracy of HR was acceptably high with all three wavelengths (all rs > 0.996, fixed biases: -0.12 to 0.10 beats per minute, proportional biases: r = -0.29 to 0.03), but that of NPV was the best with green light (r = 0.791, fixed biases: -0.01 arbitrary units, proportional bias: r = 0.11). Moreover, the signal-to-noise ratio obtained with green and blue light PPG was higher than that of red light PPG. These findings suggest that green is the most suitable color for measuring HR and NPV from the reflection mode photoplethysmogram under motion artifact conditions. We conclude that the use of green light PPG could be of particular benefit in ambulatory monitoring where motion artifacts are a significant issue. © 2014 Matsumura et al.

Matsumura K.,National Institute of Mental Health | Matsumura K.,Kanazawa University | Yamakoshi T.,Kanazawa University | Yamakoshi Y.,Chiba University | And 2 more authors.
BMC Research Notes | Year: 2011

Background: Both the act of competing, which can create a kind of mental stress, and participation in motor sports, which induces physical stress from intense g-forces, are known to increase heart rate dramatically. However, little is known about the specific effect of competition on heart rate during motor sports, particularly during four-wheel car driving. The goal of this preliminary study, therefore, was to investigate whether competition increases heart rate under such situations. Findings. The participants drove an entry-level formula kart during two competitive races and during solo driving against the clock while heart rate and g-forces were measured. Analyses showed that heart rate values during the races (168.8 beats/min) were significantly higher than those during solo driving (140.9 beats/min) and rest (75.1 beats/min). Conclusions: The results of this preliminary study indicate that competition heightens heart rate during four-wheel car driving. Kart drivers should be concerned about maintaining good health and developing physical strength. © 2011Matsumura et al; licensee BioMed Central Ltd.

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