A new noninvasive technique for heat-flux-based deep body thermometry together with possible estimation of thermal resistance of the skin tissue.

A new noninvasive core-thermometry technique, based on the use of two heat flux sensors with different very low thermal resistances, is proposed. Thermodynamically derived equations, using a pair of skin temperatures and heat fluxes detected from the sensors, can give the estimated deep body temperature (DBT) together with thermal resistance of the skin tissue itself. The validity and accuracy of this method are firstly investigated through in vitro experiments using a tissue phantom model and, secondly, as in vivo comparisons with sublingual (Tsub) or rectal temperature (Trec) measurements in 9 volunteers, attaching the sensors around the upper sternum or the nape. Model experiments showed a good agreement between the measured and estimated temperatures, ranging from approximately 36 to 42 ℃. In vivo experiments demonstrated linear correlations between the estimated DBT and both Tsub and Trec values, though the estimated DBT was 0.13 ℃ higher than Tsub and 0.42 ℃ lower than Trec on average. The results also strongly suggested the possibility to estimate the tissue thermal resistance; this is discussed herein. Although further in vivo experiments under various environmental conditions are necessary, this method appears highly promising as an accurate, useful and convenient core-thermometry system for medical and healthcare settings.

Peripheral arterial elasticity changes derived by volume-oscillometry in reaction to hyperemia as a possible assessment of flow-mediated vasodilatation.

The flow-mediated dilation (FMD) test is commonly utilized and is the only technique for the assessment of vascular endothelial cell function. With this test, the augmentation of a brachial artery diameter following reactive hyperemia is measured precisely using ultrasonography by a skilled operator. This is a hospital-only test, and would be more useful if conveniently performed at home. This paper describes a first approach for studying the impact of changes in peripheral arterial elasticity, with prospects towards possible assessment of functional reactivity. A recently developed smartphone-based instrument was used to measure elastic properties of finger and radial arteries, related to stiffness and vasodilatation, as a function of distending pressure derived by photo-plethysmographic volume-oscillometry. Elasticity changes in both arteries before and after a 5-min supra-systolic upper-arm cuff occlusion were successfully obtained in 15 normal volunteers. The index-values of stiffness and vasodilatation showed, respectively, a significant decrease and increase (p < 0.01), demonstrating clearly the expected elasticity changes with hyperemia, which could be consistent with the clinically-stated reaction in an FMD test. The results suggest that this method could easily provide important information of both elasticity and vasodilatation. It appears promising as a convenient assessment method to contribute to arteriosclerotic cardiovascular screening.

Volume elastic modulus with exponential function of transmural pressure as a valid stiffness measure derived by photoplethysmographic volume-oscillometry in human finger and radial arteries: potential for arteriosclerosis screening.

Noninvasive and convenient measurement of vascular stiffness is of considerable importance for early detection and treatment of arteriosclerosis. Volume elastic modulus ([Formula: see text]) is one of representative measures reflecting effective vascular elasticity that is strongly dependent upon blood pressure (BP) or transmural pressure ([Formula: see text] = mean BP - (externally applied pressure)). However, its nonlinear nature in terms of functional form has not been fully investigated in human vasculature. This paper therefore seeks to clarify the functional form of [Formula: see text] in the human finger and radial arteries based on photoplethysmographic volume-oscillometry developed for novel indirect BP measurement. Using a smartphone-based instrument specially designed for this study, [Formula: see text] values at various [Formula: see text] levels were obtained in 11 male and female volunteers with various ages. It was demonstrated that [Formula: see text] showed an exponential behavior with respect to [Formula: see text] changes, expressed as [Formula: see text] ([Formula: see text], α; constant) with a high coefficient of determination, the validity of which was also supported through theoretical derivation. Conclusively, the [Formula: see text] is found to increase exponentially with arterial distending pressure, and the independent measures [Formula: see text] and α would be useful parameters to conveniently evaluate progressive changes of vascular stiffness among and/or within individuals, indicating that this measurement has potential for arteriosclerosis screening (200/200). Schematic diagram of overall configuration of the measurement system of arterial elasticity in the finger and the wrist, consisting of a measuring, signal processing and control (MSC) unit (surrounded by the dashed line) and a smartphone for data display and storage. An occlusive cuff and a photoplethysmographic placement of LED and PD for the finger and the wrist are shown in the upper middle part. Measurement scenes of the finger and the wrist are also inset in the upper left and in the upper right part, respectively.

Cuffless blood pressure estimation based on haemodynamic principles: progress towards mobile healthcare.

BACKGROUND: Although cuff-sphygmomanometry is used worldwide in medical and healthcare fields, it is a fact that the use of an occlusive cuff to obtain blood pressure (BP) is troublesome and inconvenient. There have therefore been on-going efforts to devise methods that do not require the use of a cuff, almost all being based on the measurement of pulse wave velocity or pulse transit time, but so far few significant developments have been made, especially regarding measurement accuracy. We have previously reported a smartphone-based cuffless method using a linear multiple regression calibration model comprising of BP obtained with a cuff-sphygmomanometer as an objective variable and modified normalized pulse volume (mNPV: a measure of vasoconstrictive activity in a finger) and pulse rate (PR) as explanatory variables. This requires a number of subjects to construct a calibration model and thus is largely dependent on the accuracy due to the model. To address these drawbacks, we report here a new cuffless method to surpass considerably the results of our previous study as well as earlier works. METHODS: With this method we can estimate BP, with much higher accuracy, using mNPV and PR, both also obtained from a smartphone-derived photoplethysmogram. The subject firstly performs a cuff-based BP measurement in parallel with the acquisition of mNPV and PR from a smartphone. These parameters are set as initial values (BP c0, mNPV 0 and PR 0; initial calibration procedure). Then, the estimated BP (BP e) can be calculated from the relation: "BP e = (BP c0·PR·mNPV)/(PR 0·mNPV 0)", which is derived from the so-called haemodynamic Ohm's law. To validate this method, preliminary experiments using 13 volunteers were carried out to compare results from the new method with those from the cuff-sphygmomanometry, used as a reference. RESULTS: Altogether 299 paired data sets were analyzed: A good agreement was found between the cuff-based and the estimated BP values, with correlation coefficients of 0.968 for systolic BP (SBP), 0.934 for mean BP (MBP) and 0.844 for diastolic BP (DBP). Bland-Altman analyses for the BP e (SBP e, MBP e, DBP e) and the BP c (SBP c, MBP c, DBP c) values also supported these comparison results. Mean absolute differences between the BP e and the BP c values in total subjects were less than 5 mmHg. Fairly good tracking availability in terms of time series data of the BP c against the corresponding BP e values was also confirmed in each subject during the study periods (1-2 weeks for 12 subjects and about 4 months for one subject). DISCUSSION: The present study reported the successful development of the new cuffless BP estimation method, given as the status of a trial stage of investigation. This method could easily be used with various smartphones, smart watches, and finger-based devices, and it appears to have significant potential as a convenient substitute for conventional cuff-sphygmomanometers as well as for practical application to mobile healthcare.

Cuffless blood pressure estimation using only a smartphone.

Cuffless blood pressure (BP) measurement is an all-inclusive term for a method that aims to measure BP without using a cuff. Recent cuffless technology has made it possible to estimate BP with reasonable accuracy. However, mainstream methods require an electrocardiogram and photoplethysmogram measurements, and frequent calibration procedures using a cuff sphygmomanometer. We therefore developed a far simpler cuffless method, using only heart rate (HR) and modified normalized pulse volume (mNPV) that can be measured using a smartphone, based on the knowledge that ln BP = ln cardiac output (CO) + ln total peripheral resistance (TPR), where CO and TPR are correlated with HR and mNPV, respectively. Here, we show that mean arterial pressure (MAP), systolic BP (SBP), and diastolic BP (DBP) could be estimated using the exponential transformation of linear polynomial equation, (a × ln HR) + (b × ln mNPV) + constant, using only a smartphone, with an accuracy of R > 0.70. This implies that our cuffless method could convert a large number of smartphones or smart watches into simplified sphygmomanometers.

Side-scattered finger-photoplethysmography: experimental investigations toward practical noninvasive measurement of blood glucose.

The aim of this study was to discover a simple/convenient geometrical arrangement of radiation sources and detector to acquire finger-photoplethysmograms (PPGs) with wavelength regions of blood glucose (BGL) absorption, toward practical noninvasive BGL measurement. First, we compared PPGs with three wavelengths: 808 nm (without water absorption), 1160 nm (with weak water absorption), and 1600 nm (with nearly peak BGL absorption and strong water absorption), while the source-detector spacing was successively increased circumferentially around a fingertip. In 10 healthy subjects, we observed clear cardiac-related pulsatile components of PPG signals at 808 and 1160 nm in any incident positions with more than 15 dB of signal-to-noise ratio ( S / N ), but reliable PPG detections at 1600 nm with more than 10 dB of S / N was only possible when the source-detector distance was less than 3 mm around the fingertip circumference. Second, with this arrangement, an experiment was performed using six wavelengths to cover glucose absorption bands (from 1550 to 1749 nm), obtaining pulsatile PPG signals with more or less 15 dB of S / N . Through the present experiments, this orthogonal arrangement of the source and detector to detect forward- and side-scattered radiation through the tissue is appropriate for PPG measurements with wavelength regions where there is potential for BGL measurement.

Measurement of electrocardiograms in a bath through tap water utilizing capacitive coupling electrodes placed outside the bathtub wall.

BACKGROUND: Taking a bath sometimes poses a risk for subjects with chronic cardiopulmonary disorders, due to the thermal effect and water pressure on his/her body. The ECG measurement would be helpful for the early recognition of abnormal cardiac beats and respiratory conditions. This paper describes a new attempt to improve on previous bathtub ECG measurement techniques that had electrodes placed inside the bathtub that were intrusive to the subjects' bathing experience. This study is concerned with the initial development of a method to measure an electrocardiogram (ECG) through tap water without conscious awareness of the presence of electrodes that are placed outside the bathtub wall. METHODS: A configuration of capacitive coupling electrodes placed outside the bathtub was designed so that the electrodes could be hidden. The capacitive coupling was made from the electrodes to the water through the bathtub wall. Two electrodes with an active shielding amplifier covered further by an electromagnetic shield were fixed to the outside surface of the bathtub wall, near the bather's right scapula and left foot. The potential difference between these two electrodes, similar to the bipolar lead-II ECG, was amplified to obtain raw signals inclusive of ECG/QRS components. Respiration intervals were also derived from ECG/RR intervals. Comparison experiments between this bathtub method and conventional direct methods with spot-electrodes and a chest-band sensor were made using 10 healthy male volunteers (22.2 ± 0.98 years). RESULTS: The ECG signal was detectable through tap water as well as water with differing conductivity resulting from mixing bathwater additives with the water. ECG signals and respiration curves derived from ECG/RR intervals were successfully obtained in all subjects. The intervals of the ECG/RR and respiration obtained by the bathtub system and by the direct method were respectively agreed well with each other. CONCLUSION: The ECG signal, in particular ECG/QRS components, were successfully detected utilizing capacitive coupling electrodes placed outside the bathtub wall. Also, the ECG/RR and respiration intervals were determined with reasonable accuracy as compared with the conventional direct methods.

Advanced Volume-Compensation Method for Indirect Finger Arterial Pressure Determination: Comparison with Brachial Sphygmomanometry.

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.

Integrating Sphere Finger-Photoplethysmography: Preliminary Investigation towards Practical Non-Invasive Measurement of Blood Constituents.

The aim of this study was to compare conventional photoplethysmography (PPG) in a finger with PPG using an integrating sphere (ISPPG) to enhance scattered light collection. Two representative wavelengths were used; 1160 nm, a window through the absorption spectra of water and alcohol, and 1600 nm around where water absorption is high and there is an absorption peak of blood glucose. Simultaneous transmission-type measurements were made with conventional PPG and with ISPPG for each wavelength in the tips of index fingers of both hands in a total of 10 healthy young male and female volunteers (21.7 ± 1.6 years old). During a 5 min period in which subjects were in a relaxed state we determined the signal-to-noise ratio, SNR, and the PPG detectability (or sensitivity) by the two techniques. SNR during the test period was significantly higher with ISPPG as compared with conventional PPG, especially for the 1600 nm wavelength. PPG signals with 1600 nm could scarcely be detected by conventional PPG, while they could be detected with good sensitively by ISPPG. We conclude that under controlled conditions ISPPG has better SNR and higher sensitivity than conventional transmission PPG, especially in wavelength regions where water absorption is high but where there is potential for practical measurement of blood constituents including glucose.

iPhysioMeter: a smartphone photoplethysmograph for measuring various physiological indices.

iPhysioMeter is a new smartphone application ("App") for the Apple iPhone and iPod touch that allows photoplethysmography (PPG) to be implemented without the need for any additional devices. The resulting signal, the photoplethysmogram, allows the calculation of basic but valuable and frequently used physiological indices such as heart rate (HR) and pulse volume (PV). The design of iPhysioMeter has very much been influenced by a consideration of usability, as is immediately evident from ones first experience with it. However, its apparent simplicity in use should not disguise the need for correct operation, which otherwise might lead to collection of invalid or inaccurate data. There are several unexpected pitfalls that might not only produce inaccurate values, but, under some circumstances, could also damage the device or present a hazard to the user or subject. We therefore describe here, firstly, the core technology that makes it possible to perform PPG and to calculate HR and normalized PV (NPV) from the photoplethysmogram using only a smartphone, secondly, the correct and optimum methods and procedures for using iPhysioMeter that will help to ensure safety and the derivation of valid data under real operational conditions. We hope that these descriptions will help facilitate any activities related to physiological measurement when using only a smartphone.

iPhone 4s photoplethysmography: which light color yields the most accurate heart rate and normalized pulse volume using the iPhysioMeter Application in the presence of motion artifact?

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.

Potential for health screening using long-term cardiovascular parameters measured by finger volume-oscillometry: pilot comparative evaluation in regular and sleep-deprived activities.

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.

Comparison between red, green and blue light reflection photoplethysmography for heart rate monitoring during motion.

Reflection photoplethysmography (PPG) using 530 nm (green) wavelength light has the potential to be a superior method for monitoring heart rate (HR) during normal daily life due to its relative freedom from artifacts. However, little is known about the accuracy of pulse rate (PR) measured by 530 nm light PPG during motion. Therefore, we compared the HR measured by electrocadiography (ECG) as a reference with PR measured by 530, 645 (red), and 470 nm (blue) wavelength light PPG during baseline and while performing hand waving in 12 participants. In addition, we examined the change of signal-to-noise ratio (SNR) by motion for each of the three wavelengths used for the PPG. The results showed that the limit of agreement in Bland-Altman plots between the HR measured by ECG and PR measured by 530 nm light PPG (±0.61 bpm) was smaller than that achieved when using 645 and 470 nm light PPG (±3.20 bpm and ±2.23 bpm, respectively). The ΔSNR (the difference between baseline and task values) of 530 and 470nm light PPG was significantly smaller than ΔSNR for red light PPG. In conclusion, 530 nm light PPG could be a more suitable method than 645 and 470nm light PPG for monitoring HR in normal daily life.

A novel method to detect heat illness under severe conditions by monitoring tympanic temperature.

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 closed-cockpit 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 +0.01 degree C and +0.27 degrees C, with 95% confidence intervals (equal to 1.96 SD) of 0.30 degrees C and 0.58 degrees 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.

Cardiovascular hemodynamic effects of Red Bull® Energy Drink during prolonged, simulated, monotonous driving.

PURPOSE: The purpose of this study was to investigate the cardiovascular hemodynamic effects of Red Bull® Energy Drink during prolonged, simulated, monotonous driving. METHODS: This was a double-blind, within-subjects-design, crossover study. Twelve healthy volunteers (21.7 ± 0.8 years old) experienced each of three conditions at various times: 1) consumption of Red Bull® Energy Drink; 2) consumption of placebo-controlled drink; and 3) no test drink. All subjects undertook 90-min periods of simulated monotonous driving, during which physiological measurements were made. The variables recorded were cardiovascular indices, i.e., mean blood pressure (MBP), cardiac output (CO), electrocardiogram RR interval (RR), total peripheral-vascular resistance (TPR: = MBP/CO), and normalized pulse volume (NPV). Additional parameters were the standard deviation of lateral position, i.e., the weaving of the car, and subjective rating of sleepiness. RESULTS: CO, RR, and TPR during the monotonous task were significantly different in those consuming the energy drink as compared with those receiving the placebo and as compared with no drink values. The energy drink elicited a cardiac-dominant reaction pattern, while the other conditions demonstrated the vascular-dominant reaction pattern typically observed in monotonous driving tasks. The observed differences indicate the cardiovascular system being more aroused with the energy drink. CONCLUSION: The effects of Red Bull® Energy Drink were reflected in cardiovascular hemodynamic phenomena especially to the heart function, and we conclude that consumption of this drink before long-distance driving in non-sleepy drivers could facilitate more physiologically active, and possibly safer, driving.

Validation of normalized pulse volume in the outer ear as a simple measure of sympathetic activity using warm and cold pressor tests: towards applications in ambulatory monitoring.

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.

iPhysioMeter: a new approach for measuring heart rate and normalized pulse volume using only a smartphone.

Heart rate (HR) and normalized pulse volume (NPV) are physiological indices that have been used in a diversity of psychological studies. However, measuring these indices often requires laborious processes. We therefore developed a new smartphone program, named iPhysioMeter, that makes it possible to measure beat-by-beat HR and ln NPV using only a smartphone. We examined its accuracy against conventional laboratory measures. Mental stress tasks were used to alter HR and ln NPV in 12 participants. Bland-Altman analyses revealed negligible proportional bias for HR and ln NPV or for their change values, expressed as ΔHR and Δln NPV. However, a relatively large fixed bias did emerge for ln NPV, as well as a small one for Δln NPV, although both were within the limits of agreement. These findings suggest that iPhysioMeter can yield valid measures of the absolute level of HR and of relative changes in ln NPV.

Fish consumption and cardiovascular response during mental stress.

BACKGROUND: Frequent fish consumption is related to a lower risk of coronary heart disease. However, the physiological mechanisms underlying this cardioprotective effect are as yet unknown. We therefore examined certain cardiovascular physiological variables of fish eaters during rest, whilst conducting mental arithmetic, and during recovery. FINDINGS: The participants were 12 fish eaters (eating baked fish more than 3-4 times/week) and 13 controls (eating fish less than 1-2 times/week). Analysis of the collected data revealed that heart rate, blood pressure, and pulse wave velocity were significantly lower and pre-ejection period and baroreflex sensitivity were significantly higher in the fish eaters than in the controls during both rest and mental arithmetic, and that systolic and mean blood pressure recovery from mental arithmetic were faster in the fish eaters than in the controls. CONCLUSIONS: These findings suggest a possible physiological mechanism that may explain why frequent fish consumption reduces coronary heart disease risk.

The effect of competition on heart rate during kart driving: A field study.

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.

Development of a ubiquitous healthcare monitoring system combined with non-conscious and ambulatory physiological measurements and its application to medical care.

The demand for ubiquitous healthcare monitoring has been increasingly raised for prevention of lifestyle-related diseases, acute life support or chronic therapies for inpatients and/or outpatients having chronic disorder and home medical care. From these view points, we developed a non-conscious healthcare monitoring system without any attachment of biological sensors and operations of devices, and an ambulatory postural changes and activities monitoring system. Furthermore in this study, in order to investigate those applicability to the ubiquitous healthcare monitoring, we have developed a new healthcare monitoring system combined with the non-conscious and the ambulatory measurements developed by us. In patients with chronic cardiovascular disease or stroke, the daily health conditions such as pulse, respiration, activities and so on, could be continuously measured in the hospital, the rehabilitation room and subject's own home, using the present system. The results demonstrated that the system appears useful for the ubiquitous healthcare monitoring not only at medical facility, but also during daily living at home.