Some systems to measure voided volume and flow rate have been developed. Clinically, urination parameters are measured using uroflowmeters that have special receivers such as cups or bowls. Since these uroflowmeters were developed for clinical use, home use is difficult and inconvenient. Many of these devices require equipment cleaning; additionally, most are too expensive for home use. To address these problems, we developed a method to measure voided volume by noncontact matrix temperature sensors that are installed under a toilet seat. The basic concept is as follows. Urine is excreted at core temperature of 37℃. The heat radiated from urine during excretion is measured by noncontact matrix temperature sensors, and the measured radiated heat is converted to urination volume. A preliminary study was conducted to estimate the voided volume using an actual toilet bowl. The noncontact matrix temperature sensors simultaneously measure the temperature of falling water at 37℃ in 16 areas using a matrix of four lines and four rows. Four noncontact matrix temperature sensors were installed at the front, rear, left and right of the underside of a toilet seat. The toilet seat equipped with the four sensors was installed on a toilet bowl. The position of the falling water was fixed at 120 mm from the front sensor. Water volumes of 100, 200 and 300 ml were passed vertically at flow rates of 10, 20, 30 and 40 ml/s. As a result, the surface of the toilet bowl was slightly heated from the heat of the falling water, and the toilet bowl retained the heat after the water had fallen. To eliminate overestimation of heat from the toilet bowl, we proposed two analytical methods: a bias temperature elimination method and a time limitation method. For all four flow rates, the variation of U with a proportional volume obtained by the time limitation method was smaller than that by the bias temperature elimination method.
Aortic wall changes dimensions and mechanical properties in response to mechanical stimulation. As these changes are driven by the cells inside the wall, and their mechanical response has been suggested to exhibit a close correlation with nuclear deformation, it is necessary to study the deformation of the aortic wall at microscopic level. Hence, we obtained 200-µm-thick slices of rabbit thoracic aortas in the circumferential-radial and longitudinal-radial planes, and stretched them in the circumferential and longitudinal directions, respectively, under a microscope. The nuclei of smooth muscle cells (SMCs) were stained with Hoechst33342. Each slice was repeatedly stretched stepwise by 4%, while the fluorescence images of the cell nuclei as well as the elastin auto-fluorescence were captured at each step. Macroscopic and microscopic stretch ratios were obtained from the fluorescence images. Local Green strain was calculated from the change in internuclear distance in a specimen stretched in the circumferential direction. The local tissue strain in the circumferential direction was 0.8 to 2.1 times the macroscopic tissue strain, indicating that the aortic wall deformation was heterogeneous at microscopic level. The shear deformation between adjacent elastic laminas was evident at specific locations, resulting in a shear strain as large as 10%. We also evaluated the relationship between tissue deformation and nuclear deformation from the change in nuclear shape in the specimen stretched in the circumferential and longitudinal directions. In the circumferential stretch, the strain calculated from the length of the nuclei was less than 70% of the macroscopic strain, suggesting that the nuclei of the SMCs are much stiffer than the cytosolic components. Some nuclei rotated noticeably in response to the stretch, and the average and maximum rotation angle was 5° and 11°, respectively, during the entire stretching process. In the longitudinal stretch, the change in nuclear length was not significant, suggesting that mechanical stimulation to the SMCs may be smaller in this direction, as reported previously. The present study shows that the deformations of both the extracellular matrix and cell nuclei are highly heterogeneous, which may have a profound effect on the vascular biology.
Measurement of instantaneous orthostatic heart rate change has been used as a screening method for care or rehabilitation for the elderly, because it allows evaluation of the autonomic nervous system. In this study, we developed a photoplethysmogram (PPG) measurement system on the forehead. The system has five sets of green light PPG sensors to measure instantaneous orthostatic pulse rate changes and is less prone to noise caused by body movement artifacts. We aimed to verify the effectiveness of the proposed method by comparing the accuracy of pulse rate measurements at the forehead and at the wrists. In the experiment, 11 young and healthy subjects were recruited, and were asked to wear an aging simulation kit during the experiment to simulate the standing-up movement of an elderly person. The pulse rates from forehead PPG, pulse rates from wrist PPG, and heart rates from electrocardiogram were measured simultaneously. The accuracy of pulse rate was evaluated by two indices: ERb, the average of error rates for 10 s before standing up, was adopted as an index without body motion; ERs, the average of error rates within 10 s before and after standing up and including the standing-up duration, was adopted as an index with body motion. Using these indices, statistical analyses including one-way ANOVA for contact pressures and paired t-test were conducted. For the error rates estimated from wrist PPG, a significant difference was found between ERb and ERs under most conditions, and ERs was higher than ERb. Meanwhile, for the error rates estimated from forehead PPG, no significant differences were found between ERb and ERs under most conditions. In addition, the ERs was significantly different between wrist PPG and forehead PPG, especially at the center of the forehead at low contact pressure. Therefore, we confirmed that pulse rates measured by PPG placed at the center of the forehead with low contact pressure are highly accurate compared with those measured by wrist PPG. The proposed method is thus proven effective for monitoring instantaneous orthostatic pulse rate changes.
Individual capacity of recall memory varies greatly even among healthy young adults. Nevertheless, the difference in brain circuitry underlying varied memory capacity has yet to be fully investigated. We acquired electroencephalographic measurements from 43 healthy young adults while performing a demanding working memory task and studied the changes in regional cortical activity in relation to different levels of memory performance. The memory task involved sequentially presenting seven arrow pictures to a participant during the encoding period, who was then asked to recall the direction of one of the arrows in the sequence within the retrieval period. We divided the participants into three groups of high, intermediate, and low performance based on the weighted hierarchical grouping method. Regional brain activities were source-localized using multiple sparse priors method in the high- and low-performance groups, and group differences were determined by non-parametric permutation tests. Our findings showed that participants with higher memory performance exhibited wider distribution of cortical activity including the prefrontal and parieto-posterior cortices, whereas lower performance participants only exhibited stable activations across occipital regions. The results implied the importance of selective attention in order to attain optimal individual working memory performance. Furthermore, we suggest the potential role of the angular gyrus as an interplay between the prefrontal and posterior regions for the management of stimulus flow and signal control. Future works should focus on conducting more thorough connectivity analysis to investigate the relationship of cortical activations with individual working memory performance.
We investigated the delivery of rhodamine B and Oregon Green®-labeled paclitaxel (OGLP) in ex vivo porcine carotid artery wall (CAW) samples after heating the reagents to 50–70℃ for 15 s. When the isolated CAW samples were placed in the heated fluorophore solutions, the penetration depth of the hydrophobic rhodamine B increased significantly compared with reference solution at 37℃. The penetration depth of OGLP also tended to increase upon heating to 70℃ for 15 s. We also studied the mechanism of this agent delivery enhancement by observing the inner surface structure and hydrophobicity of the CAW samples after heating. An expanded mesh structure at the inner surface of the heated CAW samples was observed upon heating above 70℃, and the mean hydrophobicity of the media layer also increased significantly. We hypothesize that heating at 60–70℃ for 15 s enhances the delivery of fluorophores to CAW samples as a result of an expanded mesh structure at the inner surface of the CAW, along with a simultaneous increase in hydrophobicity.
We studied the effects of interactive pressure on the delivery of hydrophobic rhodamine B to ex vivo heated artery walls to determine the optimal drug delivery conditions. The heated artery samples, which were maintained at 63℃ on the intimal surface, were prepared by heating for 15 s. Interactive pressure up to 10 atm was directly applied with a rhodamine B solution to the artery samples from the intima side over 30 s. The fluorescence brightness distribution of rhodamine B in the samples were measured microscopically to investigate the quantity and depth of drug delivery. We found a decrease in the depth of drug delivery in the heated artery samples compared with the reference artery samples. This decrease in drug delivery depth may have resulted from increased hydrophobic binding of rhodamine B at the intima because of heating. We also found a significant increase in quantity of drug delivery at a certain interactive pressure in the heated artery samples. Hematoxylin-eosin staining of cross sections of pressurized heated artery samples revealed delamination of the intima and extension of the internal elastic lamina. We hypothesize that the dependence of drug delivery quantity on the interactive pressure is attributed to morphological changes in the intima and the internal elastic lamina.
A new Hill-type model of skeletal muscle contraction referred to as the “SL/ST model” is proposed based on recent physiological findings: intact human skeletal muscles operate on the ascending limb (hereinafter referred to as the “as-limb”) and the descending limb (“ds-limb”) of the isometric force–length relationship; and stretch-evoked force enhancement (“ST-enhancement”) is found on the ds-limb. Dynamic behaviors differ remarkably between the two limbs. The model has two modes: a sliding filament mode (“SL mode”) and a stretch-evoked force enhancement mode (“ST mode”). The SL mode operates on the as-limb, and on the ds-limb when the muscle is shortening, while the ST mode operates when ST-enhancement occurs in the ds-limb. Transient force responses of the model to length perturbations were similar to those of frog semitendinosus muscles in vitro. Length responses to step change in load of the model suggest that the muscle is unstable and not static in SL mode on the ds-limb, while it is stable and static in SL mode on the as-limb and in ST mode on the ds-limb.
We have developed a brain-machine interface (BMI) rehabilitation system for patients with stroke and motor paralysis, which provides proprioceptive feedback upon successful generation of motor-imagery (MI)-induced event-related desynchronization (ERD) and a decrease in mu band (8–13 Hz) activity derived from hand motor imagery. This system consists of an electroencephalogram (EEG) amplifier operated using the MATLAB Simulink software; a pneumatic robotic exoskeleton to provide proprioceptive feedback to the paralyzed hand; and a tablet computer placed over the paralyzed hand to display a hand-action movie to facilitate ERD generation. The EEG amplifier was connected and synchronized via the exoskeleton and tablet computer with an Arduino microcomputer. Nine patients in the subacute stage of recovery after stroke participated in a neurofeedback training experiment, which employed the aforementioned system. During the 4 weeks of this study, the participants received 2 weeks of BMI-based or control interventions in a random and counterbalanced order, in addition to their daily conventional physiotherapy. The control intervention consisted of the same MI training as the BMI-based intervention, but the exoskeleton always provided proprioceptive feedback regardless of the ERD strength. The ERD strength in the affected hemisphere showed a desirable increase with a significant improvement of finger joint spasticity, only after the DMB-based intervention period, and not after the control intervention period. The proposed neurofeedback training can help patients with stroke and movement disorders, because increased ERD strength may lead to recovery of motor function.
We developed an excretion monitoring system equipped with non-contact temperature sensor and a semiconductor gas sensor installed under a toilet seat. The gas sensor is able to detect odors due to human excretion by transiently increasing the output. The peak amplitude and duration of the gas sensor output due to defecation were significantly greater than those due to urination. These results demonstrate the capability of the gas sensor in distinguishing whether the excretion is urination or defecation.
Simulation using computational methods is well-established for investigating mechanical and haemodynamic properties of blood vessels, however few groups have applied this technology to microvascular anastomoses. This study, for the first time, employs analytic and numeric models of sutured and coupled microarterial anastomoses to evaluate the elastic and failure properties of these techniques in realistic geometries using measured arterial waveforms. Computational geometries were created of pristine microvessels and microarterial anastomoses, performed using sutures and a coupling device. Vessel wall displacement, stress, and strain distributions were predicted for each anastomotic technique using finite element analysis (FEA) software in both static and transient simulations. This study focussed on mechanical properties of the anastomosis immediately after surgery, as failure is most likely in the early post-operative period. Comparisons were also drawn between stress distributions seen in analogous non-compliant simulations. The maximum principal strain in a sutured anastomosis was found to be 84% greater than in a pristine vessel, whereas a mechanically coupled anastomosis reduced arterial strain predictions by approximately 55%. Stress distributions in the sutured anastomoses simulated here differed to those in reported literature. This result is attributed to the use of bonded connections in existing studies, to represent healed surgical sites. This has been confirmed by our study using FEA, and we believe this boundary condition significantly alters the stress distribution, and is less representative of the clinical picture following surgery. We have demonstrated that the inertial effects due to motion of the vessel during pulsatile flow are minimal, since the differences between the transient and static strain calculations range from around 0.6–7% dependent on the geometry. This implies that static structural analyses are likely sufficient to predict anastomotic strains in these simulations. Furthermore, approximations of the shear strain rate (SSR) were calculated and compared to analogous rigid-walled simulations, revealing that wall compliance had little influence on their overall magnitude. It is important to highlight, however, that SSR variations here are taken in isolation, and that changing pressure gradients are likely to produce much greater variation in vessel wall strain values than the influence of fluid flow alone. Hence, a formal fluid-structure interaction (FSI) study would be necessary to ascertain the true relationship.
It has been reported that increased intermittent non-Gaussian fluctuations in the instantaneous amplitude of low-frequency heart rate variability (LF-HRV) are related to high mortality risk in cardiac patients. However, little is known about the physiological origin of the amplitude modulation of LF-HRV. The purpose of this study was to clarify the relationship between amplitude modulation of LF-HRV and that of low-frequency blood pressure variability (LF-BPV). Eight normal male subjects performed movie-watching and calculation tasks in a sitting position for 40 min each while electrocardiogram and continuous blood pressure waveforms were recorded. From these signals, we calculated the instantaneous amplitude of the LF-band RR interval (RRILFamp) signal and that of the LF-band systolic blood pressure (SBP) signal (SBPLFamp) via band-pass filter and Hilbert transform. All subjects exhibited significant and relatively high positive correlation coefficients between RRILFamp and SBPLFamp in both tasks (mean Pearson correlation coefficient > 0.45). Mean coherence in the 0.01–0.05 Hz band between RRILFamp and SBPLFamp was also significant in all but one subject (mean coherence > 0.42). These results indicate a relatively high positive correlation between the amplitude modulation of LF-HRV and that of LF-BPV. We calculated the peak time lags of the cross correlation between RRILFamp and SBPLFamp in the 0.01–0.05 Hz band. A negative peak time lag implies that the amplitude modulation of LF-HRV precedes that of LF-BPV. All subjects exhibited negative peak time lag in the movie-watching task. All but one subject exhibited negative or zero peak time lag in the calculation task. These results imply that the amplitude modulation of LF-HRV precedes that of LF-BPV in the frequency range of 0.01–0.05 Hz.
Asthma is a chronic respiratory disease, in which symptoms appear or intensify suddenly, even when patients are being monitored by doctors. Continuous measurement is important to monitor a patient's breathing without missing asthma attacks. In this study, we propose a method of continuous breathing monitoring in daily life using a wearable device. There are several studies using microphones to continuously monitor breathing during activities, which show various possibilities of extracting qualitative characteristics related to asthma. Other studies on breathing measurement using accelerometers or belts have achieved breathing detection and measurement without ambient acoustic noises. Taking advantage of the breathing sound and chest movement signals, they are simultaneously acquired using a chest-mounted device, which consists of a microphone, a photoreflector, and a flexible cover. Various acoustic noises and body movements are present in the environment. Thus, acquiring these two different signals in a complementary manner makes it easier to detect breathing in daily life. For monitoring asthma, we focused on detecting the breathing phases. Most of the asthma symptoms appear during the exhalation phase. Thus, phase detection plays an important role as an asthma symptom identifier. We developed a new algorithm for breathing phase measurement using both acquired signals. The algorithm is based on the periodicity of the chest movement signal. Breathing sounds are analyzed considering their frequency characteristics. In this paper, the basic performance of the proposed device in an experimental condition which is quiet and without participant movements is examined. The results of performance evaluation confirm that the left medial side of the second intercostal space is appropriate for placing the device and studying the correlation between breathing sound amplitude and tidal volume, which implies a potential to acquire tidal volumes. The phase measurement experiment shows that chest movement can be used for estimating the breathing period. The portable system developed can measure breathing in external conditions and tracking the wearer's location. Making the system portable expands the measurable situations and facilitates an acquisition of time and location information, which is useful in identifying the causes of asthma attacks.