Finger Pressure Research Articles

Acanthus Condom Catheter: A Reusable and Adjustable Silicone Male External Catheter With Pressure-Sensitive Silicone Adhesive for Urinary Drainage.

Condom catheters are also called external urinary collection devices tocollect urine and monitor urine output in hospitalized and other patients with urinary incontinence. They play an important role in reducing catheter-associated urinary tract infections by using invasive indwelling catheters that are placed inside the bladder.Currently, male external catheters come with or without adhesives. Major problems with current condom catheters are finding the right size to fit, excessive slippage needing to replace too many, urine leak, skin irritation, and damage. In some cases, it's a common practice to wrapadhesive tape around the catheter and penisto keep the catheter in place which can cause skin injury. The Acanthus condom catheter is an expandable silicone male external catheter designed and developed to reduce excessive catheter slippage and keep the catheter longer.It works by applying silicone adhesive to the inner catheter wall just below the catheter rim and applying gentle pressure after the placement. It can be adjusted after the placementand can be kept in place by applying gentle pressure around the catheter to prevent slippage. After laboratory testing of the catheter showed it was able to withstand 250% more pressure and 187% higher tensile forces, we have retrospectively reviewed a nursing survey of14 hospitalized patients using the Acanthus condom catheter for urinary drainage. The mean age was 89 years. A total of 55 evaluations were collected, of which 46 were day shift and nine were night shift responses for a total of 44 catheter days.Results showed that the catheter was easy to use (100%). There was no skin irritation or damage during the application or removal (100%). The catheter was able to drain urine and stayed in place most of the time (89%) except in a few instances it came out, especially during the night shift, but the nurse was able to place it back. There was one instance of urine leak (1.8%). Nurses felt that the catheter was better than existing products in 95% of responses. In conclusion, the Acanthus condom catheter was easy to use, can be reused for up to three days, and was safe on the skin; most importantly, nurses were able to adjust the catheter when they noticed it to be slipping and kept it in place using gentle finger pressure or adding few additional drops of silicone adhesive on the inner catheter wallbelow the rim and applying brief pressure around the catheter. One size (medium-large) fits most of the patients in the study due to elasticity and stretch dimensions, which eliminated the problem of finding the right size to use.

Integrating Eye Movement, Finger Pressure, and Foot Pressure Information to Build an Intelligent Driving Fatigue Detection System

Fatigued driving is a problem that every driver will face, and traffic accidents caused by drowsy driving often occur involuntarily. If there is a fatigue detection and warning system, it is generally believed that the occurrence of some incidents can be reduced. However, everyone’s driving habits and methods may differ, so it is not easy to establish a suitable general detection system. If a customized intelligent fatigue detection system can be established, it may reduce unfortunate accidents. With its potential to mitigate unfortunate accidents, this study offers hope for a safer driving environment. Thus, on the one hand, this research hopes to integrate the information obtained from three different sensing devices (eye movement, finger pressure, and plantar pressure), which are chosen for their ability to provide comprehensive and reliable data on a driver’s physical and mental state. On the other hand, it uses an autonomous learning architecture to integrate these three data types to build a customized fatigued driving detection system. This study used a system that simulated a car driving environment and then invited subjects to conduct tests on fixed driving routes. First, we demonstrated that the system established in this study could be used to learn and classify different driving clips. Then, we showed that it was possible to judge whether the driver was fatigued through a series of driving behaviors, such as lane drifting, sudden braking, and irregular acceleration, rather than a single momentary behavior. Finally, we tested the hypothesized situation in which drivers were experiencing three cases of different distractions. The results show that the entire system can establish a personal driving system through autonomous learning behavior and further detect whether fatigued driving abnormalities occur.

Nonlinear Viscoelastic Modeling of Finger Arteries: Toward Smartphone-Based Blood Pressure Monitoring via the Oscillometric Finger Pressing Method.

Oscillometric finger pressing is a smartphone-based blood pressure (BP) monitoring method. Finger photoplethysmography (PPG) oscillations and pressure are measured during a steady increase in finger pressure, and an algorithm computes systolic BP (SP) and diastolic BP (DP) from the measurements. The objective was to assess the impact of finger artery viscoelasticity on the BP computation. Nonlinear viscoelastic models relating transmural pressure (finger BP - applied pressure) to PPG oscillations during finger pressing were developed. The output of each model to a measured transmural pressure input was fitted to measured PPG oscillations from 15 participants. A parametric sensitivity analysis was performed via model simulations to elucidate the viscoelastic effect on the derivative-based BP computation algorithm. A Wiener viscoelastic model comprising a first-order transfer function followed by a static sigmoidal function fitted the measured PPG oscillations better than an elastic model containing only the static function (median (IQR) error of 30.5% (25.6%-34.0%) vs 50.9% (46.7%-53.7%); p<0.01). In Wiener model simulations, the derivative algorithm underestimated SP, especially with high pulse pressure and low transfer function cutoff frequency (i.e., greater viscoelasticity). The mean of the normalized PPG waveform at the maximum oscillation beat was found to correlate with the cutoff frequency (r = -0.8) and could thus possibly be used to compensate for viscoelasticity. Finger artery viscoelasticity negatively impacts oscillometric BP computation algorithms but can potentially be compensated for using available measurements. These findings may help in converting smartphones into truly cuffless BP monitors for improving hypertension awareness and control.

Application of abdominal massage combined with acupoint finger pressure therapy in nursing management of post-stroke constipation

Application of abdominal massage combined with acupoint finger pressure therapy in nursing management of post-stroke constipation

Stretchable Electrodes for Interconnects in Soft Electronics.

Soft electronics have significantly enhanced user convenience and data accuracy in wearable devices, implantable devices, and human-machine interfaces. However, a persistent challenge in their development has been the disconnection between the rigid and soft components of devices due to the substantial difference in modulus and stretchability. To address this issue, establishing a durable and flexible connection that smoothly links components of varying stiffness to signal-capturing sections with a lower stiffness is essential. In this study, we developed a novel stretchable interconnect that strongly adheres to various materials, facilitating electrical connections effortlessly by applying minimal finger pressure. Capable of stretching up to 1000% while maintaining electrical integrity, this interconnect proves its applicability across multiple domains, including electrocardiogram (ECG), electromyography (EMG), and stretchable light-emitting diode (LED) circuits. Its versatility is further demonstrated through its compatibility with various manufacturing techniques such as 3D printing, painting, and spin coating, highlighting its adaptability in soft electronics.

Wearable multichannel-active pressurized pulse sensing platform

With the modernization of traditional Chinese medicine (TCM), creating devices to digitalize aspects of pulse diagnosis has proved to be challenging. The currently available pulse detection devices usually rely on external pressure devices, which are either bulky or poorly integrated, hindering their practical application. In this work, we propose an innovative wearable active pressure three-channel pulse monitoring device based on TCM pulse diagnosis methods. It combines a flexible pressure sensor array, flexible airbag array, active pressure control unit, advanced machine learning approach, and a companion mobile application for human–computer interaction. Due to the high sensitivity (460.1 kPa−1), high linearity (R2 > 0.999) and flexibility of the flexible pressure sensors, the device can accurately simulate finger pressure to collect pulse waves (Cun, Guan, and Chi) at different external pressures on the wrist. In addition, by measuring the change in pulse wave amplitude at different pressures, an individual’s blood pressure status can be successfully predicted. This enables truly wearable, actively pressurized, continuous wireless dynamic monitoring of wrist pulse health. The innovative and integrated design of this pulse monitoring platform could provide a new paradigm for digitizing aspects of TCM and other smart healthcare systems.

Experimental study on implant-abutment locking force and abutment subsidence in a pure Morse taper connection implant system.

This test aimed to investigate the factors affecting the locking force between the implant and abutment and the amount of abutment subsidence in pure Morse taper connection implant systems. With reference to the Bicon implant abutment connection design, different types of implant specimens and their corresponding types of abutments were fabricated. The implant-abutment locking taper was uniformly 1.5°. The locking depths were 1.0, 2.0, and 3.0 mm. The diameters of the locking column were 2.5, 3.0, and 3.5 mm. The thicknesses of the outer wall of the implant were 0.15 and 0.30 mm. The loading forces of the testing machine were 200, 300, and 400 N. At least 10 specimens of each group of implant-abutment were used. All specimens were loaded in the same manner using a universal testing machine (finger pressure + specified loading force, five times). The total height of the implant-abutment was measured before finger pressure, after finger pressure, and after the testing machine was loaded for five times to calculate the amount of sinking of the abutment. Finally, the implant and abutment were pulled apart using the universal testing machine, and the subluxation force was observed and recorded. The test loading force, locking depth, and locking post diameter had an effect on the implant-abutment locking force and abutment subsidence. The implant-abutment locking force increased with the increase in the test loading force, locking depth, and locking post diameter (R=0.963, 0.607, and 0.372, respectively), with the test loading force having the most significant effect. Abutment subsidence increased with the increase in test loading force (R=0.645) and decreased with the increase in locking depth and locking post diameter (R=-0.807 and -0.280, respectively), with locking depth having the most significant effect on abutment subsidence. No significant correlation was found between the thickness of the outer wall of the implant and the change in the magnitude of the implant-abutment locking force. However, an increase in the thickness of the outer wall of the implant decreased the amount of abutment subsidence, which was inversely correlated. The locking force of the implant-abutment can be increased by adjusting the design of the pure Morse taper connection implant⁃abutment connection, increasing the locking depth and locking post diameter, and increasing the amount and number of times the abutment is loaded during seating. Problems, such as loosening or detachment of the abutment, can be reduced. The recommended abutment to be loaded should be no less than five times during seating to prevent the abutment from sinking and causing changes in the occlusal relationship in the later stages. Preliminary occlusal adjustments should only be conducted in the early stages of the use of temporary restorations, and final restorations and occlusal adjustments are recommended to be performed after using the abutment for a period of time.

Flexible wide-range multidimensional force sensors inspired by bones embedded in muscle

AbstractFlexible sensors have been widely studied for use in motion monitoring, human‒machine interactions (HMIs), personalized medicine, and soft intelligent robots. However, their practical application is limited by their low output performance, narrow measuring range, and unidirectional force detection. Here, to achieve flexibility and high performance simultaneously, we developed a flexible wide-range multidimensional force sensor (FWMFS) similar to bones embedded in muscle structures. The adjustable magnetic field endows the FWMFS with multidimensional perception for detecting forces in different directions. The multilayer stacked coils significantly improved the output from the μV to the mV level while ensuring FWMFS miniaturization. The optimized FWMFS exhibited a high voltage sensitivity of 0.227 mV/N (0.5–8.4 N) and 0.047 mV/N (8.4–60 N) in response to normal forces ranging from 0.5 N to 60 N and could detect lateral forces ranging from 0.2–1.1 N and voltage sensitivities of 1.039 mV/N (0.2–0.5 N) and 0.194 mV/N (0.5–1.1 N). In terms of normal force measurements, the FWMFS can monitor finger pressure and sliding trajectories in response to finger taps, as well as measure plantar pressure for assessing human movement. The plantar pressure signals of five human movements collected by the FWMFS were analyzed using the k-nearest neighbors classification algorithm, which achieved a recognition accuracy of 92%. Additionally, an artificial intelligence biometric authentication system is being developed that classifies and recognizes user passwords. Based on the lateral force measurement ability of the FWMFS, the direction of ball movement can be distinguished, and communication systems such as Morse Code can be expanded. This research has significant potential in intelligent sensing and personalized spatial recognition.

Design of a lightweight and easy‐to‐wear hand glove with multi‐modal tactile perception for digital human

AbstractWithin the field of human–computer interaction, data gloves play an essential role in establishing a connection between virtual and physical environments for the realization of digital human. To enhance the credibility of human‐virtual hand interactions, we aim to develop a system incorporating a data glove‐embedded technology. Our proposed system collects a wide range of information (temperature, bending, and pressure of fingers) that arise during natural interactions and afterwards reproduce them within the virtual environment. Furthermore, we implement a novel traversal polling technique to facilitate the streamlined aggregation of multi‐channel sensors. This mitigates the hardware complexity of the embedded system. The experimental results indicate that the data glove demonstrates a high degree of precision in acquiring real‐time hand interaction information, as well as effectively displaying hand posture in real‐time using Unity3D. The data glove's lightweight and compact design facilitates its versatile utilization in virtual reality interactions.

Development of sensor system and data analytic framework for non-invasive blood glucose prediction

AbstractPeriodic quantification of blood glucose levels is performed using painful, invasive methods. The proposed work presents the development of a noninvasive glucose-monitoring device with two sensors, i.e., finger and wrist bands. The sensor system was designed with a near-infrared (NIR) wavelength of 940 nm emitter and a 900–1700 nm detector. This study included 101 diabetic and non-diabetic volunteers. The obtained dataset was subjected to pre-processing, exploratory data analysis (EDA), data visualization, and integration methods. Ambiguities such as the effects of skin color, ambient light, and finger pressure on the sensor were overcome in the proposed ‘niGLUC-2.0v’. niGLUC-2.0v was validated with performance metrics where accuracy of 99.02%, mean absolute error (MAE) of 0.15, mean square error (MSE) of 0.22 for finger, and accuracy of 99.96%, MAE of 0.06, MSE of 0.006 for wrist prototype with ridge regression (RR) were achieved. Bland–Altman analysis was performed, where 98% of the data points were within ± 1.96 standard deviation (SD), 100% were under zone A of the Clarke Error Grid (CEG), and statistical analysis showed p &lt; 0.05 on evaluated accuracy. Thus, niGLUC-2.0v is suitable in the medical and personal care fields for continuous real-time blood glucose monitoring.

Peeling fingers in an elastic Hele-Shaw channel

Using experiments and a depth-averaged numerical model, we study instabilities of two-phase flows in a Hele-Shaw channel with an elastic upper boundary and a non-uniform cross-section prescribed by initial collapse. Experimentally, we find increasingly complex and unsteady modes of air-finger propagation as the dimensionless bubble speed $Ca$ and level of collapse are increased, including pointed fingers, indented fingers and the feathered modes first identified by Cuttle et al. (J. Fluid Mech., vol. 886, 2020, A20). By introducing a measure of the viscous contribution to finger propagation, we identify a $Ca$ threshold beyond which viscous forces are superseded by elastic effects. Quantitative prediction of this transition between ‘viscous’ and ‘elastic’ reopening regimes across levels of collapse establishes the fidelity of the numerical model. In the viscous regime, we recover the non-monotonic dependence on $Ca$ of the finger pressure, which is characteristic of benchtop models of airway reopening. To explore the elastic regime numerically, we extend the depth-averaged model introduced by Fontana et al. (J. Fluid Mech., vol. 916, 2021, A27) to include an artificial disjoining pressure that prevents the unphysical self-intersection of the interface. Using time simulations, we capture for the first time the majority of experimental finger dynamics, including feathered modes. We show that these disordered states evolve continually, with no evidence of convergence to steady or periodic states. We find that the steady bifurcation structure satisfactorily predicts the bubble pressure as a function of $Ca$ , but that it does not provide sufficient information to predict the transition to unsteady dynamics that appears strongly nonlinear.

Highly compressible wearable sensor with CNT-coated PDMS sponge electrodes for tactile monitoring application

Electrical resistance-based sensors have attracted great attention due to their wide range of applications, among which sensors for detecting external forces are indispensable due to the complex environment of the modern era. Inspired by the capillary phenomenon, in this study, we fabricated a carbon nanotube (CNT)-polydimethylsiloxane (PDMS)-based compressive resistive sensor that is easy to fabricate and has a wide range of sensitivities. Repeated compression tests were performed to evaluate the durability of the fabricated sensors. Different coating conditions resulted in different durability depending on the extent to which the CNT electrodes were coated on the porous PDMS surface, and the sensitivity of the sensors could be controlled by CNT concentration, coating time, and coating depth. Resistive sensors with different sensitivities can easily detect changes in electrical signals due to finger pressure, which shows great promise for use in wearable electronics. In addition, the resistive sensor is biocompatible because only the pure PDMS surface is attached to the human body, and the porous structure exhibits good compressibility.

Stereomicroscope-Based in Vitro Study Evaluating the Marginal and Internal Fit of PEEK and PEKK Crowns.

The aim of the in vitro study was to compare the internal merge and marginal perfection of polyetheretherketone (PEEK) and polyetherketoneketone (PEKK) crowns under a stereomicroscope. All-ceramic preparation is done on the maxillary first premolar which is mounted on the wax block which was scanned using 3Shape scanner and duplicated into 30 acrylic CAD/CAM dies (n = 15) for the placement of PEEK and PEKK crowns. The YENADENT milling system was used to fabricate 15 samples from Group A PEEK crowns and to fabricate 15 samples from Group B PEKK crowns. According to the manufacturer's instructions, an equal amount of the dual-cure resin luting agent (Rely X U200 Self-Adhesive resin, 3M, Germany) was dispensed on the mixing pad before being mixed with cement and painted on the internal surfaces of the copings with the finger pressure crowns which were luted. The values were then analyzed using one-way ANOVA (post hoc) followed by Dunnett's t-test. Among those two groups, PEEK group materials showed the lowest mean value of (28.73.3 ± 4.01) for marginal fit and (26.72 ± 2.53) for internal gap, whereas PEKK group showed a mean value of (32.85 ± 4.63) and (33.06 ± 4.14), respectively. Among these two groups, comparatively less marginal fit and internal adaptation is seen in PEKK when compared to the PEEK crowns. While the marginal fit and internal adaptation of both PEEK and PEKK copings were in acceptable clinical range.

Finger temperature-driven thermogalvainc gel-based smart pen: Utilized for identity recognition, stroke analysis, and grip posture assessment

Inappropriate pen-holding postures can result in increased muscle strain and reduced writing speed, and may even contribute to the onset of conditions such as myopia, arthritis, and cervical spondylosis. However, challenges persist in current one-size-fits-all pens toward actively monitoring handwriting habits due to structural complexity and indispensability of power supply. In this study, a finger temperature-driven thermoelectric gel-based smart pen has been invented for identity recognition, stroke analysis, and grip posture assessment by coupling thermogalvanic and piezoresistive effects derived from finger temperature and pressure on a PVA/gelatin gel. This dual-network gel exhibits not only a high thermopower of − 2.05 mV K−1 and a rapid response of 130 ms, but also full flexibility, significant resistance to desiccation, and a high tensile capacity of up to 300%. By integrating thermogalvanic gel units within a pen shaft, our self-powered smart pen achieved a recognition accuracy of 98.1% for eight basic Chinese character strokes with the aid of deep learning. Furthermore, with a four-channel expansion, the recognition accuracy reaches 98.8% for eight distinct identities and 99.1% for nine different pen-holding postures, respectively, while offering real-time visualization of monitoring results on a user-friendly human-machine interface. This machine learning-assisted self-powered smart gel pen presents a new viable solution for wearable bioelectronics toward future intelligent era.

Artificial Octopus-Limb-Like Adhesive Patches for Cupping-Driven Transdermal Delivery with Nanoscale Control of Stratum Corneum.

Drug delivery through complex skin is currently being studied using various innovative structural and material strategies due to the low delivery efficiency of the multilayered stratum corneum as a barrier function. Existing microneedle-based or electrical stimulation methods have made considerable advances, but they still have technical limitations to reduce skin discomfort and increase user convenience. This work introduces the design, operation mechanism, and performance of noninvasive transdermal patch with dual-layered suction chamber cluster (d-SCC) mimicking octopus-limb capable of wet adhesion with enhanced adhesion hysteresis and physical stimulation. The d-SCC facilitates cupping-driven drug delivery through the skin with only finger pressure. Our device enables nanoscale deformation control of stratum corneum of the engaged skin, allowing for efficient transport of diverse drugs through the stratum corneum without causing skin discomfort. Compared without the cupping effect of d-SCC, applying negative pressure to the porcine, human cadaver, and artificial skin for 30 min significantly improved the penetration depth of liquid-formulated subnanoscale medicines up to 44, 56, and 139%. After removing the cups, an additional acceleration in delivery to the skin was observed. The feasibility of d-SCC was demonstrated in an atopic dermatitis-induced model with thickened stratum corneum, contributing to the normalization of immune response.

Survival of Endodontically Treated Maxillary Anterior Teeth with Aesthetic Post-Restoration: A Prospective Intervention Study

Introduction: There is much debate over the best choice of restorative material and the placement method for the most successful treatment. Many teeth that have undergone endodontic treatment may not have enough structure to support a restoration or crown. To improve retention for the restorative material, ferrule may be used. Adhesive techniques have transformed the way we restore teeth after root canal treatment, starting with the shift from using cast post-and-core to using fibre post. The use of fibre-reinforced posts has been found to prevent irreparable root fractures thereby improving the longevity of the treatment. Aim: To compare two different types of aesthetic fibre posts for 12 months. Materials and Methods: A prospective interventional study was carried out in the Department of Prosthodontics, Manav Rachna Dental College (Faridabad) for a period of 12 months from Nov 2022- Oct 2023. Forty participants with single rooted, endodontically treated, maxillary anterior teeth in the age bracket of 15-55 years, both males and females of the north Indian population were included in the study. Teeth were selected where a post-retained crown was indicated and post space was prepared using a piezo reamer drill at 5000 rpm. At least 4 mm of obturation is left in the canal to maintain the apical seal. Furthermore, Zircon-enriched silicon fibre and glass fibrereinforced posts were cemented into the prepared post space. Metal-ceramic crowns were cemented and baseline periapical radiographs were obtained. At the interval of one month, three months, six months and one year, the patients were evaluated. The Fischer’s exact test was utilised to establish the association between categorical variables and the level of significance (p-value &lt;0.05). Results: One year follow-up revealed no failures in crown movement when evaluated under finger pressure, recurrent caries, or root fractures. One case of glass fibre-reinforced post showed a fracture of the post and another case of glass fibre post showed periapical radiolucency at 6-month intervals on clinical and radiographical examination which was significant when compared to Zircon-enriched silicon fibre post group (p-value=0.02). Conclusion: Both aesthetic fibre-reinforced post systems used in single-rooted upper anterior teeth demonstrated similar success rates in restoring root canal treated teeth.

Quantification of mechanical behavior of rat tail under compression.

The development of vibration-induced finger disorders is likely associated with combined static and dynamic responses of the fingers to vibration exposure. To study the mechanism of the disorders, a new rat-tail model has been established to mimic the finger vibration and pressure exposures. However, the mechanical behavior of the tail during compression needs to be better understood to improve the model and its applications. To investigate the static and time-dependent force responses of the rat tail during compression. Compression tests were conducted on Sprague-Dawley cadaver rat tails using a micromechanical system at three deformation velocities and three deformation magnitudes. Contact-width and the time-histories of force and deformation were measured. Additionally, force-relaxation tests were conducted and a Prony series was used to model the force-relaxation behavior of the tail. The rat tails' force-deformation and stiffness-deformation relationships were strongly nonlinear and time-dependent. Force/stiffness increased with an increase in deformation and deformation velocity. The time-dependent force-relaxation characteristics of the tails can be well described using a Prony series. We successfully quantified the static and time-dependent force responses of rat tails under compression. The identified mechanical behavior of the tail can help improve the rat-tail model and its applications.

Effect of transmural pressure on the estimation of arterial stiffness index from the photoplethysmographic waveform.

The aim of this study was to find the effect of transmural pressure on the determination of the photoplethysmographic (PPG) waveform arterial stiffness index (PPGAI). The study was conducted on 51 subjects without diagnosis of cardiovascular disease, aged between 24 and 74years. The relation between the transmural pressure, which is the difference between the arterial blood pressure and the PPG sensor contact pressure, and the PPGAI was determined. PPG, beat-to-beat blood pressure, and sensor contact pressure signals were recorded from the index, middle, and ring finger. The PPG sensor contact pressure of the index finger was increased from 20 to 120mmHg. The aortic augmentation index (AIx@75) was estimated with a SphygmoCor device as a reference. High correlation coefficients r = 0.79 and r = 0.83 between PPGAI and AIx@75, and low PPGAI standard deviations were observed at the transmural pressures of 10 and 20mmHg, respectively. Transmural pressure of 20mmHg can be considered suitable for the PPG signal registration and PPGAI calculation for the assessment of arterial stiffness. In summary, the contact pressure of the sensor should be selected according to theblood pressure of the subject finger in order to achieve the transmural pressure suitable for the assessment of PPGAI and arterial stiffness.

Effect of finger pressure on blood pressure measurement using photoplethysmography

Photoplethysmography (PPG) is a technique that uses a light source by allowing light to pass through a fingertip and detect the reflection of light to obtain the PPG signal. The PPG signal can be used to monitor personal health and to determine the blood pressure (BP) value. However, it is difficult to obtain a reliable PPG signal due to various environmental factors. A pressure that a finger presses on the sensor during measurement is one of the main factor to obtain a wave-like PPG signal. In this work, effect of finger pressure on blood pressure measurement using PPG is intensively investigated in order to improve the reliability and accuracy. The BP prototype with a force sensor put at a location of fingertip next to the light sensor is developed in order to detect a finger pressure. An optimum condition of the fingertip pressure for the BP measurement is evaluated by using a maximum and minimum values of PPG signals from the IR light reflection. The calibration of the BP prototype is performed and back test with a commercial BP monitor. It is found that the optimum finger pressure is in medium region of 65-75 with the reliable wave-form. Moreover, the accuracy of our BP prototype is about ±2.0 mmHg compared to the accuracy of commercial BP monitor of ±3 mmHg and the accuracy of our previous work of ±9.2 mmHg. Thus, our developed BP prototype with the control of the finger pressure exhibits an improvement of reliability and accuracy. This suggests a potential application for a commercial BP monitor without a cuff.

Smartphone-Based Blood Pressure Monitoring via the Oscillometric Finger Pressing Method: Analysis of Oscillation Width Variations Can Improve Diastolic Pressure Computation.

Oscillometric finger pressing is a potential method for absolute blood pressure (BP) monitoring via a smartphone. The user presses their fingertip against a photoplethysmography-force sensor unit on a smartphone to steadily increase the external pressure on the underlying artery. Meanwhile, the phone guides the finger pressing and computes systolic BP (SP) and diastolic BP (DP) from the measured blood volume oscillations and finger pressure. The objective was to develop and evaluate reliable finger oscillometric BP computation algorithms. The collapsibility of thin finger arteries was exploited in an oscillometric model to develop simple algorithms for computing BP from the finger pressing measurements. These algorithms extract features from "width" oscillograms (oscillation width versus finger pressure functions) and the conventional "height" oscillogram for markers of DP and SP. Finger pressing measurements were obtained using a custom system along with reference arm cuff BP measurements from 22 subjects. Measurements were also obtained during BP interventions in some subjects for 34 total measurements. An algorithm employing the average of width and height oscillogram features predicted DP with correlation of 0.86 and precision error of 8.6mmHg with respect to the reference measurements. Analysis of arm oscillometric cuff pressure waveforms from an existing patient database provided evidence that the width oscillogram features are better suited to finger oscillometry. Analysis of oscillation width variations during finger pressing can improve DP computation. The study findings may help in converting widely available devices into truly cuffless BP monitors for improving hypertension awareness and control.