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PID controller design to generate pulsatile flow rate for in vitro experimental studies of physiological flows.

Mohammad Reza NAJJARI ; Michael W. PLESNIAK

Biomedical Engineering Letters.2017;7(4):339-344. doi:10.1007/s13534-017-0049-9

Producing accurate pulsatile flow rates is essential for many in vitro experimental studies in biofluid dynamics research. A controller system was developed to control a flow loop to produce easily adjustable pulsatile flow rates with sufficient accuracy. An Arduino board is used as a micro-controller to control a pump to produce various pulsatile flow rates, and an open-source proportional-integral-derivative (PID) control algorithm is developed for this purpose. Four non-trivial pulsatile waveforms were produced by the PID controller, as well as an iterative controller, and the performance of both controllers was evaluated. Both the PID and iterative controllers were able to successfully produce slowly-varying signals (single and multi-harmonic low frequency sine waves), but for high frequency signals where the flow has strong acceleration/deceleration (e.g. for physiological waveforms) the iterative controller exhibited significant undershoot. The comparison of PID and iterative controllers suggests that if the desired flow rate is a low frequency, simple waveform then the iterative controller is preferred due to simplicity of implementation. However, if the desired signal is rapidly changing and more complicated then the PID controller achieves better results. This system can be implemented in many flow loops due to its simplicity and low cost, and does not require a mathematical model of the system.
Carotid Artery, Common ; In Vitro Techniques* ; Models, Theoretical ; Pulsatile Flow*

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Transscleral LED illumination pen.

Christian LINGENFELDER ; Frank KOCH ; Philipp KOELBL ; Pia KLANTE ; Martin HESSLING

Biomedical Engineering Letters.2017;7(4):311-315. doi:10.1007/s13534-017-0039-y

Existing light sources for intraocular illumination are often bulky and expensive and pose a risk for the patient, because light guides are inserted in the eye through incisions and if the tip of these light guides get too close to the retina, the retina can be damaged photochemically within minutes or even seconds. Therefore a new, safe and simple device for intraocular illumination is developed and evaluated for its thermal and photochemical risks to the patient. It consists of a white LED which is integrated into a pen like holder. This device is pressed against the sclera by the physician who seeks for illumination during surgery or for diagnostic purposes. The LED light is transmitted through the sclera without the need for an incision. Considering the relevant standards, the device poses no harm to the patient, and in tests with the authors' own eyes a sufficient intraocular illumination is reached. The proposed device is quite simple but easy to handle and very gentle for the patient.
Humans ; Lighting* ; Retina ; Sclera

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Novel tailoring algorithm for abrupt motion artifact removal in photoplethysmogram signals.

Limeng PU ; Pedro J CHACON ; Hsiao Chun WU ; Jin Woo CHOI

Biomedical Engineering Letters.2017;7(4):299-304. doi:10.1007/s13534-017-0037-0

Photoplethysmogram (PPG) signals are widely used for wearable electronic devices nowadays. The PPG signal is extremely sensitive to the motion artifacts (MAs) caused by the subject's movement. The detection and removal of such MAs remains a difficult problem. Due to the complicated MA signal waveforms, none of the existing techniques can lead to satisfactory results. In this paper, a new framework to identify and tailor the abrupt MAs in PPG is proposed, which consists of feature extraction, change-point detection, and MA removal. In order to achieve the optimal performance, a data-dependent frame-size determination mechanism is employed. Experiments for the heart-beat-rate-measurement application have been conducted to demonstrate the effectiveness of our proposed method, by a correct detection rate of MAs at 98% and the average heart-beat-rate tracking accuracy above 97%. On the other hand, this new framework maintains the original signal temporal structure unlike the spectrum-based approach, and it can be further applied for the calculation of blood oxygen level (SpO₂).
Artifacts* ; Hand ; Methods ; Oxygen

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Variations in gait features in elderly adults during walking considering their balance.

Hyuk Jae CHOI ; Han Sung KIM ; Jeicheong RYU ; Gyoosuk KIM ; Chang Yong KO

Biomedical Engineering Letters.2017;7(4):333-338. doi:10.1007/s13534-017-0045-0

The aim of this study was to evaluate the influence of balance on the spatiotemporal features, lower-limb kinematics, and center of mass (COM) of the non-faller elderly during walking. In this study, 20 healthy elderly women (age, 76.2 ± 5.6 years; height, 150.1 ± 3.2 cm; weight, 55.8 ± 9.0 kg) were enrolled. Based on the Berg balance scale (BBS), the elderly were classified into two groups: poor balance (PB; BBS scores <46; n = 10; 43.8 ± 1.8) and good balance (GB; BBS scores C46; n = 10; 50.4 ± 2.5). The two groups had no differences in terms of the spatiotemporal features and range of motion (ROM) of the vertical COM (all p>0.05). The ROM of the mediolateral COM was greater in PB than in GB. Hip transversal movements in the two groups were different. The impairment of the lateral balance function might contribute to an increase in the incidence of fall events in the elderly with poor balance.
Adult* ; Aged* ; Biomechanical Phenomena ; Female ; Gait* ; Hip ; Humans ; Incidence ; Range of Motion, Articular ; Walking*

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Real-time biofeedback device for gait rehabilitation of post-stroke patients.

I Hung KHOO ; Panadda MARAYONG ; Vennila KRISHNAN ; Michael BALAGTAS ; Omar ROJAS ; Katherine LEYBA

Biomedical Engineering Letters.2017;7(4):287-298. doi:10.1007/s13534-017-0036-1

In this work, we develop a device, called ‘Walk-Even’, that can provide real-time feedback to correct gait asymmetry commonly exhibited in post-stroke survivors and persons with certain neurological disorders. The device computes gait parameters, including gait time, swing time, and stance time of each leg, to detect gait asymmetry and provide corresponding real-time biofeedback by means of auditory and electrotactile stimulation to actively correct the user's gait. The system consists of customized force-sensor-embedded insoles adjustable to fit any shoe size, electrotactile and auditory feedback circuits, microcontroller, and wireless XBee transceivers. The device also offers data saving capability. To validate its accuracy and reliability, we compared the gait measurements from our device with a commercial gait and balance assessment device, Zeno Walkway. The results show good correlation and agreement in a validity study with six healthy subjects and reliability study with seventeen healthy subjects. In addition, preliminary testing on six post-stroke patients after an 8-week training shows that the Walk-Even device helps to improve gait symmetry, foot pressure and forefoot loading of the affected side. Thus, initial testing indicates that the device is accurate in measuring the gait parameters and effective in improving gait symmetry using real-time feedback. The device is portable and low cost and has the potential for use in a non-clinical setting for patients that can walk independently without assistance. A more extensive testing with stroke patients is still ongoing.
Biofeedback, Psychology* ; Foot ; Gait* ; Healthy Volunteers ; Humans ; Leg ; Nervous System Diseases ; Rehabilitation* ; Shoes ; Stroke ; Survivors

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Flickering exercise video produces mirror neuron system (MNS) activation and steady state visually evoked potentials (SSVEPs).

Hyunmi LIM ; Jeonghun KU

Biomedical Engineering Letters.2017;7(4):281-286. doi:10.1007/s13534-017-0035-2

The action of observing can be used as an effective rehabilitation paradigm, because it activates the mirror neuron system. However, it is difficult to fully use this paradigm because it is difficult to get patients to engage in watching video clips of exercise. In this study, we proposed a steady state visually evoked potential (SSVEP) based paradigm that could be used in a Brain Computer Interface, and examined its feasibility by investigating whether flickering video could activate the mirror neuron system and evoke SSVEPs at the same time. Twenty subjects were recruited and asked to watch the flickering videos at a rate of 20 Hz of upper limb motion and visual white noise, while an EEG signal was recorded. The mu rhythm (8–13 Hz) suppression and the SSVEP (19–21 Hz) evocation were analyzed from recorded EEG. The results showed that SSVEPs, evoked by the flickering stimulus, was observed in both conditions on O1 and O2, but the mu rhythm suppression on C3 and C4 was observed only in the exercise video condition. These results could signify that the flickering video is applicable for the BCI rehabilitation game, activating the mirror neuron system at the same time.
Brain-Computer Interfaces ; Electroencephalography ; Evoked Potentials* ; Humans ; Mirror Neurons* ; Noise ; Rehabilitation ; Stroke ; Upper Extremity

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ECG arrhythmia classification using time frequency distribution techniques.

Safa SULTAN QURRAIE ; Rashid GHORBANI AFKHAMI

Biomedical Engineering Letters.2017;7(4):325-332. doi:10.1007/s13534-017-0043-2

In this paper, we focus on classifying cardiac arrhythmias. The MIT-BIH database is used with 14 original classes of labeling which is then mapped into 5 more general classes, using the Association for the Advancement of Medical Instrumentation standard. Three types of features were selected with a focus on the time-frequency aspects of ECG signal. After using the Wigner-Ville distribution the time-frequency plane is split into 9 windows considering the frequency bandwidth and time duration of ECG segments and peaks. The summation over these windows are employed as pseudo-energy features in classification. The “subject-oriented” scheme is used in classification, meaning the train and test sets include samples from different subjects. The subject-oriented method avoids the possible overfitting issues and guaranties the authenticity of the classification. The overall sensitivity and positive predictivity of classification is 99.67 and 98.92%, respectively, which shows a significant improvement over previous studies.
Arrhythmias, Cardiac* ; Classification* ; Decision Trees ; Electrocardiography* ; Methods

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Dielectrophoretic force measurement of red blood cells exposed to oxidative stress using optical tweezers and a microfluidic chip.

Hee Jae JEON ; Hyungbeen LEE ; Dae Sung YOON ; Beop Min KIM

Biomedical Engineering Letters.2017;7(4):317-323. doi:10.1007/s13534-017-0041-4

Red blood cell (RBC) dysfunction is often associated with a pathological intervention, and it has been proposed as a critical risk factor for certain lethal diseases. Examining the cell viability of RBCs under various physiological conditions is essential and of importance for precise diagnosis and drug discovery in the field of medicine and pharmacy. In this paper, we report a new analytical method that employs dielectrophoretic (DEP) force measurements in absolute units to assess the viability, and potentially the functionality of RBCs. We precisely quantify the frequency-dependent DEP forces of the RBCs by using a micro-electrode embedded chip combined with optical tweezers. DEP characteristics are known to be well-correlated with the viability of biological cells, and DEP forces are measured in both fresh and long-term stored RBCs to investigate the effect that the storage period has on the cell viability. Moreover, we investigate the DEP behavior of RBCs when exposed to oxidative stress and verify whether EDTA protects the RBCs from an oxidant. From the experiments, it is found that the fresh RBCs without oxidative stress display very high DEP forces over the entire frequency range, exhibiting two cutoff frequencies. However, both the RBCs stored for the long-term period and exposed to oxidative stress reveals that there exist no significant DEP forces over the frequency range. The results indicate that the DEP forces can serve as a useful parameter to verify whether the RBCs in certain blood are fresh and not exposed to oxidative stress. Therefore, it is believed that our system can be applied to a diagnostic system to monitor the cell viability of the RBCs or other types of cells.
Cell Survival ; Diagnosis ; Drug Discovery ; Edetic Acid ; Erythrocytes* ; Methods ; Microfluidics* ; Optical Tweezers* ; Oxidative Stress* ; Pharmacy ; Risk Factors

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Sex differences of cognitive load effects on object-location binding memory.

Jinsick PARK ; Ga In SHIN ; Young Min PARK ; In Young KIM ; Dong Pyo JANG

Biomedical Engineering Letters.2017;7(4):305-309. doi:10.1007/s13534-017-0038-z

In this study, we investigated where the sex differences of object-location binding memory performance were influenced by the cognitive load. We used the fractal objects version of the ‘What was where?’ task to measure object memory, location memory and objection-location binding memory. Cognitive load was controlled by task difficulty presented two sessions: one session randomly displayed three or four fractal objects (Session 34) and the other session four or five objects (Session 45). The results showed that females outperformed males on object-location binding memory. Interestingly, even when the four object trials were compared between Session 34 and Session 45, in which we believed that the level of difficulty was similar while cognitive load varied, the swap error of males was significantly increased in Session 45 compared to females. In conclusion, there may be sex differences in object-location binding memory and the males could be more sensitive about the cognitive load than females.
Female ; Fractals ; Humans ; Male ; Memory* ; Sex Characteristics*

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Spectrum analysis for assessing red blood cell aggregation using high-frequency ultrasound array transducer.

Changhan YOON

Biomedical Engineering Letters.2017;7(4):273-279. doi:10.1007/s13534-017-0034-3

The purpose of this study is to investigate a spectrum analysis technique for detecting and monitoring red blood cell (RBC) aggregation using a high-frequency array transducer. To assess the feasibility of this approach, the backscattered radio-frequency signal from non-aggregated and aggregated RBC samples with two hematocrit levels were acquired by using a 30-MHz linear array transducer and analyzed in frequency domain. Three parameters such as spectral slope, midband fit and Y intercept were extracted in a static condition. Fresh porcine blood was used and degrees of aggregation were changed by diluting plasma concentration. From the experiments, it was demonstrated that the spectral slope related to a size of scatterer progressively declined as the level of aggregation increased; its mean values at hematocrit of 40% were 1.10 and −0.22 dB/MHz for RBCs suspended in isotonic phosphate buffered saline and solution with 70% plasma concentrations, respectively. For the midband fit and Y intercept, the mean values were increased by 9.1 and 46.4 dB, respectively. These results indicated that the spectrum analysis technique is useful for monitoring RBC aggregation and can be potentially developed for assessing aggregation in clinical applications.
Erythrocytes* ; Hematocrit ; Plasma ; Spectrum Analysis* ; Transducers* ; Ultrasonography*

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