1,720,976 research outputs found
Steam sterilization processes affect the stability of clinical thermometers: Thermistor and prototypal FBG probe comparison
No full textTemperature is one of the most frequently measured physical quantities in clinical environment and a good biomarker of illness. The need for reusable probes, which have to be sterilized to prevent infections, requires the metrological qualification of thermometer probes in response to ageing effects induced by several sterilization processes. In this study, we investigated the effect of repeated sterilizations on both a commonly-used autoclavable thermistor probe and a prototypal Fiber Bragg Gratings (FBG) probe for temperature measurements. Findings highlighted a greater reliability of the proposed FBG probe than the commercial thermistor. Specifically, the FBG probe was able to withstand repeated sterilization cycles while maintaining stability in the measurement accuracy. Moreover, the proposed configuration for the FBG probe was immune to unwanted mechanical strain by providing a dynamic response fit for the measurement of temperature
Impact of pericardial effusion on cardiac mechanics in patients with dilated cardiomyopathy
Full text linkDilated cardiomyopathy (CDM) is a degenerative disease of the myocardium accompanied by left
ventricular (LV) remodeling, resulting in an impaired pump performance. Differently, pericardial effusion
(PE) is a liquid accumulation in the pericardial cavity, which may inhibit blood filling of heart chambers.
Clinical evidence show that PE may improve pump performance in patients with CDM. Therefore, this
study aims to assess wall stress and global function of patients with CDM, PE as compared to healthy
patient. These findings suggests that CDM has an important implication in the mechanical changes of LV
and right ventricle by increasing wall stress and reducing pump function. Conversely, PE determines
lowering myocardial fiber stress and improves global function as compared to those of CD
Wireless ECG and cardiac monitoring systems: State of the art, available commercial devices and useful electronic components
Full text linkWireless ElectroCardioGram (ECG) systems are employed in manifold application fields: tele-monitoring, sport applications, support to ageing people at home, fetal ECG, wearable devices and ambulatory monitoring. The presence of cables often hinders user's free movements, alongside clinicians’ routine operations. Therefore, wireless ECG systems are desirable. This paper aims at reviewing the solutions described in the literature, besides commercially available devices and electronic components useful to setup laboratory prototypes. Several systems have been developed, different in terms of the adopted technology; when approaching the development of a wireless ECG system, some important aspects should be considered: electrodes (disposable, wet/dry, without contact, insulated), analog front-end, data acquisition systems (including amplifiers, multiplexer), wireless transmission technology (e.g. WiFi, Bluetooth) and power consumption (battery lifetime, miniaturization purposes). Technological advancements and continuous research have already brought to miniaturized and comfortable devices, but there is still room for improvement on multiple sides
Design of an open-lab activity for engineering students: A case study
Full text linkProject- or discovery-based learning activities promote curiosity, enjoyment, and interest deriving from the stimulating context in which students operate. Providing a concrete contextualization of laboratory activities could improve student motivation and learning outcomes. In this contribution, a case study related to a workshop on laboratory activities proposed for Engineering Master students is presented, and designed with the aim of developing practical competencies, increasing problem-solving skills, and providing design abilities. Using the facilities available in the Measurements and Control Laboratory, the students, starting from concept knowledge acquired in basic subjects, such as Physics, Chemistry, Mathematics, and Electronics, design and implement their experiments, gaining a deeper understanding of core disciplinary concepts while strengthening soft and teamwork skills. The challenges and possibilities of these self-directed thinking and learning laboratory activities are also discussed
Fluid–Solid Interaction Analysis for Developing In-Situ Strain and Flow Sensors for Prosthetic Valve Monitoring
Full text linkTranscatheter aortic valve implantation (TAVI) was initially developed for adult patients, but there is a growing interest to expand this procedure to younger individuals with longer life expectancies. However, the gradual degradation of biological valve leaflets in transcatheter heart valves (THV) presents significant challenges for this extension. This study aimed to establish a multiphysics computational framework to analyze structural and flow measurements of TAVI and evaluate the integration of optical fiber and photoplethysmography (PPG) sensors for monitoring valve function. A two-way fluid–solid interaction (FSI) analysis was performed on an idealized aortic vessel before and after the virtual deployment of the SAPIEN 3 Ultra (S3) THV. Subsequently, an analytical analysis was conducted to estimate the PPG signal using computational flow predictions and to analyze the effect of different pressure gradients and distances between PPG sensors. Circumferential strain estimates from the embedded optical fiber in the FSI model were highest in the sinus of Valsalva; however, the optimal fiber positioning was found to be distal to the sino-tubular junction to minimize bending effects. The findings also demonstrated that positioning PPG sensors both upstream and downstream of the bioprosthesis can be used to effectively assess the pressure gradient across the valve. We concluded that computational modeling allows sensor design to quantify vessel wall strain and pressure gradients across valve leaflets, with the ultimate goal of developing low-cost monitoring systems for detecting valve deterioration
Mechanics of pericardial effusion: A simulation study
No full textPericardial effusion is a pathological accumulation of fluid within pericardial cavity, which may compress heart chambers with hemodynamic impairment. We sought to determine the mechanics underlying the physiology of the hemodynamic impairment due to pericardial effusion using patient-specific computational modeling. Computational models of left ventricle and right ventricle were based on magnetic resonance images obtained from patients with pericardial effusion and controls. Myocardial material parameters were adjusted, so that volumes of ventricular chambers and pericardial effusion agreed with magnetic resonance imaging data. End-diastolic and end-systolic pressure-volume relationships as well as stroke volume were determined to evaluate impaired cardiac function of biventricular model. Distributions of myocardial fiber stresses and their regional variation along left ventricular wall were compared between patient groups. Both end-diastolic and end-systolic pressure-volume relationships shifted to the left for patients with pericardial effusion, with right ventricle diastolic filling particularly restricted. Left ventricle function as estimated by Starling curve was reduced by pericardial effusion. End-systolic fiber stress of left ventricle was significantly reduced as compared to that found for healthy patients. Myocardial stress was found increased at interventricular septum when compared to that exerted at lateral wall of left ventricle. Right ventricular myocardial stress was reduced as a consequence of the pressure equalization between right ventricle and pericardial effusion. Diastolic right ventricle collapse in patients with pericardial effusion is related to higher myocardial fiber stress on interventricular septum and to an extensible pericardium reducing motion of ventricular chambers, with right ventricle particularly restrained. These findings likely portend progression of pericardial effusion to cardiac tamponade
Modelling cardiac mechanics of left ventricular noncompaction
Full text linkLeft ventricular noncompaction (LVNC) can be defined as a cardiomyopathy characterised by a pattern of prominent trabecular structure and deep intertrabecular recesses, that is thought to be caused by an arrest of normal endomyocardial morphogenesis. Using patient-specific computational modelling, we assessed the cardiac mechanics of five patients with LVNC and compared myocardial stress and pump performance to those of healthy controls. Findings shown that patients with LVNC have impaired left ventricular (LV) function, making it possible that the lack of fibre shortening of noncompacted layer can determine poor heart function. Pronounced end-systolic wall stress on left ventricular wall of patients with LVNC was observed when compared to that of normal hearts, and this may lead to adverse cardiac remodelling and ultimately heart failure. We hereby suggest that computational modelling can be considered as a useful tool to assess the cardiac work and pump performance of LVNC, which are responsible for progressive left ventricular deterioration and poor clinical course
A study on the effect of contact pressure during physical activity on photoplethysmographic heart rate measurements
Full text linkHeart rate (HR) as an important physiological indicator could properly describe global subject’s physical status. Photoplethysmographic (PPG) sensors are catching on in field of wearable sensors, combining the advantages in costs, weight and size. Nevertheless, accuracy in HR readings is unreliable specifically during physical activity. Among several identified sources that affect PPG recording, contact pressure (CP) between the PPG sensor and skin greatly influences the signals. Methods: In this study, the accuracy of HR measurements of a PPG sensor at different CP was investigated when compared with a commercial ECG-based chest strap used as a test control, with the aim of determining the optimal CP to produce a reliable signal during physical activity. Seventeen subjects were enrolled for the study to perform a physical activity at three different rates repeated at three different contact pressures of the PPG-based wristband. Results: The results show that the CP of 54 mmHg provides the most accurate outcome with a Pearson correlation coefficient ranging from 0.81 to 0.95 and a mean average percentage error ranging from 3.8% to 2.4%, based on the physical activity rate. Conclusion: Authors found that changes in the CP have greater effects on PPG-HR signal quality than those deriving from the intensity of the physical activity and specifically, the individual best CP for each subject provided reliable HR measurements even for a high intensity of physical exercise with a Bland–Altman plot within ±11 bpm. Although future studies on a larger cohort of subjects are still needed, this study could contribute a profitable indication to enhance accuracy of PPG-based wearable devices
DIY Wrist-Worn Device for Physiological Monitoring: Metrological Evaluation at Different Band Tightening Levels
Full text linkWearable devices are currently employed in several application fields, especially in the healthcare context, thanks to the advent of IoT technology in the global market. However, there are few studies focused on the reliability of collected data depending on the best wearing conditions, e.g. the band tightness in the case of wrist-worn devices, necessary to optimise the quality of the measured data. The aim of this study is to evaluate the variability of heart rate (HR) and tightening force data measured with a Do-It-Yourself (DIY) wrist-worn device, considering three different band tightening levels: loose, medium and tight. Results show that the increasing tightening levels produce an increasing tightening force, as expected; interestingly, the coefficient of variation is minimum (i.e., 0.16%) when the band tightening level is medium
Biomechanical implications of excessive endograft protrusion into the aortic arch after thoracic endovascular repair
Full text linkEndografts placed in the aorta for thoracic endovascular aortic repair (TEVAR) may determine malappositioning to the lesser curvature of the aortic wall, thus resulting in a devastating complication known as endograft collapse. This premature device failure commonly occurs in young individuals after TEVAR for traumatic aortic injuries as a result of applications outside the physical conditions for which the endograft was designed. In this study, an experimentally-calibrated fluid-structure interaction (FSI) model was developed to assess the hemodynamic and stress/strain distributions acting on the excessive protrusion extension (PE) of endografts deployed in four young patients underwent TEVAR. Endograft infolding was experimentally measured for different hemodynamic scenarios by perfusion testing and then used to numerically calibrate the mechanical behavior of endograft PE. Results evinced that the extent of endograft can severely alter the hemodynamic and structural loads exerted on the endograft PE. Specifically, PE determined a physiological aortic coarctation into the aortic arch characterized by a helical flow in the distal descending aorta. High device displacement and transmural pressure across the stent-graft wall were found for a PE longer than 21 mm. Finally, marked intramural stress and principal strain distributions on the protruded segment of the endograft wall may suggest failure due to material fatigue. These critical parameters may contribute to the endograft collapse observed clinically and can be used to design new devices more suitable for young individuals to be treated with an endoprosthesis for TEVAR of blunt traumatic aortic injuries
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