198 research outputs found

    The Microcirculation in Preterm Neonates

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    Perioperative comparison of the agreement between a portable fingertip pulse oximeter vs. a conventional bedside pulse oximeter in adult patients (COMFORT trial)

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    Background: Low-cost, portable fingertip pulse oximeters are widely available to health professionals and the public. They are often not tested to ISO standards, or only undergo accuracy studies in healthy volunteers under ideal laboratory conditions. This study aims to pragmatically evaluate the agreement between one such device and a conventional bedside pulse oximeter in a clinical setting, in patients with varied comorbidities and skin pigmentations. Methods: A single-centre equipment comparison study was conducted. Simultaneous measurements were obtained in 220 patients with both a Contec CMS50D Fingertip Pulse Oximeter and a Nihon Kohden Life Scope MU-631 RK conventional bedside monitor. Peripheral oxygen saturations (SpO₂) and pulse rates were documented, and patient skin tone was recorded using the Fitzpatrick scale. Data was assessed using a Bland-Altman analysis with bias, precision and limits of agreement (LOA) calculated with 95% confidence intervals. A priori acceptability for LOA was determined to be 3%, in keeping with international standards. Results: Mean difference (therefore bias) between the conventional and fingertip oximeters for all data was -0,55% (95% CI -0,73 to -0,36%). Upper and lower limits of agreement (95% CI) were 2,16 (1,84 to 2,47) and -3,25 (-3,56 to -2,94) %. Regression analysis demonstrated worsening agreement with decreasing SpO₂. When samples were separated into “normal” (SpO₂ ≥ 93%) and “hypoxaemic” (SpO₂ < 93%) groups, the normal range displayed acceptable agreement between the two oximeters (bias -0,20 with LOA 2,20 to -2,27%), while the hypoxaemic group fell outside the study’s a priori limits. Heart rate measurements had mean difference (LOA) of -0,43 (-5,61 to 4,76) beats per minute. The study was not powered to detect difference among the skin tones, but demonstrated no trend for this parameter to alter the SpO₂ measurements. Conclusions: During normoxia, portable fingertip pulse oximeters are reliable indicators of SpO₂ and pulse rates in patients with various comorbidities in a pragmatic clinical context. However, they display worsening agreement with conventional pulse oximeters during hypoxaemia. Skin tones do not appear to adversely affect measurements

    Augmentation Of Human Skill In Microsurgery

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    Surgeons performing highly skilled microsurgery tasks can benefit from information and manual assistance to overcome technological and physiological limitations to make surgery safer, efficient, and more successful. Vitreoretinal surgery is particularly difficult due to inherent micro-scale and fragility of human eye anatomy. Additionally, surgeons are challenged by physiological hand tremor, poor visualization, lack of force sensing, and significant cognitive load while executing high-risk procedures inside the eye, such as epiretinal membrane peeling. This dissertation presents the architecture and the design principles for a surgical augmentation environment which is used to develop innovative functionality to address the fundamental limitations in vitreoretinal surgery. It is an inherently information driven modular system incorporating robotics, sensors, and multimedia components. The integrated nature of the system is leveraged to create intuitive and relevant human-machine interfaces and generate a particular system behavior to provide active physical assistance and present relevant sensory information to the surgeon. These include basic manipulation assistance, audio-visual and haptic feedback, intraoperative imaging and force sensing. The resulting functionality, and the proposed architecture and design methods generalize to other microsurgical procedures. The system's performance is demonstrated and evaluated using phantoms and in vivo experiments

    Development and Implementation of Novel Bristle Tool for Surface Treatment of Metallic Components

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    Despite advances in paints and coatings technology, protective coatings are prone to eventual corrosion, degradation and/or failure. Consequently, a corrosive layer will develop that can undermine the performance and integrity of structural components. Therefore, both the corrosive layer and defunct coating must be periodically removed, and an acceptable level of surface cleanliness and texture must be obtained prior to the reapplication of new paint. Currently, an array of processes and equipment are used for efficiently cleaning and conditioning metallic surfaces, such as grit blasting, needle guns, and a variety of non-woven and coated abrasive tools. This research investigates the method termed the bristle blasting process. The process utilizes a specially designed rotary bristle tool, which is dynamically tuned to a power tool spindle that operates at approximately 2,500 rpm. The present research suggests that the repeated collision of hardened bristle tips with a corroded steel surface results in both the removal of a friable corrosive layer and simultaneous exposure of fresh subsurface material. Surfaces generated by the bristle blast process are shown to mimic the visual cleanliness and anchor profile that is characteristic of grit blasting processes. One particular application evaluated during this research was offshore pipeline refurbishment and pre-treatment of weld seams prior to the application of protective coatings. Comparative analysis was done with conventional methods of surface treatment on the basis of visual cleanliness, surface profile generation and coating adhesion strength. The results obtained suggest that this novel technology performs better than the existing conventional power tool methods and is on an equal par with grit blasting methods. Moreover, the bristle blasting process is eco-friendly and does not use or generate hazardous waste, thereby providing a green approach to corrosion removal and surface preparation of steel components

    Endoscopy

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    Endoscopy is a fast moving field, and new techniques are continuously emerging. In recent decades, endoscopy has evolved and branched out from a diagnostic modality to enhanced video and computer assisting imaging with impressive interventional capabilities. The modern endoscopy has seen advances not only in types of endoscopes available, but also in types of interventions amenable to the endoscopic approach. To date, there are a lot more developments that are being trialed. Modern endoscopic equipment provides physicians with the benefit of many technical advances. Endoscopy is an effective and safe procedure even in special populations including pediatric patients and renal transplant patients. It serves as the tool for diagnosis and therapeutic interventions of many organs including gastrointestinal tract, head and neck, urinary tract and others

    Spacesuit Integrated Carbon Nanotube Dust Mitigation System For Lunar Exploration

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    Lunar dust proved to be troublesome during the Apollo missions. The lunar dust comprises of fine particles, with electric charges imparted by solar winds and ultraviolet radiation. As such, it adheres readily, and easily penetrates through smallest crevices into mechanisms. During Apollo missions, the powdery dust substantially degraded the performance of spacesuits by abrading suit fabric and clogging seals. Dust also degraded other critical equipment such as rovers, thermal control and optical surfaces, solar arrays, and was thus shown to be a major issue for surface operations. Even inside the lunar module, Apollo astronauts were exposed to this dust when they removed their dust coated spacesuits. This historical evidence from the Apollo missions has compelled NASA to identify dust mitigation as a critical path. This important environmental challenge must be overcome prior to sending humans back to the lunar surface and potentially to other surfaces such as Mars and asteroids with dusty environments. Several concepts were successfully investigated by the international research community for preventing deposition of lunar dust on rigid surfaces (ex: solar cells, thermal radiators). However, applying these technologies for flexible surfaces and specifically to spacesuits has remained an open challenge, due to the complexity of the suit design, geometry, and dynamics. The research presented in this dissertation brings original contribution through the development and demonstration of the SPacesuit Integrated Carbon nanotube Dust Ejection/Removal (SPIcDER) system to protect spacesuits and other flexible surfaces from lunar dust. SPIcDER leverages the Electrodynamic Dust Shield (EDS) concept developed at NASA for use on solar cells. For the SPIcDER research, the EDS concept is customized for application on spacesuits and flexible surfaces utilizing novel materials and specialized design techniques. Furthermore, the performance of the active SPIcDER system is enhanced by integrating a passive technique based on Work Function Matching coating. SPIcDER aims for a self-cleaning spacesuit that can repel lunar dust. The SPIcDER research encompassed numerous demonstrations on coupons made of spacesuit outerlayer fabric, to validate the feasibility of the concept, and provide evidence that the SPIcDER system is capable of repelling over 85% of lunar dust simulant comprising of particles in the range of 10 m-75m, in ambient and vacuum conditions. Furthermore, the research presented in this dissertation proves the scalability of the SPIcDER technology on a full scale functional prototype of a spacesuit knee joint-section, and demonstrates its scaled functionality and performance using lunar dust simulant. It also comprises detailed numerical simulation and parametric analysis in ANSYS Maxwell and MATLAB for optimizing the integration of the SPIcDER system into the spacesuit outerlayer. The research concludes with analysis and experimental results on design, manufacturability, operational performance, practicality of application and astronaut safety. The research aims primarily towards spacesuit dust contamination. The SPIcDER technology developed in this research is however versatile, that can be optimized to a wide range of flexible surfaces for space and terrain applications-such as exploration missions to asteroids, Mars and dust-prone applications on Earth

    2012 Annual Research Symposium Abstract Book

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    2012 annual volume of abstracts for science research projects conducted by students at Trinity College

    Methods for the Investigation of Microvascular Control of Oxygen Distribution

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    The purpose of this thesis was to develop tools for studying oxygen-dependent regulation of red blood cell (RBC) flow distribution in the microcirculation. At the microvascular level, arterioles dictate the distribution of oxygen (O2) carrying RBCs to downstream capillaries, a process which needs to be tightly regulated and coupled to O2 off loading from capillaries to the tissue. To investigate potential regulatory mechanisms, an O2 exchange platform was developed to manipulate the RBC hemoglobin O2 saturation (SO2) at the muscle surface while limiting the changes in SO2 to only a single capillary network. Decreasing SO2 in a single capillary network resulted in an increase in supply rate, while increasing SO2 caused a decrease in supply rate. This finding is consistent with our hypothesis that ATP released in capillaries in response to low SO2 is responsible for vasodilation of upstream arterioles to regulate blood flow. To determine whether the dynamics of ATP was fast enough to enable RBC signalling in capillaries, an in vitro microfluidic system was developed to generate a rapid decrease in RBC SO2. The feasibility of this experimental design was first tested computationally using a mathematical model that consisted of blood flow, oxygen and ATP transport as well as a model for hemoglobin binding, ATP release, ATP/luciferin/luciferase reaction and digital camera light detection. The model demonstrated that the concept was theoretically feasible and yielded important insights such as the signal sensitivity to flow rate. The model further revealed that measured light intensity levels would not be directly related to ATP concentrations, thus, care must be taken when interpreting the data. It was determined that the microfluidic device would be fabricated using soft lithography techniques that resulted in a device that differed significantly from our original theoretical design since all of the layers would be oxygen permeable except for a glass coverslip with a small opening for gas exchange between the liquid and gas channel. To optimize the geometric design of this microfluidic device, to maximize the desaturation the RBCs, a finite element model was developed. Based on this design a device was constructed. To test whether the design generated a rapid decrease in RBC SO2, a low hematocrit high SO2 RBC suspension was perfused through the device exposed to 95% N2 and 5% CO2 in the gas channel. Finally, to overcome challenges with existing approaches for measuring SO2 in the device, a novel image analysis technique using digital inpainting was developed. The inpainting approach demonstrated a rapid change in RBC SO2 at the entrance to the window, thus the microfluidic device is ready to be used to measure the dynamics of O2-dependent ATP release from RBCs. The new inpainting algorithm was also applied to in vivo video sequences where it was shown to provide more accurate SO2 measurements and to work under conditions where existing approaches fail. In summary, this thesis provides a set of in vivo, in vitro and computational tools that can be used to study the mechanisms of SO2-dependent regulation of the microvascular blood flow
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