Browsing by Subject "temperature monitoring"
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Item Open Access Current conduct of deep hypothermic circulatory arrest in China.(HSR proceedings in intensive care & cardiovascular anesthesia, 2013-01) Augoustides, JGT; Patel, P; Ghadimi, K; Choi, J; Yue, Y; Silvay, GIntroduction
Deep hypothermic circulatory arrest for adult aortic arch repair is still associated with significant mortality and morbidity. Furthermore, there is still significant variation in the conduct of this complex perioperative technique. This variation in deep hypothermic circulatory arrest practice has not been adequately characterized and may offer multiple opportunities for outcome enhancement. The hypothesis of this study was that the current practice of adult deep hypothermic circulatory arrest in China has significant variations that might offer therapeutic opportunities for reduction of procedural risk.Methods
An adult deep hypothermic circulatory arrest questionnaire was developed and then administered at a thoracic aortic session at the International Cardiothoracic and Vascular Anesthesia Congress convened in Beijing during 2010. The data was abstracted and analyzed.Results
The majority of the 56 respondents were anesthesiologists based in China at low-volume deep hypothermic circulatory arrest centers. The typical aortic arch repair had a prolonged deep hypothermic circulatory arrest time at profound hypothermia. The target temperature for deep hypothermic circulatory arrest was frequently measured distal to the brain. The most common perfusion adjunct was antegrade cerebral perfusion, typically monitored with radial arterial pressure and cerebral venous oximetry. The preferred neuroprotective agents were steroids and propofol.Conclusions
The identified opportunities for outcome improvement in this delineated deep hypothermic circulatory arrest model include nasal/tympanic temperature measurement and routine cerebral perfusion, preferably with unilateral antegrade cerebral perfusion monitored with radial artery pressure and cerebral oximetry. Development and dissemination of an evidence-based consensus would enhance these practice-improvement opportunities.Item Open Access Design and Evaluation of a Transcutaneous Energy Transfer System(2009) Bossetti, Chad AA clinically viable brain-machine interface (BMI) requires a fully-implanted wireless neural acquisition system to limit the impediments of percutaneous connections. For an implanted system with an appreciable telemetry range, and where significant
neural signal processing is performed continuously, a major obstacle for clinical application is the need for a power source. Existing battery technology and wireless power delivery systems have not addressed the need for a mid-range power supply, capable
of 1-3 W delivery, that limits both induced noise and temperature rise. These factors are crucial for the succesful operation of a fully-implanted neural acquisition system. This work seeks to fill this void, and presents both a wireless power solution suitable for a neural recording device, and a system capable of real time monitoring of tissue temperature rise.
During this research, a 2 W transcutaneous energy transfer system (TETS) was designed, built and tested. The TETS was designed specifically for a 96-channel implanted neural data acquisition system, which requires continuous power. The major design constraints were tolerance to coil misalignment, low induced noise,
and reasonable efficiency. The design of the primary circuit consists of an H-bridge switching network driving a planar spiral Litz wire primary coil. The primary also incoporates a novel circuit for detecting the presence of the secondary. The implanted secondary components include a complimentary planar spiral coil connected to a voltage doubling rectifier. The key approach to mitigating axial coil misalignments was the use of step-down switching regulators in the secondary. With this approach, link efficiency remained nearly constant at 40%, for axial coil displacements of up to 2 cm.
Noise in the recorded neural signals was minimized using two techniques. First, the 250 kHz operating frequency of the system was tuned, such that the aliased harmonics of the switching frequency lay above the bandwidth of the amplifier used for neural recording. The second approach was to limit the impact of induced displacement currents in the body by physically separating the recording front end from the power supply components. A large titanium enclosure was used to house some of the secondary electronics, and provided a low impedance return path for further
reduction of current-induced noise.
Limiting the temperature rise of internal components was also a critical design constraint. The need for real time temperature information led to the design of a six channel temperature measurement system and incorporation of the temperature data into the acquisition system data transmission scheme. This system consisted of bead thermistor temperature transducers, and an off-the-shelf microcontroller with a built-in instrumentation amplifier.
The TETS and temperature system was fully tested in an ovine model during several acute studies. Recorded temperature rise was limited to approximately 5.5° C when the system was implanted at an adequate depth in muscle. The TETS was able to successfully power the 2 W neural acquisition system during a data processing task. Received rectified voltage in the secondary ranged from 14.86 V to 20.2 V, while link efficiency remained virtually constant. Acquired neural data was examined for TETS switching noise. The measured RMS noise increased by less than 1 &mu V, averaged over several experiments. These results demonstrate the first mid-range TETS solution for powering a fully implanted neural acquisition system.
Item Open Access Practice variations in the conduct of hypothermic circulatory arrest for adult aortic arch repair: focus on an emerging European paradigm.(Heart, lung and vessels, 2014-01) Gutsche, JT; Feinman, J; Silvay, G; Patel, PP; Ghadimi, K; Landoni, G; Yue, Y; Augoustides, JGTIntroduction
Hypothermic circulatory arrest for adult aortic arch repair is still high-risk. Despite decades of clinical experience, significant practice variations exist around the world. These practice variations in hypothermic circulatory arrest may offer multiple opportunities to improve practice. The hypothesis of this study was that the current conduct of adult hypothermic circulatory arrest in Europe has significant variations that might suggest opportunities for risk reduction.Methods
An adult hypothermic circulatory arrest questionnaire was developed and then administered at thoracic aortic sessions at international conferences during 2010 in Beijing and Milan. The data was collected, abstracted and analyzed.Results
The majority of the 105 respondents were anesthesiologists based in Europe and China. The typical adult aortic arch repair in Europe was with hypothermic circulatory arrest at moderate hypothermia utilizing bilateral antegrade cerebral perfusion, typically monitored with radial arterial pressure and cerebral oximetry. Brain temperature was frequently measured at distal locations. The preferred neuroprotective agents were steroids, propofol and thiopental.Conclusions
The opportunities for outcome improvement in this emerging European paradigm of tepid adult aortic arch repair include nasal/tympanic temperature measurement and adoption of unilateral antegrade cerebral perfusion monitored with radial artery pressure and cerebral oximetry. The publication of an evidence-based consensus would enhance these practice-improvement opportunities.