Closed-loop control of mean arterial blood pressure during surgery with alfentanil: clinical evaluation of a novel model-based predictive controller

BACKGROUND: In contrast to hypnosis, there is no surrogate parameter for analgesia in anesthetized patients. Opioids are titrated to suppress blood pressure response to noxious stimulation. The authors evaluated a novel model predictive controller for closed-loop administration of alfentanil using mean arterial blood pressure and predicted plasma alfentanil concentration (Cp Alf) as input parameters. METHODS: The authors studied 13 healthy patients scheduled to undergo minor lumbar and cervical spine surgery. After induction with propofol, alfentanil, and mivacurium and tracheal intubation, isoflurane was titrated to maintain the Bispectral Index at 55 (+/- 5), and the alfentanil administration was switched from manual to closed-loop control. The controller adjusted the alfentanil infusion rate to maintain the mean arterial blood pressure near the set-point (70 mmHg) while minimizing the Cp Alf toward the set-point plasma alfentanil concentration (Cp Alfref) (100 ng/ml). RESULTS: Two patients were excluded because of loss of arterial pressure signal and protocol violation. The alfentanil infusion was closed-loop controlled for a mean (SD) of 98.9 (1.5)% of presurgery time and 95.5 (4.3)% of surgery time. The mean (SD) end-tidal isoflurane concentrations were 0.78 (0.1) and 0.86 (0.1) vol%, the Cp Alf values were 122 (35) and 181 (58) ng/ml, and the Bispectral Index values were 51 (9) and 52 (4) before surgery and during surgery, respectively. The mean (SD) absolute deviations of mean arterial blood pressure were 7.6 (2.6) and 10.0 (4.2) mmHg (P = 0.262), and the median performance error, median absolute performance error, and wobble were 4.2 (6.2) and 8.8 (9.4)% (P = 0.002), 7.9 (3.8) and 11.8 (6.3)% (P = 0.129), and 14.5 (8.4) and 5.7 (1.2)% (P = 0.002) before surgery and during surgery, respectively. A post hoc simulation showed that the Cp Alfref decreased the predicted Cp Alf compared with mean arterial blood pressure alone. CONCLUSION: The authors' controller has a similar set-point precision as previous hypnotic controllers and provides adequate alfentanil dosing during surgery. It may help to standardize opioid dosing in research and may be a further step toward a multiple input-multiple output controller.

Use of a computerized closed-loop sodium nitroprusside titration system for antihypertensive treatment after open heart surgery

This study evaluates the clinical applicability of administering sodium nitroprusside by a closed-loop titration system compared with a manually adjusted system. The mean arterial pressure (MAP) was registered every 10 and 30 sec during the first 150 min after open heart surgery in 20 patients (group 1: computer regulation) and in ten patients (group 2: manual regulation). The results (16,343 and 2,912 data points in groups 1 and 2, respectively), were then analyzed in four time frames and five pressure ranges to indicate clinical efficacy. Sixty percent of the measured MAP in both groups was within the desired +/- 10% during the first 10 min. Thereafter until the end of observation, the MAP was maintained within +/- 10% of the desired set-point 90% of the time in group 1 vs. 60% of the time in group 2. One percent and 11% of data points were +/- 20% from the set-point in groups 1 and 2, respectively (p less than .05, chi-square test). The computer-assisted therapy provided better control of MAP, was safe to use, and helped to reduce nursing demands.

Experiences on using closed-loop control systems for smoke control

The main objective of ventilation systems in case of fire is the reduction of the possible consequences by achieving the best possible conditions for the evacuation of the users and the intervention of the emergency services. In the last years, the required quick response of the ventilation system, from normal to emergency mode, has been improved by the use of automatic and semi-automatic control systems, what reduces the response times through the support to the operators decision taking, and the use of pre-defined strategies. A further step consists on the use of closedloop algorithms, which takes into account not only the initial conditions but their development (air velocity, traffic situation, etc), optimizing the quality of the smoke control process

A management model for closed-loop supply chains of reusable articles

This PhD dissertation is framed in the emergent fields of Reverse Logistics and ClosedLoop Supply Chain (CLSC) management. This subarea of supply chain management has gained researchers and practitioners' attention over the last 15 years to become a fully recognized subdiscipline of the Operations Management field. More specifically, among all the activities that are included within the CLSC area, the focus of this dissertation is centered in direct reuse aspects. The main contribution of this dissertation to current knowledge is twofold. First, a framework for the so-called reuse CLSC is developed. This conceptual model is grounded in a set of six case studies conducted by the author in real industrial settings. The model has also been contrasted with existing literature and with academic and professional experts on the topic as well. The framework encompasses four building blocks. In the first block, a typology for reusable articles is put forward, distinguishing between Returnable Transport Items (RTI), Reusable Packaging Materials (RPM), and Reusable Products (RP). In the second block, the common characteristics that render reuse CLSC difficult to manage from a logistical standpoint are identified, namely: fleet shrinkage, significant investment and limited visibility. In the third block, the main problems arising in the management of reuse CLSC are analyzed, such as: (1) define fleet size dimension, (2) control cycle time and promote articles rotation, (3) control return rate and prevent shrinkage, (4) define purchase policies for new articles, (5) plan and control reconditioning activities, and (6) balance inventory between depots. Finally, in the fourth block some solutions to those issues are developed. Firstly, problems (2) and (3) are addressed through the comparative analysis of alternative strategies for controlling cycle time and return rate. Secondly, a methodology for calculating the required fleet size is elaborated (problem (1)). This methodology is valid for different configurations of the physical flows in the reuse CLSC. Likewise, some directions are pointed out for further development of a similar method for defining purchase policies for new articles (problem (4)). The second main contribution of this dissertation is embedded in the solutions part (block 4) of the conceptual framework and comprises a two-level decision problem integrating two mixed integer linear programming (MILP) models that have been formulated and solved to optimality using AIMMS as modeling language, CPLEX as solver and Excel spreadsheet for data introduction and output presentation. The results obtained are analyzed in order to measure in a client-supplier system the economic impact of two alternative control strategies (recovery policies) in the context of reuse. In addition, the models support decision-making regarding the selection of the appropriate recovery policy against the characteristics of demand pattern and the structure of the relevant costs in the system. The triangulation of methods used in this thesis has enabled to address the same research topic with different approaches and thus, the robustness of the results obtained is strengthened.

An ICT-based closed-loop model to improve care for heart failure patients

Durante las últimas décadas se ha producido un fenómeno global de envejecimiento en la población. Esta tendencia se puede observar prácticamente en todos los países del mundo y se debe principalmente a los avances en la medicina, y a los descensos en las tasas de fertilidad y mortalidad. El envejecimiento de la población tiene un gran impacto en la salud de los ciudadanos, y a menudo es la causa de aparición de enfermedades crónicas. Este tipo de enfermedades supone una amenaza y una carga importantes para la sociedad, especialmente en aspectos como la mortalidad o los gastos en los sistemas sanitarios. Entre las enfermedades cardiovasculares, la insuficiencia cardíaca es probablemente la condición con mayor prevalencia y afecta a 23-26 millones de personas en todo el mundo. Normalmente, la insuficiencia cardíaca presenta un mal pronóstico y una tasa de supervivencia bajas, en algunos casos peores que algún tipo de cáncer. Además, suele ser la causa de hospitalizaciones frecuentes y es una de las enfermedades más costosas para los sistemas sanitarios. La tendencia al envejecimiento de la población y la creciente incidencia de las enfermedades crónicas están llevando a una situación en la que los sistemas de salud no son capaces de hacer frente a la demanda de la sociedad. Los servicios de salud existentes tendrán que adaptarse para ser efectivos y sostenibles en el futuro. Es necesario identificar nuevos paradigmas de cuidado de pacientes, así como mecanismos para la provisión de servicios que ayuden a transformar estos sistemas sanitarios. En este contexto, esta tesis se plantea la búsqueda de soluciones, basadas en las Tecnologías de la Información y la Comunicación (TIC), que contribuyan a realizar la transformación en los sistemas sanitarios. En concreto, la tesis se centra en abordar los problemas de una de las enfermedades con mayor impacto en estos sistemas: la insuficiencia cardíaca. Las siguientes hipótesis constituyen la base para la realización de este trabajo de investigación: 1. Es posible definir un modelo basado en el paradigma de lazo cerrado y herramientas TIC que formalice el diseño de mejores servicios para pacientes con insuficiencia cardíaca. 2. El modelo de lazo cerrado definido se puede utilizar para definir un servicio real que ayude a gestionar la insuficiencia cardíaca crónica. 3. La introducción, la adopción y el uso de un servicio basado en el modelo definido se traducirá en mejoras en el estado de salud de los pacientes que sufren insuficiencia cardíaca. a. La utilización de un sistema basado en el modelo de lazo cerrado definido mejorará la experiencia del usuario de los pacientes. La definición del modelo planteado se ha basado en el estándar ISO / EN 13940- Sistema de conceptos para dar soporte a la continuidad de la asistencia. Comprende un conjunto de conceptos, procesos, flujos de trabajo, y servicios como componentes principales, y representa una formalización de los servicios para los pacientes con insuficiencia cardíaca. Para evaluar el modelo definido se ha definido un servicio real basado en el mismo, además de la implementación de un sistema de apoyo a dicho servicio. El diseño e implementación de dicho sistema se realizó siguiendo la metodología de Diseño Orientado a Objetivos. El objetivo de la evaluación consistía en investigar el efecto que tiene un servicio basado en el modelo de lazo cerrado sobre el estado de salud de los pacientes con insuficiencia cardíaca. La evaluación se realizó en el marco de un estudio clínico observacional. El análisis de los resultados ha comprendido métodos de análisis cuantitativos y cualitativos. El análisis cuantitativo se ha centrado en determinar el estado de salud de los pacientes en base a datos objetivos (obtenidos en pruebas de laboratorio o exámenes médicos). Para realizar este análisis se definieron dos índices específicos: el índice de estabilidad y el índice de la evolución del estado de salud. El análisis cualitativo ha evaluado la autopercepción del estado de salud de los pacientes en términos de calidad de vida, auto-cuidado, el conocimiento, la ansiedad y la depresión, así como niveles de conocimiento. Se ha basado en los datos recogidos mediante varios cuestionarios o instrumentos estándar (i.e. EQ-5D, la Escala de Ansiedad y Depresión (HADS), el Cuestionario de Cardiomiopatía de Kansas City (KCCQ), la Escala Holandesa de Conocimiento de Insuficiencia Cardíaca (DHFKS), y la Escala Europea de Autocuidado en Insuficiencia Cardíaca (EHFScBS), así como cuestionarios dedicados no estandarizados de experiencia de usuario. Los resultados obtenidos en ambos análisis, cuantitativo y cualitativo, se compararon con el fin de evaluar la correlación entre el estado de salud objetivo y subjetivo de los pacientes. Los resultados de la validación demostraron que el modelo propuesto tiene efectos positivos en el cuidado de los pacientes con insuficiencia cardíaca y contribuye a mejorar su estado de salud. Asimismo, ratificaron al modelo como instrumento válido para la definición de servicios mejorados para la gestión de esta enfermedad. ABSTRACT During the last decades we have witnessed a global aging phenomenon in the population. This can be observed in practically every country in the world, and it is mainly caused by the advances in medicine, and the decrease of mortality and fertility rates. Population aging has an important impact on citizens’ health and it is often the cause for chronic diseases, which constitute global burden and threat to the society in terms of mortality and healthcare expenditure. Among chronic diseases, Chronic Heart Failure (CHF) or Heart Failure (HF) is probably the one with highest prevalence, affecting between 23 and 26 million people worldwide. Heart failure is a chronic, long-term and serious condition with very poor prognosis and worse survival rates than some type of cancers. Additionally, it is often the cause of frequent hospitalizations and one of the most expensive conditions for the healthcare systems. The aging trends in the population and the increasing incidence of chronic diseases are leading to a situation where healthcare systems are not able to cope with the society demand. Current healthcare services will have to be adapted and redefined in order to be effective and sustainable in the future. There is a need to find new paradigms for patients’ care, and to identify new mechanisms for services’ provision that help to transform the healthcare systems. In this context, this thesis aims to explore new solutions, based on ICT, that contribute to achieve the needed transformation within the healthcare systems. In particular, it focuses on addressing the problems of one of the diseases with higher impact within these systems: Heart Failure. The following hypotheses represent the basis to the elaboration of this research: 1. It is possible to define a model based on a closed-loop paradigm and ICT tools that formalises the design of enhanced healthcare services for chronic heart failure patients. 2. The described closed-loop model can be exemplified in a real service that supports the management of chronic heart failure disease. 3. The introduction, adoption and use of a service based on the outlined model will result in improvements in the health status of patients suffering heart failure. 4. The user experience of patients when utilizing a system based on the defined closed-loop model will be enhanced. The definition of the closed-loop model for health care support of heart failure patients have been based on the standard ISO/EN 13940 System of concepts to support continuity of care. It includes a set of concept, processes and workflows, and services as main components, and it represent a formalization of services for heart failure patients. In order to be validated, the proposed closed-loop model has been instantiated into a real service and a supporting IT system. The design and implementation of the system followed the user centred design methodology Goal Oriented Design. The validation, that included an observational clinical study, aimed to investigate the effect that a service based on the closed-loop model had on heart failure patients’ health status. The analysis of results comprised quantitative and qualitative analysis methods. The quantitative analysis was focused on determining the health status of patients based on objective data (obtained in lab tests or physical examinations). Two specific indexes where defined and considered in this analysis: the stability index and the health status evolution index. The qualitative analysis assessed the self-perception of patients’ health status in terms of quality of life, self-care, knowledge, anxiety and depression, as well as knowledge levels. It was based on the data gathered through several standard instruments (i.e. EQ-5D, the Hospital Anxiety and Depression Scale, the Kansas City Cardiomyopathy Questionnaire, the Dutch Heart Failure Knowledge Scale, and the European Heart Failure Self-care Behaviour Scale) as well as dedicated non-standardized user experience questionnaires. The results obtained in both analyses, quantitative and qualitative, were compared in order to assess the correlation between the objective and subjective health status of patients. The results of the validation showed that the proposed model contributed to improve the health status of the patients and had a positive effect on the patients’ care. It also proved that the model is a valid instrument for designing enhanced healthcare services for heart failure patients.

Towards Closed-loop Deep Brain Stimulation: Behavior Recognition from Human STN

Deep brain stimulation (DBS) provides significant therapeutic benefit for movement disorders such as Parkinson’s disease (PD). Current DBS devices lack real-time feedback (thus are open loop) and stimulation parameters are adjusted during scheduled visits with a clinician. A closed-loop DBS system may reduce power consumption and side effects by adjusting stimulation parameters based on patient’s behavior. Thus behavior detection is a major step in designing such systems. Various physiological signals can be used to recognize the behaviors. Subthalamic Nucleus (STN) Local field Potential (LFP) is a great candidate signal for the neural feedback, because it can be recorded from the stimulation lead and does not require additional sensors. This thesis proposes novel detection and classification techniques for behavior recognition based on deep brain LFP. Behavior detection from such signals is the vital step in developing the next generation of closed-loop DBS devices. LFP recordings from 13 subjects are utilized in this study to design and evaluate our method. Recordings were performed during the surgery and the subjects were asked to perform various behavioral tasks. Various techniques are used understand how the behaviors modulate the STN. One method studies the time-frequency patterns in the STN LFP during the tasks. Another method measures the temporal inter-hemispheric connectivity of the STN as well as the connectivity between STN and Pre-frontal Cortex (PFC). Experimental results demonstrate that different behaviors create different m odulation patterns in STN and it’s connectivity. We use these patterns as features to classify behaviors. A method for single trial recognition of the patient’s current task is proposed. This method uses wavelet coefficients as features and support vector machine (SVM) as the classifier for recognition of a selection of behaviors: speech, motor, and random. The proposed method is 82.4% accurate for the binary classification and 73.2% for classifying three tasks. As the next step, a practical behavior detection method which asynchronously detects behaviors is proposed. This method does not use any priori knowledge of behavior onsets and is capable of asynchronously detect the finger movements of PD patients. Our study indicates that there is a motor-modulated inter-hemispheric connectivity between LFP signals recorded bilaterally from STN. We utilize a non-linear regression method to measure this inter-hemispheric connectivity and to detect the finger movements. Our experimental results using STN LFP recorded from eight patients with PD demonstrate this is a promising approach for behavior detection and developing novel closed-loop DBS systems.

Closed loop control of automotive engines. Final report.

National Highway Traffic Safety Administration, Office of Research and Development, Washington, D.C.

Study of the performance of aids to navigation systems : phase 1, closed loop model of the process of navigation /

Final report; March 1978.

Closed-Loop Deep Brain Stimulation: Bidirectional Neuroprosthetics for Tremor and BCI

Thesis (Ph.D.)--University of Washington, 2016-06

The Closed Loop Model by Regional Economics or How Big is the Ants’ Footprint?

The economy is communication between Man and Nature. It is an interaction-network between our outside and inside Nature, that is, the external Nature surrounding us and the internal nature expressing our human essence. Money is an institution of the society, an infrastructure that ensures division of labour, enables the flow of information and material between the participants. The concept of regional material and financial circular flow will be more important with the oncoming peak-oil and post-carbon era. We should describe in time the outlines of closed or semi-closed loops economy. The fundamentals of Input-Output will flourish once again; it could help us formulate the link between the efficiency and resiliency of a regional complex system.

A Closed Loop Brain-machine Interface for Epilepsy Control Using Dorsal Column Electrical Stimulation

Although electrical neurostimulation has been proposed as an alternative treatment for drug-resistant cases of epilepsy, current procedures such as deep brain stimulation, vagus, and trigeminal nerve stimulation are effective only in a fraction of the patients. Here we demonstrate a closed loop brain-machine interface that delivers electrical stimulation to the dorsal column (DCS) of the spinal cord to suppress epileptic seizures. Rats were implanted with cortical recording microelectrodes and spinal cord stimulating electrodes, and then injected with pentylenetetrazole to induce seizures. Seizures were detected in real time from cortical local field potentials, after which DCS was applied. This method decreased seizure episode frequency by 44% and seizure duration by 38%. We argue that the therapeutic effect of DCS is related to modulation of cortical theta waves, and propose that this closed-loop interface has the potential to become an effective and semi-invasive treatment for refractory epilepsy and other neurological disorders.

Power network in the loop : subsystem testing using a switching amplifier

“Hardware in the Loop” (HIL) testing is widely used in the automotive industry. The sophisticated electronic control units used for vehicle control are usually tested and evaluated using HIL-simulations. The HIL increases the degree of realistic testing of any system. Moreover, it helps in designing the structure and control of the system under test so that it works effectively in the situations that will be encountered in the system. Due to the size and the complexity of interaction within a power network, most research is based on pure simulation. To validate the performance of physical generator or protection system, most testing is constrained to very simple power network. This research, however, examines a method to test power system hardware within a complex virtual environment using the concept of the HIL. The HIL testing for electronic control units and power systems protection device can be easily performed at signal level. But performance of power systems equipments, such as distributed generation systems can not be evaluated at signal level using HIL testing. The HIL testing for power systems equipments is termed here as ‘Power Network in the Loop’ (PNIL). PNIL testing can only be performed at power level and requires a power amplifier that can amplify the simulation signal to the power level. A power network is divided in two parts. One part represents the Power Network Under Test (PNUT) and the other part represents the rest of the complex network. The complex network is simulated in real time simulator (RTS) while the PNUT is connected to the Voltage Source Converter (VSC) based power amplifier. Two way interaction between the simulator and amplifier is performed using analog to digital (A/D) and digital to analog (D/A) converters. The power amplifier amplifies the current or voltage signal of simulator to the power level and establishes the power level interaction between RTS and PNUT. In the first part of this thesis, design and control of a VSC based power amplifier that can amplify a broadband voltage signal is presented. A new Hybrid Discontinuous Control method is proposed for the amplifier. This amplifier can be used for several power systems applications. In the first part of the thesis, use of this amplifier in DSTATCOM and UPS applications are presented. In the later part of this thesis the solution of network in the loop testing with the help of this amplifier is reported. The experimental setup for PNIL testing is built in the laboratory of Queensland University of Technology and the feasibility of PNIL testing has been evaluated using the experimental studies. In the last section of this thesis a universal load with power regenerative capability is designed. This universal load is used to test the DG system using PNIL concepts. This thesis is composed of published/submitted papers that form the chapters in this dissertation. Each paper has been published or submitted during the period of candidature. Chapter 1 integrates all the papers to provide a coherent view of wide bandwidth switching amplifier and its used in different power systems applications specially for the solution of power systems testing using PNIL.

Cognitive assessment in closed head injury : stability, validity and parallel forms for two neuropsychological measures of recovery

Investigated the psychometric properties of the original and alternate sets of the Trail Making Test (TMT) and the Controlled Oral Word Association Test (COWAT; A. L. Benton and D. Hamsher, 1978) in 50 orthopedic and 15 closed head injured (1 yr after trauma) patients (aged 15–59 yrs). Although the alternate forms of both measures proved to be stable and consistent with each other in both groups, only the parallel sets of TMT reliably discriminated the clinical group from controls. Practice effects in the head injured were significant only for Trail B of TMT. Factor analysis of the control group's results identified Verbal Knowledge as a major contributor to performance on COWAT, whereas TMT was more dependent on Rapid Visual Search and Visuomotor Sequencing.