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Baquero H.,Universidad del Norte, Colombia | Alviz R.,Medicina Alta Complejidad S.A. | Castillo A.,Northeast Georgia Medical Center | Neira F.,Medicina Alta Complejidad S.A. | Sola A.,Neonatology
Acta Paediatrica, International Journal of Paediatrics | Year: 2011

Aim: To assess the time to obtain reliable oxygen saturation readings by different pulse oximeters during neonatal resuscitation in the delivery room or NICU. Methods: Prospective study comparing three different pulse oximeters: Masimo Radical-7 compared simultaneously with Ohmeda Biox 3700 or with Nellcor N395, in newborn infants who required resuscitation. Members of the research team placed the sensors for each of the pulse oximeters being compared simultaneously, one sensor on each foot of the same baby. Care provided routinely, without interference by the research team. The time elapsed until a reliable SpO2 was obtained was recorded using a digital chronometer. Statistical comparisons included chi-square and student's T-test. Results: Thirty-two infants were enrolled; median gestational age 32 weeks. Seventeen paired measurements were made with the Radical-7 and Biox 3700; mean time to a stable reading was 20.2 ± 7 sec for the Radical-7 and 74.2 ± 12 sec for the Biox 3700 (p = 0.02). The Radical-7 and the N- 395 were paired on 15 infants; the times to obtain a stable reading were 20.9 ± 4 sec and 67.3 ± 12 sec, respectively (p = 0.03). Conclusion: The time to a reliable reading obtained simultaneously in neonatal critical situations differs by the type of the pulse oximeter used, being significantly faster with Masimo Signal Extraction Technology. This may permit for better adjustments of inspired oxygen, aiding in the prevention of damage caused by unnecessary exposure to high or low oxygen. ©2011 The Author(s)/Acta Pædiatrica ©2011 Foundation Acta Pædiatrica.


Chellaboina V.S.,Tata Consultancy Services Ltd. | Haddad W.M.,Georgia Institute of Technology | Li H.,Georgia Institute of Technology | Bailey J.M.,Northeast Georgia Medical Center
International Journal of Control | Year: 2010

Acute respiratory failure due to infection, trauma or major surgery is one of the most common problems encountered in intensive care units, and mechanical ventilation is the mainstay of supportive therapy for such patients. In this article, we develop a general mathematical model for the dynamic behaviour of a multi-compartment respiratory system in response to an arbitrary applied inspiratory pressure. Specifically, we use compartmental dynamical system theory and Poincare maps to model and analyse the dynamics of a pressure-limited respirator and lung mechanics system, and show that the periodic orbit generated by this system is globally asymptotically stable. Furthermore, we show that the individual compartmental volumes, and hence the total lung volume, converge to steady-state end-inspiratory and end-expiratory values. Finally, we develop a model reference direct adaptive controller framework for the multi-compartmental model of a pressure-limited respirator and lung mechanics system where the plant and reference model involve switching and time-varying dynamics. We then apply the proposed adaptive feedback controller framework to stabilise a given limit cycle corresponding to a clinically plausible respiratory pattern. © 2010 Taylor & Francis.


Gholami B.,Georgia Institute of Technology | Bailey J.M.,Northeast Georgia Medical Center | Haddad W.M.,Georgia Institute of Technology | Tannenbaum A.R.,Georgia Institute of Technology
IEEE Transactions on Control Systems Technology | Year: 2012

Patients in the intensive care unit (ICU) who require mechanical ventilation due to acute respiratory failure also frequently require the administration of sedative agents. The need for sedation arises both from patient anxiety due to the loss of personal control and the unfamiliar and intrusive environment of the ICU, and also due to pain or other variants of noxious stimuli. While physicians select the agent(s) used for sedation and cardiovascular function, the actual administration of these agents is the responsibility of the nursing staff. If clinical decision support systems and closed-loop control systems could be developed for critical care monitoring and lifesaving interventions as well as the administration of sedation and cardiopulmonary management, the ICU nurse could be released from the intense monitoring of sedation, allowing her/him to focus on other critical tasks. One particularly attractive strategy is to utilize the knowledge and experience of skilled clinicians, capturing explicitly the rules expert clinicians use to decide on how to titrate drug doses depending on the level of sedation. In this paper, we extend the deterministic rule-based expert system for cardiopulmonary management and ICU sedation framework presented in to a stochastic setting by using probability theory to quantify uncertainty and hence deal with more realistic clinical situations. © 2011 IEEE.


Castillo A.,Northeast Georgia Medical Center | Deulofeut R.,Pediatrix Medical Group | Critz A.,Emory University | Sola A.,Iberoamerican Society of Neonatology
Acta Paediatrica, International Journal of Paediatrics | Year: 2011

Aim: To identify whether pulse oximetry technology is associated with decreased retinopathy of prematurity (ROP) and laser treatment. Methods: Inborn infants <1250 g who had eye exams were compared at two centres in three periods. In Period 1, SpO2 target was ≥93% and pulse oximetry technology was the same in both Centres. In Period 2, guidelines for SpO 2 88-93% were implemented at both centres and Centre B changed to oximeters with signal extraction technology (SET®) while Centre A did not, but did so in Period 3. One ophthalmology department performed eye exams using international criteria. Results: In 571 newborns <1250 g, birth weight and gestational age were similar in the different periods and centres. At Centre A, severe ROP and need for laser remained the same in Periods 1 and 2, decreasing in Period 3-6% and 3%, respectively. At Centre B, severe ROP decreased from 12% (Period 1) to 5% (Period 2) and need for laser decreased from 5% to 3%, remaining low in Period 3. Conclusion: In a large group of inborn infants <1250 g, a change in clinical practice in combination with pulse oximetry with Masimo SET, but not without it, led to significant reduction in severe ROP and need for laser therapy. Pulse oximetry selection is important in managing critically ill infants. © 2010 Foundation Acta Pædiatrica.


Volyanskyy K.Y.,Georgia Institute of Technology | Haddad W.M.,Georgia Institute of Technology | Bailey J.M.,Northeast Georgia Medical Center
International Journal of Adaptive Control and Signal Processing | Year: 2011

A neuroadaptive output feedback control architecture for nonlinear nonnegative dynamical systems with input amplitude and integral constraints is developed. Specifically, the neuroadaptive controller guarantees that the control amplitude as well as the integral of the control input over a given time interval are constrained, and the physical system states remain in the nonnegative orthant of the state space. The proposed approach is used to control the infusion of the anesthetic drug propofol for maintaining a desired constant level of depth of anesthesia for noncardiac surgery in the face of infusion rate constraints and an integral drug dosing constraint over a specified time period. © 2010 John Wiley & Sons, Ltd.


Zeng X.,Texas Tech University | Hui Q.,Texas Tech University | Haddad W.M.,Georgia Institute of Technology | Hayakawa T.,Tokyo Institute of Technology | Bailey J.M.,Northeast Georgia Medical Center
Journal of the Franklin Institute | Year: 2014

With advances in biochemistry, molecular biology, and neurochemistry there has been impressive progress in the understanding of the molecular properties of anesthetic agents. However, despite these advances, we still do not understand how anesthetic agents affect the properties of neurons that translate into the induction of general anesthesia at the macroscopic level. There is extensive experimental verification that collections of neurons may function as oscillators and the synchronization of oscillators may play a key role in the transmission of information within the central nervous system. This may be particularly relevant to understand the mechanism of action for general anesthesia. In this paper, we develop a stochastic synaptic drive firing rate model for an excitatory and inhibitory cortical neuronal network in the face of system time delays and stochastic input disturbances. In addition, we provide sufficient conditions for global asymptotic and exponential mean-square synchronization for this model. © 2013 The Franklin Institute. Published by The Franklin Institute. All rights reserved.


Haddad W.M.,Georgia Institute of Technology | Volyanskyy K.Y.,Georgia Institute of Technology | Bailey J.M.,Northeast Georgia Medical Center | Im J.J.,Virginia Polytechnic Institute and State University
IEEE Transactions on Control Systems Technology | Year: 2011

Critical care patients, whether undergoing surgery or recovering in intensive care units, require drug administration to regulate physiological variables such as blood pressure, cardiac output, heart rate, and degree of consciousness. The rate of infusion of each administered drug is critical, requiring constant monitoring and frequent adjustments. Nonnegative and compartmental models provide a broad framework for biological and physiological systems, including clinical pharmacology, and are well suited for developing models for closed-loop control of drug administration. In this paper, we develop a neuroadaptive output feedback control framework for nonlinear uncertain nonnegative and compartmental systems with nonnegative control inputs and noisy measurements. The proposed framework is Lyapunov-based and guarantees ultimate boundedness of the error signals. In addition, the neuroadaptive controller guarantees that the physical system states remain in the nonnegative orthant of the state space. Finally, the proposed approach is used to control the infusion of the anesthetic drug propofol for maintaining a desired constant level of depth of anesthesia for surgery in the face of noisy electroencephalographic (EEG) measurements. Clinical trials demonstrate excellent regulation of unconsciousness allowing for a safe and effective administration of the anesthetic agent propofol. © 2010 IEEE.


Haddad W.M.,Georgia Institute of Technology | Hui Q.,Texas Tech University | Bailey J.M.,Northeast Georgia Medical Center
Entropy | Year: 2014

Advances in neuroscience have been closely linked to mathematical modeling beginning with the integrate-and-fire model of Lapicque and proceeding through the modeling of the action potential by Hodgkin and Huxley to the current era. The fundamental building block of the central nervous system, the neuron, may be thought of as a dynamic element that is "excitable", and can generate a pulse or spike whenever the electrochemical potential across the cell membrane of the neuron exceeds a threshold. A key application of nonlinear dynamical systems theory to the neurosciences is to study phenomena of the central nervous system that exhibit nearly discontinuous transitions between macroscopic states. A very challenging and clinically important problem exhibiting this phenomenon is the induction of general anesthesia. In any specific patient, the transition from consciousness to unconsciousness as the concentration of anesthetic drugs increases is very sharp, resembling a thermodynamic phase transition. This paper focuses on multistability theory for continuous and discontinuous dynamical systems having a set of multiple isolated equilibria and/or a continuum of equilibria. Multistability is the property whereby the solutions of a dynamical system can alternate between two or more mutually exclusive Lyapunov stable and convergent equilibrium states under asymptotically slowly changing inputs or system parameters. In this paper, we extend the theory of multistability to continuous, discontinuous, and stochastic nonlinear dynamical systems. In particular, Lyapunov-based tests for multistability and synchronization of dynamical systems with continuously differentiable and absolutely continuous flows are established. The results are then applied to excitatory and inhibitory biological neuronal networks to explain the underlying mechanism of action for anesthesia and consciousness from a multistable dynamical system perspective, thereby providing a theoretical foundation for general anesthesia using the network properties of the brain. Finally, we present some key emergent properties from the fields of thermodynamics and electromagnetic field theory to qualitatively explain the underlying neuronal mechanisms of action for anesthesia and consciousness. © 2014 by the authors.


Hui Q.,Texas Tech University | Haddad W.M.,Georgia Institute of Technology | Bailey J.M.,Northeast Georgia Medical Center
Nonlinear Analysis: Hybrid Systems | Year: 2011

This paper focuses on multistability theory for discontinuous dynamical systems having a set of multiple isolated equilibria and/or a continuum of equilibria. Multistability is the property whereby the solutions of a dynamical system can alternate between two or more mutually exclusive Lyapunov stable and convergent equilibrium states under asymptotically slowly changing inputs or system parameters. In this paper, we extend the definition and theory of multistability to discontinuous autonomous dynamical systems. In particular, nontangency Lyapunov-based tests for multistability of discontinuous systems with Filippov and Carathéodory solutions are established. The results are then applied to excitatory and inhibitory biological neuronal networks to explain the underlying mechanism of action for anesthesia and consciousness from a multistable dynamical system perspective, thereby providing a theoretical foundation for general anesthesia using the network properties of the brain. © 2010 Elsevier Ltd.


Duke D.,Northeast Georgia Medical Center
Radiology management | Year: 2012

A plan to reduce radiation dose and improve patient safety was established in northeast Georgia by creating a CT image record in a tri-fold wallet format that patients could carry with them.The intent was for multiple facilities to take part and share this information within the community. Patient questionnaires were also distributed in the ED and were used to collect prior CT information. They gave consistency to the information and it guided the ED physician through the patient care process. Repeat CT scans were ultimately reduced, and awareness among technologists and physicians increased. However, there was poor patient compliance in using the wallet tri-fold CT image record.

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