Author
John K-J. Li
Other affiliations: Zhejiang University, University of Medicine and Dentistry of New Jersey, University of Pennsylvania
Bio: John K-J. Li is an academic researcher from Rutgers University. The author has contributed to research in topics: Blood pressure & Afterload. The author has an hindex of 26, co-authored 195 publications receiving 2117 citations. Previous affiliations of John K-J. Li include Zhejiang University & University of Medicine and Dentistry of New Jersey.
Papers published on a yearly basis
Papers
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Book•
01 Jul 2004
TL;DR: Historical Background and Book Content Vascular Biology, Structure and Function Physical Concepts and Basic Fluid Mechanics Hemodynamics of Large Arteries Vascular Branching The Venous System The Microcirculation The Integrated Vascular System and Diseased Conditions.
Abstract: Historical Background and Book Content Vascular Biology, Structure and Function Physical Concepts and Basic Fluid Mechanics Hemodynamics of Large Arteries Vascular Branching The Venous System The Microcirculation The Integrated Vascular System and Diseased Conditions.
131 citations
Patent•
19 Nov 2002
TL;DR: An inflatable circulation assist device is described in this paper consisting of an inflatable stator housing an impeller with inflatable blades of varying shapes and sizes, which is inserted along a guidewire to a target location, and then the pump is inflated.
Abstract: An inflatable circulation assist device is disclosed consisting of an inflatable stator housing an impeller with inflatable blades of varying shapes and sizes. The invention is introduced into the patient percutaneously. The circulation assist device is a small pump packaged into a compact form that is attached to a long flexible driveshaft. The pump is inserted along a guidewire to a target location, and then the pump is inflated. The circulation assist device's exterior is designed to expand only so much as to closely fit whatever cardiovascular system element in which it is placed for operation. The vascular assist device can be expanded either by inflation with a fluid. The driveshaft, which connects to the circulation assist device's impeller and extends outside the patient's body, is rotated by an external motor. After the circulation assist device is no longer needed, it is collapsed into a compact form and removed from the patient percutaneously.
108 citations
TL;DR: Results show that the nonlinear compliance model in general can more accurately predict the measured pressure waveforms during control and during acute pressure loading.
Abstract: An examination is made of the consequences of incorporating a pressure dependent compliance in a modified arterial system model. This nonlinear model is evaluated under control and acute pressure-loading conditions. Results show that the nonlinear compliance model in general can more accurately predict the measured pressure waveforms during control and during acute pressure loading. The difference between the predicted waveforms is more pronounced when blood pressure is high and when the pulse pressure is large. >
101 citations
TL;DR: A simple, fast time domain method for the resolution of aortic pressure and flow pulses into their forward and reflected components is presented.
Abstract: A simple, fast time domain method for the resolution of aortic pressure and flow pulses into their forward and reflected components is presented. Accuracy of the method depends on the estimation of characteristic impedance and the frequency responses of the transducer systems.
92 citations
Book•
05 May 2000
TL;DR: This book discusses the history, theory, and applications of Arterial Circulation, as well as new approaches to clinical evaluation, using a simple Windkessel Model of the Arteria System as a guide.
Abstract: Chapter 1. INTRODUCTION. Historical View of Arterial Circulation. Recent Developments. Book Content. References. Chapter 2. PHYSIOLOGY AND RHEOLOGY OF ARTERIES. Anatomical and Structural Organization. Material Properties of the Arterial Wall: Elastin, Collagen, and Smooth Muscle Cells. Viscoelastic Properties of Blood Vessels. References. Chapter 3. THEORIES AND MODELS OF ARTERIAL CIRCULATION. Simple Windkessel Model of the Arterial System. Oscillatory Blood Flow in Arteries. Linear Theories of Blood Flow in Arteries. Analogy of Arterial Blood Flow to Transmission Line. Distributed and Reduced Arterial Tree Models. Nonlinear Aspects and Pressure-Dependent Arterial Compliance. References. Chapter 4. ARTERIAL PULSE TRANSMISSION CHARACTERISTICS. Pressure and Flow Waveforms in Large and Small Arteries. Vascular Impedance to Blood Flow. Pulse Propagation, Wave Velocity, and Damping. Pulse Wave Reflections and Reflection Sites. Pulse Transmission at Vascular Branching. Pulse Transmission to Vascular Beds. References. Chapter 5. HEMODYNAMIC MEASUREMENTS AND CLINICAL MONITORING. Invasive Blood Pressure Measurements. Noninvasive Blood Pressure Measurements. Blood Flow Measurements. Thermodilution Measurement of Cardiac Output. Vascular Ultrasound Dimension Measurement. References. Chapter 6. ARTERIAL CIRCULATION AND THE HEART. Coupling of Heart and Arterial System. Dynamic Heart-Arterial System Interactions and the Concept of Dynamic Arterial Compliance. Coronary Arterial Circulation. Hemodynamics and Modeling of Coronary Circulation. Myocardial Function and Arterial System Load. References. Chapter 7. NEW APPROACHES TO CLINICAL EVALUATIONS. Hypertension, Vascular Stiffness, and Arterial Compliance. Vascular Hemodynamics of Aging and Isolated Systolic Hypertension. Aortic Valve Stenosis and Arterial System Afterload on Left Ventricular Hypertrophy. Allometry and Its Diagnostic Applications. References. INDEX.
92 citations
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TL;DR: The model provides a complete analysis of scaling relations for mammalian circulatory systems that are in agreement with data and predicts structural and functional properties of vertebrate cardiovascular and respiratory systems, plant vascular systems, insect tracheal tubes, and other distribution networks.
Abstract: Allometric scaling relations, including the 3/4 power law for metabolic rates, are characteristic of all organisms and are here derived from a general model that describes how essential materials are transported through space-filling fractal networks of branching tubes. The model assumes that the energy dissipated is minimized and that the terminal tubes do not vary with body size. It provides a complete analysis of scaling relations for mammalian circulatory systems that are in agreement with data. More generally, the model predicts structural and functional properties of vertebrate cardiovascular and respiratory systems, plant vascular systems, insect tracheal tubes, and other distribution networks.
4,272 citations
TL;DR: The late fall in DBP after age 60 years, associated with a continual rise in SBP, cannot be explained by "burned out" diastolic hypertension or by "selective survivorship" but is consistent with increased large artery stiffness.
Abstract: Background We attempted to characterize age-related changes in blood pressure in both normotensive and untreated hypertensive subjects in a population-based cohort from the original Framingham Heart Study and to infer underlying hemodynamic mechanisms. Methods and Results A total of 2036 participants were divided into four groups according to their systolic blood pressure (SBP) at biennial examination 10, 11, or 12. After excluding subjects receiving antihypertensive drug therapy, up to 30 years of data on normotensive and untreated hypertensive subjects from biennial examinations 2 through 16 were used. Regressions of blood pressure versus age within individual subjects produced slope and curvature estimates that were compared with the use of ANOVA among the four SBP groups. There was a linear rise in SBP from age 30 through 84 years and concurrent increases in diastolic blood pressure (DBP) and mean arterial pressure (MAP); after age 50 to 60 years, DBP declined, pulse pressure (PP) rose steeply, and MA...
2,176 citations
TL;DR: Characteristic impedance was introduced as a third element of the Windkessel model, a lumped model not suitable for the assessment of spatially distributed phenomena and aspects of wave travel, but it is a simple and fairly accurate approximation of ventricular afterload.
Abstract: Frank’s Windkessel model described the hemodynamics of the arterial system in terms of resistance and compliance. It explained aortic pressure decay in diastole, but fell short in systole. Therefore characteristic impedance was introduced as a third element of the Windkessel model. Characteristic impedance links the lumped Windkessel to transmission phenomena (e.g., wave travel). Windkessels are used as hydraulic load for isolated hearts and in studies of the entire circulation. Furthermore, they are used to estimate total arterial compliance from pressure and flow; several of these methods are reviewed. Windkessels describe the general features of the input impedance, with physiologically interpretable parameters. Since it is a lumped model it is not suitable for the assessment of spatially distributed phenomena and aspects of wave travel, but it is a simple and fairly accurate approximation of ventricular afterload.
937 citations
TL;DR: In this article, the authors present a comprehensive and critical review of the different therapeutic classes and molecules that have been investigated as potential candidates for iontophoretic delivery, including peptides and proteins.
679 citations
TL;DR: The millimolar absorptivities of the four clinically relevant derivatives of fetal and adult human hemoglobin in the visible and near-infrared spectral range (450-1000 nm) were determined, and spectral absorption curves of similar shape were found.
Abstract: We determined the millimolar absorptivities of the four clinically relevant derivatives of fetal and adult human hemoglobin in the visible and near-infrared spectral range (450-1000 nm). As expected, spectral absorption curves of similar shape were found, but the small differences between fetal and adult hemoglobin absorptivity were important enough that they should be taken into account in multicomponent analysis of hemoglobin derivatives. Common pulse oximeters, however, involving light of 660 and 940 nm, are so insensitive to the presence of fetal hemoglobin that they can be used safely in neonates. The error in pulse oximetry caused by the presence of carboxyhemoglobin is insubstantial, but methemoglobin gives either an understimation or an overestimation at high or low oxygen saturation, respectively, the turning point being near 70% saturation.
661 citations