Showing papers on "Pulsatile flow published in 1973"
157 citations
TL;DR: In this paper, the Galerkin method was used to find solutions for the case of a simply supported pipe conveying a pressurized flow whose velocity possesses a harmonic fluctuation about a mean value.
65 citations
TL;DR: A study of the flow patterns and velocity and shear stress distributions downstream of symmetrical branches has been made in steady and pulsatile flows to provide some knowledge of the fluid dynamic effects in blood vessel branches.
Abstract: A study of the flow patterns and velocity and shear stress distributions downstream of symmetrical branches has been made in steady and pulsatile flows in order to provide some knowledge of the fluid dynamic effects in blood vessel branches.
61 citations
TL;DR: Pulsatile blood flow through rigid circular tubes due to a sinusoidally varying pressure gradient is analyzed using a microcontinuum model of blood and a new boundary condition is proposed to describe red blood cell rotations at a solid boundary.
Abstract: In this paper pulsatile blood flow through rigid circular tubes due to a sinusoidally varying pressure gradient is analyzed using a microcontinuum model of blood. A new boundary condition, which is in accord with experimental observations on blood flow in small rigid tubes, has been proposed to describe red blood cell rotations at a solid boundary. General solutions to the governing equations are obtained through application of consecutive Hankel and Laplace transforms. The steady pulsatile solutions for velocity and cell rotation are also given. The plasma viscosity, rotational viscosity, and rotational gradient coefficients are determined as functions of hematocrit from the experimental in vitro steady blood flow data of Bugliarello and Sevilla. These coefficients are then used to predict their pulsatile velocity profile data. Excellent agreement is obtained when non‐Newtonian effects are absent.
56 citations
Patent•
21 May 1973TL;DR: In this paper, a portable pulsatile pumping system simulates the pumping mechanism of a human heart in pumping fluid for such applications as organ perfusion systems, which includes a regulated source of pressurized gas, a pulsatile pump having an aorta chamber providing a sustained minimum diastolic pressure and a ventricle chamber providing higher systolic pressure during a selectively variable part (1 to 99 percent) of each cyclic pumping action, the periodicity of which may be varied from 5 to 150 cycles per minute.
Abstract: A portable pulsatile pumping system simulates the pumping mechanism of a human heart in pumping fluid for such applications as organ perfusion systems. The pumping system includes a regulated source of pressurized gas, a pulsatile pump having an aorta chamber providing a sustained minimum diastolic pressure and a ventricle chamber providing a higher systolic pressure during a selectively variable part (1 to 99 percent) of each cyclic pumping action, the periodicity of which may be varied from 5 to 150 cycles per minute. The gas source is connected to the pump by a first adjustable pressure regulator to maintain the chosen diastolic pressure in the aorta chamber. The ventricle chamber is alternately coupled to gas pressure taken through a second pressure regulator and vented by a solenoid mechanism operated by a digital electronic timing control circuit. The digital electronic control system employs digital counters and selector switches to generate square wave pulses of varying duration and periodicity in a manner which provides both conservation of electrical battery energy and high reliability. At the same time, an optimum pumping system is achieved because the elasticity of the gas and connecting tubing are employed to smooth the sharp signal transitions.
43 citations
TL;DR: Analysis of renal cortical and medullary tissue oxygen availability and total renal oxygen flow in dogs showed the superiority of pulsatile bypass over nonpulsatile left heart bypass, along with previous work.
36 citations
TL;DR: In this article, the pulsatile flow of an incompressible viscous fluid in a cylindrical tube of varying cross section is investigated for small Reynolds numbers and the shear stress distribution on the wall is evaluated and discussed in detail for special geometries like tapered tubes, locally constricted tubes and peristaltic tubes.
Abstract: The pulsatile flow of an incompressible viscous fluid in a cylindrical tube of varying cross section is investigated for small Reynolds numbers. The solutions consist of a stedy and an oscillatory part. The shear stress distribution on the wall is evaluated and discussed in detail for special geometries like tapered tubes, locally constricted tubes and peristaltic tubes. The existence of separation in the flow field is noticed.
29 citations
TL;DR: In this paper, the authors used the radioactive microsphere method to estimate the distribution of coronary blood flow during cardiopulmonary bypass in pigs, and found that the endocardial side of the myocardium was markedly underperfused when the heart remained in ventricular fibrillation during bypass.
24 citations
TL;DR: The initial analysis considers the flow in a two-dimensional bifurcation with a symmetrical flow divider perfused with steady flow at variable Reynolds numbers and confirms that the flow at the apex is quite different from that at the outer angles and that the latter varies more with flow rate than the former.
23 citations
TL;DR: The canine pancreas-duodenum has been perfused for 3 h with a membrane oxygenator, a pulsatile pump and a heat exchanger at a temperature of 37 °C and among the criteria used in this study, the insulin requirement is low.
Abstract: The canine pancreas-duodenum has been perfused for 3 h with a membrane oxygenator, a pulsatile pump and a heat exchanger at a temperature of 37 °C. Among the criteria used in this study, the insulin o
17 citations
TL;DR: The present pump is satisfactory for dog perfusions, and should, with minor modifications, be suitable for use in human surgery.
Abstract: A new pulsatile pump is described, and the results of bench tests and animal experiments are presented. The arterial blood pressure and flow waveforms generated by the pump resemble those produced by the canine heart. The present pump is satisfactory for dog perfusions, and should, with minor modifications, be suitable for use in human surgery.
Patent•
09 Mar 1973
TL;DR: In this paper, a dampening unit consisting of a casing having an inner cavity and a pair of spaced-apart, flexible diaphragms attached to the casing within the cavity is provided.
Abstract: A dampening unit is provided for use in combination with a pulsatile pump, a unit which requires pulsatile flow of fluid, and a unit which requires substantially non-pulsatile flow. The dampening unit comprises a casing having an inner cavity and a pair of spaced-apart, flexible diaphragms attached to the casing within the cavity to provide a chamber between the two diaphragms. As fluid flows through the chamber, the flexible diaphragms expand and contract to dampen the pulsatile flow of the fluid. The dampening unit is connected between the pulsatile pump and the unit which requires substantially non-pulsatile flow.
Patent•
09 Aug 1973
TL;DR: In this article, a non-invasive measuring system adapted to measure arterial blood flow in human beings is provided, where a stable, strong magnetic field is produced in the region of the artery under measurement by a magnet suitably positioned near the human being and a mechanical means moves the magnet away from its normal position or back to such position.
Abstract: A non-invasive measuring system adapted to measure arterial blood flow in human beings is provided A stable, strong magnetic field is produced in the region of the artery under measurement by a magnet suitably positioned near the human being A mechanical means moves the magnet away from its normal position or back to such position The blood flow induced signals, which are pulsatile, are sensed by electrodes placed on the skin adjacent to the artery Mixed with the blood flow signals are the local electrocardiogram signals In addition, the electrodes also pick up random noises which are not synchronized with the heart The signals are amplified and processsed by a repetitive waveform averager which is synchronized by a cardiogram signal obtained from auxiliary electrodes The waveform averager accumulates a first predetermined number of composite pulsatile signals from said measuring electrodes during a first series of heart cycles occurring when the magnetic field is produced in the region of the artery, and accumulates an equal number of composite pulsatile signals from said measuring electrodes during a second series of heart cycles occurring when the magnetic field in the region is suppressed A signal selector includes a comparator connected at the input of the waveform averager for comparing each incoming pulsatile signal with predetermined acceptable signal characteristics, so that the incoming pulsatile signal will be accumulated by the waveform averager only if it is accepted by the signal selector The waveforms registered in the waveform averager respectively during the first and the second series of heart cycles are subtracted from each other to obtain the blood flow pulse substantially free from electrocardiogram and random noise influence
TL;DR: It is the relative change in blood flow rather than the absolute values of flow that is important in the bedside evaluation of a patient, and this technique could be very helpful clinically, particularly in peripheral vascular disease.
Patent•
19 Apr 1973
TL;DR: Prosthetic cardiac valves for disposition in the heart and the aorta for controlling the pulsatile flow of blood in and from the heart, wherein positive opening and closing guiding action is effected and a minimum of turbulence of the blood across the valve occurs when the valve is open.
Abstract: Prosthetic cardiac valves for disposition in the heart and the aorta for controlling the pulsatile flow of blood in and from the heart, wherein positive opening and closing guiding action is effected and a minimum of turbulence of the blood across the valve occurs when the valve is open.
TL;DR: Results are in agreement with a previously reported cross-correlation technique utilized to measure the time delay between signals from upstream and downstream photodetectors aligned in the direction of flow.
Abstract: A method for the in vivo detection of pulsatile blood velocity in transilluminated microvessels using data contained in single photometric signals is described. The system design is based on the assumption that pulsatile velocity information is contained in frequency- modulated components of the photometric signal spectrum. Results are in agreement with a previously reported cross-correlation technique utilized to measure the time delay between signals from upstream and downstream photodetectors aligned in the direction of flow.
TL;DR: In this paper, an analytical expression for the instantaneous average velocity and friction factor for pulsatile Newtonian laminar flow with mean flow was obtained for the pulsatile pressure gradients.
TL;DR: In this article, an in vitro study of pulsatile amperometric techniques suitable for application in blood and tissue was performed to reveal changes in p02 within the cardiac cycle, and for low electrode O2 consumption.
Abstract: This investigation has been an in vitro study of pulsatile amperometric techniques suitable for application in blood and tissue. Parameters of the study were selected to enhance spatial resolution, to obtain a faster time response to reveal changes in p02 within the cardiac cycle, and for low electrode O2 consumption. Faster time response may provide new physiological information for possible future application in a research or clinical setting.
TL;DR: The findings indicate that the nondirectional Doppler catheter tip velocity transducer in its present form is not suitable for accurately measuring changes in aortic blood flow velocity.
Dissertation•
01 Jan 1973
TL;DR: An ELECTROCHEMICAL INVESTIGATION of MASS TRANSFER and SHEAR STRESS in PULSATILE LAMINAR FLOW: IMPLICATIONS FOR ATHEROGENESIS as discussed by the authors.
Abstract: AN ELECTROCHEMICAL INVESTIGATION OF MASS TRANSFER AND SHEAR STRESS IN PULSATILE LAMINAR FLOW: IMPLICATIONS FOR ATHEROGENESIS
TL;DR: The statistical nature of four cardiovascular signals is described by auto-correlation functions at several stabilized arterial mean pressure levels at several stabilize arterialmean pressure levels.
01 Jan 1973
TL;DR: A pulsatile, portable, versatile pump for cardiopulmonary bypass has been developed by Bentley Laboratories, using an externally powered air piston-driven ventricle chamber, which has proven very gentle to blood cells and other blood components, including proteins, in extended extended bypass operations.
Abstract: A pulsatile, portable, versatile pump for cardiopulmonary bypass has been developed by Bentley Laboratories, using an externally powered air piston-driven ventricle chamber The pump closely approximates the action of the left ventricle with variable pulse rates (20–120 beats/min) and automatically variable stroke volume (10–100 ml/stroke) Activation from an external source such as the “R” wave of the electrocardiogram is provided The pump may thus be used in either synchronous or counterpulsation techniques during cardiac failure The system will perfuse at a rate of 1–6 liters/min providing either total or partial body perfusion The actuator is gas powered The control system utilizes fluidic-electronic interfaces, either battery or alternating current powered Thus the system may be completely portableThe ventricle is made from a negatively charged inherently antithrombogenic polyurethane The system has proven very gentle to blood cells and other blood components, including proteins, in extended i
01 Jan 1973
TL;DR: In this paper, renal cortical and medullary tissue oxygen availability (O2a) and total renal oxygen flow was compared with total renal consumption during four hours of pulsatile and nonpulsatile bypass in dogs.
Abstract: Data favoring pulsatile over nonpulsatile left heart bypass are conflicting. To study this problem, renal cortical and medullary tissue oxygen availability (O2a) and total renal oxygen flow was compared with total renal oxygen consumption during four hours of pulsatile and nonpulsatile bypass in dogs.
TL;DR: A highly stable, easily built and operated circuit was designed to linearise the output of a particular photocell operating at the isobestic point of blood, tested in vitro by simultaneously recording the total optical-density changes, and pulsatile o.d. changes.
Abstract: A highly stable, easily built and operated circuit was designed to linearise the output of a particular photocell operating at the isobestic point of blood. In addition, the system was testedin vitro by simultaneously recording the total optical-density (o.d.) changes, and pulsatile o.d. changes observed when blood was perfused through a rigid tube and tubing capable of volume changes. The results showed different pulsatile o.d. changes, both in waveform and temporal sequence, for the rigid and distensible tubes.