Showing papers on "Pulsatile flow published in 1972"
TL;DR: Minute-to-minute fluctuations of serum LH and FSH concentrations resembling a pulsatile pattern were demonstrated in both pre- and post-menopausal women, and a greater net increase of circulating LH was found in pulses during the midcycle surge which was more than double that seen during other phases of the cycle.
Abstract: Minute-to-minute fluctuations of serum LH and FSH concentrations resembling a pulsatile pattern were demonstrated in both pre- and post-menopausal women A pulsatile pattern of LH but not FSH was seen during the menstrual cycle These appear to follow a varying frequency and magnitude according to the different phases of the cycle; a periodicity of 1–2 hr was seen during the early follicular phase, early luteal phase and midcycle surge while a periodicity of 4 hr was seen in the mid- and late-luteal phase During the late follicular phase only “minor oscillations” were noted A greater net increase of circulating LH was found in pulses during the midcycle surge which was more than double that seen during other phases of the cycle In contrast, post-menopausal subjects had pulses of both gonadotropins These were usually coincident, however, a minor asynchrony between LH and FSH patterns was discernible The frequency of pulses in the postmenopausal subjects was the same as in the follicular phase and midc
446 citations
TL;DR: In this paper, an approximate numerical method for calculating flow profiles in arteries is developed, which takes into account the nonlinear terms of the Navier-Stokes equations as well as the non-linear behaviour and large deformations of the arterial wall.
Abstract: An approximate numerical method for calculating flow profiles in arteries is developed. The theory takes into account the nonlinear terms of the Navier-Stokes equations as well as the nonlinear behaviour and large deformations of the arterial wall. Through the locally measured values of the pressure, pressure gradient, and pressure-radius function, the velocity distribution and wall shear at a given location along the artery can be determined. The computed results agree well with the corresponding experimental data.
227 citations
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TL;DR: Clinical investigation of pulsatile flow is now possible with catheter-tip flowmeters that can be used in routine cardiac care, and the formulation of theories appropriate to oscillatory flow in blood vessels has gained new impetus from three recent developments.
Abstract: Hence does arise the action and function of the heart, which by pulsation it performs. [William Harvey, De Motu Cordis, 1628.] THE study of blood flow as a pulsatile phenomenon is scarcely new, but it has gained new impetus from three recent developments: the commercial production of reliable blood flowmeters, the formulation of theories appropriate to oscillatory flow in blood vessels,1 and the increasing availability of digital computers. Studies in laboratory animals have profited from these technical advances for some time, and clinical investigation of pulsatile flow is now possible with catheter-tip flowmeters that can be used in routine cardiac . . .
222 citations
TL;DR: The present findings throw light upon the CSF circulation and possibly, as will be reported separately, upon the aetiology of hydromyelia, some forms of hydrocephalus and of arachnoid cysts.
Abstract: In 1966 some radiologic observations of pulsatile movements in the cerebrospinal fluid pathways were described by DU BOULAY who was working upon O'CONNELL'S idea of a CSF pump. Now, as a result of further work, the earlier conclusions have been modified and widened. The present findings throw light upon the CSF circulation and possibly, as will be reported separately, upon the aetiology of hydromyelia, some forms of hydrocephalus and of arachnoid cysts. The work to be described here is intended to put the whole subject into perspective. A brief review of the literature may be helpful. Leaving aside early observations establishing the existence of pulsatile pressure changes, most published work is concerned with the following main topics: (1) If the source of the pulsatile pressure waves coincident with heart rate is (a) arterial in the head, (b) arterial in the spine, or (c) venous. (2) Granted that a large part of the pulse pressure wave derives from the head, the question arises if it comes from (a) expansion of arteries at the base, (b) expansion of the vessels within the brain, or (c) expansion of the choroid plexuses. (3) The means by which the respiratory fluctuation of CSF pressure is brought about. (4) The relationship of alterations in cerebral blood flow to CSF pressure changes. (There are also
133 citations
TL;DR: Diffuse nerve cell changes found in the brains of dogs subjected to total cardiac bypass are attributed to non-pulsatile blood flow but some complicating factors are recognized.
Abstract: The brains of dogs subjected to total cardiac bypass were examined for early signs of ischaemic nerve cell changes. Diffuse nerve cell changes were found immediately following two- and three-hour non-pulsatile perfusions but not following pulsatile perfusions of the same durations. The nerve cell changes found in the brains were acute cell swelling and early ischaemic cell change. Acute cell swelling was found only in the cerebellar Purkinje cells. Ischaemic cell change was found in several regions of the brain but the cerebral cortex and cerebellar Purkinje cells were most frequently affected. Diffuse nerve cell changes are attributed to non-pulsatile blood flow but some complicating factors are recognized.
Focal lesions found in three brains may have been due to embolism by blood cell aggregates and/or gas microbubbles.
104 citations
TL;DR: The results demonstrate that, contrary to the findings of another report, intracranial aneurysms are subjected to the full force of systemic blood pressure.
Abstract: ✓ Mean and pulsatile intra-aneurysmal blood pressures were recorded from four cases of human intracranial saccular aneurysms at the time of operative exposure. In each case the mean intra-aneurysmal pressure equalled the mean systemic arterial pressure, and the intra-aneurysmal pressure was pulsatile. The results demonstrate that, contrary to the findings of another report, intracranial aneurysms are subjected to the full force of systemic blood pressure.
80 citations
60 citations
TL;DR: In order to maintain nearly equal arterial pressures above and below the crossclamped aorta, a higher flow rate was required with NP than with P, and marked reduction in pH along with elevated L were consistent with NP.
60 citations
TL;DR: It is concluded that variations of pulse pressure and particularly of heart rate in the physiological range have relatively little reflex effect compared with that of the change in mean intrasinus pressure.
Abstract: SCHMIDT,ROBERT M., MAMORUKUMADA,AND KIICHI SAGAWA. Curdiovascular responses to various pulsatile pressures in the carotid sinus. Am. J. Physiol. 223 (1): l-7. 1972.-To extend the knowledge of the carotid sinus reflex, we forced the isolated sinuses of anesthetized dogs with sinusoidal (pulsatile) pressures using multiple combinations of mean level, amplitude, and frequency of pulsation. The reflex responses of mean arterial pressure, cardiac output, and total peripheral resistance were analyzed at mean sinus pressures of 75, 100, 125, and 150 mm Hg, frequencies of 1, 2, 3, and 4 Hz, and peak-to-peak amplitudes of 25, 50, and 75 mm Hg. Increasing the amplitude of pulsation from 25 to 75 mm Hg while holding the frequency at 2 Hz caused moderate and proportional reductions in arterial pressure, cardiac output, and total peripheral resistance, except when the pulsatile pressure was superimposed on mean sinus pressure of 150 mm Hg. In contrast, increasing the frequency of pulsation from 1 to 4 Hz with a fixed amplitude of 50 mm Hg evoked significant responses only after vagotomy at the mean intrasinus pressure of 75 mm Hg. An example of use of the quantitative data gained by this study is discussed in relation to evaluation of the role that the reflex system plays in maintaining mean arterial pressure after a 20$& hemorrhage. We conclude from the above findings that variations of pulse pressure and particularly of heart rate in the physiological range have relatively little reflex effect compared with that of the change in mean intrasinus pressure.
59 citations
TL;DR: A mathematical analysis of a particular model of blood rheology, the Casson fluid, which possesses finite yield stress and shear-dependent viscosity when it is subjected to a periodic pressure gradient in a long rigid tube shows that the flow behavior in arterioles and venules can be accurately approximated by the quasi-steady solution.
59 citations
TL;DR: Results show that the diffuse nerve cell changes associated with roller pump perfusions can be avoided by using a new pulsatile pump, but focal brain damage was not eliminated, and lung damage and mortality were not reduced.
Abstract: In a series of 20 dog experiments, total cardiac bypass was followed by a high rate of mortality during the first 12 postoperative hours. Only five dogs survived for one week, but a further three dogs were perfuse-fixed after shorter periods of survival. All dogs developed pulmonary alveolar haemorrhages and seven of the eight perfuse-fixed brains exhibited brain damage. Diffuse nerve cell changes were found in the brains of dogs subjected to non-pulsatile blood flow. Focal brain lesions were found following both pulsatile and non-pulsatile blood flows. The lesions varied from staining pallor and rarefaction of the neuropil to total nerve cell loss and glial infiltration depending upon the duration of survival. When considered in conjunction with a previous series of experiments, these results show that the diffuse nerve cell changes associated with roller pump perfusions can be avoided by using a new pulsatile pump, but focal brain damage was not eliminated, and lung damage and mortality were not reduced.
TL;DR: In 17 patients with normal hearts undergoing thoracotomy for right-sided pulmonary diseases, a flow pattern in the superior vena cava was traced and a typical pulsatile, phasic flow pattern was obtained, similar to the pattern previously recorded in dogs.
Abstract: In 17 patients with normal hearts undergoing thoracotomy for right-sided pulmonary diseases, a flow pattern in the superior vena cava was traced Four parameters were recorded simultaneously: pressures in the right atrium and the right ventricle, ECG, and instantaneous volume flow in the superior caval vein In 3 of the patients arrhythmias occurred, and in 1 patient the tracings were technically unsuccessful In the remaining 13 patients a typical pulsatile, phasic flow pattern was obtained, similar to the pattern previously recorded in dogs The theories about the active role of the heart on venous return to the right heart are briefly reviewed, and a more up-to-date view is presented
TL;DR: The monitoring of cervical ICA flow proved to be a reliable way to supervise the procedure and to give an indication of the collateral capacity of the cerebral vasculature and of the tolerance to trap ligation of the ICA.
Abstract: ✓ A method for intraoperative evaluation of the hemodynamic state in patients with carotid-cavernous fistula is described. Electromagnetic flow probes were applied on the internal carotid artery (ICA) in the neck and on the intracranial part of the artery distal to the fistula in five patients. Fistula “steal5 ranged from 90 to 975 ml/min. Forward flow rate in the intracranial portion of the ICA, distal to the fistula, was from 40 to 170 ml/min. The reverse flow rate during test occlusion of the ICA in the neck was between 35 and 60 ml/min. The ratio reverse flow/forward flow is assumed to give an indication of the collateral capacity of the cerebral vasculature and of the tolerance to trap ligation of the ICA. The pulsatile pattern of the intracranial ICA flow in this series varied considerably, and this parameter is also found to be of importance in the evaluation of the capacity of the collateral arterial system. The monitoring of cervical ICA flow proved to be a reliable way to supervise the procedure...
TL;DR: It is concluded that neither the inductive nor the capacitative characteristics of the aorta and peripheral vascular bed could play a significant role in the haemodynamic responses to halothane anaesthesia.
Abstract: SUMMARY Aortic input impedance, representing the effective resistance to oscillatory flow offered by the systemic vascular bed, has been measured in dogs before and during the administration of halothane, and during the infusion of phenylephrine and trimetaphan. Simultaneously, estimates of pulsatile and steady energy losses were obtained. Halothane administration had no consistent effects on aortic input impedance, but significantly reduced peak aortic power and left ventricular external (systolic) stroke work. Phenylephrine markedly increased the mean term of aortic input impedance, but had little effect on the impedance to oscillatory flow. Trimetaphan markedly decreased the mean term of aortic input impedance, but caused a moderate increase in the impedance to oscillatory flow associated with a consistent increase in the ratio of pulsatile to total work. The low values of pulsatile work by comparison with the steady and total work of the left ventricle, together with the flat pattern of aortic input impedance are in accordance with the concept that the left ventricle is effectively "decoupled" from its load resistance imposed by the systemic vascular bed, thus minimizing the work done in maintaining pulsatile flow. Within the limits of the methods used to evaluate aortic input impedance and pulsatile energy losses in the aorta, we conclude that neither the inductive nor the capacitative characteristics of the aorta and peripheral vascular bed could play a significant role in the haemodynamic responses to halothane anaesthesia.
TL;DR: The present results do not indicate the development of selective cerebral hypoxia or anaerobiosis at any time, even in the presence of moderately severe respiratory alkalosis.
Patent•
07 Sep 1972
TL;DR: A permanently implantable artificial heart utilizing a pulsatile magneto-motive pump consisting of a pump chamber, which has two cobalt rare-earth permanent magnets spaced apart relative to one another so that unlike poles of each magnet face each other across a predetermined gap, one electromagnetic coil, a ferromagnetic piston and a hydraulic fluid as mentioned in this paper.
Abstract: A permanently implantable artificial heart utilizing a pulsatile magneto-motive pump consisting of a pump chamber, which has two cobalt rare-earth permanent magnets spaced apart relative to one another so that unlike poles of each magnet face each other across a predetermined gap, one electromagnetic coil, a ferromagnetic piston and a hydraulic fluid. The complete heart consists of two separate half hearts each having one pulsatile magnetic pump, an atrium, a ventricle, respective valves and collapsible hydraulic sacs. A dc pulse applied to the coil determines the pumping stroke rate of the piston which forces hydraulic fluid in and out of the collapsible sacs causing alternating positive and negative pressure gradients in the atrium and ventricle of the heart, thus producing with the help of one directional check valves, a one-directional pulsatile blood flow circulation. The pumping mode of the pistons is designed to act counter directional to each other whereby generated torque forces are greatly neutralized. The total heart is designed to duplicate the natural heart''s pumping action by emptying both ventricles simultaneously while the atria are in the process of filling.
TL;DR: In this paper, a momentum integral solution is obtained for fully developed pulsatile flow in a circular, rigid tube of infinite length using a fourth-order polynomial with unknown coefficients to represent the radial variation of axial velocity across the tube boundary conditions applied at the tube wall and the centerline give the velocity profile in terms of centerline velocity.
TL;DR: The Strouhal number is applied to an analogue of the physiological circulation, which reproduces quasiphysiological flow conditions in a heart model and results were that stenoses having a cross-sectional area greater than 25% of the aortic area cause small losses.
Abstract: Losses of pressure, energy and performance at simulated aortic valvular stenoses have been measured with a circulation simulator, which reproduces quasiphysiological flow conditions in a heart model. In hydrodynamics, the Strouhal number is generally used in the analysis of unsteady flow. In this paper, the Strouhal number is applied to an analogue of the physiological circulation. The parameters stroke volume, pulse frequency, systolic time and cross-sectional areas of stenosis and aorta are included in the dimensionless Strouhal number. The results are presented as potential functions of the Strouhal number. Assuming that these functions are applicable to the human circulation, the cross-sectional area of a stenosis, as well as the energy and performance losses at the stenosis, can be calculated from measurements of pressure difference, stroke volume, systolic and diastolic duration and aortic diameter. A further result was that stenoses having a cross-sectional area greater than 25% of the aortic area cause small losses. However, when this area is less than 25% of the aortic area, the losses grow exponentially.
TL;DR: A two-magnet NMR flowmeter that can be used to measure pulsatile flow and the results of theoretical computations closely approximate in vitro data from a 1.6-mm ID rigid tube with respect to the shape of the NMR signal and to the proportionality of theNMR signal amplitude to flow rate.
Abstract: Nuclear magnetic resonance (NMR) techniques have been applied to the measurement of steady or quasi-steady flow by using, principally, the tag-detect method. This paper describes a two-magnet NMR flowmeter that can be used to measure pulsatile flow. The pulsatile nature of the flow causes a pulsed magnetization of the fluid, which is detected by a flow-sensitive NMR detector. A parabolic velocity profile has been assumed. The results of theoretical computations closely approximate in vitro data from a 1.6-mm ID rigid tube with respect to the shape of the NMR signal and to the proportionality of the NMR signal amplitude to flow rate. Selected in vivo results are also presented.
TL;DR: The arterial pulsatile waveform obtained by square-wave electromagnetic flowmeter in the diagnosis and therapy of the adductor canal syndrome was an effective aid in the selection and evaluation of treatment.
Abstract: A case of the adductor canal syndrome, successfully treated, is presented. The use of the arterial pulsatile waveform obtained by square-wave electromagnetic flowmeter in the diagnosis and therapy of the syndrome is described. Analysis of the arterial waveform before and after surgery was an effective aid in the selection and evaluation of treatment.
TL;DR: Steady and pulsatile flows through model branches simulating those of the arterial system were studied using flow birefringence to suggest the most probable physical mechanism for initiating the wall trauma associated with atherosclerotic disease.
Abstract: Steady and pulsatile flows through model branches simulating those of the arterial system were studied using flow birefringence.
TL;DR: Flow-regulated vs pressure-regulated and pulsatile vs nonpulsatile coronary perfusion in the fibrillating heart were studied in dogs and it was found that thebesian shunt flow fluctuated widely during coronary perfusions.
Abstract: Flow-regulated vs pressure-regulated and pulsatile vs nonpulsatile coronary perfusion in the fibrillating heart were studied in dogs. Conventional total cardiopulmonary bypass was employed and coronary perfusion was achieved via the aortic root. The coronary sinus and right and left ventricles were separately cannulated for drainage and blood sampling for the calculation of oxygen consumption and coronary vascular resistance. It was found that thebesian shunt flow fluctuated widely during coronary perfusion. When shunt flow increased suddenly, flowregulated coronary perfusion could not meet the flow requirements, resulting in inadequate perfusion, in contrast to pressureregulated perfusion. With pulsatile coronary perfusion it was found that (1) fluctuation of thebesian shunt flow was less, and (2) myocardial oxygen consumption and coronary vascular resistance were more stable than with nonpulsatile coronary perfusion.
TL;DR: A simple model is used and it is suggested that the degree of fluctuation in the pressure gradient at a given station is the major factor in determining the level of wall shear at that point.
01 Jan 1972
01 Nov 1972
TL;DR: In this paper, a signal processing system has been developed which measures the period of one or more oscillations in the frequency burst caused by a scattering particle passing through the control volume.
Abstract: Servo valves find their major application in high performance hydraulic control systems where the accurate control of position, velocity and load is essential. Because of this, it is important to determine the dynamic characteristics of the servo valve (i.e. flow rate as a function of input command signal) more precisely. Previous techniques for this evaluation depended on monitoring spool position using linear transducers, since flow measurement techniques capable of following fast transients and oscillating (or pulsating) flows were not easily applied. The introduction of the laser Doppler anemometer changes this. Steady state flow measurement, using the dual beam scatter system, is now common but since it needs a spectrum analyser to measure the Doppler frequency it is not suitable for unsteady flow. Since hydraulic systems are relatively particle free, the Doppler signals are dreceived intermittently. Because of this, a signal processing system has been developed which measures the period of one or more oscillations in the frequency burst caused by a scattering particle passing through the control volume. Using this technique steady and unsteady laminar flow profiles have been measured in order to assess its effectiveness in the performance testing of hydraulic servo systems.