Showing papers on "Pulsatile flow published in 1979"
Journal Article•
TL;DR: Application of this device to the thenar eminence of 4 healthy subjects showed that externally applied pressure was approximately twice as effective as shear in reducing pulsatile arteriolar blood flow.
299 citations
TL;DR: Findings suggest a link between the neuroendocrine mechanisms that initiate such episodic secretion and those responsible for the onset of flush episodes.
Abstract: Menopausal flush episodes were found to be invariably associated with the initiation of pulsatile pituitary release of luteinizing hormone. This was not accompanied by a significant change in circulating catecholamine or prolactin concentrations. Since pulsatile luteinizing hormone release results from episodic secretion of luteinizing hormone releasing factor by the hypothalamus, these findings suggest a link between the neuroendocrine mechanisms that initiate such episodic secretion and those responsible for the onset of flush episodes.
252 citations
Patent•
07 May 1979
TL;DR: In this article, a sealed liquid-filled catheter is inserted into a vessel such as an artery, and the pump system is operated in timed relation with the heart to aid the heart during episodes of impairment or failure of cardiac function by producing higher frequency pulsation or pressure waves within the blood during diastole and during the isometric contraction period of the heart.
Abstract: A dynamically augmenting pump system incorporates a sealed liquid-filled catheter which is inserted into a vessel such as an artery, and the pump system is operated in timed relation with the heart to aid the heart during episodes of impairment or failure of cardiac function by producing higher frequency pulsation or pressure waves within the blood during diastole and during the isometric contraction period of the heart. This frequency of pulsation is adjusted to the dynamic transmission characteristics of a selected circulatory subsystem, such as the coronary vascular system, to assure the transmission of a maximum of pulsatile energy into the subsystem. The catheter provides energy to maintain adequate blood flow through the healthy part of the myocardium and has a passage for injecting successive quantities of medication into the coronary arteries. The pump system also functions to penetrate the ischemic myocardial tissue with arterial blood and medication. The pump system may also be used to provide enhanced perfusion for other parts of the systemic circulatory system, for example, to prevent such detrimental effects as renal failure. Any one or combination of the functions may be used depending on the special medical conditions of the patient.
155 citations
TL;DR: Results indicate that pulsatile cardiopulmonary bypass prevents the rise in PVRI associated with non-pulsatile perfusion, and that this effect may be achieved by preventing excessive activation of the renin-angiotensin system, thus producing significantly lower plasma concentrations of the vasoconstrictor angiotens in II.
Abstract: The effects of pulsatile and non-pulsatile cardiopulmonary bypass (CPB) on levels of peripheral vascular resistance and plasma angiotensin II (AII) have been studied in 24 patients submitted to elective cardiac surgical procedures. Twelve patients had conventional non-pulsatile perfusion throughout the period of CPB (non-pulsatile group), while 12 had pulsatile perfusion during the central period of total CPB, using the Stockert pulsatile pump system (pulsatile group). There were no significant differences between the groups in respect of age, weight, bypass time, cross-clamp time, or in mean pump flow or mean perfusion pressure at the onset of CPB. Peripheral vascular resistance index (PVRI) and plasma AII levels were measured at the onset of total CPB and at the end of total CPB. In the non-pulsatile group PVRI rose from 19.6 units to 29.96 units during perfusion. In the pulsatile group PVRI showed little change from 20.89 units to 21.45 units during perfusion (P less than 0.001). Plasma AII levels (normal less than 35 pg/ml) rose during perfusion from 49 pg/ml to 226 pg/ml in the non-pulsatile group. The rise in the pulsatile group from 44 pg/ml to 98 pg/ml was significantly smaller than that in the non-pulsatile group (P less than 0.01). These results indicate that pulsatile cardiopulmonary bypass prevents the rise in PVRI associated with non-pulsatile perfusion, and that this effect may be achieved by preventing excessive activation of the renin-angiotensin system, thus producing significantly lower plasma concentrations of the vasoconstrictor angiotensin II.
139 citations
01 Jan 1979
TL;DR: The effects of pulsatile and non-pulsatile cardiopulmonary bypass (CPB) on levels of peripheral vascular resistance and plasma angiotensin II (AII) have been studied in 24 patients submitted to elective cardiac surgical procedures as discussed by the authors.
Abstract: Theeffects ofpulsatile andnon-pulsatile cardiopulmonary bypass (CPB) onlevels ofperipheral vascular resistance andplasma angiotensin II(AII) havebeenstudied in 24patients submitted toelective cardiac surgical procedures. Twelvepatients had conventional non-pulsatile perfusion throughout theperiod ofCPB(non-pulsatile group), while 12hadpulsatile perfusion during thecentral period oftotal CPB,using theStockert pulsatile pump system(pulsatile group). There were no significant differences betweenthe groupsinrespect ofage,weight, bypass time, cross-clamp time, orinmean pump flowor mean perfusion pressureattheonsetofCPB.Peripheral vascular resistance index(PVRI) and plasma AIIlevels weremeasured attheonsetoftotal CPBandattheendoftotal CPB.Inthenon-pulsatile groupPVRIrosefrom19-6 units to29-96 units during perfusion. Inthepulsatile groupPVRIshowed little change from20-89 units to21-45 units during perfusion (P
135 citations
TL;DR: The findings suggest that there must be a region of considerable compliance in the pulmonary venous system which can absorb pulsations from the lung capillaries and eliminate their transmission to the left atrium.
Abstract: The pattern of blood flow in the large extra parenchymal pulmonary veins is pulsatile in both dog and man. This pulsatility is dominated by the changes in left atrial pressure taking place throughout the cardiac cycle. No pulsatile component of low in the large pulmonary veins could be attributed to forward transmission of a flow pulse conducted from the lung capillaries. The findings suggest that there must be a region of considerable compliance in the pulmonary venous system which can absorb pulsations from the lung capillaries and eliminate their transmission to the left atrium.
120 citations
TL;DR: The experimental results and the theory developed indicate that for a given aortic valve it is possible to predict peak systolic and mean syStolic pressure drops from experimental pressure drop data for steady flow in the same channel.
108 citations
TL;DR: The data indicate that nitroprusside acutely alters both the mean and pulsatile components of vascular load to effect improvement in ventricular function in patients with heart failure.
Abstract: Beneficial effects of nitroprusside infusion in heart failure are purportedly a result of decreased afterload through “impedance” reduction. To study the effect of nitroprusside on vascular factors that determine the total load opposing left ventricular ejection, the total aortic input impedance spectrum was examined in 12 patients with heart failure (cardiac index 20 mm Hg). This input impedance spectrum expresses both mean flow (resistance) and pulsatile flow (compliance and wave reflections) components of vascular load. Aortic root blood flow velocity and pressure were recorded continuously with a catheter-tip electromagnetic velocity probe in addition to left ventricular pressure. Small doses of nitroprusside (9-19 μg/min) altered the total aortic input impedance spectrum as significant (P < 0.05) reductions in both mean and pulsatile components were observed within 60-90 s. With these acute changes in vascular load, left ventricular end diastolic pressure declined (44%) and stroke volume increased (20%, both P < 0.05). Larger nitroprusside doses (20-38 μg/min) caused additional alteration in the aortic input impedance spectrum with further reduction in left ventricular end diastolic pressure and increase in stroke volume but no additional changes in the impedance spectrum or stroke volume occurred with 39-77 μg/min. Improved ventricular function persisted when aortic pressure was restored to control values with simultaneous phenylephrine infusion in three patients. These data indicate that nitroprusside acutely alters both the mean and pulsatile components of vascular load to effect improvement in ventricular function in patients with heart failure. The evidence presented suggests that it may be possible to reduce vascular load and improve ventricular function independent of aortic pressure reduction.
103 citations
TL;DR: A mathematical model is developed here to explain the results obtained when pressure is applied to either covered or uncovered samples, and predicts the rate of exudation in both instances should be substantially identical for a period of time ∼0.2τ, where τ is the consolidation time.
99 citations
TL;DR: In the near vicinity of the aortic prostheses, maximum values of bulk-turbulent-shear stresses estimated from turbulence-intensity measurements and simple flow models were in the range of 10 2 –10 3 dyn/cm 2, which could damage red-blood cells and platelets and lead to thrombus formation with pulsatile flow.
97 citations
TL;DR: From dog aorta investigations, it is concluded that the orientation effect on impedance plethysmography pulse waveforms nearly equals that of blood vessel diameter change, and that waveform analysis must consider both effects.
Abstract: Erythrocyte orientation, deformation, and axial accumulation cause differences in resistance between flowing and resting blood. Through theoretical calculations and experimental measurements, we studied the effects of these factors and of sinusoidal and pulsatile flow on blood resistivity. The effect of axial accumulation is least significant. Frequency characteristics of blood resistance under sinusoidal and pulsatile flow showed that erythrocytes cannot orient in response to rapid flow changes of a few pulses per second. From dog aorta investigations, we conclude that the orientation effect on impedance plethysmography pulse waveforms nearly equals that of blood vessel diameter change, and that waveform analysis must consider both effects.
TL;DR: It is postulated that the thin walled extraperenchymal pulmonary veins together behave as a collapsible reservoir which enables outflow from them to be determined by changes in left atrial pressure, in spite of variations of pulsatile flow into them from the lungs.
Abstract: The wave form of blood flow in the large extra parenchymal pulmonary veins has an inverse relationship to the pressure wave form in the left atrium during each cardiac cycle.
However, when vein flow from the lungs is separated from the left atrium by diverting it into a constant pressure reservoir, its wave form then resembles a lung capillary flow pulse, though delayed from it in time and reduced in amplitude.
The pulsatility of flow in pulmonary veins separated from the left atrium is further reduced when transcapillary pressure is elevated by lung inflation. However, in the intact state, the relation between the pattern of pulmonary vein flow and left atrial pressure remains unaffected by lung inflation.
It is postulated that the thin walled extraparenchymal pulmonary veins together behave as a collapsible reservoir which enables outflow from them to be determined by changes in left atrial pressure, in spite of variations of pulsatile flow into them from the lungs.
TL;DR: Dynamic blood pressure was measured in 33 human finger nailfold capillaries after direct cannulation with glass micropipettes by means of a resistance servo-nulling pressure measuring method and all recordings exhibited pulsatile oscillations related to the cardiac rhythm.
Abstract: Dynamic blood pressure was measured in 33 human finger nailfold capillaries after direct cannulation with glass micropipettes by means of a resistance servo-nulling pressure measuring method. ECG, finger pulsations, and respiratory thorax excursions were monitored simultaneously. All recordings exhibited pulsatile oscillations related to the cardiac rhythm. These oscillations resembled the wave forms of arterial pulsations with steep upstroke and dicrotic notch when the pressure amplitudes were above 10 mmHg. There was no apparent dependence on respiration. In 12 instances, pressure fluctuations with frequencies ranging from 0.2 down to 0.07 Hz were observed in both the arteriolar and venular limb. Blood pressure in human skin capillaries is pulsatile and subject to remarkable fluctuations in the arteriolar as well as in the venular limb, systolic pressure values ranging from 14 to 71 mmHg and from 11 to 52 mmHg, respectively.
TL;DR: It is concluded that catecholamines and the renin-angiotensin system contribute to the production of postoperative hypertension and that pulsatile flow diminishes renin stimulation, which results in a decreased incidence of postoperatively hypertension.
Book•
01 Jul 1979TL;DR: In this article, the authors considered the reactive biological response of blood vessels to the effect of the laws of fluid mechanics at sites of predilection determined by local hydraulic conditions in the circulatory system.
Abstract: The laws of fluid mechanics apply to the natural conditions in the circulatory system as they apply to any hydraulic system. The effect of the laws of fluid dynamics is considered the primary factor in the development of atherosclerosis because it alone can account for the localization and progressive development of atherosclerotic lesions at specific areas of predilection characterized by curvature, branching, external attachment, or tapering. While such vascular configurations occur in many variations of geometry or anatomical pattern with corresponding variations in patterns of blood flow, their common feature is the production of localized segmental zones of diminished lateral pressure. The diminished lateral pressure or suction effect which occurs in some phase of pulsatile flow in the cardiac cycle is the initial stimulus which produces intimal proliferation as the first change in the progressive development of atherosclerosis. Atherosclerosis may therefore be considered the reactive biological response of blood vessels to the effect of the laws of fluid mechanics at sites of predilection determined by local hydraulic conditions in the circulatory system.
TL;DR: Few advantages of the PAD are seen in routine coronary bypass operations as conversion of roller pump flow to pulsatile flow by the pulsatile assist device is said to result in improved myocardial preservation and a decrease in the incidence of perioperativeMyocardial infarction.
TL;DR: CPB produces a marked vasopressin stress response which is beyond the physiological range for an antidiuretic effect on the kidney, and the addition of pulsatile flow creates a more physiological situation attenuating the vasopressed response and producing a decrease in systemic resistance and a less pronounced Na+ diuresis.
TL;DR: This hypothesis also accounts for hydrocephalus resulting from obliteration of the cortical subarachnoid space, obstruction to the cranial venous drainage, deformities in the region of the foramen magnum and arterial encroachment upon the ventricular system.
TL;DR: Thirty consecutive infants undergoing hypothermia and circulatory arrest for repair of ventricular septal defect, transposition of the great vessels, or atrioventricular canal defects were alternately selected for conventional high flow nonpulsatile perfusion or pulsatile perfusions during core cooling and rewarming to suggest that pulsatile perfume is safe and is more rapid and physiological than conventional high-flow nonpulse perfusion.
TL;DR: Experimental measurements of axial velocity profiles at various cross-sections in a curved tube due to a pulsatile flow of uniform entry are reported, and the results with respect to the hemodynamic theories of atherogenesis are briefly discussed.
TL;DR: Pulsatile GnRH produced a progressive increase in urinary gonadotropin excretion, a significant increase in mean basal plasma FSH, pulsatile LH release, and an increased LH response to a standard 3 hour GnRH infusion test.
Abstract: GnRH was administered subcutaneously in hourly pulses for 10 consecutive nights to two immature males with Kallmann's Syndrome using a portable, battery-operated infusion pump adapted for home use. Pulsatile GnRH produced a progressive increase in urinary gonadotropin excretion, a significant increase in mean basal plasma FSH, pulsatile LH release, and an increased LH response to a standard 3 hour GnRH infusion test. One subject developed a striking increment in plasma testosterone in response to GnRH pulses, as well as a biphasic LH response to the 3 hour infusion.
TL;DR: Early experience with converting enzyme inhibitors suggests that blockade of the formation of angiotensin II may be a useful means of treating some patients with heart failure.
Abstract: The effect on the left ventricle of changes in the state of the arterial vasculature is best identified by utilizing calculations of pulsatile rather than steady flow phenomena. Impedance is the most satisfactory term to describe this effect. The normal ventricle compensates for changes in impedance largely by changes in preload, but the damaged heart loses this compensatory ability and its stroke volume becomes inversely related to outflow resistance. Patients with heart failure behave in a similar fashion and pharmacologic vasodilation may induce marked improvement in left ventricular pump function. Inappropriate vasoconstriction in heart failure may result from stimulation of the sympathetic or renin-angiotensin system. Early experience with converting enzyme inhibitors suggests that blockade of the formation of angiotensin II may be a useful means of treating some patients with heart failure.
TL;DR: Analysis of the alterations in characteristic impedance suggests a distinct proximal pulmonary vascular mechanism of decreased vessel stiffness (decreased elastic moduli) for adaptation to chronically elevated flow loads which is in addition to the two geometric alterations of proximal arterial dilation and distal vascular channel recruitment.
Abstract: Pulsatile pulmonary hemodynamics were analyzed in a chronic awake canine high flow model. Standard mean flow and pulsatile flow hemodynamics were measured and alterations in the proximal pulmonary vascular physical properties were quantified by the characteristic impedance (Zo). Pulmonary vascular resistance (PVR), which assesses arteriolar-capillary recruitment of perfusing radius and measures a more distal pulmonary vascular response to changing flows, also was calculated. Twelve control dogs were studied and had mean Qpa (pulmonary blood flow) = 2.02 +/- 0.15 liters/min, Zo = 193 +/- 20 dyne sec cm-5 and PVR = 416 +/- 32 dyne sec cm-5. Ten dogs were studied awake 20 weeks after creation of bilateral arteriovenous fistulae. Five of these shunted dogs, designated group A, developed Qpa = 3-4 liters/min (mean = 3.80 +/- 0.09, P less than 0.001 different from control group); the other five dogs (group B) developed Qpa = 4-8 liters/min (mean = 5.87 +/- 0.16, P less than 0.001). In group A, Zo = 143 +/- 8 (P less than 0.05) and PVR = 249 +/- 6 (P less than 0.10). In group B, Zo = 90 +/- 5 (P less than 0.005) and PVR = 126 +/- 14 (P less than 0.01). The total input power (potential and kinetic) was 125% above the controls for group A (P less than 0.001) and 264% for group B (P less than 0.001), but the mean energy components increased significantly more than did the pulsatile components. These data demonstrate a lower impedance to pulsatile flow during chronically elevated total flow which effects a reduction in both the work load of the right ventricle and the transmission of energy to the precapillary bed. Analysis of the alterations in characteristic impedance suggests a distinct proximal pulmonary vascular mechanism of decreased vessel stiffness (decreased elastic moduli) for adaptation to chronically elevated flow loads which is in addition to the two geometric alterations of proximal arterial dilation and distal vascular channel recruitment.
TL;DR: Pulmonary hemodynamics is studied in terms of the quasi one-dimensional unsteady nonlinear fluid flow equations which are applied to the 40-odd generations of branched arterial, capillary and venous distensible vessel segments making up the four lobes of the complete lung.
TL;DR: A laser Doppler velocimeter was developed to study flow in individual vessels of the microcirculatory network and found to be in good agreement with those obtained by the diode cross-correlation method.
TL;DR: The data confirm the well known phenomena of a 'critical stenosis' in that there is little decrease in resting mean blood flow until there is a 70 to 80 stenosis (area reduction) and the oscillatory portions of the femoral artery data were more sensitive to the changes in stenosis than were the nonoscillatory parameters, which confirms previously reported findings from the thoracic aorta.
Abstract: Pulsatile haemodynamics associated with graded degrees of experimentally produced stenosis were studied in the canine femoral artery. Invasively determined pulsatile blood flow and noninvasively determined blood velocity with Doppler ultrasound were measured an average of 1.3 and 2.3 cm proximal to the stenosis, respectively. Pulsatile blood pressure was measured 0.6 cm proximal and 3.7 cm distal to the stenosis. With increasing severity of stenosis there were progressive increases in the femoral artery hydraulic input impedance moduli and in the ratio of the impedance moduli to the zero harmonic impedance (or total resistance). This resulted in: a) a progressive reduction in the Fourier harmonic moduli and pulsewave amplitudes of flow, velocity, and distal pressure; b) a progressive increase in the fifth-seventh proximal pressure harmonic moduli; but c) little change in mean proximal pressure or its first 4 harmonic moduli. The data confirm the well known phenomena of a 'critical stenosis' in that there is little decrease in resting mean blood flow until there is a 70 to 80 stenosis (area reduction). Also the oscillatory portions of the femoral artery data were more sensitive to the changes in stenosis than were the nonoscillatory parameters, which confirms previously reported findings from the thoracic aorta. However, the femoral artery haemodynamics exhibited a greater amount of frequency dependent behaviour than the thoracic aorta which is probably the result of a more complex interaction of reflections from the stenosis and from the periphery in the femoral artery than in the thoracic aorta. The sensitive changes in oscillatory haemodynamics may provide a useful basis for noninvasive and invasive physiological assessment of human peripheral atherosclerotic stenosis and of experimental stenosis in animals.
TL;DR: If lower perfusion pressures are to be tolerated in patients with left ventricular hypertrophy, pulsatile perfusion with the bubble tubing technique may prevent the development of subendocardial ischemia or infarction.
Abstract: To assess the potential benefit of pulsatile perfusion inthe hypertrophied heart during fibrillation, 10 dogs with left ventricular hypertrophy, produced by previous supravalvular aortic banding, were used to compare linear and pulsatile perfusion in the fibrillating heart during total cardiopulmonary bypass. The mass spectrometer was used to measure subendocardial PCO2 and PO2 (PmCO2 and PmO2), and radioactive microspheres were utilized to measure myocardial blood flow in the same layers. Pulsatile perfusion was established using the recently develop "bubble tubing," which produces a pulse pressure of at least 20 mm Hg and can be used in a standard roller-pump apparatus. Both linear and pulsatile flows were compared at mean aortic root pressures of 80 and 50 mm Hg, and these four combinations of aortic root pressure and type of flow were employed for periods of 30 minutes each. Myocardial ischemia developed during linear coronary perfusion at 50 mm Hg, as evidenced by an elevation of PmCO2. Ischemia was not evident during pulsatile perfusion at the same mean pressure. Reversal ischemia was a result of increased myocardial blood flow and pulsatile perfusion, and this increase was shown to occur maximally in the deeper subendocardial layer. Ischemia was not eviden during linear or pulsatile perfusion at an mean perfusion pressure 80 mm Hg. Thus, if lower perfusion pressures are to be tolerated in patients with left ventricular hypertrophy, pulsatile perfusion with the bubble tubing technique may prevent the development of subendocardial ischemia or infarction.
Journal Article•
TL;DR: Results indicate that although all currently available circulatory assist devices reduced peak left ventricular wall stress, a spectrum of relative effectiveness progressed from intra-aortic balloon pumping or pulsatile assist device alone through the combination intra- aortic Balloon pumping plus the pulsatile assistance device.
TL;DR: Pulsatile secretion of LH was eliminated in 6 of 12 rats treated with the highest dose of anti-GnRH, but plasma LH was still 50% of control values 3 h after treatment, suggesting that pulses of GnRH induce the pulsatile pattern of plasma LH and may be responsible for all LH secretion in ovariectomized rats.
Abstract: To evaluate the dependence of pulsatile secretion of luteinizing hormone (LH) on gonadotropin-releasing hormone (GnRH), the acute effects of immunoneutralization of endogenous GnRH on plasma LH were compared in ovariectomized rats with phenobarbital treatment and hypophysectomy. Anti-GnRH produced a rapid dose-dependent decrease in plasma LH and LH pulse amplitude. Pulsatile secretion of LH was eliminated in 6 of 12 rats treated with the highest dose of anti-GnRH, but plasma LH was still 50% of control values 3 h after treatment. Frequency of LH pulses was unchanged in animals which had persistence of pulsatile secretion of LH. Phenobarbital eliminated pulsatile secretion of LH transiently. Hypophysectomized rats displayed a striking decrease in plasma LH which could be resolved into two exponential components with half-lives of 16 and 70 min. The initial half-life of plasma LH from untreated rats determined after LH pulses was also 16 min. These studies support the hypothesis that pulses of GnRH induce the pulsatile pattern of plasma LH and may be responsible for all LH secretion in ovariectomized rats.