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PubMed1995

Time resolved flow quantification with MRI using phase methods: a linear systems approach.

Phase-related unsteady (pulsatile) flow effects in MRI have been studied by means of linear response theory. These flow effects can be described in the frequency domain: the influence of the gradients on the phase shift is described by a transfer function, the spectrum of the gradient being the determining factor. An analysis of this transfer function is shown to provide information about the process of flow encoding: instant of encoding, induced distortions and how they are related to the gradient waveform. The connection with the traditional description in terms of the gradient moment expansion has also been investigated and clarified. This approach was applied to study the response of two time-resolved flow quantification techniques (Fourier flow method and phase mapping) by analyzing their amplitude and phase transfer functions. By simulation it is shown that a better interpretation of the measured velocity waveform is obtained and that Fourier analysis in combination with a correction by the inverse transfer function results in an accurate reconstruction of the velocity waveform studied.

Algorithms↗
PubMed2002

An analysis of turbulent shear stresses in leakage flow through a bileaflet mechanical prostheses.

In this work, estimates of turbulence were made from pulsatile flow laser Doppler velocimetry measurements using traditional phase averaging and averaging after the removal of cyclic variation. These estimates were compared with estimates obtained from steady leakage flow LDV measurements and an analytical method. The results of these studies indicate that leakage jets which are free and planar in shape may be more unstable than other leakage jets, and that cyclic variation does not cause a gross overestimation of the Reynolds stresses at large distances from the leakage jet orifice.

Blood Flow Velocity↗
PubMed2001

Flow field and oscillatory shear stress in a tuning-fork-shaped model of the average human carotid bifurcation.

The oscillatory shear index (OSI) was developed based on the hypothesis that intimal hyperplasia was correlated with oscillatory shear stresses. However, the validity of the OSI was in question since the correlation between intimal thickness and the OSI at the side walls of the sinus in the Y-shaped model of the average human carotid bifurcation (Y-AHCB) was weak. The objectives of this paper are to examine whether the reason for the weak correlation lies in the deviation in geometry of Y-AHCB from real human carotid bifurcation, and whether this correlation is clearly improved in the tuning-fork-shaped model of the average human carotid bifurcation (TF-AHCB). The geometry of the TF-AHCB model was based on observation and statistical analysis of specimens from 74 cadavers. The flow fields in both models were studied and compared by using flow visualization methods under steady flow conditions and by using laser Doppler anemometer (LDA) under pulsatile flow conditions. The TF-shaped geometry leads to a more complex flow field than the Y-shaped geometry. This added complexity includes strengthened helical movements in the sinus, new flow separation zone, and directional changes in the secondary flow patterns. The results show that the OSI-values at the side walls of the sinus in the TF-shaped model were more than two times as large as those in the Y-shaped model. This study confirmed the stronger correlation between the OSI and intimal thickness in the tuning-fork geometry of human carotid bifurcation, and the TF-AHCB model is a significant improvement over the traditional Y-shaped model.

Adult↗
PubMed1999

Non-invasive measurement of mechanical properties of arteries in health and disease.

Major conduit arteries should, by their elastic nature, be able to store blood volume temporarily during systole and release it during diastole. This reduces the systolic blood pressure required for the flow of a given volume quantity and gradually suppresses the pulsatile flow pattern. The haemodynamic characteristics of arteries have consequences for the load of the heart but also for the mechanical load of the arterial wall. The repetitive stretching of the wall (strains of up to 10 per cent) may cause fragmentation of the elastic fibres in the wall, modifying wall elasticity. To maintain wall stress the elastic arteries respond with a diameter increase in combination with an increase of arterial wall thickness. A larger diameter for a smaller distension (change in artery diameter from diastole to systole) will restrict the reduction in storage capacity. Alternatively, pulse pressure may go up increasing the mechanical load on the wall. In recent years various methods have been developed to assess and monitor the above interaction. Most of these methods are based on ultrasound techniques because of its wide availability and its non-invasive and non-traumatic nature. Presently these techniques enable the assessment of wall thickness, diastolic diameter, distension waveform, i.e., the tie-dependent change in diameter, the relative pulsatile increase in diameter, and pulse wave velocity, for elastic and muscular arteries in humans but also in small animals such as rats and mice. The present paper discusses the techniques in more detail.

Arteries↗
PubMedDate not supplied

The NMR blood flowmeter--applications.

Nuclear Magnetic Resonance (NMR) permits the noninvasive measurement of blood flow signals unimpaired by clothes, bandages, casts, etc. The cylindrical crossed-coil NMR blood flowmeter was used to measure blood flow through a cross-section of the human forearm. Two calibration procedures are described: one for pulsatile flows and the other for flows with a high non-pulsatile component. Flow measurements from normal arms, from limbs with arterial obstruction, arteriovenous hemodialysis fistulas or other conditions are reported. An application of the flow scanning technique for separation of flow signals from individual arteries (e.g., ulnar and radial) is described. The flat crossed-coil NMR flowmeter was applied to detect blood flow from individual arteries (e.g., brachial, popliteal, etc.). Applications of a ranging technique developed to detect signals at predetermined depths are described.

Arteriosclerosis↗
PubMed2006

Initial European clinical experience with pulsatile extracorporeal membrane oxygenation.

BACKGROUND: Extracorporeal membrane oxygenation (ECMO) for post-cardiotomy heart failure in neonates and infants still carries high mortality and morbidity rates. In this study we present the first European clinical experience with the Medos DeltaStream DP1, a new pulsatile flow pump, in neonates and infants. METHODS: The DP1 is an extracorporeal rotary blood pump. The pump features a diagonal flow impeller, and can be used for both continuous and pulsatile output. Special characteristics include its small priming volume of approximately 30 ml and a high pumping capacity. A temperature sensor and speed sensors are integrated into the pump. The pump has a delivery rate of up to 8 liters/min and a speed range of 100 to 10,000 rpm. RESULTS: Two patients being assisted with the pulsatile pump system were successfully weaned after 36 and 53 hours, respectively. CONCLUSIONS: Based on our limited experience with 2 patients, we believe that pulsatile DP1 device is a reasonable alternative to current conventional non-pulsatile systems.

Cardiac Surgical Procedures↗
PubMed2003

The influence of cardiopulmonary bypass flow characteristics on the clinical outcome of 1820 coronary bypass patients.

OBJECTIVE: To determine whether pulsatile perfusion is clinically beneficial for adult cardiac operations. METHODS: Data concerning consecutive patients undergoing isolated coronary bypass surgery (n=1820) from January 1, 1997 to July 31, 1999 were reviewed. RESULTS: Nine hundred fifteen patients received pulsatile perfusion (PP) while perfusion in the remaining 905 patients was nonpulsatile (NP). Patients in the PP group were older (64.0 +/- 9.2 years versus 63.1 +/- 9.9 years) and experienced more of the following: urgent operations (42.4% versus 38.0%), preoperative intra-aortic balloon pump (4.8% versus 1.8%), preoperative cerebrovascular accidents (CVA; 3.1% versus 1.3%) and renal insufficiency (10.5% versus 7.0%). The PP group had higher incidence of early postoperative mortality (2.6% versus 1.5%), CVA (3.1% versus 1.3%), need for dialysis (3.2% versus 2.2%) and longer hospital stay (9.2 +/- 8.3 days versus 8.5 +/- 5.8 days). The incidence of postoperative myocardial infarction and renal dysfunction was similar in both groups (2.0% versus 2.2% and 3.3% versus 3.9% respectively; not significant). Because of the significant difference in preoperative parameters for the PP and NP groups, the following three statistical techniques were used to isolate the effect of perfusion characteristics on operative outcome: multiple regression, propensity score and risk stratification. Multivariate analysis did not find PP to be protective against mortality, morbidity and mortality, and CVA or for the development of postoperative renal dysfunction. When propensity score analysis was applied, the incidence of cardiac morbidity and mortality was strongly associated with the quintile (first quintile 6.7%, fifth quintile 27.0%, P<0.001). Multivariate analysis including quintiles did not find PP to be an independent predictor for mortality or for morbidity and mortality. Risk stratification was performed for age and for preoperative creatinine clearance levels. In all groups, PP did not seem to reduce the incidence of morbidity, morbidity and mortality, or the development of postoperative renal dysfunction. In patients with preoperative renal dysfunction, mean postoperative creatinine levels and the need for dialysis following surgery were similar in the PP and NP groups. CONCLUSION: Pulsatile flow does not appear to offer any clinical benefit over nonpulsatile flow for cardiac surgery patients.

Aged↗
PubMed2000

Opposite effects of pressurized steady versus pulsatile perfusion on vascular endothelial cell cytosolic pH: role of tyrosine kinase and mitogen-activated protein kinase signaling.

Endothelial cytosolic pH (pH(i)) modulates ion channel function, vascular tone, and cell proliferation. Steady shear induces rapid acidification in bicarbonate buffer. However, in vivo shear is typically pulsatile, potentially altering this response. We tested effects and mechanisms of pH(i) modulation by flow pulsatility, comparing pressurized steady versus pulse-flow responses in bovine aortic endothelial cells cultured within glass capillary tubes. Cells were loaded with the fluorescent pH(i) indicator carboxy seminaphthorhodafluor-1 and perfused with physiological pulsatile pressure and flow generated by a custom servo-control system. Raising mean pressure from 0 to 90 mm Hg at 0.5 mL/min steady flow in bicarbonate buffer induced sustained acidification (-0.33+/-0.09 pH units, P<0.01). A subsequent increase in steady flow resulted in further acidification. In contrast, if mean pressure and flow were unchanged but perfusion made pulsatile, pH(i) rose +0.3+/-0.03 (P<0. 0001) over 30 to 60 minutes. HCO(3)(-) removal and use of acid/base exchange inhibitors 5-(N-ethyl-N-isopropyl)amiloride or diisothiocyanato stilbene disulfonic acid identified both extracellular Na(+)-independent Cl(-)-HCO(3)(-) and Na(+)-H(+) exchangers as activated by static pressure, whereas pulsatility activated extracellular Na(+)-dependent Cl(-)-HCO(3)(-) and Na(+)-H(+) exchangers to raise pH(i). Pulse-perfusion alkalinization occurred with or without flow reversal and increased 1.6-fold in Ca(2+)-free buffer. Inhibition of c-Src tyrosine kinase (4-amino-5-[4-chlorophenyl]-7-[t-butyl]pyrazolo [3,4-d]pyrimidine; PP2) or MEK-1 (mitogen-activated protein kinase [MAP]/extracellular signal-regulated kinase [ERK]-1) (PD98059, blocking ERK1/2) blocked or reversed the pulsatile-flow pH(i) change to acidification. In contrast, PP2 had no effect on steady flow acidification, whereas MEK-1 inhibition converted it to alkalinization. Thus, pulsatile and steady flow trigger opposite effects on endothelial pH(i) by differential activation of acid/base exchangers linked to c-Src and MAP kinase phosphorylation, but not to Ca(2+). These data highlight specific signaling responses triggered by phasic shear profiles.

Animals↗
PubMedDate not supplied

Flow velocities after carotid artery stenting: impact of stent design. A fluid dynamics study in a carotid artery model with laser Doppler anemometry.

PURPOSE: To study the influence of a newly developed membrane stent design on flow patterns in a physiologic carotid artery model. METHODS: Three different stents were positioned in silicone models of the carotid artery: a stainless steel stent (Wall-stent), a nitinol stent (SelfX), and a nitinol stent with a semipermeable membrane (MembraX). To increase the contact area of the membrane with the vessel wall, another MembranX model was modified at the outflow tract. The membrane consists of a biocompatible silicone-polyurethane copolymer (Elast-Eon) with a pore size of 100 mum. All stents were deployed across the bifurcation and the external carotid artery origin. Flow velocity measurements were performed with laser Doppler anemometry (LDA), using pulsatile flow conditions (Re = 220; flow 0.39 l/min; flow rate ratio ICA:ECA = 70:30) in hemodynamically relevant cross-sections. The hemodynamic changes were analyzed by comparing velocity fluctuations of corresponding flow profiles. RESULTS: The flow rate ratio ICA:ECA shifted significantly from 70/30 to 73.9/26.1 in the MembraX and remained nearly unchanged in the SelfX and Wallstent. There were no changes in the flow patterns at the inflow proximal to the stents. In the stent no relevant changes were found in the SelfX. In the Wallstent the separation zone shifted from the orifice of the ICA to the distal end of the stent. Four millimeters distal to the SelfX and the Wallstent the flow profile returned to normal. In the MembraX an increase in the central slipstreams was found with creation of a flow separation distal to the stent. With a modification of the membrane this flow separation vanished. In the ECA flow disturbances were seen at the inner wall distal to the stent struts in the SelfX and the Wallstent. With the MembraX a calming of flow could be observed in the ECA with a slight loss of flow volume. CONCLUSIONS: Stent placement across the carotid artery bifurcation induces alterations of the physiologic flow behavior. Depending on the stent design the flow alterations are located in different regions. All the stents tested were suitable for the carotid bifurcation. The MembraX prototype has shown promising hemodynamic properties ex vivo.

Alloys↗
PubMed2003

The effect of age on ocular blood supply determined by pulsatile ocular blood flow and color Doppler ultrasonography.

PURPOSE: Pulsatile ocular blood flow (POBF) assessment measures the choroidal circulation and provides diagnostic value to certain ocular diseases such as glaucoma. This technique assumes a constant ocular rigidity and is influenced by axial length, diurnal variation, and age. This study investigated the effect of age on POBF, with consideration of the above factors. Ocular blood supply in the ophthalmic artery was also determined using color Doppler ultrasonography. METHODS: A total of 118 healthy subjects aged 19 to 75 years were recruited. They were divided into five groups (below age 30, 30 to 39, 40 to 49, 50 to 59, and 60 or above) of at least 20 subjects each. Only one eye of each subject, with axial length <24.5 mm, was considered. The subject's supine POBF was determined followed by a measurement of the blood flow velocity in the ophthalmic artery using color Doppler ultrasonography. All the measurements were at around the same time of day to eliminate any effect from diurnal variation. The scleral rigidity was measured using a Schiotz tonometer with 5.5- and 7.5-g weights. RESULTS: Linear regression analysis demonstrated a significant increase of scleral rigidity with age (Pearson correlation coefficient r = 0.26, p < 0.01) and a significant decrease of POBF with age (r = -0.35, p < 0.01). The reduction in peak systolic velocity in the ophthalmic artery with age was significant (r = -0.28, p < 0.01). Both the systolic and diastolic brachial pressure showed significant increase with age (r = 0.55, p < 0.01; r = 0.40, p < 0.01, respectively). Using multiple regression analysis, POBF showed a significant correlation with age (partial correlation r = -0.36, p < 0.01), but not with scleral rigidity or systolic or diastolic brachial pressure. The peak systolic velocity in the ophthalmic artery also showed significant correlation with age (partial correlation r = -0.29, p < 0.01). CONCLUSIONS: The reduction in POBF with age was significant. Although aging affects scleral rigidity and systemic blood pressure, multiple regression analysis indicates that the most influential factor affecting POBF is aging. The peak systolic velocity in the ophthalmic artery also decreased with age, indicating reduced ocular blood supply.

Adult↗
PubMed2007

Endocrine function is not impaired in patients with a continuous MicroMed-DeBakey axial flow pump.

OBJECTIVES: Pulsatile blood flow has been regarded to be of importance for the regulation of endocrine organs. A new generation of continuous flow mechanical blood pumps is now available for clinical application. Patients with implanted MicroMed-DeBakey axial pumps show nonphysiologic low-pulsatile blood flow profiles, and therefore it appeared to be of interest to evaluate their possible effect on the endocrine system. METHODS: Eight male patients and 1 female patients (mean age, 51 +/- 10 years) with end-stage left-sided heart failure were implanted with a MicroMed-DeBakey axial pump. After a mean period of 67 +/- 19 days, basal pituitary hormone concentrations and their responses to a bolus injection of hypothalamic releasing hormones were tested. In addition, thyroid hormones, testosterone, and plasma and urinary catecholamine levels were measured at baseline. RESULTS: Administration of the hypothalamic releasing hormones revealed normal responses of all pituitary hormones (adrenocorticotropic hormone, thyroid-stimulating hormone, luteinizing hormone, and prolactin), except for growth hormone, the response of which was slightly impaired (10.2 +/- 6.8 vs 19.9 +/- 6.5 ng/L, P < .05). Also, the cortisol response to the corticotropin-releasing hormone-stimulated adrenocorticotropic hormone release was normal, as were basal concentrations of thyroid hormones (triiodothyronine, thyroxine, free triiodothyronine, and free thyroxine), testosterone, and urinary catecholamines. CONCLUSIONS: Implantation of a continuous flow axial pump with low-pulsatile blood flow profile appears to have no major effect on the hypothalamic-pituitary-endorgan system and sympathoadrenal functions. This finding is reassuring for the growing number of patients treated with this convenient new pump and could contribute considerably to their prognosis and quality of life.

Catecholamines↗
PubMed1984

Effect of mild atherosclerosis on flow resistance in a coronary artery casting of man.

An in-vitro flow study was conducted in a mildly atherosclerotic main coronary artery casting of man using sugar-water solutions simulating blood viscosity. Steady flow results indicated substantial increases in pressure drop, and thus flow resistance at the same Reynolds number, above those for Poiseuille flow by 30 to 100 percent in the physiological Reynolds number range from about 100 to 400. Time-averaged pulsatile flow data showed additional 5 percent increases in flow resistance above the steady flow results. Both pulsatile and steady flow data from the casting were found to be nearly equal to those from a straight, axisymmetric model of the casting up to a Reynolds number of about 200, above which the flow resistance of the casting became gradually larger than the corresponding values from the axisymmetric model.

Arteriosclerosis↗
PubMed1993

Biventricular repair of hypoplastic right ventricle assisted by pulsatile bidirectional cavopulmonary anastomosis.

The right ventricle in patients with severe outflow obstruction or atresia and a small tricuspid valve often remains too hypoplastic even after optimal palliation to tolerate biventricular repair with closure of the atrial septal defect. In these patients, nonpulsatile cavopulmonary (Glenn) anastomosis has traditionally facilitated biventricular repair. In 1989, Billingsley and associates reported the addition of a bidirectional cavopulmonary anastomosis to the definitive biventricular repair in patients with hypoplastic right ventricle, pulmonary atresia, and intact ventricular septum. The atrial septal defect was left open with an adjustable snare for later closure. We report five patients with hypoplastic right ventricle (mean diastolic volume 48.4%, mean stroke volume 40.2% of predicted value) who had the atrial septal defect closed at the time of the biventricular repair. Four patients, who had the bidirectional cavopulmonary anastomosis supplementing the biventricular repair, had no evidence of excessive right atrial or superior vena cava hypertension postoperatively. One patient, who had atypical tetralogy of Fallot with tricuspid stenosis, developed recurrent pericardial tamponade and marked hepatomegaly following conventional tetralogy repair with closure of the atrial septal defect. These complications were controlled with the addition of bidirectional cavopulmonary anastomosis 2 months later. Postoperative hemodynamic or Doppler studies in these patients revealed pulsatile flow in the entire pulmonary artery system, including the artery distal to the Glenn anastomosis. This modification of biventricular repair allows primary closure of the atrial septal defect and provides pulsatile arterial flow in the entire pulmonary artery, even when the right ventricle is significantly hypoplastic.

Adult↗
PubMedDate not supplied

Pulsatile ocular blood flow during pregnancy.

PURPOSE: To study pulsatile ocular blood flow (POBF) throughout pregnancy. METHODS: We enrolled twenty-seven healthy women in the first trimester of gestation, only ten of which were followed through the second trimester, and fourteen non pregnant healthy women. In each subject we measured POBF with the POBF pneumotonometer (OBF Ltd. UK), IOP, blood pressure (BP) and heart rate (HR). An unpaired Student t-test was used to compare pregnant women with non-pregnant women, and a two-tailed paired Student t-test was used to compare the same women in the first and second trimester of pregnancy. p <0.05 is considered statistically significant. RESULTS: Results are presented as means +/- SD. In the first trimester of pregnancy the age was 32 +/- 6, POBF 1516.4 +/- 382 ml/min, IOP 13 +/- 3 mmHg, BP 92 +/- 6 mmHg, and HR 86 +/- 14 beats/min. In the second trimester POBF was 1629.11 +/- 352.4 ml/min, intraocular pressure (IOP) 12 +/- 3 mmHg, BP 96 +/- 3 mmHg, and HR 93 +/- 10 beats/min. In the control group the age was 27 +/- 9, POBF 972.23 +/- 329.3 ml/min, BP 88 +/- 4.3 mmHg, and HR 80 +/- 14 beats/min. POBF increases during the first trimester (p = 0.00008). In the second trimester POBF was higher compared to the first trimester (p = 0.0008). Non significant differences were observed for the other parameters. CONCLUSIONS: The POBF increases throughout gestation. During pregnancy there is an increase in estrogen which induces endothelial-dependent vasodilatation in several tissues. The estrogen changes may influence POBF.

Adolescent↗
PubMed1993

Pulsatile low-flow perfusion for enhanced cerebral protection.

We examined the oxygen tension, carbon dioxide tension, and pH in canine brains under profound hypothermia to evaluate the effects of perfusion (circulatory arrest for 1 hour; 25 and 50 mL.kg-1 x min-1 for 2 hours) with and without pulsatile assistance. The effects of pulsatile flow on cerebral blood flow and metabolism were also evaluated in dogs supported by low-flow perfusion (25 mL.kg-1 x min-1) for 2 hours. Profound hypoxia occurred in the brain after 20 to 60 minutes of circulatory arrest. Brain tissue acidosis with hypercapnia was moderated by perfusion at a rate of flow of 50 mL.kg-1 x min-1. Pulsatile low-flow perfusion (25 mL.kg-1 x min-1) moderated cerebral hypercapnia and made the cerebral metabolism aerobic without affecting the total cerebral blood flow and consumption of oxygen.

Acid-Base Equilibrium↗
PubMed2003

In vivo imaging of human retinal flow dynamics by color Doppler optical coherence tomography.

BACKGROUND: Color Doppler optical coherence tomography (CDOCT) combines laser Doppler velocimetry and optical coherence tomography for simultaneous micron-scale resolution cross-sectional imaging of tissue microstructure and blood flow. Recently, CDOCT was adapted to a slitlamp biomicroscope for imaging structure and blood flow in the human retina. OBJECTIVE: To demonstrate feasibility of CDOCT for imaging retinal hemodynamics. DESIGN: Enabling CDOCT to measure retinal blood flow pulsatility in humans. SETTING: Laboratory. MAIN OUTCOME MEASURES: Time-resolved flow profiles and images of retinal blood flow dynamics for measurement of pulsatility within retinal vessels. RESULTS: Rapid sequences of images were acquired over selected vessels near the optic nerve head. From these images, retinal blood flow profiles were extracted and synchronized to an external reference obtained with a photoplethysmograph. Each profile was acquired in less than 10 milliseconds. CONCLUSIONS: Our results indicate that CDOCT provides laser Doppler information in addition to conventional optical coherence tomography, allowing the observation of blood flow dynamics simultaneous to imaging retinal structure. CDOCT is a promising technology for research and clinical studies of retinal blood flow dynamics. CLINICAL RELEVANCE: Blood flow dynamics, such as pulsatility and autoregulation, have been shown to change throughout the progression of diabetic retinopathy and glaucoma. Enabling CDOCT to observe retinal dynamics improves its potential as a clinical diagnostic tool.

Blood Flow Velocity↗
PubMed1994

The application of breath hold phase velocity mapping techniques to the measurement of coronary artery blood flow velocity: phantom data and initial in vivo results.

A segmented kappa-space breath hold phase velocity mapping technique has been developed for the study of coronary artery blood flow velocity. In vitro validation has been performed using a number of pulsatile flow phantoms and the accuracy of the technique for determining the velocity increase at the site of a stenosis demonstrated in several phantom models. Examples of both in-plane and through-plane velocity maps of the left anterior descending and right coronary arteries of normal subjects in early diastole are presented. In one subject, through-plane velocity maps were obtained in the right and left anterior descending arteries throughout the cardiac cycle in order to generate flow velocity time curves. The problems associated with coronary artery velocity mapping are discussed.

Artifacts↗
PubMedDate not supplied

Effects of blood phase oscillation on gas transfer in a microporous intravascular lung.

It may be possible to design an intravascular membrane lung with gas transfer properties augmented by the natural flow oscillations in the venous and pulmonary circulation caused by the beating heart and ventilatory movements. The authors used a simple dye visualization technique, the Pierce-Donachy assist pump, and mass spectrometry to investigate these effects on membrane lungs made with tethered, blind-ended, microporous, polypropylene fibers using in vitro tests in water saturated with O2, CO2, and He. Prototypes were constructed on a 7.5 Fr pulmonary artery catheter. The fibers had an outer diameter (OD) of 380 microns and a wall thickness of 50 microns and were mounted on 4.8 mm OD sleeves. Control measurements were taken over a range of steady water flows from 0.4 l/min to 3 l/min. While pumping the same water flow rates with a roller pump, the Pierce-Donachy pump generated pulsatile flow at a rate of 45 beats/min and a systolic duration of 300 msec. This produced a phasic flow with an instantaneous average flow velocity varying from 0 to as high as 46 cm/sec. O2 and CO2 transfer increased by as much as 91% and 59%, respectively. The largest effects were seen at the lower water flow rates.

Artificial Organs↗