Showing papers on "Pulsatile flow published in 1991"
TL;DR: It is demonstrated that EC can discriminate between different types of pulsatile flow environments, and changes in shape and orientation changed less rapidly but cells took on a more elongated shape than their steady flow controls long-term.
Abstract: Endothelial cells (EC) appear to adapt their morphology and function to the in vivo hemodynamic environment in which they reside In vitro experiments indicate that similar alterations occur for cultured EC exposed to a laminar steady-state flow-induced shear stress However, in vivo EC are exposed to a pulsatile flow environment; thus, in this investigation, the influence of pulsatile flow on cell shape and orientation and on actin microfilament localization in confluent bovine aortic endothelial cell (BAEC) monolayers was studied using a 1-Hz nonreversing sinusoidal shear stress of 40 +/- 20 dynes/cm2 (type I), 1-Hz reversing sinusoidal shear stresses of 20 +/- 40 and 10 +/- 15 dynes/cm2 (type II), and 1-Hz oscillatory shear stresses of 0 +/- 20 and 0 +/- 40 dynes/cm2 (type III) The results show that in a type I nonreversing flow, cell shape changed less rapidly, but cells took on a more elongated shape than their steady flow controls long-term For low-amplitude type II reversing flow, BAECs changed less rapidly in shape and were always less elongated than their steady controls; however, for high amplitude reversal, BAECs did not stay attached for more than 24 hours For type III oscillatory flows, BAEC cell shape remained polygonal as in static culture and did not exhibit actin stress fibers, such as occurred in all other flows These results demonstrate that EC can discriminate between different types of pulsatile flow environments(ABSTRACT TRUNCATED AT 250 WORDS)
290 citations
TL;DR: The investigation shows complex flow patterns especially in the carotid sinus where flow separation occurs at the outer wall throughout the systolic deceleration phase and the changing sign of the velocity near the outer sinus wall results in oscillating shear stress during the pulse cycle.
Abstract: Numerical analysis of flow phenomena and wall shear stresses in the human carotid artery bifurcation has been carried out using a three-dimensional geometrical model. The primary aim of this study is the detailed discussion of non-Newtonian flow velocity and wall shear stress during the pulse cycle. A comparison of non-Newtonian and Newtonian results is also presented. The applied non-Newtonian behavior of blood is based on measured dynamic viscosity. In the foreground of discussion are the flow characteristics in the carotid sinus. The investigation shows complex flow patterns especially in the carotid sinus where flow separation occurs at the outer wall throughout the systolic deceleration phase. The changing sign of the velocity near the outer sinus wall results in oscillating shear stress during the pulse cycle. At the outer wall of the sinus at maximum diameter level the shear stress ranges from -1.92 N/m2 to 1.22 N/m2 with a time-averaged value of 0.04 N/m2. At the inner wall of the sinus at maximum diameter level the shear stress range is from 1.16 N/m2 to 4.18 N/m2 with a mean of 1.97 N/m2. The comparison of non-Newtonian and Newtonian results indicates unchanged flow phenomena and rather minor differences in the basic flow characteristics.
288 citations
TL;DR: Incubation of the donor vessel with NG-nitro-L-arginine methyl ester, an inhibitor of nitric oxide synthesis, or removal of its endothelium by rubbing abolished both the frequency- and the amplitude-dependent effects observed in the detector tissue, indicating that these were mediated by changes in EDRF release.
Abstract: We have dissociated the effects of frequency and amplitude of pulsatile flow on flow-induced release of endothelium-derived relaxing factor (EDRF) using cascade bioassay. Rat aortic segments were b...
213 citations
TL;DR: Numerical results are presented for axial and secondary flow velocity and wall shear stresses with special emphasis on the fluid dynamics in the carotid sinus, of major interest because it is affected preferentially by lesions.
212 citations
TL;DR: The results show that the complex flow in the sinus is affected by the angle variation, and the haemodynamic phenomena, which are important in atherogenesis, are more pronounced in the large angle bifurcation.
211 citations
TL;DR: Pulmonary blood flow after the total cavopulmonary shunt operation is critically dependent on changes in intrathoracic pressure, and has important implications in terms of the immediate postoperative management of these patients.
Abstract: The pattern of pulmonary blood flow was studied in three patients after a total cavopulmonary shunt procedure. Doppler studies showed a phasic pattern of flow which varied with the respiratory cycle. Pulmonary blood flow was increased with normal inspiration, and was much augmented by the Mueller manoeuvre. This suggests that flow was occurring when a negative intrathoracic pressure was generated. During a brief Valsalva manoeuvre blood flowed away from the lungs. With a sustained Valsalva manoeuvre there was no spontaneous forward flow; instead there was low velocity pulsatile pulmonary blood flow that coincided with ventricular systole. Left ventricular cavity dimensions decreased, reflecting a considerably reduced pulmonary blood flow. Pulmonary blood flow after the total cavopulmonary shunt operation is critically dependent on changes in intrathoracic pressure. This has important implications in terms of the immediate postoperative management of these patients.
131 citations
TL;DR: There was a significant reduction in weight, which did not correlate with changes in serum testosterone levels, and LH pulsatile release was not altered by training in the subset of 5 runners.
Abstract: Cross-sectional studies have suggested that total and bioavailable testosterone levels are reduced in some male athletes. Such changes may be related to loss of body weight, increased serum cortisol, and/or alterations in LH pulsatile release. To determine how endurance training may affect androgen levels, we measured serum total testosterone, sex hormone-binding globulin, free androgen index, LH, FSH, PRL, cortisol, and weight in 15 previously sedentary males. We also examined pulsatile LH release in a subset of 5 subjects. Over 6 months of training, the men increased weekly running mileage to an average of 56 km/week. Total testosterone and free androgen index levels decreased significantly. PRL and cortisol also decreased, while single sample LH and FSH remained unchanged. There was a significant reduction in weight, which did not correlate with changes in serum testosterone levels. LH pulsatile release was not altered by training in the subset of 5 runners. These data confirm previous findings of physiological reduction in serum testosterone and PRL levels and suggest that the testosterone decrease is not related to changes in LH pulsatile release, weight, or increased serum cortisol levels.
123 citations
TL;DR: Evidence that the choroidal blood flow decreases with the severity of the retinopathy in diabetes due to increased vascular resistance and a decreased ocular perfusion pressure is provided.
116 citations
TL;DR: Comparison of the values obtained in patients with glaucoma (COAG) after withdrawal of treatment with those in subjects with ocular hypertension revealed that there was no significant difference in intraocular pressure between the two groups.
Abstract: The pulsatile ocular blood flow (POBF) has been recorded in 15 patients with chronic open angle glaucoma. Measurements were performed during regular treatment with timolol 0.25% eyedrops, two weeks after withdrawal of this treatment, and then a further two weeks after its reinstitution. Readings were taken with subjects in both the erect and supine positions by means of a pneumotonometric probe to measure intraocular pressure (IOP), linked to a Langham ocular blood flow system. Assumption of the supine posture was associated with a significant increase in IOP in all phases of the study. Treatment with timolol lowered the mean IOP in comparison with the untreated phase (-4.4 (SEM 0.6) mmHg, p less than 0.001) but had no effect on the postural change. A significant reduction in POBF was recorded on assumption of the supine posture (-66 (SEM 18) microliters/min, p less than 0.001), representing a mean decrement of 19%. However, there were no significant differences in POBF between treated and untreated phases of the study. Comparison of the values obtained in patients with glaucoma (COAG) after withdrawal of treatment with those in subjects with ocular hypertension revealed that there was no significant difference in intraocular pressure between the two groups. However, both POBF (-68 (SEM 29) microliters/min) and the pulse amplitude of the intraocular pressure (ocular pulse: -0.45 (SEM) 0.14 mmHg) were significantly lower in the COAG patients. Pulsatile ocular blood flow is significantly lower in patients with chronic open angle glaucoma. Furthermore, the POBF and the postural response of these patients is not improved by the use of topical timolol therapy.
113 citations
TL;DR: The results indicate that, with reductions in flow at constant pressure in vitro, S/D ratio does not relate to calculated resistance in the same linear manner as PI and RI.
Abstract: Using an in vitro flow model, volume flow and pressure were measured to compare calculated resistance with simultaneously measured continuous-wave Doppler indices during imposed changes in downstream resistance to pulsatile flow. With stepwise reductions in flow, the peak (S) and trough (D) points of the maximum shifted-frequency envelope fell in parallel in a linear fashion until D reached zero. Pressure remained constant, and the pressure waveform remained unchanged. As calculated resistance increased, resistance index (RI) and pulsatility index (PI) both increased in a linear fashion until the point at which D became zero. However, S/D ratio was not linear, and the slope increased as resistance increased. The results obtained from microspheres suspended in water and with heparinized sheep's blood were similar. The results indicate that, with reductions in flow at constant pressure in vitro, S/D ratio does not relate to calculated resistance in the same linear manner as PI and RI.
109 citations
TL;DR: Pulsatile and circadian TSH secretions are predominantly controlled by TRH, and the 24-h TSH secretion pattern achieved under stimulation with exogenous TRH in two patients with hypothalamic destruction through surgical removal of a craniopharyngioma provided circumstantial evidence for this assumption.
Abstract: To determine the mechanism underlying pulsatile TSH secretion, 24-h serum TSH levels were measured in three groups of five healthy volunteers by sampling blood every 10 min. The influence of an 8-h infusion of dopamine (200 mg), somatostatin (500 μg), or nifedipine (5 mg) on the pulsatile release of TSH was tested using a cross-over design. The amount of TSH released per pulse was significantly lowered by these drugs, resulting in significantly decreased mean basal TSH serum levels. However, pulses of TSH were still detectable at all times. The TSH response to TRH (200 μg) tested in separate experiments was significantly lowered after 3 h of nifedipine infusion compared to the saline control value. Nifedipine treatment did not alter basal, pulsatile, or TRH-stimulated PRL secretion. The persistence of TSH pulses under dopamine and somatostatin treatment and the blunted TSH response to nifedipine infusion support the hypothesis that pulsatile TSH secretion is under the control of hypothalamic TRH. The 24-h...
TL;DR: Several non-Newtonian fluids were studied to determine how closely they simulate the flow behavior of human blood and showed large differences in velocity profiles compared to Newtonian fluids.
TL;DR: Pulsatile ocular blood flow is reduced in the supine posture, and this may result in tissue hypoxia in subjects at risk of developing glaucoma, a companion paper describes the measurement of POBF in a group of patients with chronic open angle glauca treated with topical timolol.
Abstract: Measurements of pulsatile ocular blood flow (POBF) have been recorded in a group of healthy, ocular normotensive volunteers and ocular hypertensive patients recruited from outpatients. Use of a pneumotonometric probe linked to a Langham ocular blood flow system enabled readings of intraocular pressure and its variation with heart rate (ocular pulse) to be taken in erect and supine positions. Pulsatile ocular blood flow was calculated from these values by means of the pressure-volume relationship previously described for living human eyes. Assumption of the supine posture was accompanied by a significant rise in intraocular pressure; in normal eyes (mean, with SEM) (3.1 (0.4) mmHg, p less than 0.0001) and to a greater extent in ocular hypertensive eyes (4.7 (0.6) mmHg, p less than 0.0001). The POBF did not differ significantly between normotensive and ocular hypertensive groups in either the erect or supine postures. In both groups, however, assumption of the supine posture was accompanied by a significant fall in POBF (normals: -121 (21) microliters/min, p less than 0.0001; ocular hypertensives: -75 (16) microliters/min, p less than 0.0002). These reductions in POBF represent decrements of 27.5 (3.0)% and 17.1 (3.8)% respectively. Pulsatile ocular blood flow is reduced in the supine posture, and this may result in tissue hypoxia in subjects at risk of developing glaucoma. A companion paper describes the measurement of POBF in a group of patients with chronic open angle glaucoma treated with topical timolol 0.25%.
TL;DR: Major changes in elasticity and pulsatile load are primarily due to an increase in pulmonary pressure, and the structural changes present in the HA calves' arterial wall did not separately produce any measurable changes in arterial distensibility or the oscillatory load.
Abstract: We compared main pulmonary arterial elasticity and global pulmonary arterial compliance in control and high-altitude (HA) calves to determine whether 1) changes in pulmonary arterial elasticity are contributing to an increase in the oscillatory load of the right ventricle in this model of pulmonary hypertension and 2) measured changes in stiffness of the HA calves' arterial wall are the result of both an increase in pressure and an alteration of the material properties of the HA calves' arterial wall. Newborn calves were placed at 4,300 m simulated altitude for 14 days, and control calves were kept at 1,500 m. The HA calves were then reacclimatized to 1,500 m for 24 h so that baseline pressures of the two groups were similar. Open-chest main pulmonary arterial and right ventricular micromanometric pressures, ultrasonic main pulmonary arterial diameter, and green dye flow were measured under baseline conditions and then under moderate and severely hypoxic conditions to make measurements at both baseline and increased pulmonary pressures. At elevated pressures, the pressure-diameter relationship was noted to be nonlinear, and a characteristic late systolic peaking of the right ventricular pressure waveform was seen. The Peterson pressure-strain modulus, pulse wave velocity, characteristic impedance, and global compliance (3 element windkessel) were calculated. The calculated variables were all shown to be pressure dependent, and no intrinsic differences in stiffness were seen between the control and HA animals when mean pressure was taken into account. Pulmonary arterial histology demonstrated, however, a characteristic increase in wall thickness in the HA animals. Thus, in this model of pulmonary hypertension, major changes in elasticity and pulsatile load are primarily due to an increase in pulmonary pressure. The structural changes present in the HA calves' arterial wall did not separately produce any measurable changes in arterial distensibility or the oscillatory load.
TL;DR: In this article, with the help of finite Hankel and Laplace transforms, analytic expressions for axial velocity, fluid acceleration, wall shear and instantaneous volume flow rate have been obtained.
TL;DR: It is concluded that extensive intravascular streaming accompanies supraophthalmic ICA infusions in patients and those who perform intra-arterial infusion should consider using DPPI to assure uniform drug delivery to brain.
Abstract: ✓ Intra-arterial carotid artery chemotherapy for malignant gliomas is limited by focal injuries to the eye and brain which may be caused by poor mixing of the drug with blood at the infusion site. This inadequate mixing can be eliminated in animal models with diastole-phased pulsatile infusion (DPPI) which creates 1-ml/sec spurts during the slow blood flow phase of diastole. Before treatment with intracarotid cisplatin, 10 patients with malignant gliomas were studied to determine whether intravascular streaming occurs after intracarotid infusion in humans, and if so, if it is reduced with DPPI. Regional cerebral blood flow (rCBF) studies were performed by intravenous injection of H215O and positron emission tomography. This was followed by supraor infraophthalmic internal carotid artery (ICA) injections of H215O with either continuous infusion or DPPI. Local H215O concentration in the brain was determined and the images of radiotracer distribution in the continuous infusion and DPPI studies were compared ...
TL;DR: Data demonstrate that in older patients with dilated cardiomyopathy the left ventricle is coupled to an arterial circulation that has a greater pulsatile load, despite a similar steady load, and these age-related changes in the arterial system affect the hemodynamic response to pharmacologically-induced vasodilatation.
Abstract: The effects of aging on arterial mechanical properties and the response to nitroprusside were examined in 25 patients with dilated cardiomyopathy. High-fidelity pressures were recorded with a multisensor catheter. Pulse wave velocity was determined between two sensors in the thoracic aorta. Arterial compliance was determined by an analysis of the diastolic waveform and cardiac output. At baseline, despite a similar systemic vascular resistance, the pulsatile load (e.g., arterial compliance) and wave transmission characteristics (e.g., pulse wave velocity) were altered with aging. Arterial compliance was reduced in older (greater than 50 yr, n = 8) versus younger (less than 35 yr, n = 8) patients (0.51 +/- 0.17 vs. 1.33 +/- 0.63 ml/mmHg, P less than 0.01) and intermediate in those 35-50 yr of age (n = 9, 0.72 +/- 0.40 ml/mmHg). There was a positive correlation between age and pulse wave velocity (r = +0.90). Nitroprusside infusion decreased resistance, increased arterial compliance, and lowered pulse wave velocity in all groups. Yet, advancing age was associated with a greater fall in wave velocity for a given fall in aortic pressure. The slope (K) of the relation between pulse wave velocity and aortic diastolic pressure progressively increased with age (0.01 +/- 0.03, 0.06 +/- 0.02, and 0.09 +/- 0.03 m/s-mmHg). Multiple linear regression analysis revealed a significant relation between K and age. These data demonstrate that in older patients with dilated cardiomyopathy the left ventricle is coupled to an arterial circulation that has a greater pulsatile load, despite a similar steady load. Furthermore, these age-related changes in the arterial system affect the hemodynamic response to pharmacologically-induced vasodilatation.
TL;DR: The pulsatile parameters of the CRH-41 measured with this technique at 2.5 or 5 min intervals in a series of unanesthetized male rats under basal conditions were explored quantitatively and the physiological relevance of the neurohormone's pulsatility was discussed.
Abstract: Having recently improved the sensitivity of the RIA CRH-41 measurements in perfusates from push-pull cannulas implanted in the rat median eminence, we explored quantitatively the pulsatile parameters of the CRH-41 measured with this technique at 2.5 or 5 min intervals in a series of unanesthetized male rats under basal conditions. The data were analysed by computer using 4 algorithms, i.e. Santen & Bardin, Ultra, Pulsar and Periodogram. Under a basal mean secretion rate of 15.5 pg CRH-41/15 min, the pulsatile pattern of CRH-41 release was statistically assessed with the 4 methods, with a mean pulse frequency of 3.1 c/h, pulse length of 11.6 min and a peak amplitude above mean levels of 4 pg. The respective advantages of the 4 algorithms and the physiological relevance of the neurohormone's pulsatility are discussed.
TL;DR: To investigate the influence of aging on dopaminergic modulation of pulsatile thyrotropin (TSH) secretion, changes in circulating TSH levels during the day and night are examined in healthy young and old subjects, with and without a dopamine antagonist metoclopramide.
Abstract: To investigate the influence of aging on dopaminergic modulation of pulsatile thyrotropin (TSH) secretion, we examined changes in circulating TSH levels during the day and night, with and without a...
TL;DR: The purpose of this study was to assess the accuracy of Doppler-based measurement of instantaneous aortic blood flow and waveform morphology throughout ventricular ejection when compared with an established invasive method.
Abstract: Assessment of the pulsatile mechanical behavior of the coupled left ventricle and the peripheral arterial circulation requires accurate estimation of instantaneous aortic flow. Before the availability of Doppler technologies, this could only be achieved by invasive techniques. The purpose of this study was to assess the accuracy of Doppler-based measurement of instantaneous aortic blood flow and waveform morphology throughout ventricular ejection when compared with an established invasive method. Accordingly, data from electromagnetic flow and continuous-wave aortic Doppler recordings were simultaneously acquired and compared in five monkeys over a wide range of flows generated by intravenous infusions of the beta-adrenoceptor agonist dobutamine and the alpha-receptor agonist methoxamine. Instantaneous aortic pressure was measured using a high-fidelity micromanometer-tipped catheter placed in the ascending aorta. Excellent correlations were noted for stroke volume, cardiac output, left ventricular ejection time, maximal flow velocity, and maximal rate of change of flow velocity (dQ/dtmax). When compared with electromagnetic flows, continuous-wave aortic Doppler had significantly lower times to maximal flow velocity and dQ/dtmax. Frequency domain analysis indicated that both the magnitude and phase were within +/- 6% up to the third harmonic. Instantaneous comparison disclosed that during early systole (up to 10% of ejection) Doppler was higher than electromagnetic flow rate by 11 +/- 19% (p less than 0.05). At 20-30% of systolic ejection, electromagnetic flow rates were slightly higher than Doppler (5 +/- 4% at 20% of ejection, p less than 0.001 and 2 +/- 3% at 30% of ejection, p less than 0.05). From 40% of ejection to the end of systole, flow rates using both techniques were virtually identical.(ABSTRACT TRUNCATED AT 250 WORDS)
TL;DR: Aortic diameter pulse waves apparently yield no unequivocal information as to peripheral resistance, for which purpose blood flow velocity waveform analysis would seem, at least at present, to be the only available method.
Abstract: An ultrasound phase-locked, echo-tracking system was used for noninvasive measurements of pulsatile diameter changes in the descending aorta of 60 small, for gestational age (SGA), fetuses and of 60 fetuses appropriate for gestational age (AGA). Pulsed Doppler ultrasound was used for the recording of blood flow velocity in the aorta and in the umbilical artery of the SGA fetuses. In the SGA fetuses, a weight-related higher end-diastolic diameter and a lower relative pulse amplitude suggest that diastolic blood pressure was increased; a less steep rise of the initial ascending part of the pulse wave and a lower relative pulse amplitude suggest that the absolute stroke volume was decreased. Except for a positive correlation between relative pulse amplitude and mean velocity in the aorta, no correlation was found between diameter pulse waves and blood flow velocity. Aortic diameter pulse waves apparently yield no unequivocal information as to peripheral resistance, for which purpose blood flow velocity waveform analysis would seem, at least at present, to be the only available method.
TL;DR: The body weight gains in both sexes of hypophysectomized rats were much greater when rat growth hormone was introduced to the animals in a masculine (pulsatile) pattern that appeared to be independent of pulse frequency, rather than in a continuous feminine profile.
Abstract: Hypophysectomy resulted in a total elimination of measurable circulating growth hormone with an associated loss of body weight gain. The typical sexually dimorphic plasma growth hormone patterns: pulsatile profiles in male rats and tonic-like secretion in female rats, were lost. The male- and female-dependent profiles of plasma growth hormone, monitored from serial blood collections, were restored by administering the hormone through a single electrically controlled external pump attached to an indwelling catheter, and by implanting osmotic pumps intraperitoneally, respectively. Restoring the natural patterns of plasma growth hormone in animals devoid of pituitaries, re-initiated body growth. However, the body weight gains in both sexes of hypophysectomized rats were much greater when rat growth hormone was introduced to the animals in a masculine (pulsatile) pattern that appeared to be independent of pulse frequency, rather than in a continuous feminine profile. Subcutaneous injections, the most commonly reported method of administration, produced low-amplitude, long-lasting plasma peaks that were not as effective as pulse infusion in restoring growth. The procedure allows manipulation of the hormone profile (i.e. number of pulses/day, pulse amplitude, and through duration in the pulsatile pattern, and plasma concentration in the tonic pattern) in order to identify, and thus study the presumed salient components of the pattern regulating growth hormone responses.
TL;DR: The accuracy of quantifying the degree of vascular stenosis with color Doppler flow imaging was determined in an experimental study carried out on six concentric and five eccentric model stenoses.
Abstract: The accuracy of quantifying the degree of vascular stenosis with color Doppler flow imaging (75-MHz, linear array system) was determined in an experimental study carried out on six concentric and five eccentric model stenoses (cross-sectional area reduction, 134%-938%) The measurements were made with use of pulsatile flow at four different flow rates (708-3390 mL/min) The degree of stenosis was calculated from the ratio of prestenotic to intrastenotic flow velocity The most exact measurement of the degree of stenosis could be achieved with Doppler spectral analysis by determining the maximum peak systolic velocity (r = 994, y = 098x - 32) With the velocity values derived only from the color-coded image, it was also possible to find the most exact degree of stenosis (r = 995, y = 099x - 29) For quantification of stenosis, pre- and intrastenotic Doppler spectral analysis is no longer necessary if the stenosis can be imaged sufficiently with color Doppler
TL;DR: Both the IOP and ocular blood flow increased significantly after tracheal intubation, and lignocaine failed to attenuate either response.
Abstract: Pulsatile ocular blood flow, intraocular pressure, systemic blood pressure, and heart rate was measured in two groups of 15 patients. One received lignocaine 1.5 mg/kg intravenously prior to induction. There was a significant increase in intraocular pressure after suxamethonium, which was not associated with any rise in ocular blood flow. Both the IOP and ocular blood flow increased significantly after tracheal intubation. A rise in ocular blood flow reflects the stress response associated with intubation. Lignocaine failed to attenuate either response.
TL;DR: A new radiographic technique for determining pulsatile volume flow in arteries following an intraarterial injection of contrast material is validated using an experimental phantom of blood circulation to simulate a pulsatile flow waveform, which includes reverse flow.
TL;DR: This study is the first to prove that in the broiler chicken, the pattern of exogenous p-cGH administration is a factor influencing in vitro responses to the hormone.
TL;DR: The data confirm previous findings of physiological reduction in serum testosterone and PRL levels and suggest that the testosterone decrease is not related to changes in LH pulsatile release, weight, or increased serum cortisol levels.
Abstract: Cross-sectional studies have suggested that total and bioavailable testosterone levels are reduced in some male athletes. Such changes may be related to loss of body weight, increased serum cortisol, and/or alterations in LH pulsatile release. To determine how endurance training may affect androgen levels, we measured serum total testosterone, sex hormone-binding globulin, free androgen index, LH, FSH, PRL, cortisol, and weight in 15 previously sedentary males. We also examined pulsatile LH release in a subset of 5 subjects. Over 6 months of training, the men increased weekly running mileage to an average of 56 km/week. Total testosterone and free androgen index levels decreased significantly. PRL and cortisol also decreased, while single sample LH and FSH remained unchanged. There was a significant reduction in weight, which did not correlate with changes in serum testosterone levels. LH pulsatile release was not altered by training in the subset of 5 runners. These data confirm previous findings of physiological reduction in serum testosterone and PRL levels and suggest that the testosterone decrease is not related to changes in LH pulsatile release, weight, or increased serum cortisol levels.
TL;DR: The aim of this new three-leaflet valve development was to design a leaflet with minimum membrane stresses during performance, which shows superior hydrodynamic performance thereby reducing potential thrombus formation.
Abstract: The aim of this new three-leaflet valve development was to design a leaflet with minimum membrane stresses during performance. This is achieved by manufacturing the valve leaflets shaped almost flat in a medium opening position. Thus, the leaflets have two stable positions, one with maximum opening area and the other with favorable stress distribution in the closed position. The transition between the two end positions is achieved through a two-dimensional rolling motion without buckling and with minimum membrane stresses (bulge forces). The manufacturing technique is dip-coating in polyurethane. Hydrodynamic evaluation of the J-3 valve in steady and pulsatile flow showed minimum pressure drop compared to other commercially available valves. Laser-Doppler-anemometry studies indicated very low shear stresses in the flow field downstream of the valve. In durability tests prototypes have reached lifetimes of up to 17 years. In conclusion, the J-3 valve shows superior hydrodynamic performance thereby reducing potential thrombus formation. Minimization of stresses within the valve leaflets through design could reduce calcification.
TL;DR: It is concluded that pulsatile perfusion during open heart surgical procedure has no advantages in regard to lung water content and monoatrial cannulation with partial bypass at all times during CPB seems to be beneficial, probably owing to the maintenance of pulmonary circulation during the bypass period.
Abstract: Several efforts have been made to improve the technique of cardiopulmonary bypass (CPB), including the use of pulsatile flow and the modification of cannulation technique. The present study focused upon extravascular lung water (EVLW) in 60 aortocoronary bypass patients subjected to four different perfusion techniques during CPB: group 1 (n = 15): non-pulsatile flow and standard cannulation; group 2 (n = 15); pulsatile flow and standard cannulation; group 3 (n = 15): nonpulsatile flow and monoatrial cannulation (i.e., always "partial" bypass during CPB); group 4 (n = 15): pulsatile flow and monoatrial cannulation. EVLW content was measured using the double-indicator dilution technique with indocyanine green; in addition, various hemodynamic and laboratory variables were measured. Lung water content rose above normal values (mean: 5.79 +/- 0.33 ml/kg) only in the groups submitted to the standard cannulation technique, irrespective of whether the perfusion flow was pulsatile or not (group 1: + 27.4%; group 2: + 25.5%). Pulmonary gas exchange, too, was compromised only in these patients (PaO2 in group 1 -19% and in group 2 -17%; Qs/Qt in group 1 + 36 rel. % and in group 2 + 29 rel. %), whereas all patients with monoatrial cannulation and partial bypass throughout the CPB period showed no rise in EVLW content or Qs/Qt and no drop in PaO2. From the results of this study we conclude that pulsatile perfusion during open heart surgical procedure has no advantages in regard to lung water content. Monoatrial cannulation with partial bypass at all times during CPB, however, seems to be beneficial, probably owing to the maintenance of pulmonary circulation during the bypass period.