Blood flow measurement during exercise in sheep using Doppler ultrasonic method

Continuous recording of blood flow to the coronary, renal and hindlimb vascular beds of sheep has been carried out using flow probes implanted around the major vessels supplying these regions. Blood flow has been recorded at rest, with the sheep running at speeds of 1–16 kmh⁻¹ on a treadmill, and during the recovery period. A Doppler flowmeter has been developed to facilitate compatibility with existing equipment, to enable reliable reproduction of the unit and to keep costs to a minimum. To minimize interference accompanying the violent movements of exercise great care must be taken with the electrical connections and flow probes require streamlining to facilitate implantation. Blood flow to both hindlimb and coronary vascular beds increased during exercise while that to the renal vascular bed did not change. Thus continuous recording with the Doppler ultrasonic flowmeter can be utilised during all phases of exercise, unlike other methods such as the use of radioactive microspheres which provides only point estimations and has limited application for repeated measurement.     

Leg blood flow during static exercise

Summary Leg blood flow was studied with the constant infusion dye technique during static exercise of the thigh muscles (quadriceps) and during hand-grips at 15 and 25–30% of MVC.Blood flow and oxygen uptake in the leg increased in quadriceps exercise and reached their highest values (around 1.2 l/min and 165 ml/min respectively) at 25–30% of MVC, whereas leg vascular resistance decreased. Regional circulatory adaptations and the oxygen uptake — leg blood flow relationship were in close agreement with the responses found in dynamic leg exercise. In view of the marked rise in intramuscular pressure previously observed during quadriceps contractions, a restriction of blood flow and an increased vascular resistance had been expected. Involuntary activation of leg muscles other than the quadriceps may explain the finding.Contractions of the contralateral quadriceps induced a slight increase in leg blood flow, whereas hand-grips had no influence on blood flow or vascular resistance in the leg. The distribution of the cardiac output during static contractions is discussed, and it is concluded that during hand-grips the increase in blood flow is predominantly distributed to the upper part of the body.     

超声多普勒血流和管壁搏动信号的分离研究

目的针对超声多普勒血流检测中,传统的高通滤波法在滤除管壁搏动信号的同时也会滤除低频血流信号的问题,本研究提出一种以心电信号（electrocardiography,ECG）作为参考信号的自适应滤波的方法消除管壁干扰。方法包括两方面：其一,采用心电信号作为参考信号对超声多普勒信号进行自适应滤波;其二,采用多级自适应滤波并选择不同的参考信号的滤波方案。分别使用上述方法和高通滤波法对仿真的超声多普勒信号进行处理,并将结果进行比较。结果与传统的高通滤波法相比,该方法在有效抑制管壁搏动信号的同时保留一部分低频血流信号成分。结论该方法能较准确地提取出完整的血流超声多普勒信号,具有一定的临床应用价值。     

Effect of heat stress on muscle blood flow during dynamic handgrip exercise

Summary During exercise in a hot environment, blood flow in the exercising muscles may be reduced in favour of the cutaneous circulation. The aim of our study was to examine whether an acute heat exposure (65–70°C) in sauna conditions reduces the blood flow in forearm muscles during handgrip exercise in comparison to tests at thermoneutrality (25° C). Nine healthy men performed dynamic handgrip exercise of the right hand by rhythmically squeezing a water-filled rubber tube at 13% (light), and at 34% (moderate) of maximal voluntary contraction. The left arm served as a control. The muscle blood flow was estimated as the difference in plethysmographic blood flow between the exercising and the control forearm. Skin blood flow was estimated by laser Doppler flowmetry in both forearms. Oesophageal temperature averaged 36.92 (SEM 0.08) ° C at thermo-neutrality, and 37.74 (SEM 0.07) ° C (P<0.01) at the end of the heat stress. The corresponding values for heart rate were 58 (SEM 2) and 99 (SEM 5) beats -min^–1 (P<0.01), respectively. At 25° C, handgrip exercise increased blood flow in the exercising forearm above the control forarm by 6.0 (SEM 0.8) ml · 100 ml^–1 · min^–1 during light exercise, and by 17.9 (SEM 2.5) ml · 100 ml^–1 · min^–1 during moderate exercise. In the heat, the increases were significantly higher: 12.5 (SEM 2:2) ml · 100 ml^–1 · min^–1 at the light exercise level (P<0.01), and 32.2 (SEM 5.9) ml · 100 ml^–1·min^–1 (P<0.05) at the moderate exercise level. Skin blood flow was not significantly different in any of the test conditions between the two forearms. These results suggested that hyperthermia of the observed magnitude did not reduce blood flow in active muscles during light or moderate levels of dynamic handgrip exercise.     

The exercise pressor response to sustained handgrip does not augment blood flow in the contracting forearm skeletal muscle

Previous studies have advanced the concept that during sustained handgrip (SHG) reflex increases in blood pressure are able to partially offset increases in tissue pressure and thus effectively maintain increases in muscle blood flow during mild to moderate levels of sustained handgrip. However, this concept is based upon measurements of blood flow to the entire forearm. The aim of this study was to evaluate this concept by simultaneously measuring time-dependent changes in systemic arterial pressure and blood flow in an active muscle during the actual period of exercise. To accomplish this aim, we measured ¹³³Xenon washout from the extensor carpi radialis longus muscle over 3 min of SHG at 15, 30 and 45% of maximal voluntary contraction (MVC). During sustained handgrip at 15% MVC, muscle blood flow increased more than 20 fold from rest to exercise (P < 0.05), even though mean arterial pressure increased by only 12 ± 4 mmHg. This large exercise-induced hyperaemia was abolished during SHG at both 30 and 45% MVC, despite large and progressive increases in mean arterial pressure of 29 ± 3 and 54 ± 5 mmHg, respectively. We conclude that at levels of handgrip above 15% MVC blood pressure ceases to be an important determinant of blood flow in the active skeletal muscle. Importantly, the increases in forearm blood flow that have been reported previously with such levels of static handgrip do not appear to be directed to the most active muscle.     

Middle cerebral artery blood velocity during rowing

Dynamic exercise increases the transcranial Doppler determined mean blood velocity in basal cerebral arteries corresponding to the cortical representation of the active limb(s) and independent of the concomitant rise in the mean arterial pressure. In 12 rowers we evaluated the middle cerebral artery blood velocity response to ergometer rowing when regulation of the cerebral perfusion is challenged by stroke synchronous fluctuation in arterial pressure. Rowing increased mean cerebral blood velocity (57 ± 3 to 67 ± 5 cm s^?1; mean ± SE) and mean arterial (86 ± 6 to 97 ± 6 mmHg) and central venous pressures (0 ± 2 to 8 ± 2 mmHg; P < 0.05). The force on the oar triggered an averaging procedure that demonstrated stroke synchronous sinusoidal oscillations in the cerebral velocity with a 12 ± 2% amplitude upon the average exercise value. During the catch phase of the stroke, the mean velocity increased to a peak of 88 ± 7 cm s^?1 and it was in phase with the highest mean arterial pressure (125 ± 14 mmHg), while the central venous pressure was highest after the stroke (20 ± 3 mmHg). The results suggest that during rowing cerebral perfusion is influenced significantly by the rapid fluctuations in the perfusion pressure.     

Doppler ultrasound investigation of uterine and ovarian blood flow in infertility and early pregnancy

This review describes the current use of Doppler ultrasoundto examine blood flow in the uterus and ovaries in infertilepatients and during early pregnancy. The basics of Doppler ultrasoundand the different methods of measuring blood flow are discussedfrom the viewpoint of the clinician who may be unfamiliar withDoppler physics and terminology. Normal values in the menstrualcycle and the relationship of uterine and ovarian blood flowto infertility and to implantation following in-vitro fertilizationare presented. Normal values for uterine blood flow in the first16 weeks of pregnancy and the effect of sex steroids and ovulationinduction on their values are described. The possible relationshipof defective uterine blood flow, and the effect of drugs areexplored. The findings of this review indicate that Dopplerblood flow studies may provide significant information aboutpossible causes of some disorders of infertility and early pregnancyand methods of treatment for the same.     

Factors affecting endometrial and subendometrial blood flow measured by three-dimensional power Doppler ultrasound during IVF treatment

BACKGROUND: No information exists in the literature regarding the factors affecting the blood flow towards the endometrial and subendometrial regions during IVF treatment. METHODS: We examined the effect of women's age, their smoking habits, their type of infertility (i.e. primary or secondary) and parity, causes of infertility and serum estradiol (E2) concentration on endometrial and subendometrial blood flows as measured by a three-dimensional (3D) power Doppler ultrasound during IVF treatment. All patients received a standard long protocol of ovarian stimulation and serum E2 concentration was determined on the day of hCG. 3D ultrasound examination with power Doppler was performed on the day of oocyte collection to determine vascularization index (VI), flow index (FI) and vascularization flow index (VFI) of endometrial and subendometrial regions. RESULTS: The age of women, their smoking habits, their types of infertility and parity and causes of infertility had no effect on the endometrial and subendometrial 3D power Doppler flow indices. There was a negative correlation between serum E(2) concentration and endometrial FI (r = -0.109; P = 0.006). CONCLUSIONS: Endometrial blood flow in IVF treatment was negatively affected by serum E2 concentration only.     

Orthostatic reactions during recovery from exhaustive exercise of short duration

We studied the responses of six healthy volunteers to standard 70° head-up tilt tests before exhaustive exercise of short duration (control) and after 5, 25, 50, 80, and 110 min of recovery, all tests lasting for 6 min except when impending syncope (IS) necessitated premature termination of a test. Marked impairment of orthostatic tolerance was apparent during the first half-hour of recovery as manifested by symptoms of IS in five subjects in one or both of the first two postexercise tilt tests. In none of the subjects who developed symptoms of IS did central venous pressure fall to a lower level than it did in the control test. From the central venous and arterial pressure reactions we conclude that when IS developed, declining systematic resistance rather than diminished cardiac filling was the responsible factor. The increased tendency for orthostatic collapse occurred during a period of recovery marked by persistent postexercise acidemia and hyperthermia suggesting interference of these conditions and associated events with the normal ability to vasoconstrict during orthostasis     

Skin blood flow during incremental exercise in a thermoneutral and a hot dry environment

Summary Eight physically fit men performed two incremental bicycle ergometer tests, one in an ambient temperature of 25° C and the other at 40° C. Oesophageal temperature (T_es) increased continuously throughout the tests up to 38.0 and 38.3° C, respectively. In both enviroments, forearm blood flow (plethysmography) was linearly related to T_es above the T_es threshold for vasodilation, but at the heaviest work loads this relationship was clearly attenuated and therefore indicated skin vasoconstriction, which tended to be more pronounced at 25° C. During recovery at 25° C, in some subjects the forearm blood flow increased above the levels observed at the end of the graded exercise in spite of a decreasing T_es. Skin blood flow, measured by laser Doppler flow meter at the shoulder, was quantitatively different but, on average, seemed to reveal the same response pattern as the forearm blood flow. In spite of the higher level of skin blood flow in the heat, blood lactate accumulation did not differ between the two environments. The present results suggest that there is competition between skin vasoconstriction and vasodilation at heavy work rates, the former having precedence in a thermoneutral environment to increase muscle perfusion. During short-term graded exercise in a hot environment, skin vasoconstriction with other circulatory adjustments seems to be able to maintain adequate muscle perfusion at heavy work levels, but probably not during maximum exercise.     

Effect of arm-cranking on leg blood flow and noradrenaline spillover during leg exercise in man

Controversy exists whether recruitment of a large muscle mass in dynamic exercise may outstrip the pumping capacity of the heart and require neurogenic vasoconstriction in exercising muscle to prevent a fall in arterial blood pressure. To elucidate this question, seven healthy young men cycled for 70 minutes at a work load of 5540%VO_2max. At 30 to 50 minutes, arm cranking was added and total work load increased to (mean ± SE) 82 ± 4% of Vo_2max. During leg exercise, leg blood flow average 6.15 4.511 minutes^-1, mean arterial blood pressure 137 ± 4 mmHg and leg conductance 42.3 ± 2.2 ml minutes^-1 mmHg^-1. When arm cranking was added to leg cycling, leg blood flow did not change significantly, mean arterial blood pressure increased transiently to 147 ± 5 mmHg and leg vascular conductance decreased transiently to 33.5 ± 3.1 ml minutes^-1 mmHg^-1. Furthermore, arm cranking doubled leg noradrenaline spillover. When arm cranking was discontinued and leg cycling continued, leg blood flow was unchanged but mean arterial blood pressure decreased to values significantly below those measured in the first leg exercise period. Furthermore, leg vascular conductance increased transiently, and noradrenaline spillover decreased towards values measured during the first leg exercise period. It is concluded that addition of arm cranking to leg cycling increases leg noradrenaline spillover and decreases leg vascular conductance but leg blood flow remains unchanged because of a simultaneous increase in mean arterial blood pressure. The decrease in leg vascular conductance observed when arm cranking increased mean arterial blood pressure could be regarded more as a measure to prevent overperfusion than a measure to maintain arterial blood pressure.     

多普勒超声观察创伤性寰枢椎不稳手术前后椎动脉血流的变化

目的探讨创伤性寰枢椎不稳患者内固定手术前后椎动脉血流的变化。方法32例创伤性寰枢椎不稳患者,其中男性22例,女性10例;年龄22～57岁,平均年龄38岁。手术前及内固定术后,均应用彩色多普勒超声测量颈椎1、2间和颈椎5、6间椎动脉血流速度、阻力指数。并对检查结果进行对比分析。结果32例创伤性寰枢椎不稳患者术前椎动脉血流39侧异常,25侧正常。内固定术后39侧异常者中35侧恢复正常,4侧无变化,3侧术前正常变为术后异常。结论创伤性寰枢椎不稳可导致椎动脉血流变化,手术复位内固定后增加了寰枢椎稳定性,可改善椎动脉血液供应。     

A new pulsatile flow visualization method using a photochromic dye with application to Doppler ultrasound

A nonintrusive method for the visualization of pulsatile flow velocity profiles is described. The method is based on the use of a photochromic dye that is added to the fluid being studied and a nitrogen laser which excites the dye producing a marker “line” whose movement can be photographed. A microcomputer is used as a system controller, to coordinate the system timing and to manage the data transfer. The method used for analysis of the photographs to determine the velocity profiles is described. Examples are presented of instantaneous velocity profiles obtained from velocity waveforms that are similar to those of the femoral artery. In addition, application of the system for studying the relationship between Doppler ultrasound spectral recordings and flow velocity profiles is discussed.     

Endometrial and subendometrial blood flow measured by three-dimensional power Doppler ultrasound in patients with small intramural uterine fibroids during IVF treatment

BACKGROUND: The impact of intramural fibroids on the success of IVF treatment is controversial and the mechanisms leading to poor treatment outcomes remain unknown. We compared endometrial and subendometrial blood flow between women with and without intramural fibroids during IVF treatment. METHODS: Three-dimensional (3D) ultrasound examination with power Doppler was performed on the day of oocyte retrieval in 50 patients with intramural fibroids not distorting the uterine cavity and in 50 matched controls to measure endometrial thickness, uterine pulsatility index (PI)/resistance index (RI), endometrial volume and vascularization index (VI)/flow index (FI)/vascularization flow index (VFI) of endometrial and subendometrial regions. Smokers, patients with serum estradiol concentrations > or =20,000 pmol/l on the day of HCG and previous history of myomectomy were excluded. RESULTS: Endometrial thickness and pattern, averaged uterine PI and RI and endometrial and subendometrial VI/FI/VFI were similar between the fibroid group and the control group. There was no correlation between the total volume of fibroids and endometrial and subendometrial 3D power Doppler flow indices in the fibroid group. CONCLUSION: Endometrial and subendometrial 3D power Doppler flow indices were similar in patients with and without small intramural fibroids.     

Measurement of forearm blood flow by venous occlusion plethysmography: Influence of hand blood flow during sustained and intermittent isometric exercise

Summary The requirement for using an arterial occlusion cuff at the wrist when measuring forearm blood flows by plethysmography was tested on a total of 8 subjects at rest and during and after sustained and intermittent isometric exercise. The contribution of the venous effluent from the hand to the forearm flow during exercise was challenged by immersing the arm in water at 20, 34, and 40 C. Occlusion of the circulation to the hand reduced the blood flow through the resting forearm at all water temperatures. There was an inverse relationship between the temperature of the water and the proportion in the reduction of forearm blood flow upon inflation of the wrist-cuff, ranging from 45 to 19% at 20 to 40 C, respectively. However, during sustained isometric exercise at 10% of the subjects maximum voluntary contraction (MVC) there was no reduction in the measured forearm flow when an arterial occlusion cuff was inflated around the wrist. Similarly, there was no alteration in the blood flow measured 2 s after each of a series of intermittent isometric contractions exerted at 20% or 60% MVC for 2 s whether or not circulation to the hand was occluded nor of the post-exercise hyperemia following 1 min of sustained contraction at 40% MVC. These results indicate that a wrist-cuff is not required for accurate measurement of forearm blood flows during or after isometric exercise.This work was supported by N.I.H. training grant HLO 7050-03, H.E.W. contract 210-77-0044 and Air Force grant AFOSR-76-3084 B     

Effects of rhythmic muscle compression on arterial blood pressure at rest and during dynamic exercise in humans

This study was designed to examine the hypothesis that a rhythmic mechanical compression of muscles would affect systemic blood pressure regulation at rest and during dynamic exercise in humans. We measured the changes in mean arterial pressure (MAP) occurring (a) at rest with pulsed (350 ms pulses at 50 pulses min^–1) or static compression (50 and 100 mmHg) of leg muscles with or without upper thigh occlusion, and (b) during 12‐min supine bicycle exercise (75 W, 50 r.p.m.) with or without pulsed compression (50, 100, 150 mmHg) of the legs in synchrony with the thigh extensor muscle contraction. At rest with thigh occlusion, MAP increased by 4–8 mmHg during static leg compression, and by 5–9 mmHg during pulsed leg compression. This suggests that at rest pulsed leg compression elicits a reflex pressor response of similar magnitude to that evoked by static compression. During dynamic exercise without leg compression, MAP (having risen initially) gradually declined, but imposition of graded pulsed leg compression prevented this decline, the MAP values being significantly higher than those recorded without pulsed leg compression by 7–10 mmHg. These results suggest that the rhythmic increase in intramuscular pressure that occurs during dynamic exercise evokes a pressor response in humans.     

Priority of blood flow to splanchnic organs in humans during pre- and post-meal exercise

Cardiac output and superior mesenteric arterial flow in five healthy young men were followed using Doppler ultrasound techniques at rest and during 4 min bouts of bicycle exercise in both a pre- and a post-meal situation. The meal given was mixed and heavy, with an energy content (related to body size) of about 1400–1600 kcal (5.9-6.9 MJ). Two levels of exercise, 50–65 W and 150–200 W (about 75% of Vo_tmax), were tested, with the subjects cycling in a reclining position. Superior mesenteric arterial flow increased threefold, to about 1.11 min^-1, after the meal. During exercise in the fasting situation there were only modest changes in splanchnic vascular conductance, and moderate increases in superior mesenteric arterial flow were actually recorded. Exercise in the post-prandial state caused appreciable reductions in splanchnic vascular conductance, and a 38% reduction was observed during the most heavy exercise. However, not even such a decrease in conductance resulted in any definite reduction in superior mesenteric arterial blood flow, which was maintained at the pre-exercise level. Cardiac output increased by about 1.3 1 min^-1 after the meal. The exercise-induced increases in cardiac output were of the same order in the fasting and in the post-prandial state. Variance analyses showed the high cardiac output levels reached during postprandial exercise to be no different from levels that would be reached by pure summation of the changes caused by eating alone and by exercise alone. It is concluded that blood flow to the splanchnic organs in reclining man retains its high pre- and post-prandial priority during short exercise bouts of up to 75% of Vo_Smax.     

Effect of pulsatile arterial diameter variations on blood flow estimated by Doppler ultrasound

High-resolution measurements of common carotid and femoral arterial diameters have been performed by ultrasound echo devices. When combined with pulsed Doppler measurements of cross-sectional averaged velocity in the same vessels, exact calculations of flow were made possible. The median peak-to-peak pulsatile diameter variations were 0.19 mm (2.8 per cent) in the femoral artery and 0.49mm (6.7 per cent) in the common carotid artery. Flow values were calculated either by taking the time-averaged diameter as a constant value, or by taking into account the dynamic variations in diameter. In comparing the two values, a quantification of the magnitude of error introduced by the averaging of the diameter was made possible. An error in the range 1.5–3.8 per cent was found for the femoral artery, whereas the error in the common carotid artery was in the range 0.4–3.6 per cent despite the larger amplitude of the pulsations in this vessel.     

Skin blood flow in humans as a function of environmental temperature measured by ultrasound

We have measured the blood velocities in arteries supplying the skin in humans both in areas with arteriovenous anastomoses (AVA) and in skin areas without AVA in different temperature situations by means of a pulsed, bidirectional doppler ultrasound instrument. The instrument measures the time average of the instantaneous mean of the blood velocities present in a cross-section of a vessel. So long as the cross-sectional area of the vessel is constant, this average velocity is proportional to volume flow. We observe rapid and large fluctuations in blood velocities in arteries supplying skin areas with AVA in a comfortably warm environment. These fluctuations are substantially larger and more rapid than described by previous authors who have used plethysmograph methods. The blood velocities are more constant both at higher and lower environmental temperatures. There are no similar fluctuations in blood velocity in arteries supplying skin areas without AVA.