Measurement of Blood Flow in the Femoral Artery in Man at Rest and during Exercise by Local Thermodilution

Assessing Leg Blood Flow and Cardiac Output During Running Using Thermodilution

Cardiac output (Q̇C) and leg blood flow (Q̇LEG) can be measured simultaneously with high accuracy using transpulmonary and femoral vein thermodilution with a single-bolus injection. The invasive measure has offered important insight into leg hemodynamics and blood flow distribution during exercise. Despite being the natural modality of exercise in humans, there has been no direct measure of Q̇LEG while running in humans. We sought to determine the feasibility of the thermodilution technique for measuring Q̇LEG and conductance during high-intensity running, in an exploratory case study. A trained runner (30 years male) completed two maximal incremental tests on a cycle ergometer and motorized treadmill. Q̇LEG and Q̇C were determined using the single-bolus thermodilution technique. Arterial and venous blood were sampled throughout exercise, with continuous monitoring of metabolism, intra-arterial and venous pressure, and temperature. The participant reached a greater peak oxygen uptake (V̇O2peak) during running relative to cycling (74 vs. 68 mL/kg/min) with comparable Q̇LEG (19.0 vs. 19.5 L/min) and Q̇C (27.4 vs. 26.2 L/min). Leg vascular conductance was greater during high-intensity running relative to cycling (82 vs. 70 mL/min/mmHg @ ~80% V̇O2peak). The "beat phenomenon" was apparent in femoral flow while running, producing large gradients in conductance (62-90 mL/min/mmHg @ 70% V̇O2peak). In summary, we present the first direct measure of Q̇LEG and conductance in a running human. Our findings corroborate several assumptions about Q̇LEG during running compared with cycling. Importantly, we demonstrate that using thermodilution in running exercise can be completed effectively and safely.

Deceived by the Fick principle: blood flow distribution in heart failure

AIMS

The Fick principle states that oxygen uptake (V̇O2) is cardiac output (Qc)*arterial-venous O2 content difference [ΔC(a-v)O2]. Blood flow distribution is hidden in Fick principle and its relevance during exercise in heart failure (HF) is undefined.To highlight the role of blood flow distribution, we evaluated peak-exercise V̇O2, Qc and ΔC(a-v)O2, before and after HF therapeutic interventions.

METHODS

Symptoms-limited cardiopulmonary exercise tests with Qc measurement (inert-gas-rebreathing) was performed in 234 HF patients before and 6 months after successful exercise training, cardiac-resynchronization therapy or percutaneous-edge-to-edge mitral valve repair.

RESULTS

Considering all tests (n=468) a direct correlation between peakV̇O2 and peakQc (R2=0.47) and workload (R2=0.70) were observed. Patients were grouped according to treatment efficacy in group 1 (peakV̇O2 increase >10%, n=93), group 2 (peakV̇O2 change between 0 and 10%, n=60) and group 3 (reduction in peakV̇O2, n=81). Post-treatment peakV̇O2 changes poorly correlated with peakQc and peakΔC(a-v)O2 changes. Differently, post-procedures peakQc vs. peakΔC(a-v)O2 changes showed a close negative correlation (R2=0.46), becoming stronger grouping patients according to peakV̇O2 improvement (R2=0.64, 0.79 and 0.58 in group 1, 2 and 3, respectively). In 76% of patients peakQc and ΔC(a-v)O2 changes diverged regardless of treatment.

CONCLUSION

The bulk of these data suggests that blood flow distribution plays a pivotal role on peakV̇O2 determination regardless of HF treatment strategies. Accordingly, for assessing HF treatment efficacy on exercise performance the sole peakV̇O2 may be deceptive and the combination of V̇O2, Qc and ΔC(a-v)O2, must be considered.

Fatal exsanguination following complete transection of femoral vessels due to angle grinder injury in an industrial accident

Angle grinders are one of the most dangerous and frequently used tools in industrial settings. Angle grinder injuries range from superficial cuts to deep penetrating injuries with underlying fracture-dislocation and vascular trauma. The injuries caused by angle grinders mostly involve the head, face, or upper limbs, while the lower limb is an unusual site. The high-speed rotating disc of the angle grinders does not respect anatomical boundaries or structures; therefore, the injuries caused may be disfiguring, permanently incapacitating, or even fatal. We report a fatal case of an angle grinder injury to the lower limb. The victim sustained a sharp cut over the left thigh while woodworking in an industrial setup. The rotating disc of an angle grinder had transected the skin, subcutaneous fat and muscles, and both the femoral vessels of the left side, which led to fatal exsanguination within 10 min of the incident.

Methods for the determination of skeletal muscle blood flow: development, strengths and limitations

Since the first measurements of limb blood flow at rest and during nerve stimulation were conducted in the late 1800s, a number of methods have been developed for the determination of limb and skeletal muscle blood flow in humans. The methods, which have been applied in the study of aspects such as blood flow regulation, oxygen uptake and metabolism, differ in terms of strengths and degree of limitations but most have advantages for specific settings. The purpose of this review is to describe the origin and the basic principles of the methods, important aspects and requirements of the procedures. One of the earliest methods, venous occlusion plethysmography, is a noninvasive method which still is extensively used and which provides similar values as other more direct blood flow methods such as ultrasound Doppler. The constant infusion thermodilution method remains the most appropriate for the determination of blood flow during maximal exercise. For resting blood flow and light-to-moderate exercise, the non-invasive ultrasound Doppler methodology, if handled by a skilled operator, is recommendable. Positron emission tomography with radiolabeled water is an advanced method which requires highly sophisticated equipment and allows for the determination of muscle-specific blood flow, regional blood flows and estimate of blood flow heterogeneity within a muscle. Finally, the contrast-enhanced ultrasound method holds promise for assessment of muscle-specific blood flow, but the interpretation of the data obtained remains uncertain. Currently lacking is high-resolution methods for continuous visualization and monitoring of the skeletal muscle microcirculation in humans.

Lower limb phantom design and production for blood flow and pressure tests

Phantoms are specifically designed objects that are utilized or imaged to evaluate, analyze and tune the performance of experimental devices. In this project, it is aimed to design a phantom that responds in a similar manner with how human blood circulation would act in specific flow and pressure tests such as pulse measurement. Ballistic gelatin is a member of hydrogel family with 250 Bloom value which resembles human muscle tissue in terms of mechanical features. That’s why we carried out a uniaxial compression test on our gelatin sample to analyze its similarity of human muscle tissue in terms of elastic modulus, stiffness and rupture strength. Test results indicated that our gelatin sample has approximate values with organic human muscle tissue. Designed model was X-rayed and the similarities of the model to human texture were compared. After producing of lower limb phantoms, we carried out a circulation test through them by the aid of a peristaltic pump to simulate the actual blood circulation of human body limbs. This designed phantom is made ready for available flow and pressure tests.

Microsystems for biomimetic stimulation of cardiac cells

The heart is a complex integrated system that leverages mechanoelectrical signals to synchronize cardiomyocyte contraction and push blood throughout the body. The correct magnitude, timing, and distribution of these signals is critical for proper functioning of the heart; aberrant signals can lead to acute incidents, long-term pathologies, and even death. Due to the heart's limited regenerative capacity and the wide variety of pathologies, heart disease is often studied in vitro. However, it is difficult to accurately replicate the cardiac environment outside of the body. Studying the biophysiology of the heart in vitro typically consists of studying single cells in a tightly controlled static environment or whole tissues in a complex dynamic environment. Micro-electromechanical systems (MEMS) allow us to bridge these two extremes by providing increasing complexity for cell culture without having to use a whole tissue. Here, we carefully describe the electromechanical environment of the heart and discuss MEMS specifically designed to replicate these stimulation modes. Strengths, limitations and future directions of various designs are discussed for a variety of applications.

Physiological aspects of the determination of comprehensive arterial inflows in the lower abdomen assessed by Doppler ultrasound

Non-invasive measurement of splanchnic hemodynamics has been utilized in the clinical setting for diagnosis of gastro-intestinal disease, and for determining reserve blood flow (BF) distribution. However, previous studies that measured BF in a "single vessel with small size volume", such as the superior mesenteric and coeliac arteries, were concerned solely with the target organ in the gastrointestinal area, and therefore evaluation of alterations in these single arterial BFs under various states was sometimes limited to "small blood volumes", even though there was a relatively large change in flow. BF in the lower abdomen (BF(Ab)) is potentially a useful indicator of the influence of comprehensive BF redistribution in cardiovascular and hepato-gastrointestinal disease, in the postprandial period, and in relation to physical exercise. BF(Ab) can be determined theoretically using Doppler ultrasound by subtracting BF in the bilateral proximal femoral arteries (FAs) from BF in the upper abdominal aorta (Ao) above the coeliac trunk. Prior to acceptance of this method of determining a true BF(Ab) value, it is necessary to obtain validated normal physiological data that represent the hemodynamic relationship between the three arteries. In determining BF(Ab), relative reliability was acceptably high (range in intra-class correlation coefficient: 0.85-0.97) for three arterial hemodynamic parameters (blood velocity, vessel diameter, and BF) in three repeated measurements obtained over three different days. Bland-Altman analysis of the three repeated measurements revealed that day-to-day physiological variation (potentially including measurement error) was within the acceptable minimum range (95% of confidence interval), calculated as the difference in hemodynamics between two measurements. Mean BF (ml/min) was 2951 ± 767 in Ao, 316 ± 97 in left FA, 313 ± 83 in right FA, and 2323 ± 703 in BF(Ab), which is in agreement with a previous study that measured the sum of BF in the major part of the coeliac, mesenteric, and renal arteries. This review presents the methodological concept that underlies BF(Ab), and aspects of its day-to-day relative reliability in terms of the hemodynamics of the three target arteries, relationship with body surface area, respiratory effects, and potential clinical usefulness and application, in relation to data previously reported in original dedicated research.

Limb and skeletal muscle blood flow measurements at rest and during exercise in human subjects

The aim of the present review is to present techniques used for measuring blood flow in human subjects and advice as to when they may be applicable. Since blood flow is required to estimate substrate fluxes, energy turnover and metabolic rate of skeletal muscle, accurate measurements of blood flow are of extreme importance. Several techniques have therefore been developed to enable estimates to be made of the arterial inflow to, venous outflow from, or local blood flow within the muscle. Regional measurements have been performed using electromagnetic flow meters, plethysmography, indicator methods (e.g. thermodilution and indo-cyanine green dye infusion), ultrasound Doppler, and magnetic resonance velocity imaging. Local estimates have been made using 133Xe clearance, microdialysis, near i.r. spectroscopy, positron emission tomography and laser Doppler. In principle, the aim of the study, the type of interventions and the limitations of each technique determine which method may be most appropriate. Ultrasound Doppler and continuous indo-cyanine green dye infusion gives the most accurate limb blood flow measurements at rest. Moreover, the ultrasound Doppler is unique, as it does not demand a steady-state, and because its high temporal resolution allows detection of normal physiological variations as well as continuous measurements during transitional states such as at onset of and in recovery from exercise. During steady-state exercise thermodilution can be used in addition to indo-cyanine green dye infusion and ultrasound Doppler, where the latter is restricted to exercise modes with a fixed vessel position. Magnetic resonance velocity imaging may in addition be used to determine blood flow within deep single vessels. Positron emission tomography seems to be the most promising tool for local skeletal muscle blood-flow measurements in relation to metabolic activity, although the mode and intensity of exercise will be restricted by the apparatus design.

Reduced blood flow in abdominal viscera measured by Doppler ultrasound during one-legged knee extension

The redistribution of blood flow (BF) in the abdominal viscera during right-legged knee extension-flexion exercise at very low intensity [peak heart rate (HR), 76 beats/min] was examined by using Doppler ultrasound. While sitting, subjects performed a right-legged knee extension-flexion exercise every 6 s for 20 min. BF was measured in the upper abdominal aorta (Ao), right common femoral artery (RCFA), and left common femoral artery (LCFA). Visceral BF (BFVis) was determined by the equation [BFAo - (BFRCFA + BFLCFA)]. A comparison with the change in BF (DeltaBF) preexercise showed a greater increase in DeltaBFRCFA than in DeltaBFAo during exercise. This resulted in a reduction of BFVis to 56% of its preexercise value or a decrease in flow by 1,147 +/- 293 (+/-SE) ml/min at the peak workload. Oxygen consumption correlated positively with DeltaBFAo, DeltaBFRCFA, and DeltaBFLCFA but inversely with DeltaBFVis during exercise and recovery. Furthermore, BFVis (% of preexercise value) correlated inversely with both an increase in HR (r = -0.89), and percent peak oxygen consumption (r = -0.99). This study demonstrated that, even during very-low-intensity exercise (HR <90 beats/min), there was a significant shift in BF from the viscera to the exercising muscles.

Muscle blood flow at onset of dynamic exercise in humans

To evaluate the temporal relationship between blood flow, blood pressure, and muscle contractions, we continuously measured femoral arterial inflow with ultrasound Doppler at onset of passive exercise and voluntary, one-legged, dynamic knee-extensor exercise in humans. Blood velocity and inflow increased (P < 0.006) with the first relaxation of passive and voluntary exercise, whereas the arterial-venous pressure difference was unaltered [P = not significant (NS)]. During steady-state exercise, and with arterial pressure as a superimposed influence, blood velocity was affected by the muscle pump, peaking (P < 0.001) at approximately 2.5 +/- 0.3 m/s as the relaxation coincided with peak systolic arterial blood pressure; blood velocity decreased (P < 0.001) to 44.2 +/- 8.6 and 28.5 +/- 5.5% of peak velocity at the second dicrotic and diastolic blood pressure notches, respectively. Mechanical hindrance occurred (P < 0.001) during the contraction phase at blood pressures less than or equal to that at the second dicrotic notch. The increase in blood flow (Q) was characterized by a one-component (approximately 15% of peak power output), two-component (approximately 40-70% of peak power output), or three-component exponential model (> or = 75% of peak power output), where Q(t) = Qpassive + delta Q1.[1 - e-(t - TD1/tau 1)]+ delta Q2.[1 - e-(t - TD2/tau 2)]+ delta Q3.[1 - e-(t - TD3/tau 3)]; Qpassive, the blood flow during passive leg movement, equals 1.17 +/- 0.11 l/min; TD is the onset latency; tau is the time constant; delta Q is the magnitude of blood flow rise; and subscripts 1-3 refer to the first, second, and third components of the exponential model, respectively. The time to reach 50% of the difference between passive and voluntary asymptotic blood flow was approximately 2.2-8.9 s. The blood flow leveled off after approximately 10-150 s, related to the power outputs. It is concluded that the elevation in blood flow with the first duty cycle(s) is due to muscle mechanical factors, but vasodilators initiate a more potent amplification within the second to fourth contraction.

Ultrasound Doppler estimates of femoral artery blood flow during dynamic knee extensor exercise in humans

Ultrasound Doppler has been used to measure arterial inflow to a human limb during intermittent static contractions. The technique, however, has neither been thoroughly validated nor used during dynamic exercise. In this study, the inherent problems of the technique have been addressed, and the accuracy was improved by storing the velocity tracings continuously and calculating the flow in relation to the muscle contraction-relaxation phases. The femoral arterial diameter measurements were reproducible with a mean coefficient of variation within the subjects of 1.2 +/- 0.2%. The diameter was the same whether the probe was fixed or repositioned at rest (10.8 +/- 0.2 mm) or measured during dynamic exercise. The blood velocity was sampled over the width of the diameter and the parabolic velocity profile, since sampling in the center resulted in an overestimation by 22.6 +/- 9.1% (P < 0.02). The femoral arterial Doppler blood flow increased linearly (r = 0.997, P < 0.001) with increasing load [Doppler blood flow = 0.080 . load (W) + 1.446 l/min] and was correlated positively with simultaneous thermodilution venous outflow measurements (r = 0.996, P < 0.001). The two techniques were linearly related (Doppler = thermodilution . 0.985 + 0.071 l/min; r = 0.996, P < 0.001), with a coefficient of variation of approximately 6% for both methods.

Critical analysis of methods for assessing regional blood flow and their reliability in clinical medicine

The advantages and inadequacies of the currently available techniques to measure regional blood flow in the lower limbs are being reviewed. Thermodilution technique and local 133xenon washout technique have the advantage of allowing determination of blood flow during exercise, while venous occlusion plethysmography and pulsed-Doppler duplex ultrasonography only allow determination of blood flow at rest. Overall, measurements of lower limb blood flow are not highly reproducible by any technique, and the variability in measurements of regional blood flow should lead to careful interpretation of derived parameters such as vascular conductance and resistance. Determination of vascular input impedance by Fourier analysis of pressure data, recorded with high fidelity catheter, and flow velocity measurements obtained transcutaneously by Doppler ultrasonography, may offer a more accurate quantitative analysis of the characteristics of the lower limb vascular system.

[Doppler ultrasound measurement of blood circulation in the lower extremity of man. I. Normal values at rest and changes in trauma and vascular diseases]

A duplex ultrasonographic system was used to examine the common femoral artery in left and right legs of 49 fit young men and 15 fit young women, to find out the normal blood flow in the human leg during rest. By this method the diameter of the vessel and the time average velocity could be measured and the blood flow calculated. Each person underwent three examinations of each leg after 10-min rests. The average diameter of the common femoral artery was 91 +/- 10 mm (95 mm in the men and 80 mm in the women), the average blood flow 226.2 +/- 82.1 ml/min (235.9 ml/min in the men and 189.6 ml/min the the women). Compared with other methods used for femoral blood flow studies, we found the duplex ultrasound system reliable, non-invasive, and infinitely repeatable. This method therefore also seems appropriate for clinical studies. In a few tests carried out in trauma patients we found a pronounced increase in blood flow after a few days, and also an expected increase in a patient with arterio-venous fistula and an expected decrease in one with arterial occlusive disease. These examinations were performed to establish a method for further examinations of long-lasting blood flow alterations in trauma patients, which will be reported in another paper.

Decreased effect of insulin to stimulate skeletal muscle blood flow in obese man. A novel mechanism for insulin resistance

Obesity is characterized by decreased rates of skeletal muscle insulin-mediated glucose uptake (IMGU). Since IMGU equals the product of the arteriovenous glucose difference (AVGd) across muscle and blood flow into muscle, reduced blood flow and/or tissue activity (AVGd) can lead to decreased IMGU. To examine this issue, we studied six lean (weight 68 +/- 3 kg, mean +/- SEM) and six obese (94 +/- 3 kg) men. The insulin dose-response curves for whole body and leg IMGU were constructed using the euglycemic clamp and leg balance techniques over a large range of serum insulin concentrations. In lean and obese subjects, whole body IMGU, AVGd, blood flow, and leg IMGU increased in a dose dependent fashion and maximal rates of all parameters were reduced in obese subjects compared to lean subjects. The dose-response curves for whole body IMGU, leg IMGU, and AVGd were right-shifted in obese subjects with an ED50 two- to threefold higher than that of lean subjects for each parameter. Leg blood flow increased approximately twofold from basal 2.7 +/- 0.2 to 4.4 +/- 0.2 dl/min in lean, P less than 0.01, and from 2.5 +/- 0.3 to 4.4 +/- 0.4 dl/min in obese subjects, P less than 0.01. The ED50 for insulin's effect to increase leg blood flow was about fourfold higher for obese (957 pmol/liter) than lean subjects (266 pmol/liter), P less than 0.01. Therefore, decreased insulin sensitivity in human obesity is not only due to lower glucose extraction in insulin-sensitive tissues but also to lower blood flow to these tissues. Thus, in vivo insulin resistance can be due to a defect in insulin action at the tissue level and/or a defect in insulin's hemodynamic action to increase blood flow to insulin sensitive tissues.

Effects of diltiazem and long-term beta 1-adrenergic blockade on hemodynamics and blood flow during exercise in patients with stable angina pectoris

The short-term effects of oral diltiazem on hemodynamics and distribution of cardiac output at rest and during semiupright bicycle exercise were evaluated in eight patients with stable effort angina on long-term beta 1-adrenergic blockade. Cardiac output and iliofemoral blood flow were measured using thermodilution. The patients were exercised to the same work load on a bicycle before and 2 h after oral diltiazem (60 mg in two patients and 120 mg in six). At maximal exercise, diltiazem reduced heart rate from 94 +/- 5 to 88 +/- 6 beats/min (p less than 0.01), mean arterial pressure from 139 +/- 5 to 127 +/- 4 mm Hg (p less than 0.01) and systemic vascular resistance from 9.7 +/- 0.7 to 8.4 +/- 0.4 x 10(2) dynes.s.cm-5 (p less than 0.05) compared with control. During exercise, cardiac output, iliofemoral blood flow, mean pulmonary wedge pressure and mean right atrial pressure were not altered, but stroke volume increased from 119 +/- 11 to 131 +/- 10 ml (p less than 0.05). Maximal ST segment depression during exercise was decreased and angina was less. Diltiazem does not alter the distribution of the cardiac output during exercise but improves ischemia.

Effects of nisoldipine on systemic and leg blood flow, oxygen transport and metabolism, and hemodynamics during exercise in effort angina pectoris

The acute effects of 10 mg of oral nisoldipine on hemodynamics, oxygen transport and metabolism, and distribution of cardiac output, at rest and during semiupright bicycle exercise, were evaluated in 10 men with effort angina receiving long-term beta 1 blockade. Cardiac output and leg blood flow were measured using the thermodilution technique. At rest, nisoldipine decreased systemic resistance from 18.9 +/- 1.0 to 15.9 +/- 1.2 dynes.s.cm-5.10(2) (p less than 0.05) and cardiac output increased from 4.8 +/- 0.2 to 5.3 +/- 0.3 liters/min (p less than 0.05) without changing leg blood flow. During maximal exercise with nisoldipine, systemic resistance was reduced (10.6 +/- 0.9 to 8.6 +/- 0.5 dynes.s.cm-5.10(2), p less than 0.05) and cardiac output increased 18% (10.3 +/- 0.7 to 12.2 +/- 0.6 liters/min, p less than 0.05) when compared with control values. Exercise heart rate was higher with nisoldipine (113 +/- 4 vs 106 +/- 4 beats/min, p less than 0.01), but the mean arterial pressure was not significantly changed, giving a higher rate-pressure product. The increase in mean pulmonary artery wedge pressure was attenuated (26 +/- 3 vs 30 +/- 3 mm Hg during control exercise, p less than 0.05), but ST depression was unaltered. Exercise leg flow was reduced by nisoldipine from 4.3 +/- 0.4 to 3.9 +/- 0.3 liters/min (p = 0.07) and the proportion of cardiac output distributed to the legs was reduced from 42 +/- 3 to 33 +/- 3% (p less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Rates and tissue sites of non-insulin- and insulin-mediated glucose uptake in humans

In vivo glucose uptake can occur via two mechanisms, namely, insulin-mediated glucose uptake (IMGU) and non-insulin-mediated glucose uptake (NIMGU). Although the principal tissue sites for IMGU are skeletal muscle, the tissue sites for NIMGU at a given serum glucose concentration are not known. To examine this issue, rates of whole body glucose uptake (Rd) were measured at basal and during glucose clamp studies performed at euglycemia (approximately 90 mg/dl) and hyperglycemia (approximately 220 mg/dl) in six lean healthy men. Studies were performed during hyperinsulinemia (approximately 70 microU/ml) and during somatostatin-induced insulinopenia to measure IMGU and NIMGU, respectively. During each study, leg glucose balance (arteriovenous catheter technique) was also measured. With this approach, rates of whole body skeletal muscle IMGU and NIMGU can be estimated, and the difference between overall Rd and skeletal muscle glucose uptake represents non-skeletal muscle Rd. The results indicate that approximately 20% of basal Rd is into skeletal muscle. During insulinopenia approximately 86% of body NIMGU occurs in non-skeletal muscle tissues at euglycemia. When hyperglycemia was created, whole body NIMGU increased from 128 +/- 6 to 213 +/- 18 mg/min (P less than 0.01); NIMGU into non-skeletal muscle tissues was 134 +/- 11 and 111 +/- 6 mg/min at hyperglycemia and euglycemia, respectively, P = NS. Therefore, virtually all the hyperglycemia induced increment in NIMGU occurred in skeletal muscle. During hyperinsulinemia, IMGU in skeletal muscle represented 75 and 95% of body Rd, at euglycemia and hyperglycemia, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Regional distribution of cardiac output at rest and during exercise in patients with exertional angina pectoris before and after nifedipine therapy

The short-term effects of sublingual nifedipine (20 mg) on cardiac output and its distribution at rest and during exercise were evaluated by measurement of iliofemoral blood flow and cardiac output in 10 men with stable angina pectoris controlled by metoprolol. At rest, nifedipine significantly decreased iliofemoral vascular resistance from 294 +/- 36 to 165 +/- 29 dynes.s.cm-5.10(2) (p less than 0.01) and significantly increased iliofemoral blood flow from 0.34 +/- 0.04 to 0.57 +/- 0.11 liters/min (p less than 0.05). Systemic vascular resistance was reduced from 19 +/- 1 to 13 +/- 1 dynes.s.cm-5.10(2) (p less than 0.001) and cardiac output increased significantly from 4.7 +/- 0.3 to 5.8 +/- 0.5 liters/min (p less than 0.05). Mean arterial pressure decreased significantly and heart rate increased significantly. During maximal upright bicycle exercise during nifedipine therapy, iliofemoral vascular resistance and leg blood flow were unchanged compared with control (23 +/- 2 versus 21 +/- 3 dynes.s.cm-5.10(2) and 4.7 +/- 0.5 versus 4.4 +/- 0.6 liters/min), cardiac output remained significantly increased (12.8 +/- 0.8 to 15.2 +/- 1.2 liters/min, p less than 0.05) and systemic vascular resistance remained significantly reduced (8 +/- 1 to 5 +/- 1 dynes.s.cm-5.10(2); p less than 0.001). The proportion of cardiac output distributed to the working lower limbs was significantly reduced at all exercise levels. In summary, nifedipine caused a redistribution of cardiac output by vasodilating nonexercising vascular beds without altering the locally mediated vasodilation in exercising muscle. In patients with coronary artery disease given nifedipine therapy, an increase in exercise tolerance is due to relief of myocardial ischemia rather than to increased peripheral oxygen delivery.

Measurement of volume flow in the human common femoral artery using a duplex ultrasound system

A duplex ultrasound system was used to measure volumetric flow in the human common femoral artery. The accuracy of the technique was validated using a flow rig. The average resting common femoral artery flow rate in a population of subjects clinically unaffected by peripheral vascular disease was 350 +/- 141 mls min-1. Although mean common femoral artery diameter was greater in males (10 +/- 0.9 mm) than in females (7.8 +/- 0.7 mm) (p less than 0.01), there was no significant difference in resting blood flow. Repeated measurements in individual subjects showed a high variability, largely due to physiological fluctuations (75 percent of total variability). There was a close correlation between volume flow and the reciprocal of pulsatility index (100/PI). In normal subjects 100/PI represents a simpler method of determining individual changes in blood flow. The temporal variations in volume flow during periods of reactive hyperaemia had a characteristic profile, which was dependent on the duration of circulatory arrest. The data derived from the resting hyperaemia flow profile provides normal ranges for future comparison with patients suffering from peripheral vascular disease.

Hand exercise effect in maturation and blood flow of dialysis arteriovenous fistulas ultrasound study

With the help of the Doppler Ultrasound we have measured the radial artery blood flow of 20 healthy volunteers and the fistula flow of 40 uraemic patients. The measurements were made at rest and repeated one, three and five minutes after initiation of hand exercise, and one minute after the exercise had finished. Radial artery mean flow increased significantly with the exercise (p less than 0.001); radial arteries with greater baseline flow had less flow increase (p less than 0.002). However, we were not able to demonstrate any fistula flow increase with the hand exercise. Therefore, we conclude that there is no benefit in advising uraemic patients to squeeze a rubber ball which, otherwise, supposes an unnecessary preoccupation for these patients.

Impaired skeletal muscle nutritive flow during exercise in patients with congestive heart failure: role of cardiac pump dysfunction as determined by the effect of dobutamine

The maximal exercise capacity of patients with congestive heart failure (CHF) is frequently reduced, partly because of inadequate skeletal muscle nutritive flow. To investigate whether this altered muscle nutritive flow is a result of inability of the heart to increase cardiac output normally during exercise, the effect of dobutamine on systemic and leg blood flow and metabolism during maximal exercise was examined in 11 patients with CHF. At maximal exercise before dobutamine, all patients were limited by fatigue and had reduced maximal systemic oxygen uptake (11.9 +/- 1.1 ml/min/kg) (+/- standard error of the mean), markedly elevated leg oxygen extraction (85 +/- 2%) and elevated femoral venous lactate (53 +/- 5 mg/dl), consistent with impaired nutritive flow to working muscle. Dobutamine increased the peak cardiac output from (6.5 +/- 0.9 0.74 +/- 0.7 liters/min, p less than 0.01) and peak leg flow (from 1.7 +/- 0.3 to 2.1 +/- 0.3 liters/min, p less than 0.05) during exercise. In contrast, no change occurred in maximal exercise duration (5.5 +/- 0.8 vs 5.8 +/- 0.8 min), peak systemic VO2 (829 +/- 97 vs 869 +/- 77 ml/min), peak arterial lactate (34 +/- 2 vs 35 +/- 4 mg/dl) or peak leg lactate output (248 +/- 39 vs 275 +/- 53 mg/min), whereas peak leg oxygen extraction decreased (85 +/- 2 to 80 +/- 2%, p less than 0.01), suggesting no improvement in muscle nutritive flow. These data suggest that nutritive flow to working skeletal muscle is impaired in patients with CHF and that this impairment is not due simply to an inability of the heart to increase the cardiac output normally during exercise.

Transcutaneous quantitation of arterial flow with ultrasound

Arterial blood flow was measured in dogs simultaneously with electromagnetic flow probes and with ultrasonic "flow probes." The ultrasonic probes were used to determine transcutaneously the mean velocity of arterial flow and the cross-sectional area of the blood vessel. A 10 MHz probe was used for blood vessels 1 cm deep or less, while a 5 MHz probe was used for vessels between 1.0 and 2.5 cm deep. The correlation coefficient between the flow calculated with the ultrasound method and the flow measured with the electromagnetic flow probes was 0.966, p less than 0.01. Blood flow was also measured intraoperatively in five patients. There was a correlation coefficient of 0.999, p less than 0.01, between the flow obtained with the ultrasound method and that determined simultaneously by the electromagnetic flow probes. The coefficient of determination for the regression of electromagnetic-determined flow on ultrasound-determined flow was 0.99. Thus, accurate transcutaneous determination of blood flow is possible with slightly modified ultrasound equipment.

Quantitative ultrasonographic studies of lower extremity flow velocities in health and disease

Quantitative Doppler ultrasonographic flow velocity determinations are reported from 39 normal control subjects and 80 patients with angiographically documented peripheral arterial disease, in whom femoral, posterior tibial and dorsalis pedis arteries were studied. The mean control values of the most useful parameters were: femoral artery: peak forward velocity (PFV) cm/sec: 40.7 +/- 10.9, deceleration (Dec.) cm/sec2:250.9 +/- 60.0, peak/mean velocity (P/MV): 4.8 +/- 1.6; posterior tibial artery: PFV: 16.0 +/- 10.0, Dec.: 129.8 +/- 75.7, P/MV: 4.8 +/- 2.5; dorsalis pedis artery: PFV: 168 +/- 5.7, Dec.: 137.9 +/- 54.5, P/MV: 6.0 +/- 4.1. The values of these measurements in the patients with arterial occlusive disease were all significantly lower, and also permitted distinguishing those with multilevel disease from those with a single site of occlusion. Quantitative evaluation of the Doppler ultrasonogram permits obtaining detailed functional information on the degree of arterial flow impairment in patients with peripheral arterial occlusive disease.

Muscular angiographic patterns in lower extremities before and after exercise: technic for study of blood flow and diagnostic applications

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Lactate and pyruvate metabolism in the exercising ischemic limb

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