The Centre for Physical Activity Research (CFAS) is supported by TrygFonden (grants ID 101390 and ID 20045. JPH was supported by grants from Helsefonden and Rigshospitalet. During this work, RMGB was supported by a post.doc. grant from Rigshospitalet.

The study was evaluated by the Regional Ethical Committee of the Capital Region of Denmark (file no. H-21054272), who determined that this was a quality study. In accordance with Danish legislation, the study was thus approved locally by the internal Research and Quality Improvement Board at the Department of Clinical Physiology and Nuclear Medicine, Rigshospitalet (file no. KF-509-22). The study was performed according to the guidelines of the Declaration of Helsinki. All subjects provided oral and written informed consent prior to enrolment. Men and women, &#8805;18 years, were included in the study. Individuals with peripheral arterial disease, heart failure, neurological and musculoskeletal disease hindering KEE effort, and symptoms of disease within 2 weeks prior to the study, were excluded.
1. Setup of the participant
<ol>
	<li>Place the participant in the single-leg knee-extensor chair with the back of the participant resting against the chair (Supplementary Figure 1). Dress the participant in underwear that makes it possible to access the inguinal region with an ultrasound probe.</li>
	<li>Place three ECG electrodes (see Table of Materials) on the participant. Place the electrodes on the right side of the chest wall in the third intercostal space, on the left side in the third intercostal space, and on the left side in the eleventh intercostal space so that the electrodes are equidistant from the heart.</li>
	<li>Place the participant at a &#62;90-degree angle between the abdomen and thigh.</li>
	<li>Adjust the arm connecting the single-knee extensor chair to the flywheel to enable the participant to extend the knee fully.</li>
	<li>Tie the leg of the participant tightly to the pedal of the chair to avoid the usage of muscles in the lower part of the limb.</li>
	<li>Place a chair or a bench to stabilize the inactive leg. 
	NOTE: The angle of &#62;90 degrees is considered a minimum. Increasing the angle will open the inguinal area allowing better access to the femoral artery with the ultrasound probe. This approach is often used when subjects have abdominal adiposity that can interfere with scanning. 
	Adding resistance to the single-leg knee-extensor chair is done differently depending on the type and model and is thus not described in detail. Both absolute and relative intensity can be reported. In order to report relative intensity, perform a test to exhaustion on a preceding day.</li>
</ol>
2. Setup of the ultrasound apparatus
<ol>
	<li>Press the Turn on button.</li>
	<li>Press Patient to create a file where the examination will be saved. Move the cursor to &#34;new patient&#34; and press enter. Fill out the &#34;patient ID&#34; move the cursor to &#34;Create&#34; and press Enter (Supplementary Figure 2 and Supplementary Figure 3).</li>
	<li>Press Probe, choose the linear probe (9 MHz), and apply ultrasound gel (see Table of Materials) to the probe. 
	&#8203;NOTE: It is not possible to save the data from the participant without assigning a &#34;Patient ID&#34;. Assigning more data to this sheet is possible but not necessary for the examination to be performed.</li>
</ol>
3. Doppler ultrasound scan
<ol>
	<li>Operate the linear probe with the hand closest to the participant and place it in the inguinal region. Find the best arterial section for obtaining LBF measurements carefully. This is below the inguinal ligament and 3-4 cm above the bifurcation of the common femoral artery on a straight segment of the artery.</li>
	<li>Hold the probe perpendicular to the vessel. Press the 2D button and make a cross-sectional image of the common femoral artery (CFA).</li>
	<li>Optimize gain and depth, which are to be maintained throughout the experiment, to ensure that the artery is in the middle of the screen and that the blood is black. Turn the Gain button clockwise to increase gain and counterclockwise to decrease gain. Turn the Depth clockwise to increase the depth and counterclockwise to decrease it. 
	NOTE: Please see Supplementary Figure 2 and Supplementary Figure 3 for the localization of the buttons and Supplementary Figure 4 for an ultrasound image optimized with gain and depth.</li>
	<li>While in 2D mode, press Freeze once and scroll using the trackball to find an end-systolic image. Perform this under ECG-guidance by stopping the image at the end of the T-wave.</li>
	<li>Press Measure once and move the cursor to the superficial intimal layer of the artery, and press Enter. Move the cursor to the deep intimal layer of the artery and then press Enter to obtain the diameter at end-systole. The diameter will be shown in the top left corner.</li>
	<li>Press Freeze and turn the probe 90 degrees clockwise while keeping the artery in the middle of the screen and holding it parallel to the artery to create a longitudinal view. Press the pulse wave button PW and then press Measure. This will create a drop-down menu on the right side of the screen. Move the cursor to CFA and press enter.</li>
	<li>Move the cursor to &#34;Auto&#34; and press Enter. Move the cursor to &#34;Flow volume&#34; and press Enter. Move the cursor to &#34;Live,&#34; and press Enter to obtain the trace and finish by pressing Measure once.</li>
	<li>Obtain the velocity at the lowest possible insonation angle and always below 60 degree. Turn the Steer Angle button clockwise to decrease it and counterclockwise to increase it. Turn the Angle correction button to ensure the trace is obtained with the cursor being horizontal to the artery, as shown in Supplementary Figure 4.</li>
	<li>Press Sample vol. to adjust according to the width of the artery and keep clear of the walls of the artery. To decrease the sample size, press the left arrow. To increase the sample size, press the right arrow.</li>
	<li>Obtain the blood flow velocity trace with simultaneous 2D visualization of the artery and audio-visual blood velocity feedback. Ensure that the sound is on by turning the Sound button clockwise.</li>
	<li>Obtain the first trace during seated rest for a minimum of 30 s and press Image Store twice to save the trace. Then instruct the participant to keep a pace of 60 rounds per minute (RPM) during the test and to only use the quadriceps muscle to perform the leg extensions and keep the hamstring muscle relaxed. Keep the probe fixed during the entire experiment.</li>
	<li>Instruct the participant to keep a pace of 60 rounds per minute (RPM) at 0 W and only to use the quadriceps muscle to perform the leg extensions and keep the hamstring muscle relaxed. Keep the probe fixed during the entire experiment and press Image Store twice to save the trace.</li>
	<li>Add resistance and have the participant complete at least 150 s of exercise before obtaining the 30 s of trace and then press Image Store twice to save the trace.</li>
</ol>
4. Quantitation of blood flow
<ol>
	<li>Once all the images are obtained, press Review.</li>
	<li>Press Track Ball and move the cursor to the image of desire, and double-click on Enter.</li>
	<li>Once the desired trace appears, press Measure and move the cursor to &#34;Flow volume&#34; in the drop-down menu on the right side of the screen and press Enter.</li>
	<li>Move the cursor to the 2D ultrasound image, press Enter, then drag the cursor until it reaches the diameter measured during rest and press Enter again.</li>
	<li>Turn the Cursor Select button clockwise twice and choose the 30 s of trace that will be shown between two vertical lines by scrolling the trackball and pressing Enter.</li>
	<li>Calculate the LBF as the product of mean blood velocity (cm/s) and cross-sectional area of the femoral artery (cm2), which will be shown in the top left corner. 
	NOTE: Perform quality control prior to data analysis by visual inspection of the trace and exclude pulse waves affected by motion artifacts as well as irregular heartbeats. It is possible to adjust angle correction after completing the examination by turning the Angle Corr. button clockwise to decrease it and counterclockwise to increase it to ensure the cursor is horizontal to the artery.</li>
</ol>

Assessing Leg Blood Flow in Training Workloads

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

This study assessed the reliability of Doppler ultrasound methodology for evaluating leg blood flow (LBF) during submaximal single-leg knee-extensor exercise in healthy participants. The results indicated high within-day reliability and acceptable between-day reliability, while inter-rater reliability was found to be unacceptable at rest and at 0 W.
Although probe removal between measurements appeared to have little impact, the difference in reliability between within-day and between-day measu...

Doppler ultrasound, introduced in the 1980s, has been extensively used to determine contracting muscle blood flow, particularly in the single-leg knee-extensor model, allowing measurement of blood flow in the common femoral artery (CFA) during small muscle mass activation1,2,3,4,5,6. Doppler ultrasound-based blood flow technology has provided valuable insights into vascular regulation in various populations, including healthy adults7,8, individuals with diabetes9, hypertension10, COPD11,12, and heart failure13,14.
One advantage of Doppler ultrasound is its non-invasiveness compared to other blood flow determination methods like thermodilution, and it can be combined with arterial and venous catheterization if necessary3,4,6,15. It also enables beat-to-beat blood flow velocity measurement, allowing for the detection of rapid changes16. However, Doppler ultrasound-based blood measurements have limitations, including difficulties in obtaining stable recordings during excessive limb movement at near-maximal exercise intensities and the requirement for ultrasound accessibility to the targeted blood vessel, excluding evaluations during ergometer bicycling15. Hence, the single-leg knee-extensor model is well-suited for LBF evaluation using Doppler ultrasound during dynamic exercise at submaximal intensities17, minimizing the influence of exercise-related heart and lung limitations and facilitating comparisons between healthy subjects and patients with cardio-pulmonary diseases11.
Despite being widely used, the between-day reliability of the single-leg knee-extensor model using Doppler ultrasound has not been investigated on a larger scale in recent decades, with prior studies involving small populations (n = 2)3,18,19,20.
This study aimed to investigate (1) the within-day test-retest reliability, (2) the between-day test-retest reliability, and (3) the inter-rater reliability of Doppler ultrasound for LBF evaluation during single-leg knee-extensor exercise at 0 W, 6 W, 12 W, and 18 W. The measurements were conducted in a clinically realistic scenario where the probe was removed between measurements. It is important to note that several intrinsic and extrinsic environmental factors known to influence LBF were not controlled during the measurements, which could introduce variability and affect reliability. Considering advancements in Doppler ultrasound technology and blood flow analysis software, we hypothesized that, even in an uncontrolled setting, acceptable within- and between-day reliability of LBF measurements could be achieved at all intensities when performed by the same sonographer.

<table><tbody><tr><td>EKO GEL</td><td>EKKOMED A7S</td><td>DK-7500 Holstebro</td><td></td></tr><tr><td>RStudio, version 1.4.1717</td><td>R Project for Statistical Computing</td><td></td><td></td></tr><tr><td>Saltin Chair</td><td></td><td></td><td>This was built from an ergometer bike and a carseat owned by Professor Bengt Saltin. The steelconstruction was built from a specialist who custommade it.</td></tr><tr><td>Ultrasound apparatus equipped with a linear probe (9 MHz, Logic E9)</td><td>GE Healthcare</td><td>Unknown</td><td>GE Healthcare, Milwaukee, WI, USA</td></tr><tr><td>&amp;nbsp; &amp;nbsp;</td><td>&amp;nbsp; &amp;nbsp;</td><td>&amp;nbsp; &amp;nbsp;</td><td>Ultrasound gel</td></tr></tbody></table>

doppler ultrasound-based leg blood flow assessment during single-leg knee-extensor exercise in an uncontrolled setting

Doppler ultrasound has revolutionized the assessment of organ blood flow and is widely used in research and clinical settings. While Doppler ultrasound-based assessment of contracting leg muscle blood flow is common in human studies, the reliability of this method requires further investigation. Therefore, this study aimed to investigate the within-day test-retest, between-day test-retest, and inter-rater reliability of Doppler ultrasound for assessing leg blood flow during rest and graded single-leg knee-extensions (0 W, 6 W, 12 W, and 18 W), with the ultrasound probe being removed between measurements. The study included thirty healthy subjects (age: 33 &#177; 9.3, male/female: 14/16) who visited the laboratory on two different experimental days separated by 10 days. The study did not control for major confounders such as nutritional state, time of day, or hormonal status. Across different exercise intensities, the results demonstrated high within-day reliability with a coefficient of variation (CV) ranging from 4.0% to 4.3%, acceptable between-day reliability with a CV ranging from 10.1% to 20.2%, and inter-rater reliability with a CV ranging from 17.9% to 26.8%. Therefore, in a real-life clinical scenario where controlling various environmental factors is challenging, Doppler ultrasound can be used to determine leg blood flow during submaximal single-leg knee-extensor exercise with high within-day reliability and acceptable between-day reliability when performed by the same sonographer.

Participants 
From May 2022 to October 2022, a total of thirty healthy men and women were recruited to participate in the study. All participants had no history of cardiovascular, metabolic, or neurological diseases. They were not instructed to make any changes to their usual habits, including caffeine, alcohol, nicotine, vigorous exercise, or any other factors that could potentially impact vascular function.
Experimental procedures 
Participants rep...

Watch this Scientific Journal Video about Assessing the Reliability of Doppler Ultrasound in Measuring Leg Blood Flow at JoVE.com

Author Spotlight: Assessing the Reliability of Doppler Ultrasound in Measuring Leg Blood Flow 

This test-retest study evaluated leg blood flow measured by the Doppler ultrasound technique during single-leg knee-extensor exercise. The within-day, between-day, and inter-rater reliability of the method was investigated. The approach demonstrated high within-day and acceptable between-day reliability. However, the inter-rater reliability was unacceptably low during rest and at low workloads.

Doppler Ultrasound-Based Leg Blood Flow Assessment During Single-Leg Knee-Extensor Exercise in an Uncontrolled Setting

Doppler ultrasound has revolutionized the assessment of organ blood flow and is widely used in research and clinical settings. While Doppler ...

doppler-ultrasound-based-leg-blood-flow-assessment-during-single-leg

Research

JoVE Journal

Medicine

2.7K Views.  Copenhagen University Hospital. Deze methode wordt algemeen erkend en toegepast in tal van klinische en onderzoeksomgevingen. Het primaire doel van dit onderzoek was om de reproduceerbaarheid van de methode te ondersteunen en zo waardevolle inzichten te verschaffen in de meetfout. Door dit te doen, kunnen we zeggen wat echte fysiologische verandering is en wat te wijten is aan meetfouten.Uiteindelijk zal dit ons begrip van deze methode vergroten. Het belangrijkste obstakel ligt in het onderzoeken van fysiologische ve...

Video: Auteur in de schijnwerpers: beoordeling van de betrouwbaarheid van Doppler-echografie bij het meten van de bloedstroom in de benen 

A Novel Application of Musculoskeletal Ultrasound Imaging

Ultrasound is an attractive modality for imaging muscle and tendon motion during dynamic tasks and can provide a complementary methodological approach for biomechanical studies in a clinical or laboratory setting. Towards this goal, methods for quantification of muscle kinematics from ultrasound imagery are being developed based on image processing. The temporal resolution of these methods is typically not sufficient for highly dynamic tasks, such as drop-landing. We propose a new approach that utilizes a Doppler method for quantifying muscle kinematics. We have developed a novel vector tissue Doppler imaging (vTDI) technique that can be used to measure musculoskeletal contraction velocity, strain and strain rate with sub-millisecond temporal resolution during dynamic activities using ultrasound. The goal of this preliminary study was to investigate the repeatability and potential applicability of the vTDI technique in measuring musculoskeletal velocities during a drop-landing task, in healthy subjects. The vTDI measurements can be performed concurrently with other biomechanical techniques, such as 3D motion capture for joint kinematics and kinetics, electromyography for timing of muscle activation and force plates for ground reaction force. Integration of these complementary techniques could lead to a better understanding of dynamic muscle function and dysfunction underlying the pathogenesis and pathophysiology of musculoskeletal disorders.

We describe a new ultrasound-based vector tissue Doppler imaging technique to measure muscle contraction velocity, strain and strain rate with sub-millisecond temporal resolution during dynamic activities. This approach provides complementary measurements of dynamic muscle function and could lead to a better understanding of mechanisms underlying musculoskeletal disorders.

Ultrasound is an attractive modality for imaging muscle and tendon  motion during dynamic tasks and can provide a complementary methodological  approach ...

Computerized Dynamic Posturography for Postural Control Assessment in Patients with Intermittent Claudication

Computerized dynamic posturography with the EquiTest is an objective technique for measuring postural strategies under challenging static and dynamic conditions. As part of a diagnostic assessment, the early detection of postural deficits is important so that appropriate and targeted interventions can be prescribed. The Sensory Organization Test (SOT) on the EquiTest determines an individual&#39;s use of the sensory systems (somatosensory, visual, and vestibular) that are responsible for postural control. Somatosensory and visual input are altered by the calibrated sway-referenced support surface and visual surround, which move in the anterior-posterior direction in response to the individual&#39;s postural sway. This creates a conflicting sensory experience. The Motor Control Test (MCT) challenges postural control by creating unexpected postural disturbances in the form of backwards and forwards translations. The translations are graded in magnitude and the time to recover from the perturbation is computed.
Intermittent claudication, the most common symptom of peripheral arterial disease, is characterized by a cramping pain in the lower limbs and caused by muscle ischemia secondary to reduced blood flow to working muscles during physical exertion. Claudicants often display poor balance, making them susceptible to falls and activity avoidance. The Ankle Brachial Pressure Index (ABPI) is a noninvasive method for indicating the presence of peripheral arterial disease and intermittent claudication, a common symptom in the lower extremities. ABPI is measured as the highest systolic pressure from either the dorsalis pedis or posterior tibial artery divided by the highest brachial artery systolic pressure from either arm. This paper will focus on the use of computerized dynamic posturography in the assessment of balance in claudicants.

Individuals with intermittent claudication exhibit poor balance compared to healthy controls. Computerized dynamic posturography is an objective method for measuring an individual's postural responses to balance disturbances. This provides an objective reflection of the person&#x2019;s ability to respond to situations under which sensory stimuli are altered and unexpected perturbations occur.

Computerized dynamic posturography with the EquiTest is an objective technique for measuring postural strategies under challenging static and dynamic ...

Ultrasound Based Assessment of Coronary Artery Flow and Coronary Flow Reserve Using the Pressure Overload Model in Mice

Transthoracic Doppler echocardiography (TTDE) is a clinically useful, noninvasive tool for studying coronary artery flow velocity and coronary flow reserve (CFR) in humans. Reduced CFR is accompanied by marked intramyocardial and pericoronary fibrosis and is used as an indication of the severity of dysfunction. This study explores, step-by-step, the real-time changes measured in the coronary flow velocity, CFR and systolic to diastolic peak velocity (S/D) ratio in the setting of an aortic banding model in mice. By using a Doppler transthoracic imaging technique that yields reproducible and reliable data, the method assesses changes in flow in the septal coronary artery (SCA), for a period of over two weeks in mice, that previously either underwent aortic banding or thoracotomy. 
During imaging, hyperemia in all mice was induced by isoflurane, an anesthetic that increased coronary flow velocity when compared with resting flow. All images were acquired by a single imager. Two ratios, (1) CFR, the ratio between hyperemic and baseline flow velocities, and (2) systolic (S) to diastolic (D) flow were determined, using a proprietary software and by two independent observers. Importantly, the observed changes in coronary flow preceded LV dysfunction as evidenced by normal LV mass and fractional shortening (FS). 
The method was benchmarked against the current gold standard of coronary assessment, histopathology. The latter technique showed clear pathologic changes in the coronary artery in the form of peri-coronary fibrosis that correlated to the flow changes as assessed by echocardiography. 
The study underscores the value of using a non-invasive technique to monitor coronary circulation in mouse hearts. The method minimizes redundant use of research animals and demonstrates that advanced ultrasound-based indices, such as CFR and S/D ratios, can serve as viable diagnostic tools in a variety of investigational protocols including drug studies and the study of genetically modified strains.

Coronary flow reserve (CFR) is useful for assessment of myocardial oxygen demand and evaluation of cardiovascular risk. This study establishes a step-by-step transthoracic Doppler echocardiographic (TTDE) method for longitudinal monitoring of the changes in CFR, as measured from coronary artery in mice, under the experimental pressure overload of aortic banding.

Transthoracic Doppler echocardiography (TTDE) is a clinically useful, noninvasive tool for studying coronary artery flow velocity and coronary flow ...

Using an Ingestible Telemetric Temperature Pill to Assess Gastrointestinal Temperature During Exercise

Exercise results in an increase in core body temperature (Tc), which may reduce exercise performance and eventually can lead to the development of heat-related disorders. Therefore, accurate measurement of Tc during exercise is of great importance, especially in athletes who have to perform in challenging ambient conditions. In the current literature a number of methods have been described to measure the Tc (esophageal, external tympanic membrane, mouth or rectum). However, these methods are suboptimal to measure Tc during exercise since they are invasive, have a slow response or are influenced by environmental conditions. Studies described the use of an ingestible telemetric temperature pill as a reliable and valid method to assess gastrointestinal temperature (Tgi), which is a representative measurement of Tc. Therefore, the goal of this study was to provide a detailed description of the measurement of Tgi using an ingestible telemetric temperature pill. This study addresses important methodological factors that must be taken into account for an accurate measurement. It is recommended to read the instructions carefully in order to ensure that the ingestible telemetric temperature pill is a reliable method to assess Tgi at rest and during exercise.

This study describes an accurate, reliable and non-invasive technique to continuously measure gastrointestinal temperature during exercise. The ingestible telemetric temperature pill is suitable to measure gastrointestinal temperature in laboratory settings as well as in field based settings.

Exercise results in an increase in core body temperature (Tc), which may reduce exercise performance and eventually can lead to the development of ...

Ultrasound Assessment of Endothelial Function: A Technical Guideline of the Flow-mediated Dilation Test

Cardiovascular disease is the primary cause of mortality and a major cause of disability worldwide. The dysfunction of the vascular endothelium is a pathological condition characterized mainly by a disruption in the balance between vasodilator and vasoconstrictor substances and is proposed to play an important role in the development of atherosclerotic cardiovascular disease. Therefore, a precise evaluation of endothelial function in humans represents an important tool that could help better understand the etiology of multiple cardio-centric pathologies.
Over the past twenty-five years, many methodological approaches have been developed to provide an assessment of endothelial function in humans. Introduced in 1989, the FMD test incorporates a forearm occlusion and subsequent reactive hyperemia that promotes nitric oxide production and vasodilation of the brachial artery. The FMD test is now the most widely utilized, non-invasive, ultrasonic assessment of endothelial function in humans and has been associated with future cardiovascular events.
Although the FMD test could have clinical utility, it is a physiological assessment that has inherited several confounding factors that need to be considered. This article describes a standardized protocol for determining FMD including the recommended methodology to help minimize the physiological and technical issues and improve the precision and reproducibility of the assessment.

The flow mediated dilation (FMD) test is the most commonly utilized, non-invasive, ultrasound assessment of endothelial function in humans. Although the FMD test has been related with the prediction of future cardiovascular disease and events, it is a physiological assessment with many inherent confounding factors that need to be considered.

Cardiovascular disease is the primary cause of mortality and a major cause of disability worldwide. The dysfunction of the vascular endothelium is a ...

A Novel Non-invasive Method for the Detection of Elevated Intra-compartmental Pressures of the Leg

Acute Compartment Syndrome is a devastating consequence of musculoskeletal trauma. Currently the diagnosis is based on clinical signs and symptoms, and while adjuncts such as invasive intra-compartmental pressure measurements are often used to corroborate the physical exam findings, there remains no reliable objective test to aid in the decision to perform a decompressive fasciotomy. In a cadaver model of compartment syndrome, an ultrasound (US) based method has been shown to be a reliable measurement of increased intra-compartmental pressure. An absolute pressure of &#62;100 mbar or a difference of 50 mbar in the CFFP between the legs can be considered pathologic. Using an ultrasound transducer, coupled with a pressure sensor, the pressure needed to flatten the superficial fascia of the anterior compartment of lower legs (Compartment Fascia Flattening Pressure [CFFP]) can be measured. The CFFP of the injured leg is compared to the CFFP of the uninjured leg. This US measured index can then serve as an adjunct to the physical exam in evaluating injured lower extremities and assessing the need for decompressive fasciotomy. The advantages of this protocol include: being a non-invasive method and an easily reproducible technique.

An ultrasound probe coupled with a pressure sensor is used to assess the intra-compartmental pressure of the leg by directly measuring the compartment fascia flattening pressure (CFFP). This non-invasive protocol will provide reliable assessment of the pressure inside the anterior muscular compartment of the lower leg.

Acute Compartment Syndrome is a devastating consequence of musculoskeletal trauma. Currently the diagnosis is based on clinical signs and symptoms, and ...

Continuous Venous-Arterial Doppler Ultrasound During a Preload Challenge

A preload challenge (PC) is a clinical maneuver that, first, increases the cardiac filling (i.e., preload) and, second, calculates the change in cardiac output. Fundamentally, a PC is a bedside approach for testing the Frank-Starling-Sarnoff (i.e., "cardiac function") curve. Normally, this curve has a steep slope such that a small change in the cardiac preload generates a large change in the stroke volume (SV) or cardiac output. However, in various disease states, the slope of this relationship flattens such that increasing the volume into the heart leads to little rise in the SV. In this pathological scenario, additional cardiac preload (e.g., intravenous fluid) is unlikely to be physiologically effective and could lead to harm if organ congestion evolves. Therefore, inferring both the cardiac preload and output is clinically useful as it may guide intravenous (IV) fluid resuscitation. Accordingly, the goal of this protocol is to describe a method for contemporaneously tracking the surrogates of cardiac preload and output using a novel, wireless, wearable ultrasound during a well-validated preload challenge.

The Frank-Starling-Sarnoff curve is clinically important and describes the relationship between cardiac preload and output. This report illustrates a novel method of simultaneous jugular venous and carotid arterial Doppler velocimetry as transient surrogates of cardiac preload and output, respectively; this approach is enabled by wireless, wearable Doppler ultrasound.

A preload challenge (PC) is a clinical maneuver that, first, increases the cardiac filling (i.e., preload) and, second, calculates the change in cardiac ...

Optimizing NIRS for Assessing Lower Limb Vascular Function

Near-Infrared Spectroscopy During Reactive Hyperemia for the Assessment of Lower Limb Vascular Function

Vascular diseases of the lower limb contribute substantially to the&#160;global burden of cardiovascular disease and comorbidities such as diabetes. Importantly, microvascular dysfunction can occur prior to, or alongside, macrovascular pathology, and both potentially contribute to patient symptoms and disease burden. Here, we describe a non-invasive approach using near-infrared spectroscopy (NIRS) during reactive hyperemia, which provides a standardized assessment of lower limb vascular (dys)function and a potential method to evaluate the efficacy of therapeutic interventions. Unlike alternative methods, such as contrast-enhanced ultrasound, this approach does not require venous access or sophisticated image analysis, and it is inexpensive and less operator-dependent. This description of the NIRS method includes representative results and standard terminology alongside the discussion of measurement considerations, limitations, and alternative methods. Future application of this work will improve standardization of vascular research design, data collection procedures, and harmonized reporting, thereby enhancing translational research outcomes in the areas of lower limb vascular (dys)function, disease, and treatment.

Author Spotlight: Enhancing Vascular Function and Physical Capacity in Cardiovascular Disease Through Novel Interventions and NIRS Technology

Here, we describe a non-invasive approach using near-infrared spectroscopy to assess reactive hyperemia in the lower limb. This protocol provides a standardized assessment of vascular and microvascular responsiveness that may be used to determine the presence of vascular dysfunction as well as the efficacy of therapeutic interventions.

Vascular diseases of the lower limb contribute substantially to the&#160;global burden of cardiovascular disease and comorbidities such as diabetes. ...

Biology

Peripheral Vascular Exam Using a Continuous Wave Doppler

Source: Joseph Donroe, MD, Internal Medicine and Pediatrics, Yale School of Medicine, New Haven, CT
Peripheral vascular disease (PVD) is a common condition affecting older adults and includes disease of the peripheral arteries and veins. While the history and physical exam offer clues to its diagnosis, Doppler ultrasound has become a routine part of the bedside vascular examination. The video titled &#34;The Peripheral Vascular Exam&#34; gave a detailed review of the physical examination of the peripheral arterial and venous systems. This video specifically reviews the bedside assessment of peripheral arterial disease (PAD) and chronic venous insufficiency using a handheld continuous wave Doppler.
The handheld Doppler (HHD) is a simple instrument that utilizes continuous transmission and reception of ultrasound (also referred to as continuous wave Doppler) to detect changes in blood velocity as it courses through a vessel. The Doppler probe contains a transmitting element that emits ultrasound and a receiving element that detects ultrasound waves (Figure 1). The emitted ultrasound is reflected off of moving blood and back to the probe at a frequency directly related to the velocity of blood flow. The reflected signal is detected and transduced to an audible sound with a frequency directly related to that of the received Doppler signal (thus, faster blood flow produces a higher frequency sound).
<img alt="Figure 1" src="/files/ftp_upload/10123/10123fig1.jpg" /> 
Figure 1. Generation of a Doppler signal. The handheld Doppler emits an ultrasound signal, which is then reflected back by moving blood, and finally received by the Doppler probe.
The HHD is easily used in the office or hospital setting to detect pulses, screen for PAD using the ankle brachial pressure index (ABPI), and localize venous insufficiency. This video reviews these procedures; however, it is not intended to be a comprehensive review of non-invasive vascular testing.

Source: Joseph Donroe, MD, Internal Medicine and Pediatrics, Yale School of Medicine, New Haven, CT
Peripheral vascular disease (PVD) is a common ...

Education

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Clinical Skills

Physical Examinations I

Assessing Blood pressure using a doppler ultrasound

To obtain accurate blood pressure measurements in clinical settings, especially when traditional methods are insufficient, healthcare professionals utilize the Doppler ultrasound technique. This method uses high-frequency sound waves to detect blood flow within the arteries, which is crucial for patients with conditions that complicate circulatory system assessment.
Pre-Procedural Guidelines for Doppler Ultrasound Blood Pressure Assessment:
Preparation of Equipment:
<ul>
	<li>&#8226; Assemble the necessary equipment, including a Doppler ultrasound device, a blood pressure cuff, a sphygmomanometer, and conducting gel.</li>
	<li>&#8226;&#160;Choose a cuff size that matches the patient&#39;s arm circumference, covering 40% of the limb.</li>
	<li>&#8226;&#160;Various cuff sizes are available to accommodate pediatric patients, adults, and individuals who need bariatric sizes.</li>
</ul>
Patient Identification and Preparation:
<ul>
	<li>&#8226;&#160;Confirm the patient&#39;s identity and briefly explain the Doppler ultrasound technique, emphasizing its importance in assessing blood pressure.</li>
	<li>&#8226;&#160;Obtain the patient&#39;s consent and prepare them for the procedure, aiming to reduce anxiety and promote cooperation.</li>
	<li>&#8226;&#160;Ensure the environment is calm, allowing the patient at least five minutes of rest before the assessment to improve accuracy and comfort.</li>
</ul>
Positioning and Environment:
<ul>
	<li>&#8226;&#160;Position the patient seated or reclining with adequate back support to eliminate hydrostatic pressure effects.</li>
	<li>&#8226;&#160;The arm selected for assessment should be free from restrictive clothing and supported at heart level for an accurate reading.</li>
	<li>&#8226;&#160;Create a relaxing atmosphere with privacy measures, such as keeping the curtains or doors closed.</li>
</ul>
Pre-procedural Assessment and Instructions:
<ul>
	<li>&#8226;&#160;Perform hand hygiene using bactericidal soap or an alcohol-based hand rub to maintain aseptic technique and avoid cross-infection.</li>
	<li>&#8226;&#160;Provide pre-procedure instructions, such as having an empty bladder, which can affect sympathetic nervous system activity, resulting in altered blood pressure readings.</li>
	<li>&#8226;&#160;Evaluate any factors that might interfere with the measurement, like tight clothing on the limb, recent consumption of stimulants or alcohol, or any conditions that could contraindicate using a Doppler ultrasound for blood pressure measurement, such as severe peripheral vascular disease or recent limb surgery.</li>
</ul>
Conducting the Assessment:
<ul>
	<li>&#8226;&#160;Begin by applying sufficient conducting gel at the site over the artery to be assessed, ensuring effective transmission of ultrasound waves and accurate detection of arterial blood flow.</li>
	<li>&#8226;&#160;Hold the Doppler probe steadily and gently on the skin surface, maneuvering carefully to locate the strongest pulse signal. This step is critical as it confirms the return of blood flow, indicating the systolic blood pressure.</li>
	<li>&#8226;&#160;After finding a pulse, inflate the blood pressure cuff beyond the estimated systolic pressure until the Doppler no longer detects the pulse signal. Then, carefully deflate the cuff, watching the gauge for the pressure at which the pulse reappears, indicating the systolic blood pressure.</li>
	<li>&#8226;&#160;Continue to slowly deflate the cuff and listen for the disappearance of the pulse sound, which indicates the diastolic blood pressure. This measurement is equally important as it reflects the pressure in the arteries when the heart is at rest between beats.</li>
</ul>
Post-procedure:
<ul>
	<li>&#8226;&#160;Following the measurement, clean any gel residue from the Doppler probe and the patient&#39;s skin, follow equipment maintenance protocols, and maintain patient hygiene.</li>
	<li>&#8226;&#160;Document the blood pressure readings and any relevant observations during the procedure in the patient&#39;s medical record, providing a vital part of their health history.</li>
</ul>

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