This experimental protocol has been reviewed and approved by our hospital&#8217;s institutional review board (IRB) and follows all guidelines set forth by our institution&#8217;s human research ethics committee.
1. Identify the Fascia of the Anterior Compartment of the Leg
<ol>
	<li>Identify a starting site for the ultrasound probe. Place the probe directly over the anterior compartment, just lateral to the tibial crest and one handbreadth distal to the tibial tubercle.</li>
	<li>Identify the fascia as the bright, white strip just below the subcutaneous tissue on the ultrasound. Move the probe until the fascia is seen at the point where it attaches to the tibial crest.</li>
	<li>Note the geometry of the fascia. With minimal pressure applied, this should be a convex shape.</li>
</ol>
2. Measure the Compartment Fascia Flattening Pressure of the InjuredLeg
<ol>
	<li>Once the fascia of the anterior compartment is identified, apply slow and steady pressure to the ultrasound probe until the fascia changes shape from convex to completely flat. Make several attempts including passing the flattening point to produce a concave shape in an effort to gently hone in on the exact CFFP.</li>
	<li>Once the anterior compartment fascia is perfectly flat, record the pressure sensor measurement.</li>
	<li>Repeat the CFFP measurement 2 more times. Record and average all 3 pressures to define the final CFFP.</li>
</ol>
3. Calculate the Delta CFFP Compared to the Uninjured (Contralateral) Leg
<ol>
	<li>Measure and record the CFFP in the contralateral leg in the same manner described above.</li>
	<li>Calculate the delta CFFP by taking the difference between the CFFP of the injured leg the well leg.</li>
</ol>

<ol>
	<li>Ulmer, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+clinical+diagnosis+of+compartment+syndrome+of+the+lower+leg:+are+clinical+findings+predictive+of+the+disorder?.">The clinical diagnosis of compartment syndrome of the lower leg: are clinical findings predictive of the disorder?.</a> Journal of Orthopaedic Trauma. 16 (8), 572-577 (2002).</li><li>Whitesides, T. E., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Tissue+pressure+measurements+as+a+determinant+for+the+need+of+fasciotomy.">Tissue pressure measurements as a determinant for the need of fasciotomy.</a> Clinical Orthopaedics and Related Research. 113, 43-51 (1975).</li><li>McQueen, M. M., Court-Brown, C. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Compartment+monitoring+in+tibial+fractures:+the+pressure+threshold+for+decompression.">Compartment monitoring in tibial fractures: the pressure threshold for decompression.</a> The Journal of Bone and Joint Surgery. British Volume. 78 (1), 99-104 (1996).</li><li>McQueen, M. M., Christie, J., Court-Brown, C. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Compartment+pressures+after+intramedullary+nailing+of+the+tibia.">Compartment pressures after intramedullary nailing of the tibia.</a> The Journal of Bone and Joint Surgery. British Volume. 72 (3), 395-397 (1990).</li><li>Masquelet, A. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Acute+compartment+syndrome+of+the+leg:+pressure+measurement+and+fasciotomy.">Acute compartment syndrome of the leg: pressure measurement and fasciotomy.</a> Orthopaedics &amp; Traumatology: Surgery &amp; Research. 96 (8), 913-917 (2010).</li><li>McQueen, M. M., Duckworth, A. D., Aitken, S. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+estimated+sensitivity+and+specificity+of+compartment+pressure+monitoring+for+acute+compartment+syndrome.">The estimated sensitivity and specificity of compartment pressure monitoring for acute compartment syndrome.</a> Journal of Bone and Joint Surgery. 95 (8), 673-677 (2013).</li><li>Whitney, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Do+one-time+intracompartmental+pressure+measurements+have+a+high+false-positive+rate+in+diagnosing+compartment+syndrome?.">Do one-time intracompartmental pressure measurements have a high false-positive rate in diagnosing compartment syndrome?.</a> Journal of Trauma and Acute Care Surgery. 76 (2), 479-483 (2014).</li><li>Sellei, R. M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Assessment+of+elevated+compartment+pressures+by+pressure-related+ultrasound:+a+cadaveric+model.">Assessment of elevated compartment pressures by pressure-related ultrasound: a cadaveric model.</a> European Journal of Trauma and Emergency Surgery. 41 (6), 639-645 (2015).</li><li>Sellei, R. M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Compartment+elasticity+measured+by+pressure-related+ultrasound+to+determine+patients+&#8220;at+risk&#8221;+for+compartment+syndrome:+an+experimental+in+vitro+study.">Compartment elasticity measured by pressure-related ultrasound to determine patients &#8220;at risk&#8221; for compartment syndrome: an experimental in vitro study.</a> Patient Safety in Surgery. 9 (1), 4 (2015).</li><li>Bloch, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Compression+sonography+for+non-invasive+measurement+of+lower+leg+compartment+pressure+in+an+animal+model.&amp;#34;.">Compression sonography for non-invasive measurement of lower leg compartment pressure in an animal model.&amp;#34;.</a> Injury. 49 (3), 532-537 (2018).</li><li>Marmor, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Use+of+standard+musculoskeletal+ultrasound+to+determine+the+need+for+fasciotomy+in+an+elevated+muscle+compartment+pressure+cadaver+leg+model.">Use of standard musculoskeletal ultrasound to determine the need for fasciotomy in an elevated muscle compartment pressure cadaver leg model.</a> Injury. , (2019).</li></ol>

The authors have nothing to disclose

This article demonstrates a novel, clinically applicable technique for the non-invasive measurement of intra-compartmental pressures in the leg using an ultrasound coupled with a pressure sensor. This technique only requires a hand-held ultrasound and a commercially available pressure sensing transducer. It is quick and easy to perform and is well tolerated by patients. The entire diagnostic procedure can be performed in under 5 min with no additional resources. The calculated delta CFFP may then be used in conjunction w...

The purpose of this novel protocol is to evaluate the intra-compartmental pressure of the leg in a non-invasive way by using an ultrasound transducer coupled with a pressure sensor. Compartment syndrome is a well-known complication in musculoskeletal trauma and is the result of elevated intra-compartmental pressures which compromise the perfusion of tissues leading to irreversible ischemic injury if not intervened upon. Its diagnosis is primarily based on clinical exam. Unfortunately, clinical exam alone has been shown to have poor sensitivity and specificity in the diagnosis of compartment syndrome1. Invasive intra-compartmental pressure measuring by needle manometry is commonly used in the assessment of compartment syndrome2,3,4. The disadvantage of needle manometry is that it is an invasive procedure, being quite uncomfortable for the patient and not amenable to serial measurements. Furthermore, invasive intra-compartmental pressure measuring measurement is not routinely performed by some surgeons due to considerable disagreement over the appropriate threshold pressure for diagnosis of ACS and the high (35%) false positive rate and variability of a single invasive measurement5,6,7.
It has been previously demonstrated in artificial, animal, and human cadaver models that a rise in the intra-compartmental pressure results in a decreased elasticity of the fascia overlying the anterior compartment suggesting a correlation between the intra-compartmental pressure and compliance of the facial compartment as measured by ultrasound8,9,10. Further work has described using the pressure required to flatten the fascia of the anterior compartment as measured by ultrasound (Compartment Fascia Flattening Pressure [CFFP]) as a surrogate measure of the intra-compartmental pressure11. The anterior compartment fascia can be readily visualized with standard ultrasonography and, with the addition of a pressure sensor to the probe, CFFPs can be easily and reliably measured. This protocol offers a non-invasive diagnostic alternative for evaluating intra-compartmental pressures and can be performed quickly and serially with little to no patient discomfort.

<table><tbody><tr><td>Pressure sensor: Venous pressure measurement device</td><td>Vein press</td><td>VP 2014</td><td>A peripheral venous measuring device used in conjuction with an ultrasound to measure peripheral venous pressure.</td></tr><tr><td>Ultrasound probe: Vscan Extend R2 Dual Probe DICOM Base Package</td><td>GE Healthcare</td><td>H8038VP</td><td>Any ultrasound probe will be sufficent for this test. Using the narrow tranducer will function best when coupled to the pressure sensor</td></tr></tbody></table>

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.

This technique has been used to measure 10 consecutive patients with injured legs without evidence of compartment syndrome and 3 patients with a clinical diagnosis of compartment syndrome necessitating decompressive fasciotomies. The average delta CFFP for patients without compartment syndrome was 10.7 &#177; 10.6 mbar compared to 157 &#177; 51.7 mbar for patients with compartment syndrome and single-tailed t-test identified the differences in pressures between the groups as being statistically significant (P &#60; 0.02)...

Watch this Scientific Journal Video about A Novel Non-invasive Method for the Detection of Elevated Intra-compartmental Pressures of the Leg at JoVE.com

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

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 ...

a-novel-non-invasive-method-for-detection-elevated-intra

Research

JoVE Journal

Medicine

8.5K Views.  University of California, San Francisco. 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.

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

Vascular Occlusion Training for Inclusion Body Myositis: A Novel Therapeutic Approach

Inclusion body myositis (IBM) is a rare idiopathic inflammatory myopathy. It is known to produces remarkable muscle weakness and to greatly compromise function and quality of life. Moreover, clinical practice suggests that, unlike other inflammatory myopathies, the majority of IBM patients are not responsive to treatment with immunosuppressive or immunomodulatory drugs to counteract disease progression1. Additionally, conventional resistance training programs have been proven ineffective in restoring muscle function and muscle mass in these patients2,3. Nevertheless, we have recently observed that restricting muscle blood flow using tourniquet cuffs in association with moderate intensity resistance training in an IBM patient produced a significant gain in muscle mass and function, along with substantial benefits in quality of life4. Thus, a new non-pharmacological approach for IBM patients has been proposed. Herein, we describe the details of a proposed protocol for vascular occlusion associated with a resistance training program for this population.

The present article presents the details pertaining to the application of resistance training associated to vascular occlusion in IBM patients.

Inclusion body myositis (IBM) is a rare idiopathic inflammatory myopathy. It is known to produces remarkable muscle weakness and to greatly compromise ...

Tilt Testing with Combined Lower Body Negative Pressure: a "Gold Standard" for Measuring Orthostatic Tolerance

Orthostatic tolerance (OT) refers to the ability to maintain cardiovascular stability when upright, against the hydrostatic effects of gravity, and hence to maintain cerebral perfusion and prevent syncope (fainting). Various techniques are available to assess OT and the effects of gravitational stress upon the circulation, typically by reproducing a presyncopal event (near-fainting episode) in a controlled laboratory environment. The time and/or degree of stress required to provoke this response provides the measure of OT. Any technique used to determine OT should: enable distinction between patients with orthostatic intolerance (of various causes) and asymptomatic control subjects; be highly reproducible, enabling evaluation of therapeutic interventions; avoid invasive procedures, which are known to impair OT1.
In the late 1980s head-upright tilt testing was first utilized for diagnosing syncope2. Since then it has been used to assess OT in patients with syncope of unknown cause, as well as in healthy subjects to study postural cardiovascular reflexes2-6. Tilting protocols comprise three categories: passive tilt; passive tilt accompanied by pharmacological provocation; and passive tilt with combined lower body negative pressure (LBNP). However, the effects of tilt testing (and other orthostatic stress testing modalities) are often poorly reproducible, with low sensitivity and specificity to diagnose orthostatic intolerance7.
Typically, a passive tilt includes 20-60 min of orthostatic stress continued until the onset of presyncope in patients2-6. However, the main drawback of this procedure is its inability to invoke presyncope in all individuals undergoing the test, and corresponding low sensitivity8,9. Thus, different methods were explored to increase the orthostatic stress and improve sensitivity.
Pharmacological provocation has been used to increase the orthostatic challenge, for example using isoprenaline4,7,10,11 or sublingual nitrate12,13. However, the main drawback of these approaches are increases in sensitivity at the cost of unacceptable decreases in specificity10,14, with a high positive response rate immediately after administration15. Furthermore, invasive procedures associated with some pharmacological provocations greatly increase the false positive rate1.
Another approach is to combine passive tilt testing with LBNP, providing a stronger orthostatic stress without invasive procedures or drug side-effects, using the technique pioneered by Professor Roger Hainsworth in the 1990s16-18. This approach provokes presyncope in almost all subjects (allowing for symptom recognition in patients with syncope), while discriminating between patients with syncope and healthy controls, with a specificity of 92%, sensitivity of 85%, and repeatability of 1.1&plusmn;0.6 min16,17. This allows not only diagnosis and pathophysiological assessment19-22, but also the evaluation of treatments for orthostatic intolerance due to its high repeatability23-30. For these reasons, we argue this should be the "gold standard" for orthostatic stress testing, and accordingly this will be the method described in this paper.

We describe a "gold standard" for evaluating orthostatic tolerance (OT) using tilt testing with combined lower body negative pressure (LBNP). This can be combined with non-invasive evaluations of cardiovascular reflex control. Normal and abnormal responses are defined.

Orthostatic tolerance (OT)  refers to the ability to maintain cardiovascular stability when upright,  against the hydrostatic effects of gravity, and ...

Non-invasive Assessment of Microvascular and Endothelial Function

The authors have utilized capillaroscopy and forearm blood flow techniques to investigate the role of microvascular dysfunction in pathogenesis of cardiovascular disease. Capillaroscopy is a non-invasive, relatively inexpensive methodology for directly visualizing the microcirculation. Percent capillary recruitment is assessed by dividing the increase in capillary density induced by postocclusive reactive hyperemia (postocclusive reactive hyperemia capillary density minus baseline capillary density), by the maximal capillary density (observed during passive venous occlusion). Percent perfused capillaries represents the proportion of all capillaries present that are perfused (functionally active), and is calculated by dividing postocclusive reactive hyperemia capillary density by the maximal capillary density. Both percent capillary recruitment and percent perfused capillaries reflect the number of functional capillaries. The forearm blood flow (FBF) technique provides accepted non-invasive measures of endothelial function: The ratio FBFmax/FBFbase is computed as an estimate of vasodilation, by dividing the mean of the four FBFmax values by the mean of the four FBFbase values. Forearm vascular resistance at maximal vasodilation (FVRmax) is calculated as the mean arterial pressure (MAP) divided by FBFmax. Both the capillaroscopy and forearm techniques are readily acceptable to patients and can be learned quickly.
The microvascular and endothelial function measures obtained using the methodologies described in this paper may have future utility in clinical patient cardiovascular risk-reduction strategies. As we have published reports demonstrating that microvascular and endothelial dysfunction are found in initial stages of hypertension including prehypertension, microvascular and endothelial function measures may eventually aid in early identification, risk-stratification and prevention of end-stage vascular pathology, with its potentially fatal consequences.

Capillaroscopy is a non-invasive, relatively inexpensive methodology for directly visualizing the microcirculation. The forearm blood flow technique provides accepted non-invasive measures of endothelial function.

The authors have utilized capillaroscopy and forearm blood flow techniques to investigate the role of microvascular dysfunction in pathogenesis of ...

Direct Pressure Monitoring Accurately Predicts Pulmonary Vein Occlusion During Cryoballoon Ablation

Cryoballoon ablation (CBA) is an established therapy for atrial fibrillation (AF). Pulmonary vein (PV) occlusion is essential for achieving antral contact and PV isolation and is typically assessed by contrast injection. We present a novel method of direct pressure monitoring for assessment of PV occlusion.
Transcatheter pressure is monitored during balloon advancement to the PV antrum. Pressure is recorded via a single pressure transducer connected to the inner lumen of the cryoballoon. Pressure curve characteristics are used to assess occlusion in conjunction with fluoroscopic or intracardiac echocardiography (ICE) guidance. PV occlusion is confirmed when loss of typical left atrial (LA) pressure waveform is observed with recordings of PA pressure characteristics (no A wave and rapid V wave upstroke). Complete pulmonary vein occlusion as assessed with this technique has been confirmed with concurrent contrast utilization during the initial testing of the technique and has been shown to be highly accurate and readily reproducible.
We evaluated the efficacy of this novel technique in 35 patients. A total of 128 veins were assessed for occlusion with the cryoballoon utilizing the pressure monitoring technique; occlusive pressure was demonstrated in 113 veins with resultant successful pulmonary vein isolation in 111 veins (98.2%). Occlusion was confirmed with subsequent contrast injection during the initial ten procedures, after which contrast utilization was rapidly reduced or eliminated given the highly accurate identification of occlusive pressure waveform with limited initial training.
Verification of PV occlusive pressure during CBA is a novel approach to assessing effective PV occlusion and it accurately predicts electrical isolation. Utilization of this method results in significant decrease in fluoroscopy time and volume of contrast.

Effective pulmonary vein isolation utilizing a cryoballoon depends on complete pulmonary vein occlusion. The point of occlusion can be effectively predicted by direct analysis of pulmonary vein pressure waveform analysis during balloon inflation using a simple and reproducible technique.

Cryoballoon  ablation (CBA) is an established therapy for atrial fibrillation (AF).  Pulmonary vein (PV) occlusion is essential for achieving antral ...

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 ...

Intra-Abdominal Pressure Measurements in Neurocritical Patients

Intra-abdominal pressure (IAP) is increasingly being recognized as an indispensable and significant physiological parameter in intensive care units (ICU). IAP has been measured in a variety of ways with the development of many techniques in recent years. The level of intra-abdominal pressure under normal conditions is generally equal to or less than 12 mmHg. Accordingly, abdominal hypertension (IAH) is defined as two consecutive IAP measurements higher than 12 mmHg within 4-6 h. When IAH deteriorates further with IAP higher than 20 mmHg along with organ dysfunction and/or failure, this clinical manifestation can be diagnosed as abdominal compartment syndrome (ACS). IAH and ACS are associated with gastrointestinal ischemia, acute renal failure, and lung injury, leading to severe morbidity and mortality. Elevated IAP and IAH may affect the cerebral venous return and outflow of the cerebrospinal fluid by increasing the intrathoracic pressure (ITP), ultimately leading to increased intracranial pressure (ICP). Therefore, it is essential to monitor IAP in critically ill patients. The reproducibility and accuracy of intra-bladder pressure (IBP) measurements in previous studies need to be further improved, although the indirect measurement of IAP is now a widely used technique. To address these limitations, we recently used a set of IAP monitoring systems with advantages of convenience, continuous monitoring, digital visualization, and long-term IAP recording and data storage in critically ill patients. This IAP monitoring system can detect intra-abdominal hypertension and potentially analyze clinical status in real time. The recorded IAP data and other physiological indicators, such as intracranial pressure, can be further used for correlation analysis to guide treatment and predict a patient&#39;s possible prognosis.

This protocol details the use of a set of intra-abdominal pressure monitoring systems with advantages of convenience, continuous monitoring, digital visualization, and long-term IAP recording and data storage in neurocritical patients to detect intra-abdominal hypertension, which is used for correlation analysis to guide treatment and predict prognoses.

Intra-abdominal pressure (IAP) is increasingly being recognized as an indispensable and significant physiological parameter in intensive care units (ICU). ...

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 ...

Assessing Leg Blood Flow in Training 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 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.

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

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.