Limb Hemodynamics Research Articles

Skeletal muscle desmin alterations following revascularization in peripheral artery disease claudicants

Peripheral artery disease (PAD) is characterized by varying severity of arterial stenosis, exercise induced claudication, malperfused tissue precluding normal healing and skeletal muscle dysfunction. Revascularization interventions improve circulation, but post-reperfusion changes within the skeletal muscle are not well characterized. This study investigates if revascularization enhanced hemodynamics increases walking performance with concurrent improvement of mitochondrial function and reverses abnormal skeletal muscle morphological features that develop with PAD. Fifty-eight patients completed walking performance testing and muscle biopsy before and 6 months after revascularization procedures. Muscle fiber morphology, desmin structure, and mitochondria respiration assessments before and after the revascularization were evaluated. Revascularization improved limb hemodynamics, walking function, and muscle morphology. Qualitatively not all participants recovered normal structural architecture of desmin in the myopathic myofibers after revascularization. Heterogenous responses in the recovery of desmin structure following revascularization may be caused by other underlying factors not reversed with hemodynamic improvements. Revascularization interventions clinically improve patient walking ability and can reverse the multiple subcellular functional and structural abnormalities in muscle cells. Further study is needed to characterize desmin structural remodeling with improvements in skeletal muscle morphology and function.

Abstract 1153: Adipose-derived Mesenchymal Stem-cell Therapy Improves Arteriogenesis, Hemodynamics, And Walking Performance In A Porcine Model Of Peripheral Artery Disease

Background: There are few effective alternatives to revascularization for peripheral artery disease (PAD). We used our porcine model of PAD to test the hypothesis that adipose derived mesenchymal stem cells (ADMSC) injected around the aortic trifurcation in the pelvis improve ischemic limb hemodynamics and walking performance (WP). Methods: In Ossabaw miniswine (N=13, Age=6 mo) with metabolic syndrome, right (R) hindlimb ischemia was induced with R External Iliac and Superficial Femoral artery coil occlusion (T0) via carotid artery access. All swine had weekly testing of WP on a treadmill. At weeks 0 (T0), 4 (T4), and 8 (T8), ankle brachial indices (ABI) and muscle tissue oximetry (STO 2 ) were measured. At T4 and T8 all swine underwent angiography. At T4, in treatment (Tx) swine (N=4) ADMSC were isolated using stromal vascular fractionation of autologous abdominal wall fat. Using jugular vein access, a catheter with a retractable side-deploying needle was inserted in the R iliac vein and stabilized by a juxtaposed angioplasty balloon. The needle was deployed to access the retroperitoneum and ADMSC were infused around the aortic trifurcation. Results: Ischemic controls (IC) had no differences between T4 and T8 in ABIs, and mean STO 2 differences between R and L in calves and thighs. Tx improved both ABI and mean STO 2 measurements (table 1). IC had no changes in WP between T4 and T8, while Tx showed improvements (table1). On angiography, IC had growth of R Internal iliac artery (RIIA, the main inflow to the ischemic R hindlimb) and shorter appearance time (AT) of RIIA compared to L with no difference between T4 and T8. Tx showed increased growth of RIIA and shorter AT at T8 compared to T4 (table 1). Conclusion: In a clinically-relevant (similar to humans in size, anatomy, physiology and comorbidities) porcine model of PAD we found that ADMSC injection around the aortic trifurcation in the pelvis induces arteriogenesis and improves ischemic limb hemodynamics and walking performance.

Endovascular Denervation for the Improvement of Limb Ischemia in Patients with Peripheral Artery Disease: A Randomized Clinical Trial

ObjectivesTo evaluate the safety and efficacy of endovascular denervation (EDN) as an adjunct to percutaneous vascular intervention (PVI) for peripheral artery disease (PAD). MethodsFrom August 2019 to April 2021, 38 eligible patients with PAD enrolled in this study were randomly and equally assigned into two groups: the PVI group and the PVI+EDN group treated with EDN at the iliac and femoral arteries before PVI. The primary endpoint was the improvement in the ankle brachial index (ABI) at 6 months after the procedure. The secondary endpoints were transcutaneous oxygen pressure (TcPO2), Rutherford category, numerical rating scale (NRS) score, and safety. ResultsThe technical success rates of PVI and EDN were 100%, and no device- or procedure-related major adverse events occurred in either group. Compared with PVI alone, PVI+EDN demonstrated a significant improvement in limb hemodynamics at 6 months (ΔABI 0.44 ± 0.31 vs. 0.24 ± 0.15, P = 0.018). Microcirculatory perfusion of PAD was significantly better at 6 months in the PVI+EDN group (ΔTcPO2, 15.68 ± 16.72 vs. 4.95 ± 13.43, P = 0.036). The Rutherford category was significantly improved in the PVI+EDN group in comparison with the PVI group at the 3-month follow-up (100.00% vs. 68.42%, P = 0.02). The decrease in the NRS score in the PVI+EDN group was greater than that in the PVI group at 1 week following the procedure (3 [2-5] vs. 4 [4-6], P = 0.022). ConclusionIn this single-center pilot analysis of a heterogeneous cohort of patients with PAD, PVI with EDN demonstrated a significant improvement in limb ischemia at 6 months compared with PVI alone.

Role of Hemodynamic Assessment and Limitations in Ankle-Brachial Pressure Index, Toe- Brachial Pressure Index to Predict Wound Healing After Revascularization.

Chronic limb-threatening ischemia (CLTI) represents one of the most severe forms of peripheral arterial disease implying impaired wound healing and tissue loss at the same time posing a significant impact on the quality of life of patients and a serious economic burden on healthcare systems around the world. A major challenge in the management of patients with CLTI is the validity and role of non-invasive hemodynamic parameters in assessing their clinical status before and after revascularization. Traditionally, the diagnosis of CLTI is routinely based on clinical symptoms and confirmed by measurements of non-invasive limb hemodynamics including ankle-brachial pressure index (ABPI) and toe-brachial pressure index (TBPI). However, whether these indices alone can provide definitive treatment or be used as adjunctive tool along with the implementation of novel techniques to help guide revascularization for CLI patients still remains unclear.

Effect of foot stato-dynamic disorders on hemodynamics of the lower limb using strain-gauge plethysmography

BackgroundThe plantar venous pump (PVP), composed of deep plantar veins, is the most distal contributor to venous return from the lower limbs. A pressing need still exists to assess how plantar muscle contraction and gait affect PVP function, how foot stato-dynamic disorders (FSDs) can contribute to venous insufficiency, and how venous return can be optimally stimulated. Our first objective is to compare the venous blood hemodynamics in lower limbs between healthy subjects with a FSD and healthy subjects without a FSD to understand the influence of foot morphology in the performance of the PVP. Our second objective is to evaluate whether PVP function varies with different plantar pressures. MethodsA total of 52 healthy volunteers (26 feet with a normal arch as the control group and 26 feet with dysmorphism [13 flat feet and 13 hollow feet]) were included. Strain-gauge plethysmography was performed 8 cm above the medial malleolus at different conditions of PVP stimulation: (1) toe flexion, (2) intermittent pneumatic compression (IPC) with and without an insole, and (3) 3-km/h speed walking on a treadmill barefoot, with shoes, and with shoes and insoles. From the strain-gauge plethysmography, we measured the venous blood ejection fraction (EF). From the pressure sensor placed at the midfoot on the plantar arch during IPC, we obtained the maximal pressure (N/cm2). ResultsToe flexion allowed for ejection of an average of 20% of the total venous volume in both groups. IPC and gait generated a mean EF superior to 100% of the available venous volume. The maximal pressure applied at the midfoot during IPC was lower than the pressure set. No significant differences in the EF or maximal pressure were observed between the two groups. The mean EF was not significantly affected for the pronator and supinator walkers compared with those with normal walking dynamics. Wearing shoes did not significantly affect the mean EF. However, wearing insoles during gait significantly increased the venous return in feet with plantar dysmorphism. ConclusionsTo the best of our knowledge, this clinical study is the first to assess the PVP function in 52 healthy volunteers with and without FSDs. We found that wearing shoes did not significantly affect PVP efficiency but that wearing morphologically adapted insoles significantly improved the venous return in the dysmorphic feet. In our sample of healthy volunteers, the differences observed between the control group and feet with FSDs were not statistically significant.

Lower limb hyperthermia augments functional hyperaemia during small muscle mass exercise similarly in trained elderly and young humans.

What is the central question of the study? Ageing is postulated to lead to underperfusion of human limb tissues during passive and exertional hyperthermia, but findings to date have been equivocal. Thus, does age have an independent adverse effect on local haemodynamics during passive single-leg hyperthermia, single-leg knee-extensor exercise and their combination? What is the main finding and its importance? Local hyperthermia increased leg blood flow over three-fold and had an additive effect during knee-extensor exercise with no absolute differences in leg perfusion between the healthy, exercise-trained elderly and the young groups. Our findings indicate that age per se does not compromise lower limb hyperaemia during local hyperthermia and/or small muscle mass exercise. Heat and exercise therapies are recommended to improve vascular health across the lifespan. However, the haemodynamic effects of hyperthermia, exercise and their combination are inconsistent in young and elderly people. Here we investigated the acute effects of local-limb hyperthermia and exercise on limb haemodynamics in nine healthy, trained elderly (69±5 years) and 10 young (26±7 years) adults, hypothesising that the combination of local hyperthermia and exercise interact to increase leg perfusion, albeit to a lesser extent in the elderly. Participants underwent 90min of single whole-leg heating, with the contralateral leg remaining as control, followed by 10min of low-intensity incremental single-leg knee-extensor exercise with both the heated and control legs. Temperature profiles and leg haemodynamics at the femoral and popliteal arteries were measured. In both groups, heating increased whole-leg skin temperature and blood flow by 9.5±1.2°C and 0.7±0.2Lmin-1 (>3-fold), respectively (P<0.0001). Blood flow in the heated leg remained 0.7±0.6 and 1.0±0.8Lmin-1 higher during exercise at 6 and 12W, respectively (P<0.0001). However, there were no differences in limb haemodynamics between cohorts, other than the elderly group exhibiting a 16±6% larger arterial diameter and a 51±6% lower blood velocity following heating (P<0.0001). In conclusion, local hyperthermia-induced limb hyperperfusion and/or small muscle mass exercise hyperaemia are preserved in trained older people despite evident age-related structural and functional alterations in their leg conduit arteries.

IGF-1 Therapy Improves Muscle Size and Function in Experimental Peripheral Arterial Disease

Lower-extremity peripheral arterial disease (PAD) has increased in prevalence, yet therapeutic development has remained stagnant. Skeletal muscle health and function has been strongly linked to quality of life and medical outcomes in patients with PAD. Using a rodent model of PAD, this study demonstrates that treatment of the ischemic limb with insulin-like growth factor (IGF)-1 significantly increases muscle size and strength without improving limb hemodynamics. Interestingly, the effect size of IGF1 therapy was larger in female mice than in male mice, highlighting the need to carefully examine sex-dependent effects in experimental PAD therapies.

Impact of Oxygen Supplementation on Brachial Artery Hemodynamics and Vascular Function During Ascent to 5,050 m

Vizcardo-Galindo, Gustavo A., Connor A. Howe, Ryan L. Hoiland, Howard H. Carter, Christopher K. Willie, Philip N. Ainslie, and Joshua C. Tremblay. Impact of oxygen supplementation on brachial artery hemodynamics and vascular function during ascent to 5,050 m. High Alt Med Biol. 24:27-36, 2023.-High-altitude trekking alters upper limb hemodynamics and reduces brachial artery vascular function in lowlanders. Whether these changes are reversible with the removal of hypoxia is unknown. We investigated the impact of 20 minutes of oxygen supplementation (O2) on brachial artery hemodynamics, reactive hyperemia (RH; microvascular function), and flow-mediated dilation (FMD; endothelial function). Participants (aged 21-42 years) were examined before and with O2 at 3,440 m (n = 7), 4,371 m (n = 7), and 5,050 m (n = 12) using Duplex ultrasound (days 4, 7, and 10 respectively). At 3,440 m, O2 decreased brachial artery diameter (-5% ± 5%; p = 0.04), baseline blood flow (-44% ± 15%; p < 0.001), oxygen delivery (-39 ± 16; p < 0.001), and peak RH (-8% ± 8%; p = 0.02), but not RH normalized for baseline blood flow. Elevated FMD (p = 0.04) with O2 at 3,440 m was attributed to the reduction in baseline diameter. At 5,050 m, a reduction in brachial artery blood flow (-17% ± 22%; p = 0.03), but not oxygen delivery, diameter, RH, or FMD occurred with O2. These findings suggest that during early trekking at high altitude, O2 causes vasoconstriction in the upper limb along the arterial tree (conduit and resistance arteries). With incremental high-altitude exposure, O2 reduces blood flow without compromising oxygen delivery, RH, or FMD, suggesting a differential impact on vascular function modulated by the duration and severity of high-altitude exposure.

Thigh-length graduated compression stocking cannot increase blood velocity of the common femoral vein in patients awaiting total hip arthroplasty

ObjectivesGraduated compression stocking (GCS) is one of the mechanical prophylaxes commonly used for deep vein thrombosis (DVT). The present study was designed to observe the effects of graduated compression stockings on the vein deformation and hemodynamics of lower limbs in patients awaiting total hip arthroplasty (THA).MethodsThe lower extremity veins of 22 patients awaiting THA were examined by ultrasound, when they rested in supine position with or without thigh-length GCS. The deformation parameters we measured included antero-posterior (AP) diameters, latero-medial (LM) diameters, and cross-sectional area (CSA) of great saphenous vein (GSV), posterior tibial vein (PTV), popliteal vein (PV), gastrocnemius vein (GV), and superficial femoral vein (SFV). We measured peak velocity and mean velocity of GSV, common femoral vein (CFV), junction of GSV and CFV to represent for hemodynamics of veins.ResultsSignificant compression was observed in almost all measured veins with the use of thigh-length GCS, while it was unable to significantly compress GSV in latero-medial diameter. The mean latero-medial diameter reductions for GSV, PTV, GV, PV and SFV were 19.4, 30.2, 43.2, 29.7 and 20.4%, respectively. GCS significantly compressed antero-posterior diameter of GSV, PTV, GV, PV and SFV by 43.4, 33.3, 42.1, 37.5, and 27.8%, respectively. The mean reduction of cross-section area was 44.8% for GSV, 49.6% for PTV, 60.0% for GV, 57.4% for PV, and 36.2% for FV. No significant changes were observed in the mean blood velocity of GSV, CFV, and junction. GCS was able to significantly reduce peak velocity of CFV (17.6 ± 5.6 cm/s to 16.1 ± 6.0 cm/s) and junction (23.3 ± 9.5 cm/s to 21.3 ± 9.7 cm/s), while it did not change the peak velocity of GSV.ConclusionThigh-length GCS is sufficient to compress lower extremity veins in patients awaiting THA in supine position with the greatest compression in GV, while it was unable to significantly increase blood velocity of common femoral vein or GSV. GCS may prevent DVT through more than simply increasing blood flow. Further studies are needed to determine the specific effects of GCS.

Dietary nitrate supplementation and small muscle mass exercise hemodynamics in patients with essential hypertension.

Exaggerated blood pressure and diminished limb hemodynamics during exercise in patients with hypertension often are not resolved by antihypertensive medications. We hypothesized that, independent of antihypertensive medication status, dietary nitrate supplementation would increase limb blood flow, decrease mean arterial pressure (MAP), and increase limb vascular conductance during exercise in patients with hypertension. Patients with hypertension either abstained from (n = 14, Off-Meds) or continued (n = 12, On-Meds) antihypertensive medications. Within each group, patients consumed (crossover design) nitrate-rich or nitrate-depleted (placebo) beetroot juice for 3 days before performing handgrip (HG) and knee-extensor exercise (KE). Blood flow and MAP were measured using Doppler ultrasound and an automated monitor, respectively. Dietary nitrate increased plasma-[nitrite] Off-Meds and On-Meds. There were no significant effects of dietary nitrate on blood flow, MAP, or vascular conductance during HG in Off-Meds or On-Meds. For KE, dietary nitrate decreased MAP (means ± SD across all 3 exercise intensities, 118 ± 14 vs. 122 ± 14 mmHg, P = 0.024) and increased vascular conductance (26.2 ± 6.1 vs. 24.7 ± 7.0 mL/min/mmHg, P = 0.024), but did not affect blood flow for Off-Meds, with no effects On-Meds. Dietary nitrate-induced changes in blood flow (r = -0.67, P < 0.001), MAP (r = -0.43, P = 0.009), and vascular conductance (r = -0.64, P < 0.001) during KE, but only vascular conductance (r = -0.35, P = 0.039) during HG, were significantly related to the magnitude of placebo values, with no differentiation between groups. Thus, the effects of dietary nitrate on limb hemodynamics and MAP during exercise in patients with hypertension are dependent on the values at baseline, independent of antihypertensive medication status, and dependent on whether exercise was performed by the forearm or quadriceps.NEW & NOTEWORTHY Adverse hemodynamic responses to exercise in patients with hypertension, despite antihypertensive medication, indicate a sustained cardiovascular risk. The efficacy of dietary nitrate to improve limb vascular conductance during exercise was inversely dependent on the magnitude of exercising limb vascular conductance at baseline, rather than antihypertensive medication status. The effects of dietary nitrate on hemodynamics during exercise in patients with hypertension are dependent on the values at baseline and independent of antihypertensive medication status.

The changes of the calf-vein deformation and femoral vein peak velocity during ankle pump exercise with or without graduated compression stockings

ObjectivesTo analyze the changes of lower limb hemodynamics parameters before and after wearing graduated compression stockings (GCS) during ankle pump exercise in patients preparing for arthroplastic surgery.MethodThe leg veins of 16 patients awaiting arthroplasty were analyzed using a Sonosite M-Turbo ultrasound system during ankle pump exercise with or without GCS. The age of them was 70 ± 7 years (mean ± SD) (range 56—82 years) and body mass index was 25.8 ± 3.0 kg/m2 (range 18.0—30.5 kg/m2). Measured data including the cross-sectional area (CSA), anteroposterior (AP) diameter and lateromedial (LM) diameter of the soleus vein (SV), posterior tibial vein (PTV) and great saphenous vein (GSV). Additionally, the peak velocities of femoral vein (FV) were also measured.ResultsGCS could significantly decrease the cross-sectional area of SV, PTV and GSV in supine position at rest and maximum ankle plantar flexion. But the compression effect of GCS to SV and GSV was not observed during maximum ankle dorsiflexion. It was found that GCS application reduced the peak flow velocity of the femoral vein from 61.85 cm/s (95% CI = 50.94–72.75 cm/s) to 38.01 cm/s (95% CI = 28.42–47.59 cm/s) (P < 0.001) during ankle plantar flexion and decreased the femoral vein in these patients from 80.65 cm/s (95% CI = 70.37–90.92 cm/s) to 51.15 cm/s (95% CI = 42.58–59.73 cm/s) (P < 0.001) during ankle dorsiflexion. But this effect was not significant in supine position at rest.ConclusionsGCS could significantly reduce the peak flow velocity of the femoral vein during ankle pump exercise in the patients preparing for arthroplastic surgery.

Effect of ankle pump exercise on fatigue sensation, comfort, and lower limb hemodynamics among deep vein thrombosis patients

Background: Ankle pumping exercises utilize a calf muscle pump function to pump blood to the heart by muscle contraction. Ankle pumping exercises are often used for the relief of edema and the prevention of deep vein thrombosis. So, the current study aimed to evaluate the effect of ankle pump exercise on fatigue sensation, comfort, and lower limb hemodynamics among deep vein thrombosis patients. Design: This study was carried out using a quasi-experimental research design. Setting: This study was applied in the Orthopedic Department at Ain Shams University Hospital. Subjects: It consisted of a convenient sampling technique enrolled to select a sample of 100 patients with deep vein thrombosis in the previously selected department who agreed to participate in the study and were randomly assigned into two equal groups, with 50 patients in each group (the intervention group who received ankle pump exercise and the control group who received routine hospital care only). Tools: three tools were used (I): A patient interviewing sheet, (II): Rating of Perceived Exertion (RPE), and (III): Comfort evaluation scale.

Effect of obesity on venous hemodynamics of the lower limbs during laparoscopic cholecystectomy.

The present study aims to compare the changes of venous flow parameters of the lower limbs under the assessment based on the duplex ultrasound scanning in obese and non-obese individuals by complying with body mass index during laparoscopic cholecystectomy. A prospective cohort study was conducted in non-obese (body mass index <25kg/m2) and obese individuals (body mass index >30kg/m2) during laparoscopic cholecystectomy to analyze venous hemodynamics of the lower limbs. The assessment was conducted on Femoral vein diameter, Femoral vein cross-sectional area, Femoral vein peak velocity, and Femoral vein volume flow. The change values (%) of venous flow parameters of the lower limbs were calculated as a percentage by: (intra-operative parameter-pre-operative parameter)/ pre-operative parametersX100%. 45 right lower limbs were examined in 45 non-obese individuals and 33 right lower limbs in 33 obese individuals during laparoscopic cholecystectomy. The statistically significant difference was identified in the pre-operative and intra-operative values of Femoral vein diameter, Femoral vein cross-sectional area, Femoral vein peak velocity, as well as Femoral vein volume flow in both groups when these were analyzed independently (p = .00). When the change values of venous flow parameters of the lower limbs of the two groups were compared, more changes were identified significantly in the obese group, Femoral vein diameter (p = .042), Femoral vein cross-sectional area (p = .013), Femoral vein peak velocity (p = .002), and Femoral vein volume flow (p = .032). The changes of lower limb venous flow parameters showed more significant difference in obese than in non-obese individuals during laparoscopic cholecystectomy. The mentioned findings may in part explain why obese patients undergoing laparoscopic cholecystectomy have a higher rate of post op deep venous thrombosis.

ГЕМОДИНАМИКА В ТАЗОВЫХ КОНЕЧНОСТЯХ ПРИ ТРАВМЕ СПИННОГО МОЗГА В УСЛОВИЯХ ПРИМЕНЕНИЯ ПРОТИВОСПАЕЧНОГО ГИАЛУРОНСОДЕРЖАЩЕГО ГЕЛЯ

It is possible to reduce the degree of systemic complications arising in response to spinal cord injury by providing timely medical care. Positive therapeutic effect of intrathecal administration of hyaluron gels is known for such injuries. In turn, these medications can be used as carriers of other medical substances. The aim of the research is to study hemodynamics in hind limbs in case of traumatic spinal cord injury using an anti-adhesion gel which contains Na-carboxymethyl cellulose. Rats’ spinal cord injury at the level of the thoracic section of the spine was simulated and a hyaluronic-containing anti-adhesion absorbable gel was injected into the injury area. Hemodynamics and temperature response of pelvic limb tissues were studied. Heart rate dynamics and general body temperature were assessed. The quantitative data were compared with the physiological norm. The animals were observed for 90 days. No heart rhythm disturbances were noted. During the experiment, hyperthermy of central genesis was recorded, which was characterized by an increase of the total body temperature to a maximum of 37.11 ± 0.6 ° C (p = 0.004) and local temperature - up to 34.48 ± 2.24 ° C (p = 0.002). The phenomena of vasodilatation of the arteries were observed, which were more pronounced after 60 days of the experiment. Further on, the visco-elastic properties of the vessels improved. Difficulties in venous outflow in the created conditions were not found. According to available literature data, when modeling a spinal cord injury without application of antiadhesion hyaluronic medications, vascular disorders are more explicit. Conclusion. The application of a hyaluronic anti-adhesion gel for traumatic spinal cord injury can reduce the intensity of emerging pathological conditions.

Changes in cortical hemodynamics with the emergence of skilled motor ability in infants: An fNIRS study

The brain activity changes during infancy that underpin the emergence of functional motor skills, such as reaching and stepping, are not well understood. The current study used functional near-infrared spectroscopy (fNIRS) to examine the hemodynamic response across the frontal, mid-coronal plane (sensorimotor cortex) and external occipital protuberance (cerebellar cortex) regions of typically developing infants (5 to 13 months) during reach-to-grasp or supported treadmill stepping behaviour. Motor ability was assessed using the third edition of the Motor Subscale of the Bayley Scales of Infant Development (BSID-III). Infants with enhanced motor ability demonstrated greater oxy-hemoglobin (HbO) concentration in the contralateral anterior mid-coronal and frontal-dorsal areas during right-handed reach-to-grasp. During bilateral reaching behavior, infants with enhanced motor ability showed greater HbO increases in right frontal-dorsal regions and lower HbO increases in left anterior mid-coronal areas. In contrast, infants' motor ability was associated with changes in de-oxyhemoglobin (HbR) concentration in the ipsilateral anterior mid-coronal, contralateral frontal and left external occipital protuberance regions during left-handed reaching behavior. These relationships between upper limb hemodynamics and infant motor ability are consistent with increased lateralization and cognitive-motor coupling as motor skills emerge. During stepping behavior, infants with enhanced motor ability demonstrated smaller increases in HbR concentration in the bilateral external occipital protuberance region consistent with an emerging efficiency as cruising and independent stepping behavior is still nascent. Together, the current results identify several distinct neural markers of functional motor ability during infancy that may be relevant to diagnostic testing and rehabilitation of developmental movement disorders.

Regional thermal hyperemia in the human leg: Evidence of the importance of thermosensitive mechanisms in the control of the peripheral circulation.

Hyperthermia is thought to increase limb blood flow through the activation of thermosensitive mechanisms within the limb vasculature, but the precise vascular locus in which hyperthermia modulates perfusion remains elusive. We tested the hypothesis that local temperature‐sensitive mechanisms alter limb hemodynamics by regulating microvascular blood flow. Temperature and oxygenation profiles and leg hemodynamics of the common (CFA), superficial (SFA) and profunda (PFA) femoral arteries, and popliteal artery (POA) of the experimental and control legs were measured in healthy participants during: (1) 3 h of whole leg heating (WLH) followed by 3 h of recovery (n = 9); (2) 1 h of upper leg heating (ULH) followed by 30 min of cooling and 1 h ULH bout (n = 8); and (3) 1 h of lower leg heating (LLH) (n = 8). WLH increased experimental leg temperature by 4.2 ± 1.2ºC and blood flow in CFA, SFA, PFA, and POA by ≥3‐fold, while the core temperature essentially remained stable. Upper and lower leg blood flow increased exponentially in response to leg temperature and then declined during recovery. ULH and LLH similarly increased the corresponding segmental leg temperature, blood flow, and tissue oxygenation without affecting these responses in the non‐heated leg segment, or perfusion pressure and conduit artery diameter across all vessels. Findings demonstrate that whole leg hyperthermia induces profound and sustained elevations in upper and lower limb blood flow and that segmental hyperthermia matches the regional thermal hyperemia without causing thermal or hemodynamic alterations in the non‐heated limb segment. These observations support the notion that heat‐activated thermosensitive mechanisms in microcirculation regulate limb tissue perfusion during hyperthermia.

Comparison of the Hemodynamic Performance of Two Neuromuscular Electrical Stimulation Devices Applied to the Lower Limb.

Currently, 1% of the population of the Western world suffers from venous leg ulcers as a result of chronic venous insufficiency. Current treatment involves the use of moist wound healing, compression bandages, and intermittent pneumatic compression. Neuromuscular electrical stimulation is a novel potential new therapeutic method for the promotion of increased lower limb hemodynamics. The aim of this study was to measure the hemodynamic changes in the lower limb with the use of two neuromuscular electrical stimulation devices. Twelve healthy volunteers received two neuromuscular stimulation device interventions. The GekoTM and National University of Ireland (NUI) Galway neuromuscular electrical stimulation devices were randomized between dominant and non-dominant legs. Hemodynamic measurements of peak venous velocity (cm/s), the time average mean velocity (TAMEAN) (cm/s), and ejected volume (mL) of blood were recorded. Peak venous velocity was significantly increased by the GekoTM and the NUI Galway device compared to baseline blood flow (p < 0.0001), while only the voluntary contraction produced significant increases in TAMEAN and ejected volume (both p < 0.05). Neuromuscular muscular electrical stimulation can produce adequate increases in lower limb hemodynamics sufficient to prevent venous stasis. Greater use of neuromuscular stimulation devices could be considered in the treatment of conditions related to chronic venous insufficiency but requires further research.

Lower limb massage in humans increases local perfusion and impacts systemic hemodynamics.

Massage is commonly used as a complementary therapy for many different conditions. Demonstration of its physiological impact and understanding of its therapeutic mechanisms is still insufficient and often inconclusive. This study aims to characterize the physiological effects of effleurage, one of the most popular techniques, on human in vivo microcirculation and its impact on cardiovascular function. Two differently oriented variations of the technique, referred to influence physiological outcomes, were applied to 32 young (mean 19.8 ± 1.6 yr old) healthy volunteers of both sexes in a single, randomly chosen limb after informed written consent. Each protocol included a 10-min baseline (Phase I), a 5-min massage (Phase II), and a 10-min recovery (Phase III) register. A 30-min washout period separated both protocols. Perfusion was assessed by laser Doppler flowmetry (LDF) and reflection photoplethysmography (PPG), with their sensors applied distally in both feet. Blood pressure and pulse were also obtained. LDF signals were further analyzed in their components by the (Morlet) wavelet transform to probe the mechanisms involved. Results showed that effleurage consistently evoked a significant (P < 0.001) perfusion increase in the massaged limb, also visible in the contralateral limb (not significant) independently from the orientation (variant) used. No matter the perfusion differences known between sexes, the adaptive response was equivalent in both sexes. The component analysis of the LDF curves also suggests that these procedures, although brief and superficial, do modify multiple components of cardiovascular integration, with cardiac, respiratory, and myogenic components appearing to play a major role in reestablishing distal microcirculatory homeostasis.NEW & NOTEWORTHY The impact of effleurage, a well-known massage procedure used in human rehabilitation, in the lower limb hemodynamics, is demonstrated. When applied in a sole limb, massage increases skin microcirculatory flowmotion not only locally but also beyond, affecting systemic hemodynamics. This observation is an interesting example of the efficacy of cardiovascular integration mechanisms involving distal microcirculatory homeostasis. The proposed methodology allows a mechanistic view over skin flowmotion regulation, being applicable to further explore massage and its impact on microcirculatory physiology.

Investigating Lower Limb Hemodynamics during Flap Training Regimens and Patient-led Isometric Contraction Protocols.

The evidence for lower limb flap (LLF) training regimens is equivocal. The commonest cause of LLF failure is venous congestion. The aim of this study was to investigate whether venous congestion could be reduced by patient-led isometric calf contractions during flap training. A prospective clinical study was conducted using photospectroscopy and laser Doppler (Oxygen to See) to assess healthy limbs and LLF characteristics during flap training and isometric calf contractions. Tissue oxygen saturation, venous congestion, and blood flow were measured at rest, as well as during and after limb dangling and calf contraction exercises. In the acute postoperative period following LLF surgery, dependency markedly reduced superficial flow (-55.20% ± 19.17%), with a concurrent increase in venous congestion (33.80% ± 28.80%); supine isometric contractions improved superficial flow and reduced venous congestion from postoperative day 5. Contractions cause a significant increase in blood flow in the outpatient cohort (+84.40% ± 7.86%, P = 0.009), with a mean time since discharge of 14 weeks. Our data suggest patient-led isometric calf exercises are well tolerated and may reduce venous congestion in the acute phase. Progressive changes toward normal physiological function were demonstrated in the outpatient rehabilitation period. Incorporating calf exercises into LLF rehabilitation may allow longer periods of leg dependency, quicker recovery from surgery, and ultimately improve outcomes.

A Noninvasive, Electromagnetic, Epidermal Sensing Device for Hemodynamics Monitoring.

Non-intrusive monitoring of blood flow parameters is vital for obtaining physiological and pathophysiological information pertaining to dynamic cardiovascular events and is feasible to achieve via non-invasive, conformal, wearable technologies. Here, we present a proof-of-concept of a fully integrated, high frequency (bandwidth 40 MHz), electromagnetic sensing device for monitoring limb hemodynamics and morphology associated with blood flow. The sensing architecture integrates a novel radio frequency (RF) skin patch resonator embedded with a coplanar outer loop antenna and a scalable, standalone wireless readout hardware based on standing wave ratio (SWR) bridge. The resonator itself is a copper-based open circuit planar Archimedean spiral with a rectangular cross-sectional area, chemically etched on a flexible polyimide substrate. The readout hardware is developed exploiting off-the-shelf components, fabricated on the top of a rigid FR4 substrate. The proposed readout circuit can measure resonant frequency of an RLC network. When energized by the external oscillating RF field via loop antenna, the resonator produces an electromagnetic field response which can be perturbed by dielectric variation inside its field boundary. Through leveraging this principle, the in-vitro experimental results from the benchtop models suggest that the resonator's RF attributes such as resonant frequency shift and magnitude variation of reflection coefficient due to fluid volume displacement can be successfully detected through the proposed hardware architecture. Hence, the system could be an alternative to the conventional, multimodal, non-invasive wearable sensing with an unprecedented capability of ubiquitous fluid phenomena detection from multiple sites of the human body.