Doppler Probe Research Articles

Inter-ankle Systolic Blood Pressure Difference Is a Marker of Increased Fasting Blood-Glucose in Asian Pregnant Women.

ObjectiveThis cross-sectional study aimed to determine the relationship between clinical blood pressures and blood pressures measured using Doppler with blood glucose in pregnancy by ethnicity.MethodsWe recruited 179 (52% White European, 48% Asian) pregnant women at 24-28 weeks of gestation who underwent a glucose tolerance test in an antenatal clinic in Bradford Royal Infirmary, the UK, from 2012 to 2013. Systolic blood pressures in the arm (left and right brachial) and ankle [left and right posterior tibial (PT) and dorsalis pedalis (DP)] blood pressures were measured using a Doppler probe. The inter-arm (brachial) and inter-ankle (PT and DP) systolic blood pressure differences were obtained. A multivariate linear regression model adjusted for age, body mass index, and diabetes risk was used to assess the relationship between blood pressures and blood glucose.ResultsAsian pregnant women had higher blood glucose but lower ankle blood pressures than White Europeans. In White Europeans, brachial blood pressures and clinical blood pressures were positively associated with fasting blood glucose (FBG), but brachial blood pressures did not perform better as an indicator of FBG than clinical blood pressures. In Asians, increased inter-ankle blood pressure difference was associated with increased FBG. For each 10 mmHg increase in the inter-ankle blood pressure difference, FBG increased by 0.12 mmol/L (Beta=0.12, 95%CI: 0.01-0.23).ConclusionThe relationship between blood pressures with blood glucose differed by ethnicity. In Asians, inter-ankle systolic blood pressure difference was positively associated with blood glucose. This is first ever report on ankle blood pressures with blood glucose in pregnancy which suggests future potential as a non-invasive gestational diabetes risk screening tool.

Multiple Laser Doppler Flowmetry Probes Increase the Reproducibility of Skin Blood Flow Measurements.

Cutaneous microcirculatory perfusion is commonly measured using laser Doppler flowmetry (LDF) probes, which provide a continuous, non-invasive quantification of skin blood flow (SkBF). However, inhomogeneities in the skin’s microvasculature density contribute to a decrease in reproducibility whenever an LDF probe is removed and replaced, as is the case during pre- and post-intervention or between-day measurements. Therefore, this study aimed to determine whether increasing the total number of individual LDF probes in a localized area improves the reproducibility of the measurement. Seven laser Doppler probes were secured in a custom-made acrylic holder designed to attach to the skin’s surface easily. SkBF, local skin temperature (Tsk), and blood pressure (BP) were assessed in 11 participants (6 M, 5 F, 42 ± 15 years). SkBF and Tsk were measured from the dorsal forearm (arm trial) for 5 min. Next, the multi-laser device was moved to the lateral side of the calf (leg trial), and measurements were obtained for 5 min. Each arm and leg trial was cyclically repeated three times, and all trials were separated by intermissions lasting 10–15 min. The average SkBF and the cutaneous vascular conductance (CVC) from all possible LDF probe combinations were not statistically different across the three arm and leg trials. Two-way mixed-effects models with absolute agreement were used to compute the intraclass correlation coefficient (ICC) for CVC, and the minimum ICC increased with the addition of LDF probes. The ICC of the average CVC from seven LDF probes was 0.96 between the arm trials and 0.91 between the leg trials, which suggests that there is excellent reliability and little difference between trials following the removal and replacement of the device. Moreover, all individual ICC values from ≥3 LDF probe combinations were greater than 0.70 (i.e., good reliability). These data suggest that SkBF measurements with multiple laser Doppler probes in a custom-made holder have excellent reproducibility after replacing the probes within the same participant. Therefore, this application could provide more reproducible assessments between repeated measurements (e.g., before and after exercise or clinical procedures) where the LDF probes must be removed and replaced within the same location.

Microvascular Doppler Assisted Microsurgical Denervation of the Spermatic Cord in Treating Chronic Orchialgia.

Chronic orchialgia is a common disease in department of urology and andrology. The etiology is complex, and the treatment is difficult. In severe cases, orchiectomy is even necessary. In recent years, microsurgical denervation of the spermatic cord (MDSC) is a minimally invasive and effective surgical method for the treatment of chronic orchialgia. Its greatest advantage is to preserve the testis and epididymis, avoid the possible organ resection. The key of the operation is to dissect all the fibrous tissues in the spermatic cord, while protecting the arteries (especially the testicular arteries) and several lymphatic vessels. Combined with the use of microvascular doppler in the operation, when separating the structure of spermatic cord under the microscope, the testicular arteries can be objectively and accurately protected (pulse "whistle" sound can be heard when the microvascular doppler probes the arterial surface), while artery injury and venous missed ligation can be avoided. The postoperative blood supply of the testis is also maximumly safeguarded. At the same time, we can be more fearless to cut the cremaster muscle, fatty and connective tissues surrounding the spermatic cord blood vessels and vas deferens after the arteries and lymphatic vessels being accurately protected under the microscope, finally achieve the spermatic cord completely "skeletonized" (only the testicular arteries, lymphatic vessels and vas deferens remained after the surgery). Thus we can better ensure the clinical curative effect (denervation thoroughly), avoid serious complications (testicular atrophy), and achieve better surgical results.

Interarterial Pseudoaneurysm

Femoral artery pseudoaneurysm (FAP) is one of the most troublesome complications related to femoral artery access site after cardiovascular catheterization procedures and occurs in 0.8%–2.2% of the cases of cardiovascular interventional procedures. Management is by ultrasound-guided compression repair (UGCR). A 75-year-old male presented with anterior wall ST-elevation myocardial infarction and after percutaneous transluminal coronary angioplasty, developed FAP. This pseudoaneurysm had an interarterial communication between superficial femoral artery and deep femoral artery. It is unusual to have communication of pseudoaneurysm with two branches of femoral artery. Diagnosis was made using vascular sonography and Doppler study. Closure of this aneurysm was done by simple pressure with Doppler probe at both the narrow ends of the aneurysm. Arterial color Doppler is the mainstay for diagnosing FAPs. This case describes an interarterial pseudoaneurysm which is a rare entity to witness and the different modalities for its management, the most common one being UGCR.

Delayed Reperfusion of the Renal Outer Medulla Attenuates Ischemia Reperfusion‐Induced Vascular Congestion

Vascular congestion, or red blood cell (RBC) trapping, of the renal outer medulla (OM) is a common finding in acute tubular necrosis caused by ischemia reperfusion (IR). Work from our laboratory suggests that vascular congestion originates in the renal venous vasculature of the cortex and OM during the ischemic phase. Following reperfusion, RBCs then fill the OM plexus capillaries as the venous drainage vessels of this region remain blocked. We have also previously reported that pretreatment with low dose lipopolysaccharide (LPS) attenuates IR‐induced vascular congestion, however the mechanisms remain unknown. In the current study, we hypothesized that pretreatment with LPS prevents vascular congestion by delayed reperfusion of blood to the OM following ischemia.To test this hypothesis, WKY rats (male, 12 weeks) were pretreated (i.p) with 1mg/kg LPS (n=6) or saline control (n=7) once daily for 3 days. Rats were then anesthetized, and Transonic Laser Doppler probes were inserted in the renal cortex and OM. Doppler flux, as a determinate of regional kidney blood flow was then measured over 10 minutes of baseline, 45 minutes of renal artery clamping and 30 minutes of reperfusion.We found no differences in baseline blood flow of the cortex (pTREATMENT=0.0543) or OM (pTREATMENT=0.5085) between rats pretreated with low dose LPS or saline control. Following removal of the renal artery clamp, the return of blood flow to the cortex was gradual over the first several minutes of reperfusion (pTIME<0.0001), reaching a plateau following 10 minutes of reperfusion in both treatment groups (pINTERACTION=0.9999) (Fig. A). The reperfusion of blood to the OM, however, rapidly returned to baseline levels within 1 minute of reperfusion in control animals (1 min: 0 to 0.43AU) (Fig. B). In contrast, OM blood flow returned slowly in LPS treated rats (1 min: 0 to ‐0.08AU) and did not return to baseline levels during the 30‐minute reperfusion period (pINTERACTION=0.0127) (Fig. B).These data indicate that LPS pretreatment, paradoxically, delayed early reperfusion of the renal OM via a regional vasoconstriction response. We speculate that delayed reperfusion of the OM attenuates medullary plexus congestion by allowing time for the RBCs in the shared venous circulation to clear. These findings support the hypothesis that reperfusion of the renal outer medullary plexus before cortical perfusion is restored, is responsible for the development of prolonged vascular congestion. New therapeutics focused on renal hemodynamics to prevent congestion after ischemia may prevent much of the injury associated with acute kidney injury.

Mechanical Fetal Simulator for Fetal Doppler Testing

The continuous use of fetal Doppler allows for discrepancies in values ​​that lead to misdiagnoses in patients. This study aims to determine the effect of sound source distance on the fetal simulator with the measurement point. The contribution of this research is that the mechanical fetal heart system has 4 distances so that later it can be analyzed whether there is an influence of the location of the sound source on the accuracy of measurements using a fetal simulator. To get the desired distance, a solenoid is used which ends with a pipe of 2 cm, 5 cm, 10 cm, and 50 cm respectively. The solenoid used in the fetal simulator functions as a producer of the fetal heart. There is a rotary switch that functions for solenoid selection, namely 2 cm, 5 cm, 10 cm and 50 cm solenoids. Data collection was carried out on each solenoid and by placing the Doppler probe perpendicular and tilted. On the solenoid with a distance of 50 cm all measurement results exceed the allowable tolerance limit. The results showed that the BPM value of the two Doppler brands did not have a significant difference in value. When measuring fetal Doppler, the largest error value was 2.67%. The results of this study can be used as a reference when conducting an examination

Implantable Doppler Probe as a Vascular Monitoring Device in Kidney Transplant Patients: Investigation of Use at a Single Center.

Vascular complications account for 30% to 35% of total kidney grafts lost during the first 3 months posttransplant. Early detection of vascular complications allows an opportunity for prompt intervention, which is critical to reducing graft loss. In this study, we evaluated the usefulness of an implantable Doppler probe as a vascular monitoring device in kidney transplant patients. An implantable Doppler probe is used intermittently for postoperative monitoring of kidney transplant patients at our center. In this retrospective study, we analyzed prospectively maintained medical data in which we compared clinical outcomes of kidney transplant recipients who had postoperative implantable Doppler probe monitoring versus standard care clinical observation. Between January 2016 and October 2021, 324 kidney transplant patients were seen at our center. Patients were divided into 2 groups: group 1 (n = 194; 60%) included kidney transplant recipients with postoperative implantable Doppler probe monitoring and group 2 (n = 129; 40%) included kidney transplant recipients with standard care clinical observation. We compared number of vascular complications, number of departmental ultrasonographic scans required posttransplant, and graftloss at 3 months between the 2 groups. Vascular complications were identified in 13.5% of total patients, with graft loss identified in 2.1%. Both groups were similar in demographical characteristics. Group 1 had more vascular complications (17.5% vs 9.3%; relative risk = 1.88), fewer ultrasonographic scans during the first 24 hours posttransplant (71.1% vs 83.7%; relative risk = 0.84), and lower graft loss (1.5% vs 3.1%; relative risk = 0.48) than group 2. All probes were removed safely after 72 hours, and no complications related to the device were reported. The monitoring device may be used as an additional adjunct for graft monitoring in kidney transplant patients. Further controlled studies are warranted to evaluate this device in clinical practice.

Safety of Internal Electronic Fetal Heart Rate Monitoring During Labor

Abstract Objective: To investigate the safety and efficacy of internal electronic fetal heart rate (FHR) monitoring during labor. Methods: This was a retrospective case-control study, which was an analysis of monitoring FHR with a fetal scalp electrode or a Doppler probe (94 pregnant women per group). In the internal monitoring group, when the opening of the uterine orifice was ≥3 cm, the fetal scalp electrode was placed after natural or artificial rupture of the membrane. FHR was simultaneously monitored using a Doppler probe. In the external monitoring group, continuous FHR monitoring was performed using an ultrasound Doppler transducer fixed on the maternal abdomen. The toco transducer was used to record uterine contractions. Pathological examination of the placenta was performed prospectively in 49 and 48 cases in the internal electronic FHR monitoring group and control group, respectively. Maternal-infant outcomes (e.g. fever, puerperal infection, puerperal morbidity, delivery mode, Apgar score, and scalp injury) were recorded. Umbilical artery blood was extracted for blood gas analysis. Differences between the two groups were compared using the paired t-test, χ 2 test, Yates corrected χ 2 test or Fisher exact test. Results: Non-statistically significant differences between the internal and external monitoring groups were observed in the incidence of neonatal acidosis (1/94 (1.06%) vs. 3/94 (3.19%), respectively; χ 2 = 0.255, P = 0.613), cesarean section/operative vaginal delivery (8/94 (8.51%) vs. 15/94 (15.96%), respectively; χ 2 = 2.427, P = 0.181), fever during labor (18/94 (19.15%) vs. 15/94 (15.96%), respectively; χ 2 = 0.331, P = 0.565), puerperal morbidity (2/94 (2.13%) vs. 3/94 (3.19%), respectively; χ 2 = 0.000, P = 1.000), chorioamnionitis (9/49 (18.37%) vs. 7/48 (14.58%), respectively; χ 2 = 0.252, P = 0.616), and neonatal asphyxia (0/94 (0.00%) vs. 1/94 (1.06%), respectively; χ 2 = 0.000, P = 1.000). There were no puerperal infections, neonatal scalp injuries, or scalp abscesses found in either group. Using the internal monitoring value as reference, the incidence of FHR false deceleration in external FHR monitoring was 20.21% (19/94 women). Conclusion: Internal FHR monitoring during labor does not increase the incidence of adverse perinatal outcomes. External monitoring was associated with FHR false decelerations.

The Scratch Collapse Test for Diagnosis and Treatment of Trigger Sites for Migraine Surgery.

Summary:Diagnosis of trigger sites for migraine surgery relies on history to detect a constellation of symptoms and secondarily, nerve blocks, imaging studies, and Doppler probe examination. The scratch collapse test (SCT) has been described for localization of compressive neuropathies in the upper and lower extremities. In this study, we hypothesized that the SCT could also be used to diagnose trigger sites for surgical planning in migraine surgery. Eleven consecutive patients presenting for migraine surgery, and four patients presenting with recurrent headaches and secondary trigger sites after initial successful migraine surgery were examined with the SCT using a standard protocol to assess involvement of bilateral sites I, II, IV, V, and VI, with the carpal tunnel as a negative control. The SCT was positive bilaterally at sites I, II, IV, V, and VI for all patients presenting primarily for migraine surgery, regardless of trigger sites localized by history and other secondary modalities. The SCT, however, correlated with secondary trigger sites localized through history and examination for patients presenting with recurrent migraine headaches after previous primary surgery. The SCT is not reliable for localization of trigger sites in patients presenting primarily for migraine surgery. This likely relates to central sensitization of migraine headaches, leading to global cutaneous allodynia in the head and neck. In patients with recurrent migraine headaches, abrogation of central sensitization following the initial surgery allows diagnosis of secondary trigger sites through the SCT.

Success of Implantable Doppler Probes for Monitoring Buried Free Flaps.

The objective of this study is to describe the operative success of completely buried free flaps and to determine the safety/reliability of using implantable dopplers for postoperative monitoring in completely buried free flaps. A retrospective chart review was conducted from 2014 to 2020. Patients were included who had implantable dopplers placed for monitoring a completely buried free flap without a visible skin paddle. Single academic cancer hospital. Patient charts were reviewed to determine flap viability after surgery, need for reoperation, and ability of implanted doppler probes to detected change in free flap status. A total of 65 patients were included. Locations of flaps were as follows: pharynx, 76.9%; skull base, 7.7%; trachea, 6.2%; esophagus, 4.6%; and facial reanimation, 4.6%. Types of free flaps performed included radial forearm (50.8%), anterolateral thigh (44.6%), and gracilis (4.6%). One patient (1.5%) returned to the operating room for vascular compromise, which was accurately detected by the implantable doppler and salvaged. All free flaps were viable upon hospital discharge based on clinical examination and implantable doppler signals. There were no complications related to implantable doppler use. Implantable dopplers are an effective method for evaluating postoperative success of completely buried free flaps. In our series utilizing implantable dopplers, buried free flap survival was higher than traditionally thought. The use of implanted dopplers for monitoring buried free flaps allows for an effective, cosmetically appealing, and simplified reconstructive technique.

Confirming subarachnoid hemorrhage induction in the endovascular puncture mouse model

Background and purposeExperimental studies of subarachnoid hemorrhage (SAH) using the endovascular perforation model routinely use either cerebral blood flow (CBF) or intracranial pressure (ICP) monitoring to confirm SAH induction. We designed this study to test the hypothesis that contralateral CBF is a better marker of SAH induction than ipsilateral CBF. MethodsSixty-eight adult C57BL/6J mice were subjected to endovascular perforation. Mice were monitored using laser Doppler (for relative CBF) or ICP probes. ResultsThe ipsilateral CBF significantly decreased prior to ICP rising. However, reduction of the CBF in the contralateral hemisphere occurred at the same time as the rise in ICP. When CBF is monitored on both hemispheres simultaneously, the drop in ipsilateral CBF precedes the drop in the contralateral CBF. ConclusionsThe most suitable method for confirming puncture and induction of SAH in the endovascular mouse model is by ICP. Monitoring the CBF of the contralateral hemisphere is also able to detect the moment of SAH induction, but is not able to distinguish SAH severity. However, monitoring the ipsilateral CBF is not satisfactory for determining induction of SAH.

Optimal probe position for precordial Doppler ultrasound inchildren.

Precordial Doppler ultrasound technology can be used to confirm correct peripheral intravenous access in children. Changes in precordial Doppler sound from the baseline after injecting normal saline are detected using a correct peripheral intravenous access. However, the location of the precordial Doppler probe has been inconsistent in previous studies. Our study aimed to determine whether the right or left parasternal border is the optimal location for precordial Doppler probe placement. This single-center, prospective interventional study was conducted between July 2021 and January 2022 and included children aged 1-6 years. The Doppler probe was placed under general anesthesia at the most audible site on the right and left parasternal borders of patients. Baseline heartbeat was recorded by the Doppler for 10 s on the right and left parasternal borders. After randomizing the order of the recorded data, two blinded raters separately listened to the data and decided the audibility of the sounds. A total of 77 patients were enrolled in the study. The proportion of the audible baseline heartbeat was significantly higher on the left parasternal borders than on the right by both rater 1 (96.1%, 22.1%, p< 0.001) and rater 2 (96.1%, 27.3%, p< 0.001). Regarding inter-rater reproducibility, Cohen's kappa statistics for the left and right parasternal borders were significant (0.65 and 0.79, both p< 0.001). The baseline heartbeat was more audible on the left parasternal border than on the right parasternal border with acceptably high interrater reproducibility. This is inconsistent with the interpretations of previous reports.

Dynamics of skin microvascular blood flow in 4-6-year-old children in association with pre- and postnatal black carbon and particulate air pollution exposure.

A growing body of evidence indicates that cardiovascular health in adulthood, particularly that of the microcirculation, could find its roots during prenatal development. In this study, we investigated the association between pre- and postnatal air pollution exposure on heat-induced skin hyperemia as a dynamic marker of the microvasculature. In 139 children between the ages of 4 and 6 who are followed longitudinally within the ENVIRONAGE birth cohort, we measured skin perfusion by Laser Doppler probes using the Periflux6000. Residential black carbon (BC), particulate (PM10 and PM2.5) air pollution, and nitrogen dioxide (NO2) levels were modelled for each participant's home address using a high-resolution spatiotemporal model for multiple time windows. We assessed the association between skin hyperemia and pre- and postnatal air pollution using multiple regression models while adjusting for relevant covariates. Residential BC exposure during the whole pregnancy averaged (IQR) 1.42 (1.22-1.58) µg/m3, PM10 18.88 (16.64 - 21.13) µg/m3, PM2.5 13.67 (11.5 - 15.56) µg/m3 and NO2 18.39 (15.52 - 20.31) µg/m3. An IQR increment in BC exposure during the third trimester of pregnancy was associated with an 11.5 % (95% CI: -20.1 to -1.9; p=0.020) lower skin hyperemia. Similar effect estimates were retrieved for PM10, PM2.5 and NO2 (respectively 13.9 % [95% CI: -21.9 to -3.0; p=0.003], 17.0 % [95% CI: -26.7 to -6.1; p=0.004] and 12.7% [95 % CI: -22.2 to -1.9; p=0.023] lower skin hyperemia). In multipollutant models, PM2.5 showed the strongest inverse association with skin hyperemia. Postnatal exposure to BC, PM10, PM2.5 or NO2, was not associated with skin hyperemia at the age of 4 to 6, and did not alter the previous reported prenatal associations when taken into account. Our findings support that BC, particulate air pollution, and NO2 exposure, even at low concentrations, during prenatal life, can have long-lasting consequences for the microvasculature. This proposes a role of prenatal air pollution exposures over and beyond postnatal exposure in the microvascular alterations which were persistent into childhood.

Propagation characteristics of Doppler ultrasonic wave in gas–liquid two-phase flow in an offshore deepwater riser

During offshore deepwater drilling, the strata with abnormal pressure are often encountered and gas invasion and overflow occur easily. If they cannot be detected and controlled in time, blowout may happen and even get out of control, which will cause considerable economic loss and irreparable casualties and may even damage the marine ecologic environment seriously. How to monitor overflow early during deepwater drilling is a global research hot, focus and difficulty at present. In order to provide theoretical guidance for the early monitoring of overflow in the riser during offshore deepwater drilling, this paper designed an experimental device for the early monitoring of gas invasion based on the propagation principle of Doppler ultrasonic wave. Then, the installation mode and angle of Doppler probe were optimized. Finally, the propagation of Doppler ultrasonic wave in the gas–liquid two-phase flow with a void fraction of 0–46% and a liquid flow velocity of 0–0.7 m/s was experimentally studied, and the change laws of Doppler ultrasonic wave with void fraction were revealed. And the following research results are obtained. First, when the void fraction changes, the signal voltage will jump up and down at different amplitudes and frequencies on the basis of initial curve. The signal voltage amplitude increases firstly and then decreases with the increase of void fraction. Second, when the increase amplitude of mean signal voltage caused by multiple reflection is greater than the attenuation degree of ultrasonic wave, the mean signal voltage increases. Otherwise, the signal voltage decreases. Third, the fitting curve of mean signal voltage scatters and void fraction under different flow velocities and void fractions during pump stopping and starting present a change law of quadratic function. In conclusion, void fraction can be quantitatively predicted based on the measured signal voltage, so as to provide guidance for the early monitoring of riser overflow and well kill operation during offshore deepwater drilling.

Abstract 10665: Pulse Wave Velocity Measured at End-Diastole Underestimates Aortic Stiffness

Introduction: Aortic stiffness (AS) is assessed using pulse wave velocity (= distance (D) between two aortic sites / foot-to-foot transit time of pressure or velocity pulse (ffPTT) between the sites ) which is considered as “gold standard”. But, PWV varies with cyclic pressure in the normal aorta and PWV measured at end-diastole underestimates AS. This underestimation is greatest when aorta is the stiffest. Hypothesis: We hypothesize that PWV measured at diastole is lower than that measured at systole and that PWV should be measured over the entire cardiac cycle for better representation of AS. Methods: We measured pressures invasively with a dual sensor catheter (0.46 mm dia) at two descending aortic sites (25 mm apart) in normal rats. We measured blood velocities noninvasively with two Doppler probes placed at aortic arch and abdominal aorta. The pressure and blood velocity signals were acquired simultaneously (at baseline &amp; post-esmolol admin). From the two pressure signals we measured PWVsp (at dicrotic notch; end-systolic fiducial marker) and PWVdp (at end-diastole; foot fiducial marker). PWVd (end-diastole; foot) was measured from the two blood velocity signals. Results &amp; Conclusions: We plotted the PWV versus blood pressure. We found that the slope of aPWVsp &gt; the slope of aPWVdp indicating that PWV varies with blood pressure within the cardiac cycle. We also found that slope of aPWVd &lt; aPWVdp because, D used to calculate PWVdp is fixed at 25mm, whereas D used to calculate aPWVd was estimated as the distance between Doppler probe tips on the surface of the skin (aortic arch curvature was not accounted for). In conclusion, a more representative AS can be assessed through 1. PWV measurement at systole &amp; diastole within the cardiac cycle of a noninvasively measured vessel wall motion (a pressure signal surrogate) where the systolic and diastolic fiducial points can be identified, and 2. use of two aortic sites on the straight part of the descending aorta for better estimating of D.

Effect of Beach-Chair Position on Cerebral Blood Flow in Patients Undergoing Shoulder Surgery—A Preliminary Observational Study

Abstract Background Hypotension and cerebral hypoperfusion, commonly encountered in beach-chair position under general anesthesia, carry the risk of neurologic complications. There is a paucity of data on monitoring cerebral perfusion. Our objective was to compare the mean arterial pressure (MAP) and middle cerebral artery velocity (Vmca) in the supine and beach-chair position and estimate its correlation during hypotension. Materials and Methods Twenty ASA class I and II patients undergoing elective shoulder surgery in beach-chair position were included in the study. MAP was measured invasively with the pressure transducer leveled to the phlebostatic axis. Vmca was measured with a 2 MHz transcranial Doppler (TCD) probe through the temporal window. Both MAP and Vmca were measured at baseline after anesthetic induction in the supine position (BL), on assuming the beach-chair position (AP), at steady-state hemodynamics in beach-chair position (P1), whenever there was a drop in MAP &gt; 20% (P2), and on the restoration of MAP (P3). Results A mean decrease in MAP and Vmca by 24.76% and 27.96%, respectively, from supine to beach-chair position with a significant linear correlation between MAP and Vmca along with a Pearsons' coefficient of 0.77 was seen. A change in MAP of 1 mm of Hg resulted in a change in Vmca by 0.53 cm/sec (p &lt; 0.05). Conclusion A significant decrease in MAP and Vmca was observed in the beach-chair position. TCD could be used as a point-of-care noninvasive technique to reliably assess cerebral perfusion.

Transition to Turbulence Downstream of a Stenosis for Whole Blood and a Newtonian Analog Under Steady Flow Conditions.

Blood, a multiphase fluid comprised of plasma, blood cells, and platelets, is known to exhibit a shear-thinning behavior at low shear rates and near-Newtonian behavior at higher shear rates. However, less is known about the impact of its multiphase nature on the transition to turbulence. In this study, we experimentally determined the critical Reynolds number at which the flow began to transition to turbulence downstream of eccentric stenosis for whole porcine blood and a Newtonian blood analog (water-glycerin mixture). Velocity profiles for both fluids were measured under steady-state flow conditions using an ultrasound Doppler probe placed 12 diameters downstream of eccentric stenosis. Velocity was recorded at 21 locations along the diameter at 11 different flow rates. Normalized turbulent kinetic energy was used to determine the critical Reynolds number for each fluid. Blood rheology was measured before and after each experiment. Tests were conducted on five samples of each fluid inside a temperature-controlled in vitro flow system. The viscosity at a shear rate of 1000 s-1 was used to define the Reynolds number for each fluid. The mean critical Reynolds numbers for blood and water-glycerin were 470 ± 27.5 and 395 ± 10, respectively, indicating a ∼19% delay in transition to turbulence for whole blood compared to the Newtonian fluid. This finding is consistent with a previous report for steady flow in a straight pipe, suggesting some aspect of blood rheology may serve to suppress, or at least delay, the onset of turbulence in vivo.

СИНТЕЗ ДОПЛЕРОГРАМ КВАЗІВЕРТИКАЛЬНОГО ЗОНДУВАННЯ ІОНОСФЕРИ ДОПЛЕРІВСЬКИМ ВЧ РАДАРОМ ІЗ РОЗНЕСЕНИМ ПРИЙМАННЯМ

Purpose: The ionospheric channel is widely used for the communication, radio navigation, radar, direction finding, radio astronomy, and remote radio probing systems. The radio channel parameters are characterized by nonstationarity due to the dynamic processes in the ionosphere, and therefore their study is one of the topical problems of space radio physics and earth-space radio physics of geospace. This work aims at presenting the results of synthesis of temporal variations in the Doppler spectra obtained by the Doppler probing of the ionosphere at vertical and quasi-vertical incidence. Design/methotology/approach: One of the most effective methods of ionosphere research is the Doppler sounding technique. It has a high time resolution (about 10 s), a Doppler shift resolution (0.01–0.1 Hz), and the accuracy of Doppler shift measurements (~0.01 Hz) that permits monitoring the variations in the ionospheric electron density (10–4–10–3) or the study of the ionospheric plasma motion with the speed of 0.1-1 m/s and greater. The solution of the inverse radio physical problem, consisting in determination of the ionosphere parameters, often means solving the direct radio physical problem. In the Doppler sounding technique, it belongs with the construction of variations in Doppler spectra and comparing them with the Doppler spectra measurements. Findings: For the radio wave ordinary component, three echoes being produced by three rays are observed. Influence of the geomagnetic fi eld and large horizontal gradients in the electron density of δ≥10 % give rise to complex ray structures with caustic surfaces. The ionospheric disturbances traveling along the magnetic meridian form the skip zones. The longitudinal and transverse displacement of the ray reflection point attains a few tens of kilometers along the vil. Haidary to vil. Hrakove quasi-vertical radiowave propagation path, for which the great circle range is 50 km. For the vertical incidence, the signal azimuth at the receiver coincides with the traveling ionospheric disturbance azimuth. The synthesis of temporal variations in the HF Doppler spectra has been made and compared with the temporal variations in the Doppler spectra recorded with the V. N. Karazin Kharkiv National University radar. The estimate of δ=15 % obtained confirms the existence of large horizontal gradients in electron density. Conclusions: Temporal variations in Doppler spectra and in azimuth have been calculated for the vertical and quasi-vertical incidence with allowance for large horizontal gradients of the electron density caused by traveling ionospheric disturbances. Key words: ionosphere, Doppler sounding at oblique incidence, synthesis of temporal variations in HF Doppler spectra, traveling ionospheric disturbances, electron density

Relationship Between Medication Adherence and Ankle-Brachial Index Value in Patients With Hypertention

Background: Hypertension is one of the leading causes of death and physical disabilities. The ankle-brachial index (ABI) is one of the useful indicators of blood pressure with the ability to show the risk of peripheral artery disease. This study aims to investigate the relationship between medication adherence and the ABI lavue in patients with hypertension. Methods: In this descriptive cross-sectional study, 250 patients with hypertension referred to medical health centers in Karaj, Iran were enrolled using a convenience sampling method. To collect data, a demographic form and the 8-item morisky medication adherence scale (MMAS-8) were used. Also, the ABI was measured manually using an acoustic Doppler probe. Data were analyzed in SPSS software, v. 25. Findings: The Mean±SD of the right and left ABI were 1.055±0.134 and 1.036±0.113, respectively. The Mean±SD of MMAS-8 score was 5.88±1.74. It was found that 127 patients (50.8%) had low adherence level, 68 (27.2%) had moderate adherence level, and only 55 (22%) had high adherence level. There was a positive significant correlation between patients’ medication adherence and the ABI value. Moreover, a statistically significant difference was observed in the mean scores of the ABI in patients with three different levels of medication adherence. Conclusion: The medication adherence is poor among hypertensive patients in Karaj. It is related to the ABI such that with the decrease of medication adherence, the ABI value decreases. Therefore, adherence to medication regimen in patients with hypertension can be effective in preventing arterial complications.

Monofiber optical probe using Doppler signals detection for Drop Size and Velocity measurement in air assisted atomization

Reliable measurement of droplet/bubble size and velocity distributions in dense flows is desired in a variety of research fields, both for laboratory and industrial use. A new type of single-mode monofiber optical probe manufactured by A2 Photonic Sensors is introduced in this paper: it combines traditional phase detection with the collection of a Doppler signal returned by an incoming gas-liquid interface to provide information on residence times, drop concentration and velocity, which afford then drop chords and liquid flux measurements. Compared with classical optical probes, that new sensor does not require any calibration. The purpose of the present work is to test this technique in assisted atomization in order to provide a mean for spray characterization and ultimately to improve our understanding of atomization mechanisms. The probe has been tested downstream of a coaxial air-assisted atomizer operated at liquid velocity =. to. / , and gas velocity from = to about /. We first analyzed raw signals in various flow conditions. It happens that, when increasing the gas velocity and the number density of drops, the signal experiences very strong fluctuations of the gas level, making the identification of individual droplets more difficult. That leads us to develop a new signal processing routine specifically adapted to such complex working conditions. At = / and for three liquid flow rates, the spatial integration of local liquid fluxes represents 92 to 99% of the injected liquid flow rate. These good results demonstrate that the Doppler probe provides reliable statistics on drops velocity and size.