Volume Flow Measurements Research Articles

Magnetic resonance venous velocity mapping during intermittent pneumatic compression of the calf and foot

Assessment and optimization of intermittent pneumatic compression (IPC) devices for prophylaxis of deep vein thrombosis has previously used duplex ultrasound. The aim was to investigate novel magnetic resonance (MR) venous velocity mapping (VM) for IPC research and development. Twelve normal subjects were scanned in the supine position using realtime MR VM with sequential foot and calf IPC (120 mmHg) at 1.5 T. Measurements were taken in the popliteal vein at baseline using both cuffs and each cuff individually recording 60 seconds continuously. Temporal resolution was 310 ms per independent image, at 1 × 1 mm spatial resolution. Peak velocity (V(p)) measurements: baseline, V(p) = 2.1 cm/second (range = 1.1-3.5); using both compression cuffs, V(p) = 41.5 cm/second (18.0-58.1); calf cuff alone, V(p) = 40.6 cm/second (18.1-62.2); foot cuff alone, V(p) = 7.9 cm/second (4.2-15.3). Flow volume measurements per compression cycle (F): baseline, F = 2.3 cm³ (0.5-11.4); both compression cuffs, F = 7.1 cm³ (2.5-24.6); calf cuff only, F = 7.1 cm³ (2.4-24.5); foot cuff only, F = 2.6 cm³ (0.9-10.7). The foot cuff contribution was insignificant when combined with the calf cuff (P < 0.01). The MR venous VM results were similar to those reported elsewhere using ultrasound. This novel technique for MR venous VM can measure the realtime variations in venous blood flow during IPC.

Imaging congenital heart disease in adults.

Transthoracic echocardiography is the first-line modality for cardiovascular imaging in adults with congenital heart disease (ACHD). The windows of access that are possible with transthoracic echocardiography are, however, rarely adequate for all regions of interest. The choice of further imaging depends on the clinical questions that remain to be addressed. The strengths of MRI include comprehensive access and coverage, providing imaging of all parts of the right ventricle, the pulmonary arteries, pulmonary veins and aorta. Cine images and velocity maps are acquired in specifically aligned planes, with stacks of cines or dynamic contrast angiography providing more comprehensive coverage. Tissues can be characterised if necessary, and MRI provides relatively accurate measurements of biventricular function and volume flow. These parameters are important in the assessment and follow-up of adults after repairs for tetralogy of Fallot or transposition of the great arteries and after Fontan operations. The superior spatial resolution and rapid acquisition of CT are invaluable in selected situations, including the visualisation of anomalous coronary or aortopulmonary collateral arteries, the assessment of luminal patency after stenting and imaging in patients with pacemakers. Ionising radiation is, however, a concern in younger patients who may need repeated investigation. Adults with relatively complex conditions should ideally be imaged in a specialist ACHD centre, where dedicated echocardiographic and cardiovascular MRI services are a necessary facility. General radiologists should be aware of the nature and pathophysiology of congenital heart disease, and should be alert for previously undiagnosed cases presenting in adulthood, including cases of atrial septal defect, aortic coarctation, patent ductus arteriosus, double-chambered right ventricle and congenitally corrected transposition.

Three-Dimensional Volumetric Spatially Angle-Corrected Pixelwise Fetal Flow Volume Measurement

Early attempts to calculate fetal global perfusion used 2 D images. The results were not sufficiently reliable. That's why RI measurements are still in use despite the fact that they do not reflect the amount of blood passing through the fetus. We present a novel three-dimensional approach to overcome these limitations. In 124 singleton pregnancies between the 23rd and 4st gestational week, a three-dimensional color Doppler sonographic record of the umbilical cord was made, resulting in 281 volume data sets. With dedicated software (PixelFlux) the spatial angle of the umbilical vein was calculated and the true global fetal perfusion was calculated from its horizontal transection as the product of the area of all pixels and the spatial angle-corrected velocity. To validate the PixelFlux technique, phantom flow measurements were carried out. Phantom flow measurements revealed a highly significant correlation of actual flow volumes and those measured by the PixelFlux technique (p < 0.001; rPearson = 0.987 - 0.991) with an even higher interobserver correlation (p < 0.001; rPearson = 0.997). We found a significant correlation of fetal volume flow to gestational age and weight (r = 0.529 at spatial angles below 30° to r = 0.724 at spatial angles below 5°) and a significant influence of the spatial angle on this correlation (p = 0.003; r = -0.865). Spatial angle-corrected global fetal perfusion measurement improves existing approaches to fetal perfusion evaluation, and is feasible, simple and fast. Thus, it can be recommended to explore the relationship of fetal perfusion and disturbances of fetal development.

Caval flow reflects Fontan hemodynamics: quantification by magnetic resonance imaging

Failing Fontan circulation is a multifactorial problem without clear predictors and with uncertain onset. We sought to investigate the correlations between systemic venous flow return and the clinical condition of Fontan patients. Flow measurements using phase contrast magnetic resonance imaging (MRI) were performed in the superior and inferior vena cava (SVC, IVC) in 61 Fontan patients. Median postoperative follow-up time was 6.7 (0.6-14.1)years; median age at MRI was 11.6 (4.0-44.6)years. Eight patients were identified clinically as a subgroup with suboptimal hemodynamics. The effective forward flow of combined SVC and IVC flow volume was defined as the venous cardiac index (vCI, l/min/m(2)). SVC flow ratio was defined as SVC flow in relation to vCI. The vCI and flow distribution between the SVC and IVC were investigated in relation to the hemodynamics and patients' age at MRI. Venous flow return through the SVC was 1.1 (0.6-3.4)l/min/m(2) and through the IVC 1.8 (0.6-3.2)l/min/m(2); total vCI was 3l/min/m(2) (1.2-5.1). Patients with suboptimal Fontan hemodynamics showed significantly lower IVC flow return (median of 1.5 vs. 1.9l/min/m(2), p=0.027) and increased SVC flow ratio (0.56 vs. 0.35, p=0.005) in comparison to those with good clinical condition. The total vCI decrease was correlated with older patient age (r=0.575, p<0.001). Altered systemic venous flow return is associated with suboptimal Fontan hemodynamics and seems to progress with patients' age and long-term follow-up after Fontan operation. Thus, MRI flow volume measurements might help in monitoring Fontan patients before the onset of clinical signs of suboptimal hemodynamics.

Quantitative dynamic contrast‐enhanced MRI for mouse models using automatic detection of the arterial input function

Dynamic contrast-enhanced MRI (DCE-MRI) is widely accepted for the evaluation of cancer. DCE-MRI, a noninvasive measurement of microvessel permeability, blood volume and blood flow, is extremely useful for understanding disease mechanisms and monitoring therapeutic responses in preclinical research. For the accurate quantification of pharmacokinetic parameters using DCE-MRI, determination of the arterial input function (AIF) from a large arterial vessel near the tumor is required. However, a manual determination of AIF in mouse MR images is often difficult because of the small spatial dimensions or the location of the tumor. In this study, we propose an algorithm for the automatic detection of AIF from mouse DCE-MR images using Kendall's coefficient of concordance. The proposed method was tested with computer simulations and then applied to tumor-bearing mice (n = 8). Results from computer simulations showed that the proposed algorithm is capable of categorizing simulated AIF signals according to their noise levels. We found that the resulting pharmacokinetic parameters computed from our method were comparable with those from the manual determination of AIF, with acceptable differences in K(trans) (5.14 ± 3.60%), v(e) (6.02 ± 3.22%), v(p) (5.10 ± 7.05%) and k(ep) (5.38 ± 4.72%). The results of the current study suggest the usefulness of an automatically defined AIF using Kendall's coefficient of concordance for quantitative DCE-MRI in mouse models for cancer evaluation.

Spatial Angle-Corrected Fetal Volume Flow Measurement (SAFM)

Fetal perfusion measurement is an important factor in describing the actual state of a fetus. Attempts to derive reliable flow volume data from 2D images failed so far. Therefore, we developed a novel method of three-dimensional flow volume measurements.

In situ measuring osmosis effect of Selemion CMV/ASV module during ED process of concentrated brine from DSW

Continuing our previous work, in which we analyzed the performance of Selemion ASV membrane (Asahi Glass Engineering) used to reduce the content of sulfate ions in concentrated brine from deep sea water (DSW) via a laboratory-scale electrodialysis (ED) apparatus, we analyze in situ the osmosis effect for Selemion CMV/ASV module (Asahi Glass Engineering) during ED process in this work. By recording the liquid volume in both concentrate and dilute tanks, it is found possible that the water flow across the membranes due to the osmosis effect could be estimated through the measurement of ionic volume flow. The analysis reveals that, when a higher DC voltage is applied, water flows from the concentrate to the dilute at initial stage of ED process, and it flows reversely at later stage; however if a lower DC voltage is applied, water flows from the concentrate to the dilute during whole ED process. Via a carpet searching process, a reasonable effective dynamic hydration number for hydrated ions is found as 3.5, and the water permeability of CMV/ASV module is estimated as 0.25214 cm/h.

Assessment of natural and hybrid ventilation models in whole-building energy simulations

Natural ventilation is a traditional cost-effective technique to cool and ventilate buildings. Proper simulation tools are highly desired to ensure acceptable thermal performance of naturally ventilated buildings and to assist the design and optimization of such buildings. This study is to advance the use of natural and hybrid ventilation concepts in building design by assessing the accuracy and usability of current thermal-ventilation models. Because of the similarity noted among various models and tools, a prevalent airflow-thermal modeling program, EnergyPlus, was evaluated by simulating three selected real buildings that were supplied with most detailed building and measurement information. The study of these cases reveals that the current model has (1) significant functional limitations for venting and exhaust fan control schemes; (2) need for additional relationships to describe horizontal openings and fully-open connections between zones; and (3) possible over-prediction of buoyancy-driven flows in the case of multi-story buildings. The study further indicates the building and measurement data that are critical for a more accurate validation of thermal-ventilation models, including, on-site measured temperature, wind, and solar conditions; measured volume flow rate data, at critical points throughout the building; and effective area and discharge coefficients for specific vents used in building.

Surface runoff and sub-surface drainage phosphorus losses under regular free drainage and controlled drainage with sub-irrigation systems in southern Ontario

Tan, C. S. and Zhang, T. Q. 2011. Surface runoff and sub-surface drainage phosphorus losses under regular free drainage and controlled drainage with sub-irrigation systems in Southern Ontario. Can. J. Soil Sci. 91: 349–359. Soil phosphorus (P) loss and its partition in various pathways may differ depending on water management practices. A study was conducted using large field plots equipped with automatic flow volume measurement and sampling systems over a 5-yr period to determine the effectiveness of regular free drainage (RFD) and controlled drainage with sub-irrigation (CDS) for mitigating soil P losses of various forms [dissolved reactive P (DRP), dissolved un-reactive P (DURP), and particulate P (PP)] and to identify the relative roles of surface runoff and sub-surface tile drainage in soil P loss. For RFD, flow weighted-means (FWM) of DRP, DURP, PP and the total P (TP) concentrations over the 5-yr period were averaged at 0.057, 0.057, 0.627, and 0.741mg P L−1 in surface runoff water and at 0.034, 0.053, 0.393, and 0.480 mg P L−1 in tile drainage water, respectively. CDS increased FWM of DRP, DURP and the TP concentrations in surface runoff water and DRP concentration in tile drainage, but decreased the FWM of DURP, PP and the TP concentrations in tile drainage water. The CDS produced similar annual total dissolved P (TDP) loss, the sum of DRP and DURP, but reduced losses of PP by 15% and of TP by 12%, relative to RFD. The PP loss accounted for over 80% of TP loss for both CDS and RFD. Of the total soil P loss, from 3 to 5% was accounted for in surface runoff water, while from 95 to 97% was accounted for in tile drainage water, for RFD. For CDS, from 29 to 35% of the total soil P loss was in surface runoff water, while 65 to 71% was in tile drainage water. Subsurface tile drainage played a predominant role in soil P loss. CDS can be considered a beneficial management practice to reduce soil P loss under the similar climate and relatively flat field conditions in Southern Ontario.

The accuracy and reproducibility of rhinospirometry in detecting flow asymmetry in a nasal cavity model

The objective of this study is to investigate the appropriateness of the NV1 rhinospirometer in the assessment of asymmetrical nasal airflow using a nasal cavity model. The Study is a laboratory-based basic-science study using an artificial model of nasal airflow. It is conducted in Medical Physics Department, Singleton Hospital, Swansea, Wales. A nasal cavity model was created with a series of parallel flow symmetry/asymmetries that were each assessed using standard flow volume measurements. The results were converted into Nasal Partition Ratios (NPRs) for each trial scenario and were examined against a mathematically calculated NPR derived using Pouseille's law. Experimental scenario results were assessed for correlation, accuracy and precision against the mathematically derived result. In this study 300 individual test scenarios were completed using 2 different flow volumes and 15 different symmetry/asymmetry combinations. Correlation of the attained results against the mathematically derived figure gave a very strong correlation, using Spearman's Rho=0.975. Accuracy was excellent within one Standard deviation of the expected results. It was concluded that the NV1 rhinospirometer is an accurate and precise objective marker of airflow symmetry in the nasal cavity model giving strong correlation, accuracy, precision and reproducibility. The rhinospirometer, as a precision tool, has displayed potential to become an effective objective marker of nasal airflow in the assessment of nasal obstruction; however, clinical trials are required to examine whether the accurate results of this laboratory study are transferable to clinical practice.

Uterine artery blood flow volume in pregnant women with an abnormal pulsatility index of the uterine arteries delivering normal or intrauterine growth restricted newborns

The aim of this study was to assess and compare uterine artery (UtA) blood flow volume in pregnant patients with an abnormal uterine Doppler pulsatility index (PI) who delivered fetuses with an appropriate weight for gestational age (AGA) or with intrauterine growth restricted (IUGR). We prospectively recruited singleton pregnancies with abnormal uterine arteries P.I. between 18 and 38 weeks of gestation regardless of estimated fetal weight (EFW). Vessel diameter and blood flow velocity were measured along the UtA upstream to the vessel bifurcation in both the right and left UtAs. Uterine blood flow volumes measured in these pregnancies were compared to historical Control-pregnancies. Forty-three patients delivered at term a normal weight newborn (AGA-pregnancies). Thirty patients delivered growth restricted newborns at 32 weeks (i.r. 29–36w) with a median weight of 1160 gr (i.r. 1000–2065 gr) (IUGR-pregnancies). At mid-gestation (18 + 0 − 25 + 6 weeks + days of gestation) a significantly lower uterine blood flow volume per unit weight was observed between the two study groups and compared to controls: 142 ml/min/kg in IUGR-pregnancies, 217 ml/min/kg in AGA-pregnancies and 538 ml/min/kg in Control-pregnancies. These striking differences in blood flow volume were already present at mid-gestation, at a time when EFW was still normal. In late gestation (27 + 0 − 37 + 6 weeks + days of gestation), pregnancies with an abnormal uterine P.I. showed persistently low UtA flow (<50% of controls) even when corrected for fetal weight: 81 ml/min/kg in IUGR-pregnancies, 105 ml/min/kg in AGA-pregnancies, and 193 ml/min/kg in Control-pregnancies; p < 0.0001. Our findings are consistent with other recent studies regarding the association between reduced uterine blood flow volume and fetal growth restriction. However, the study brings new insight into the finding of abnormal uterine P.I. in normally grown fetuses typically dismissed as “falsely abnormal” or “false positive” findings. Our study suggests that blood flow volume measurement may serve as a new tool to assess this group of patients and possibly those with ischemic placental diseases that may provide some basis for therapeutic interventions.

Melt Volume Flow Measurement in the Mineral-Wool Production Process

The quality of the end product in mineral wool production depends on the fiberisation process on the spinning machine. An important process variable is the fluctuation of melt volume flow from the melter. In this paper, a method for measuring melt volume flow, which is based on the measuring the diameter and flow velocity using machine vision, is presented. The velocity is measured by measuring the time of the travel of flow disturbances on two consecutive images using a correlation method. The flow disturbances are generated using a pneumatic system. The results of laboratory calibration using water as well as the results of field measurements in a mineral wool plant are presented. The field measurements were performed by comparison with the weight of the final product. The results of laboratory calibration show agreement with reference volume flow measurements with R2 = 0.96 for water. The agreement among field measured values and available comparison method is also very good.

Traitement de l’hyperplasie bénigne de prostate par Prostiva ® : à propos d’une série de 76 patients

To evaluate the efficacy and morbidity of BPH treatment by radiofrequency in the general population and attempt to identify factors of prognostic value for this technique. This retrospective study examined 76 consecutive patients of mean age 68.9 years with symptomatic BPH in failure of medical treatment and treated at University Hospital of Caen between April 2004 and October 2008. Urine status was assessed before and after treatment with radiofrequency by the international prostate symptom score (IPSS), the quality of life (QOL) score related to urinary symptoms, the measurement of maximum urinary flow (Qmax) and residual postvoid volume (RPV). Erectile function was assessed by the International Index of Erectile Function (IIEF-5). The primary endpoint was treatment failure by radiofrequency regarded as the reintroduction of medical treatment or the need for surgical treatment. The secondary endpoints were the improvement of IPSS and QOL score, Qmax and RPV. Morbidity per and post-operative was also evaluated. A significant improvement in voiding status was observed with an average IPSS score from 24.7 to 15.1 (P<0.0001), and a QOL score from 5.2 to 2.9 (P<0,0001) in all patients. The Qmax and the RPV were significantly improved from 8.6 to 13.1ml/s (P<0.0001) and 177 to 100ml (P=0.0002) respectively. The IIEF-5 score was improved from 9.04 to 9.97 (P=0.0164). Twenty-five percent of acute urinary retention, 7.9% of haematuria and 1.3% of prostatitis were observed postoperatively. The overall retreatment rate was 46% after 14.6 months mean follow-up. When stratified into groups, patients with the inclusion criteria to this treatment showed a treatment rates of 34.8% after 16.2 months mean follow-up against 51% after 13.8 months of monitoring patients outside the inclusion criteria. Without showing significant difference between retentionist and no retentionist concerning subjective and objective parameters, the rate of retreat was more important for retentionist (51.2% after 11.8 months of mean follow against 39.4% after 18.4 months) with a significant difference on the actuarial cumulative survival curve without reprocessing. There was no significant difference found in patients with a median lobe. The results showed an improvement in Qmax significantly greater in the group with prostates less than 60 g without being able to demonstrate significant differences in other parameters. The retreatment rates in this group was 44.4% after 14.7 months of follow-up against 53.8% after 13.8 months of follow-up in the group of patients with prostate over 60 g. Moreover, the irritative component made a better initial response to treatment with a need for retreatment delayed compared to the group of patients with obstructive symptom, without noting significant differences in terms of improvement of objective and subjective parameters. The rate of retreatment was 63.6% after 16.4 months of mean follow and 51.6% after 11.2 months in the "obstructive" group. High rates of reprocessing are observed in the treatment of BPH by radiofrequency if inclusion criteria are not respected.

Calibration-Free Volume Flow Measurement Principle Based on Thermal Time-of-Flight (TToF)

For measurement problems with unknown fluids a new calibration-free volume flow measurement technique is developed. This measurement technique includes a discontinuous heat source associated with a minimum of two thermal sensors arranged downstream. The heat source is used to generate a signal code [dT/dt] by injection of local thermal pulses into the flow line. The thermal sensors detect the time-dependent thermal gradients in the fluid at different positions. Herewith, the measurement technique aims at the determination of the flow velocity by ToF, with the particular advantage of applying to measurements of any fluids with unknown properties. The volume flow is determined by integrating the flow profile.

SCALE-PWI: A Pulse Sequence for Absolute Quantitative Cerebral Perfusion Imaging

The Bookend technique is a magnetic resonance imaging (MRI) dynamic susceptibility contrast method that provides reliable quantitative measurement of cerebral blood flow (CBF) and cerebral blood volume (CBV). The quantification is patient specific, is derived from a steady-state measurement of CBV, and is obtained from T(1) changes in the white matter and the blood pool after contrast agent injection. In the current implementation, the Bookend technique consists of three scanning steps requiring a cumulative scan time of 3 minutes 47 seconds, a well-trained technologist, and extra time for offline image reconstruction. We present an automation and acceleration of the multiscan Bookend protocol through a self-calibrating pulse sequence, namely Self-Calibrated Epi Perfusion-Weighted Imaging (SCALE-PWI). The SCALE-PWI is a single-shot echo-planar imaging pulse sequence with three modules and a total scan time of under 2 minutes. It provides the possibility of performing online, quantitative perfusion image reconstruction, which reduces the latency to obtain quantitative maps. A validation study in healthy volunteers (N=19) showed excellent agreement between SCALE-PWI and the conventional Bookend protocol (P>0.05 with Student's t-test, r=0.95/slope=0.98 for quantitative CBF, and r=0.91/slope=0.94 for quantitative CBV). A single MRI pulse sequence for absolute quantification of cerebral perfusion has been developed.

Transit-Time Volume Flow Measurements in Autogenous Femorodistal Bypass Surgery for Intraoperative Quality Control

The aim of this study was to assess intraoperative transit-time volume flow measurements (VFMs) as a tool for intraoperative evaluation of lower extremity arterial bypass grafts and to predict their patency. We analyzed 273 consecutive patients who had an infrainguinal bypass procedure using the great saphenous vein from 1998 until 2008; 103 had an intraoperative VFM. All intraoperative revisions were recorded and analyzed. Patency and revision rates were compared between those receiving and those not receiving intraoperative VFM. Cox regression was used for analysis of predictors of patency. Primary patency at 1 and 2 years was 75 and 67%, respectively, in patients receiving intraoperative VFM versus 72 and 69% in those without VFM (p = .79). In the VFM group, 12% had an immediate revision versus 6% without VFM (p = .06). In the VFM group, 4% underwent revision to salvage the bypass within the first postoperative 30 days versus 6% without VFM (p = .32). Patency was not associated with the use of VFM. Receiver operating characteristic curve was significant for occlusion at 30 days postoperatively but with a low predictive value (p = .019,area under the curve 0.648). VFM may be helpful in selecting bypasses requiring immediate revision to prevent postoperative occlusion. The use of VFM is not significantly associated with patency.

Ensemble smoother assimilation of hydraulic head and return flow data to estimate hydraulic conductivity distribution

Numerical groundwater models, frequently used to enhance understanding of the hydrologic and chemical processes in local or regional aquifers, are often hindered by an incomplete representation of the parameters which characterize these processes. In this study, we present the use of a data assimilation algorithm that incorporates all past model results and data measurements, an ensemble smoother (ES) to provide enhanced estimates of aquifer hydraulic conductivity (K) through assimilation of hydraulic head (H) and groundwater return flow volume (RFV) measurements into groundwater model simulation results. On the basis of the Kalman filter methodology, residuals between forecasted model results and measurements, together with covariances between model results at measurement locations and nonmeasurement locations, are used to correct model results. Parameter estimation is achieved by incorporating model parameters into the algorithm, thus allowing the correlation between H, RFV, and K to correct the K fields. The applicability of the ES is demonstrated using a synthetic two‐dimensional transient groundwater modeling simulation. Sensitivity analyses are carried out to show the performance of the ES in regard to measurement error, number of measurements, number of assimilation times, correlation length of the K fields, and the number of stream gage locations. Results show that the departure of the K fields from a reference K field is greatly reduced through data assimilation and demonstrate that the ES scheme is a promising alternative to other inverse modeling techniques because of low computational burden and the ability to run the algorithm entirely independent of the groundwater model simulation.

Polycyclic Aromatic Hydrocarbons in Stormwater Runoff from Sealcoated Pavements

Coal-tar based sealcoat has been identified as a source of polycyclic aromatic hydrocarbons (PAHs) in the environment. This study measured the long-term release of PAHs in parking lot runoff and found that the presence of coal tar sealant increased the mass of PAHs released in runoff by over an order of magnitude. PAH concentrations in stormwater from two coal tar sealed parking lots and one unsealed parking lot (control) were monitored over a two-year period. The measured flow volume and concentrations were used to calculate a mass of 9.8-10.8 kg total Σ16 PAHs per hectare exported in stormwater runoff from the two sealed parking lots and 0.34 kg total Σ16 PAHs per hectare from the unsealed control. The study also measured sediment PAH concentration changes in a receiving drainage and found that even partial coverage of a drainage area by coal tar sealant resulted in measurable increases in PAH sediment concentrations; PAH concentrations in sediment in a stormwater swale receiving runoff from both sealed and unsealed lots increased near the outfall from less than 4 mg/kg prior to sealing to 95.7 mg/kg after sealing. Compound ratio plots and principal components analysis were examined and were able to clearly differentiate between pre- and postsealant samples.

Patient tolerance of neuromuscular electrical stimulation (NMES) in the presence of orthopaedic implants

Neuromuscular electrical stimulation (NMES) may help reduce the incidence of deep vein thrombosis (DVT) in the postoperative total hip and knee arthroplasty patient. However, discomfort associated with stimulus may reduce patient acceptance of NMES as therapy. The aim of this study was to determine if patient comfort and tolerance of NMES was affected by applying stimulation in proximity to an orthopaedic implant. There was a concern that this may cause a concentration of current around the metal which could result in hypersensitivity of NMES and reduce its effectiveness. Twenty patients took part in this study, 10 total hip and 10 total knee arthroplasty patients. Each patient was at least 3 weeks post surgery. NMES was applied to the calf muscles of each leg using skin surface electrodes. Four excitatory levels were recorded, which were: sensory threshold, motor threshold, pain threshold and pain tolerance. Following this, patients underwent a 5 min stimulation session and indicated their overall comfort level on a visual analogue scale. Measurements of peak venous velocity, mean velocity and volume flow were recorded by duplex scanning from the popliteal vein at rest and in response to NMES elicited contractions during this session. Finally, patients completed a short verbal interview detailing their experience with the NMES treatment. The blood flow results showed increases in peak venous velocities, mean velocities and volume flow produced by NMES of 200%, 60% and 60% respectively when compared to resting blood flow. Comfort assessment indicated that the presence of a metallic implant did not give rise to hypersensitivity due to NMES. Patients found the application of calf muscle NMES comfortable and acceptable as a treatment. We conclude that the use of NMES on postoperative orthopaedic patients can be safely administered as a DVT prevention method.

Association of Urinary Biomarkers With Disease Severity in Patients With Autosomal Dominant Polycystic Kidney Disease: A Cross-sectional Analysis

Disease monitoring of autosomal dominant polycystic kidney disease (ADPKD) will become more important with potential upcoming therapeutic interventions. Because serum creatinine level is considered of limited use and measurement of effective renal blood flow (ERBF) and total renal volume are time consuming and expensive, there is a need for other biomarkers. We aimed to investigate which urinary markers have increased levels in patients with ADPKD; whether these urinary markers are associated with measured glomerular filtration rate (mGFR), ERBF, and total renal volume; and whether these associations are independent of albuminuria (urine albumin excretion [UAE]). Diagnostic test study. 102 patients with ADPKD (Ravine criteria) and 102 age- and sex-matched healthy controls. 24-hour urinary excretion of glomerular (immunoglobulin G), proximal tubular (kidney injury molecule 1 [KIM-1], N-acetyl-β-d-glucosaminidase, neutrophil gelatinase-associated lipocalin [NGAL], and β(2)-microglobulin), and distal tubular (heart-type fatty acid binding protein [H-FABP]) damage markers and inflammatory markers (monocyte chemotactic protein 1 [MCP-1] and macrophage migration inhibitory factor). Disease severity assessed using measures of kidney function (mGFR and ERBF, measured using clearance of iothalamate labeled with iodine 125 and hippuran labeled with iodine 131 during continuous infusion, respectively) and structure (total renal volume, measured using magnetic resonance imaging). 24-hour UAE. In 102 patients with ADPKD (aged 40 ± 11 years; 58% men), levels of all measured urinary biomarkers were increased compared with healthy controls. Excretion of immunoglobulin G and albumin relatively were most increased. ERBF and mGFR values were associated with urinary excretion of β(2)-microglobulin, NGAL, and H-FABP independent of UAE, whereas total renal volume was associated with KIM-1, NGAL, and MCP-1 independent of UAE. Cross-sectional, single center. Levels of markers for multiple parts of the nephron are increased in patients with ADPKD. In addition to measurement of UAE, measurement of urinary β(2)-microglobulin, KIM-1, H-FABP, MCP-1, and especially NGAL could be of value for determination of disease severity in patients with ADPKD.