Segmental bioimpedance for measuring amlodipine-induced pedal edema: a placebo-controlled study

Bioimpedance Measurement of Knee Injuries Using Bipolar Electrode Configuration

Currently, there is no suitable solution for the point-of-care diagnosis of knee injuries. A potential portable and low-cost technique for accessing and monitoring knee injuries is bioimpedance measurement. This study validated the feasibility of the bipolar electrode configuration for knee bioimpedance measurement with two electrodes placed on a fixed pair of knee acupuncture locations called Xiyan. Then, the study collected 76 valid samples to investigate the relationship between bioimpedance and knee injuries, among whom 39 patients have unilateral knee injuries, and 37 individuals have healthy knees. The self-contrast results indicated that knee injuries caused a reduction of bioimpedance of the knee by about 5% on average, which was detectable at around 100 kHz (p ≈ 0.001). Furthermore, the results analyzed by principal component analysis and support vector machines show that the detection sensitivity can reach 87.18% using the leave-one-out cross-validation. We also proposed a low-cost and portable bioimpedance measurement device that meets the needs for measuring knee joint bioimpedance.

A randomized phase 1b cross-over study of the safety of low-dose pioglitazone for treatment of autosomal dominant polycystic kidney disease

Background

Autosomal dominant polycystic kidney disease (ADPKD) is one of the most common monogenetic disorders in humans and is characterized by numerous fluid-filled cysts that grow slowly, resulting in end-stage renal disease in the majority of patients. Preclinical studies have indicated that treatment with low-dose thiazolidinediones, such as pioglitazone, decrease cyst growth in rodent models of PKD.

Methods

This Phase 1b cross-over study compared the safety of treatment with a low dose (15 mg) of the peroxisome proliferator-activated receptor-γ (PPAR-γ) agonist pioglitazone or placebo in PKD patients, with each treatment given for 1 year. The study monitored known side effects of PPAR-γ agonist treatment, including fluid retention and edema. Liver enzymes and risk of hypoglycemia were assessed throughout the study. As a secondary objective, the efficacy of low-dose pioglitazone was followed using a primary assessment of total kidney volume (TKV), blood pressure (BP) and kidney function.

Results

Eighteen patients were randomized and 15 completed both arms. Compared with placebo, allocation to pioglitazone resulted in a significant decrease in total body water as assessed by bioimpedance analysis {mean difference 0.16 Ω [95% confidence interval (CI) 0.24–2.96], P = 0.024} and no differences in episodes of heart failure, clinical edema or change in echocardiography. Allocation to pioglitazone led to no difference in the percent change in TKV of −3.5% (95% CI −8.4–1.4, P = 0.14), diastolic BP and microalbumin:creatinine ratio.

Conclusions

In this small pilot trial in people with ADPKD but without diabetes, pioglitazone 15 mg was found to be as safe as placebo. Larger and longer-term randomized trials powered to assess effects on TKV are needed.

Prediction of hemodialysis vascular access failure using segmental bioimpedance analysis parameters

PURPOSE

Segmental bioimpedance analysis (BIA) can identify fluid volume changes in the arms of patients on hemodialysis (HD) after vascular access surgery. We investigated whether the difference in fluid volumes between the arms of the patients using segmental BIA is associated with vascular access outcome.

METHODS

Body composition measurements were taken for 127 patients on HD with segmental, multi-frequency BIA equipment (InBody 1.0, Biospace Co. Ltd, Seoul, Korea). The difference in fluid volume between the arms of the patients was calculated from the fluid volume of the arm with the vascular access minus that of the other. The primary outcome was the loss of vascular access patency within 3 months of BIA measurement.

RESULTS

The median absolute and relative inter-arm fluid volume differences were 150 ml [interquartile range (IQR) 90-250 ml] and 9.6% (IQR 4.9-14.4%), respectively. Within 3 months of BIA measurement, 38 patients (30.0%) experienced vascular access failure. When the patients were divided into three groups based on the tertiles of relative inter-arm fluid volume differences (lowest tertile: < 6.8%; middle tertile: 6.8-12.7%; highest tertile: > 12.7%), greater difference in relative inter-arm fluid volume differences was associated with higher vascular access failure rates (14 vs. 28 vs. 48%, p value for trend across tertiles = 0.003).

CONCLUSIONS

We conclude that segmental BIA may be used as a tool that can predict vascular access failure in patients on HD by calculating the relative difference in fluid volume between the arms of the patients with and without vascular access.

Distribution of Extracellular Fluid in Legs with Venous Edema and Lymphedema

BACKGROUND

This study aimed to determine the specific fluid distribution pattern in legs with lymphedema (LE) in comparison to normal legs and legs with venous edema (VE) using bioelectrical impedance analysis (BIA).

METHODS AND RESULTS

BIA was performed in 47 patients with lymphedema (LE; 63 legs), 33 patients with venous edema (VE; 60 legs), and 33 normal subjects (N; 66 legs). The ratio of intracellular fluid (ICF) resistance (Ri) to extracellular fluid (ECF) resistance (Re) of a whole leg normalized to the right arm (Ri/Re leg), a surrogate parameter for ECF/ICF, and the Ri/Re of the thigh and calf without normalization (Ri/Re thigh, Ri/Re calf, respectively) were obtained. Increases in Ri/Re leg (N 2.5 ± 0.7, VE 3.9 ± 3.7, LE 3.7 ± 1.5), Ri/Re thigh (N 1.8 ± 0.5, VE 3.2 ± 3.8, LE 3.8 ± 1.9), and Ri/Re calf (N 2.6 ± 0.6, VE 4.6 ± 1.7, LE 4.4 ± 2.2) were confirmed in VE and LE compared to normal subjects. However, the ratios of Ri/Re calf to Ri/Re thigh in normal subjects and those with untreated VE/LE were all ∼1.5 (N 1.5 ± 0.3, VE 1.5 ± 0.7, LE 1.6 ± 0.7).

CONCLUSIONS

Fluid content was increased in legs with VE and LE compared to normal subjects, while the mode of gravitational fluid distribution was similar among all legs. Thus, no specific finding for LE was confirmed.

Overhydration measured by bioimpedance analysis and the survival of patients on maintenance hemodialysis: a single-center study

BACKGROUND

Bioimpedance analysis (BIA) helps measuring the constituents of the body noninvasively. Prior studies suggest that BIA-guided fluid assessment helps to predict survival in dialysis patients. We aimed to evaluate the clinical usefulness of BIA for predicting the survival rate of hemodialysis patients in Korea.

METHODS

We conducted a single-center retrospective study. All patients were diagnosed with end-stage renal disorder and started maintenance hemodialysis between June 2009 and April 2014. BIA was performed within the 1(st) week from the start of hemodialysis. The patients were classified into 2 groups based on volume status measured by the body composition monitor (BCM; Fresenius): an overhydrated group [OG; overhydration/extracellular water (OH/ECW) >15%] and a nonoverhydrated group (NOG; OH/ECW ≤15%).

RESULTS

A total of 344 patients met the inclusion criteria. Of these, 252 patients (73.3%) were categorized into the OG and 92 patients (26.7%) into the NOG. Age- and sex-matching patients were selected with a rate of 2:1. Finally, 160 overhydrated patients and 80 nonoverhydrated patients were analyzed. Initial levels of hemoglobin and serum albumin were significantly lower in the OG. During follow-up, 43 patients from the OG and 7 patients from the NOG died (median follow-up duration, 24.0 months). The multivariate-adjusted all-cause mortality was significantly increased in the OG (odds ratio, 2.569; P = 0.033) and older patients (odds ratio, 1.072/y; P < 0.001). No significant difference of all-cause or disease-specific admission rate was observed between the 2 groups.

CONCLUSION

The ratio of OH/ECW volume measured with body composition monitor is related to the overall survival of end-stage renal disorder patients who started maintenance hemodialysis.

Leg edema quantification for heart failure patients via 3D imaging

Heart failure is a common cardiac disease in elderly patients. After discharge, approximately 50% of all patients are readmitted to a hospital within six months. Recent studies show that home monitoring of heart failure patients can reduce the number of readmissions. Still, a large number of false positive alarms as well as underdiagnoses in other cases require more accurate alarm generation algorithms. New low-cost sensors for leg edema detection could be the missing link to help home monitoring to its breakthrough. We evaluated a 3D camera-based measurement setup in order to geometrically detect and quantify leg edemas. 3D images of legs were taken and geometric parameters were extracted semi-automatically from the images. Intra-subject variability for five healthy subjects was evaluated. Thereafter, correlation of 3D parameters with body weight and leg circumference was assessed during a clinical study at the Medical University of Graz. Strong correlation was found in between both reference values and instep height, while correlation in between curvature of the lower leg and references was very low. We conclude that 3D imaging might be a useful and cost-effective extension of home monitoring for heart failure patients, though further (prospective) studies are needed.

An amplitude-to-time conversion technique suitable for multichannel data acquisition and bioimpedance imaging

In this paper we exploit the high timing resolution offered by microprocessors to develop an amplitude measurement approach that is convenient for high channel count portable sinusoidal recording systems such as the bioimpedance measurements used in impedance imaging. This approach reduces the number of components required per channel, reducing cost, size and power consumption compared to the traditional approaches. The setup uses two high performance comparators to convert amplitude difference to a timing difference. This is captured by a high speed microprocessor. A straightforward algorithm removes DC and timing offsets. We suggest three modes of operation: fast: less than one period of the input, normal: exactly one input period and high precision: multiple input periods. The mean signal-to-noise ratio was 40, 81, and 112.4 dB in fast, normal, and high precision mode respectively for a range of resistive loads.