Simultaneous Electrical Bio-Impedance Plethysmography at Different Body Parts: Continuous and Non-Invasive Monitoring of Pulse Wave Velocity

A simultaneous and time-synchronized electrical bio-impedance plethysmography (BPG) sensor system is implemented for long-term, continuous, and non-invasive measurement of arterial pulse wave velocity (PWV). The proposed BPG sensor system electrically separates each ground plane of two BPG channels and controller, and the two different BPG channels are time-synchronized by the controller transmitting periodic pulse signal to the two BPG channels. Furthermore, net parasitic capacitance between the ground planes is minimized by removing isolated DC-DC converter, limiting the number of digital capacitive isolators, and adopting optimal layout of the ground planes. The proposed sensor system is integrated on 278cm² printed circuit board. The sensor system consumes 0.35 W/channel, and outstanding channel-to-channel isolation is expected by coupling factor performance of -77.7 dB. In addition, modified electrode configuration for BPG at chest drastically reduces baseline wandering by respiratory motion artifact, thereby further facilitating long-term, continuous, and non-invasive PWV measurement. As a result, long-term, continuous, and non-invasive PWV measurement more than 95 minutes is successfully performed to pave the way for developing pulse transit time (PTT)-based cuff-less blood pressure (BP) estimation technique.

Impedance Plethysmography as an Alternative Measure of Reactive Hyperemia

Peripheral vascular flow in response to induced reactive hyperemia of the radial artery is used as a benchmark for non-invasive assessment of the endothelial function. As an alternative to standard modalities, this study investigates the suitability of impedance plethysmography to estimate peripheral vascular flow variations associated with the reactive hyperemia process. Results indicate a consistent variation of bio-impedance during the reactive hyperemia process at higher measurement frequencies and these variations are compatible with a standard tissue impedance model. Further, calculated features of bioimpedance has shown the capability of differentiating healthy and diabetic groups which is useful in estimating the endothelial dysfunction.

Compressive Sensing of Cuff-less Biosensor for Energy-Efficient Blood Pressure Monitoring

Compressive Sensing (CS) is an emerging technique in Internet of Medical Things (IoMT) application especially for smart wearable devices to prolong the sensor lifetime, and enable a continuous healthcare monitoring system. This paper describes the performance of CS on our wrist-based cuff-less biosensor for estimating blood pressure (BP) continuously. The proposed biosensor offers a novel BP estimation method by only using the biosignal from subject wrist. A CS technique is implemented to encrypt and reduce the data transmission load of the dual biosignal, which include impedance plethysmography (IPG) and photo plethysmography (PPG). Therefore, multiple compression ratio (CR) were tested to the original signal. We further compare the CS-based extracted features called pulse transit times (PTTs). Based on our experiments, CS-based PTT value that calculated from the IPG peak point to the PPG max₂ point (F2), achieved the best correlation coefficient (R) of -0.85 and -0.43 to the systolic BP and diastolic BP, respectively. These results suggest that the implementation of CS on our proposed wrist biosensor is suitable for non-intrusive, yet long-term continuous BP monitoring.

Percent Body Fat Measurement in the Medical Management of Children with Obesity

Sustaining weight loss can be challenging, as physiological responses to weight loss, including metabolic and hormonal adaptations and decreased energy expenditure, promote weight regain. Paired with sustained dietary changes, physical activity can promote weight maintenance after successful weight loss, as physical activity can help maintain fat-free mass. We present several illustrative cases to highlight the potential use of body composition measurement using a bioelectrical impedance analysis (BIA) scale to augment obesity management counseling in a tertiary care pediatric weight-management clinic. BIA does require some interpretation, as it can be affected by hydration status and time of day, as well as patient age, sex, and body mass index. Nonetheless, BIA can be a helpful aid to obesity counseling. More research is needed to better understand how to use change in percent body fat over time as a motivational tool for management of children with obesity. [Pediatr Ann. 2018;47(12):e487-e493.].

Physical activity classification using time-frequency signatures of motion artifacts in multi-channel electrical impedance plethysmographs

Physical activities are known to introduce motion artifacts in electrical impedance plethysmographic (EIP) sensors. Existing literature considers motion artifacts as a nuisance and generally discards the artifact containing portion of the sensor output. This paper examines the notion of exploiting motion artifacts for detecting the underlying physical activities which give rise to the artifacts in question. In particular, we investigate whether the artifact pattern associated with a physical activity is unique; and does it vary from one human-subject to another? Data was recorded from 19 adult human-subjects while conducting 5 distinct, artifact inducing, activities. A set of novel features based on the time-frequency signatures of the sensor outputs are then constructed. Our analysis demonstrates that these features enable high accuracy detection of the underlying physical activity. Using an SVM classifier we are able to differentiate between 5 distinct physical activities (coughing, reaching, walking, eating and rolling-on-bed) with an average accuracy of 85.46%. Classification is performed solely using features designed specifically to capture the time-frequency signatures of different physical activities. This enables us to measure both respiratory and motion information using only one type of sensor. This is in contrast to conventional approaches to physical activity monitoring; which rely on additional hardware such as accelerometers to capture activity information.

Virtual Spirometry and Activity Monitoring Using Multichannel Electrical Impedance Plethysmographs in Ambulatory Settings

Continuous monitoring of respiratory patterns and physical activity levels can be useful for remote health management of patients with conditions such as heart disease and chronic obstructive pulmonary disease. In a clinical setting, spirometers serve as the gold standard for monitoring respiratory patterns such as breathing rate and changes in lung volume. However, direct measurements using a spirometer requires placement of a sensor in the patient's airway and is thus infeasible for continuous monitoring in nonclinical, ambulatory settings. Under these conditions, indirect respiration monitoring using electrical impedance plethysmographs (EIP) is more suitable but are susceptible to motion artifacts. In this paper, we investigate whether multichannel EIP can be used to perform virtual spirometry under ambulatory settings. The experiments presented in this paper are based on preliminary data collected from 19 adult human subjects under realistic ambulatory and nonambulatory settings. We first highlight the salient features of the signal acquired from a standard spirometer. We then compare the performance of different biosignal processing algorithms in estimating the spirometer signal using multiple EIP sensors and in the presence of motion artifacts and real-world interferences. We demonstrate that in addition to reliably determining different respiratory patterns and states, multichannel EIP could also be used to reliably extract information regarding different patient physical activity states like bending or stretching.

An Investigation on Ground Electrodes of Capacitive Coupling Human Body Communication

Utilizing the body surface as the signal transmission medium, capacitive coupling human body communication (CC-HBC) can achieve a much higher energy efficiency than conventional wireless communications in future wireless body area network (WBAN) applications. Under the CC-HBC scheme, the body surface serves as the forward signal path, whereas the backward path is formed by the capacitive coupling between the ground electrodes (GEs) of transmitter (TX) and receiver (RX). So the type of communication benefits from a low forward loss, while the backward loss depending on the GE coupling strength dominates the total transmission loss. However, none of the previous works have shown a complete research on the effects of GEs. In this paper, all kinds of GE effects on CC-HBC are investigated by both finite element method (FEM) analysis and human body measurement. We set the TX GE and RX GE at different heights, separation distances, and dimensions to study the corresponding influence on the overall signal transmission path loss. In addition, we also investigate the effects of GEs with different shapes and different TX-to-RX relative angles. Based on all the investigations, an analytical model is derived to evaluate the GE related variations of channel loss in CC-HBC.

A Cuffless Blood Pressure Measurement Based on the Impedance Plethysmography Technique

In the last decade, cuffless blood pressure measurement technology has been widely studied because it could be applied to a wearable apparatus. Electrocardiography (ECG), photo-plethysmography (PPG), and phonocardiography are always used to detect the pulse transit time (PTT) because the changed tendencies of the PTT and blood pressure have a negative relationship. In this study, the PPG signal was replaced by the impedance plethysmography (IPG) signal and was used to detect the PTT. The placement and direction of the electrode array for the IPG measurement were discussed. Then, we designed an IPG ring that could measure an accurate IPG signal. Twenty healthy subjects participated in this study. The changes in blood pressure after exercise were evaluated through the changes of the PTT. The results showed that the change of the systolic pressure had a better relationship with the change of the PTT_IPG than that of the PTT_PPG (r = 0.700 vs. r = 0.450). Moreover, the IPG ring with spot electrodes would be more suitable to develop with the wearable cuffless blood pressure monitor than the PPG sensor.

Investigation and Modeling of Capacitive Human Body Communication

This paper presents a systematic investigation of the capacitive human body communication (HBC). The measurement of HBC channels is performed using a novel battery-powered system to eliminate the effects of baluns, cables and instruments. To verify the measured results, a numerical model incorporating the entire HBC system is established. Besides, it is demonstrated that both the impedance and path gain bandwidths of HBC channels is affected by the electrode configuration. Based on the analysis of the simulated electric field distribution, an equivalent circuit model is proposed and the circuit parameters are extracted using the finite element method. The transmission capability along the human body is also studied. The simulated results using the numerical and circuit models coincide very well with the measurement, which demonstrates that the proposed circuit model can effectively interpret the operation mechanism of the capacitive HBC.

Does Fetal Growth Restriction Cause Later Obesity? Pitfalls in Analyzing Causal Mediators as Confounders

Recent studies finding that small-for-gestational-age (SGA) birth is associated with increased adiposity in childhood and adulthood have been based on analyses "adjusting" for height, weight, or body mass index (BMI; weight (kg)/height (m)2) measured concurrently with the adiposity measurement. To assess the potential for bias due to overadjustment for a causal mediator, we compared 2 approaches to analyzing the association between SGA birth and adiposity outcomes (skinfold thicknesses and bioelectrical impedance measurement of body fat) at age 11.5 years using the same data set in a cohort of Belarusian children followed from birth in 1996-1997 to age 11.5 years in 2008-2010. We 1) studied the association of SGA birth with adiposity, adjusting for baseline covariates only, and 2) made additional regression adjustment for concurrent height, weight, or BMI. The first approach yielded negative associations between SGA birth and all adiposity outcomes. Additional adjustment for concurrent weight or BMI reversed (i.e., to positive) the SGA-adiposity association. To explore the latter anthropometric measures as causal mediators, we also used marginal structural models to estimate the controlled direct effect of SGA birth. That effect was similar to the effect seen with the first approach when modeled on height, was null when modeled on BMI, but was confounded by differences in lean mass versus fat mass when modeled on weight.

Nutritional status and body composition by bioelectrical impedance vector analysis: A cross sectional study in mild cognitive impairment and Alzheimer's disease

AIMS

Analysis of nutritional status and body composition in Alzheimer's disease (AD) and Mild Cognitive Impairment (MCI).

METHODS

A cross-sectional study was performed in a University-Hospital setting, recruiting 59 patients with AD, 34 subjects with MCI and 58 elderly healthy controls (HC). Nutritional status was assessed by anthropometric parameters (body mass index; calf, upper arm and waist circumferences), Mini Nutritional Assessment (MNA) and body composition by bioelectrical impedance vector analysis (BIVA). Variables were analyzed by analysis of variance and subjects were grouped by cognitive status and gender.

RESULTS

Sociodemographic variables did not differ among the three groups (AD, MCI and HC), except for females' age, which was therefore used as covariate in a general linear multivariate model. MNA score was significantly lower in AD patients than in HC; MCI subjects achieved intermediate scores. AD patients (both sexes) had significantly (p<0.05) higher height-normalized impedance values and lower phase angles (body cell mass) compared with HC; a higher ratio of impedance to height was found in men with MCI with respect to HC. With BIVA method, MCI subjects showed a significant displacement on the RXc graph on the right side indicating lower soft tissues (Hotelling's T2 test: men = 10.6; women = 7.9;p < 0,05) just like AD patients (Hotelling's T2 test: men = 18.2; women = 16.9; p<0,001).

CONCLUSION

Bioelectrical parameters significantly differ from MCI and AD to HC; MCI showed an intermediate pattern between AD and HC. Longitudinal studies are required to investigate if BIVA could reflect early AD-changes in body composition in subjects with MCI.

Systematic review of field-based physical fitness tests for children and adolescents with intellectual disabilities

BACKGROUND

Testing physical fitness in children and adolescents with intellectual disabilities (ID) can be challenging. This review provides an overview on psychometric properties of field-based physical fitness tests studied in children and adolescents with ID.

METHODS

A literature search was performed in March 2014. Studies were included if they evaluated feasibility, reliability and/or validity of a field-based physical fitness test in children and adolescents with ID.

RESULTS

Twenty-six papers met the inclusion criteria and described 18 tests on body composition (4), muscular strength (4), muscular endurance (6), and cardiorespiratory fitness (4). Best results on feasibility, reliability and/or validity were found for bioelectric impedance analysis, body mass index, grip strength, arm hang and distance run/walk tests. These results were mainly found in adolescents with mild to moderate ID.

CONCLUSION

Some tests were found feasible, reliable and/or valid in subgroups of children and adolescents with ID, but not in children and adolescents with all ages and levels of ID. Further assessment is needed before wider application in all children and adolescents with ID.

Mechanisms of Vasovagal Syncope in the Young: Reduced Systemic Vascular Resistance Versus Reduced Cardiac Output

BACKGROUND

Syncope is a sudden transient loss of consciousness and postural tone caused by cerebral hypoperfusion. The most common form is vasovagal syncope (VVS). Presyncopal progressive early hypotension in older VVS patients is caused by reduced cardiac output (CO); younger patients have reduced systemic vascular resistance (SVR). Using a priori criteria for reduced CO (↓CO) and SVR (↓SVR), we studied 48 recurrent young fainters comparing subgroups of VVS with VVS-↓CO, VVS-↓SVR, and both VVS-↓CO&↓SVR.

METHODS AND RESULTS

Subjects were studied supine and during 70-degrere upright tilt with a Finometer to continuously measure blood pressure, CO, and SVR and impedance plethysmography to estimate thoracic, splanchnic, pelvic, and calf blood volumes, blood flows, and vascular resistances and electrocardiogram to measure heart rate and rhythm. Central blood volume was decreased in all VVS compared to control. VVS-↓CO was associated with decreased splanchnic blood flow and increased splanchnic blood pooling compared to control. Seventy-five percent of VVS patients had reduced SVR, including 23% who also had reduced CO. Many VVS-↓SVR increased CO during tilt, with no difference in splanchnic pooling, caused by significant increases in splanchnic blood flow and reduced splanchnic resistance. VVS-↓CO&↓SVR patients had splanchnic pooling comparable to VVS-↓CO patients, but SVR comparable to VVS-↓SVR. Splanchnic vasodilation was reduced, compared to VVS-↓SVR, and venomotor properties were similar to control. Combined splanchnic pooling and reduced SVR produced the earliest faints among the VVS groups.

CONCLUSIONS

Both ↓CO and ↓SVR occur in young VVS patients. ↓SVR is predominant in VVS and is caused by impaired splanchnic vasoconstriction.

Electrical Impedance imaging of the Thorax

In this paper, we propose to develop a new imaging technology, computerized impedance tomography (CIT) for imaging the thorax. Our study involves reconstructing images of thoracic transverse plane impedance distributions noninvasively and nondestructively and exploring the potential of CIT. We overcome the reconstruction problem due to nonlinear and nonplanar current paths in impedance imaging by solving Laplace's equation numerically for every iteration and by using a new back-projection algorithm to modify the impedance profile. We discuss advantages and disadvantages associated with impedance imaging, the computer model, and back-projection algorithms used in reconstructing impedance images. We present reconstructed impedance images with 8 projection angles and different projection methods. We identify important variables affecting the quality of reconstructed images, and discuss the resolution and accuracy of this imaging technique. We summarize numerical aspects, computer requirement, and limitations of impedance imaging. We also discuss the future of impedance imaging.

Microwave Methods of measuring Changes in Lung Water

Two microwave methods for measuring changes in lung water content have been investigated. The first is based on measuring changes in the phase of an active microwave signal transmitted through the thorax, while the other is based on measuring the natural microwave radiation emitted by the body with a radiometer. The feasibility of using the active microwave method is investigated by making measurements on phantoms, on anesthetized dogs with induced pulmonary edema, and on isolated dog lungs. The obtained results clearly illustrated that the method is sensitive enough to measure small changes in lung water content. In the radiometer method, on the other hand, both calculations and preliminary measurements in phantoms indicate that the natural microwave emission changes with lung water content and that conventional radiometry systems should be able to detect as little as three to four percent change in lung water content. Initial results from both methods, therefore, indicate the soundness of the basic ideas and justify further development of these methods for clinical use.

Greater Early Gains in Fat-Free Mass, but Not Fat Mass, Are Associated with Improved Neurodevelopment at 1 Year Corrected Age for Prematurity in Very Low Birth Weight Preterm Infants

OBJECTIVE

This work investigates the relationship between early body composition changes and neurodevelopment at 1 year age corrected for prematurity (CA).

STUDY DESIGN

A prospective, longitudinal study to measure body composition weekly in 34 very low birth weight preterm infants using air displacement plethysmography, beginning when infants stabilized after birth until discharge. Neurodevelopmental testing (Bayley Scales of Infant Development-III) was performed at 12 months CA. Linear mixed effects models were used to obtain inpatient subject-specific changes in fat-free mass (FFM) and fat mass (FM), which were then used as predictors of Bayley subscale scores in subsequent linear regression models, adjusting for potential confounders. Protein and energy provision were calculated for the first week of life.

RESULTS

Greater FFM gains while inpatient were associated with improved cognitive and motor scores at 12 months CA (P = .002 for both). These relationships remained significant when adjusting for birth weight, gestational age, and intraventricular hemorrhage (P ≤ .05 for both). Similar analysis was performed for FM gains without significant findings. Increased provision of protein and calories during the first week of life was positively associated with FFM gains (P ≤ .01 for both), but not FM gains (P ≥ .2 for both), throughout hospitalization.

CONCLUSIONS

Increased FFM gains, but not FM gains, during hospitalization are associated with improved neurodevelopment at 12 months CA. As early FM gains may be associated with long-term risk, more research is needed to develop strategies that optimize FFM gains while minimizing FM gains in very low birth weight preterm infants.

Analysis of cardiorespiratory phase coupling and cardiovascular autonomic responses during food ingestion

The present study analyzed whether the phase coherency (λ) of respiratory sinus arrhythmia (RSA) is altered by food ingestion in healthy young subjects. After 5min of resting control, 13 healthy volunteers were asked to eat a solid meal with access to water at their own pace, followed by 5min of the postprandial state. The R-R interval (RRI), beat-to-beat blood pressure (BP), and respiratory activity were recorded using electrocardiography, a Finapres device, and inductance plethysmography, respectively. The stroke volume was calculated by the pulse-contour method from continuous BP measurement, and the cardiac output (CO) was obtained by multiplying the stroke volume by the heart rate. From the oscillatory signals of RSA and respiration, λ was computed; additionally, frequency domain indexes of the heart rate variability (HRV) were calculated using a short-time Fourier transform. A steady-state 3-min resting period (R), food ingestion period (FOOD), and the first 2-min and the last 3-min of the post prandial period were analyzed separately. We also compared the responses to gum chewing (GUM) and water intake (WATER) using the same protocol on separate days. A shortening of RRI and increases in BP and CO were observed in FOOD compared to R, suggesting a shift of sympathovagal balance toward sympathetic activation. Similar responses but smaller magnitudes were observed in the GUM condition, whereas only transient shortening of RRI was observed in the WATER condition. The HRV indexes did not show any significant changes in response to GUM and WATER but sympathovagal balance was shifted in favor of sympathetic dominance in FOOD. λ decreased during all of the conditions. There was a significant negative correlation between λ and the indirect measure of sympathovagal balance. These results suggest that ingestion of food induces enhanced cardiac sympathetic activity and that a phase coherence of RSA could provide a sensitive measure for evaluating the cardiac autonomic profile.

[PECULIARITIES OF COURSE OF TRAUMATIC DISEASE IN THE INJURED PERSONS IN COMBINED CRANIOABDOMINAL TRAUMA]

Prospective investigation of the traumatic disease course was conducted in 71 injured persons, suffering a combined cranioabdominal trauma with the objective to determine the main functional systems and dynamics of their state severity. The occurrence rate and the severity degree of cardiovascular insufficiency were determined--in accordance to indices of the integrative body rheography and integrative dual frequency impedansometry, respiratory insufficiency (PaO₂/FiO₂ ratio), the organ insufficiency severity (in accordance to SOFA scale). There was established, that changes in respiratory and cardiovascular systems are corresponding to the staged pathogenetic characteristics of the traumatic disease periods. So on, it is expedient to perform the urgent and postponed operative interventions in a period of their relative stabilization. The presence of severe craniocerebral trauma, as a part of a combined cranioabdominal trauma causes significant and durable impairment of the functional systems activity.

Low testosterone levels are associated with endothelial dysfunction in oophorectomized early postmenopausal women

BACKGROUND

The actual consequences of low testosterone levels in women remain uncertain.

OBJECTIVE

To assess endogenous testosterone influence on body composition, vascular and metabolic function in recent postmenopausal women.

DESIGN

We studied 81 postmenopausal women under transdermal estradiol (E2) replacement therapy, 36 with bilateral oophorectomy (group O), and 45 controls (group C) through venous occlusion plethysmography, bioimpedance, DEXA, biochemical, hormonal, and inflammatory profile.

RESULTS

Total testosterone level (TT) in group O was 11.0 (4.0-17.75) vs 23.0 (10.0-42.5) ng/dl in group C (P=0.001). Forearm blood flow, in ml/min/100  ml tissue, was lower in group O compared to group C at baseline (1.57 (1.05-2.47) vs 2.19 (1.59-2.66) P=0.036), following reactive hyperemia response (endothelium-dependent flow mediated dilatation, 3.44 (2.38-4.35) vs 4.3 (3.09-5.52), P=0.031) and following nitroglycerin (endothelium-independent dilation, 1.39 (0.99-1.7) vs 1.76 (1.15-2.0), P=0.025), with a positive correlation between TT and all parameters except for the reactive hyperemia response (r=0.233-0.312, P=0.036-0.004). The sVCAM1 levels were negatively correlated with TT (r=-0.320, P=0.005). E2 and other hormone levels, biochemical parameters and body composition did not differ between groups. Multiple linear regressions showed that the levels of TT, compared with other confounding variables, may explain the variation observed on endothelial parameters, with low explanatory power.

CONCLUSION

The absence of ovarian testosterone production in recent postmenopausal oophorectomized women was associated with deleterious effects on endothelial function.

[FUNCTIONAL STATE OF PERIPHERAL VESSELS OF THE LOWER EXTREMITIES AND INTRAOSSEOUS PRESSURE IN PATIENTS, SUFFERING OBLITERATING ATHEROSCLEROSIS ON BACKGROUND OF DIABETES MELLITUS]

Results of examination of 46 patients, suffering obliterating atherosclerosis of the lower extremities arteries solely or in combination with diabetes mellitus (DM), were analyzed. The malleolar pressure index (MPI), regional systolic pressure (RSP), velocity of the volume blood flow (VVBF), rheographic index (RI), using test with nitroglycerine, postocclusion venous pressure (POVP) and intaosseous pressure (IOP) in tibiae were studied. The RI reduction, parallel to the arterial ischemia progression, was established. The test indices with nitroglycerine in patients with obliterating atherosclerosis have reduced step by step. With coexistent DM the efficacy of nitroglycerine was practically absent. POVP is upgraded in patients of all the groups and it have lowered step by step in a laying position of the patient, and while transition into standing position--it have upgraded progressively with a progress of arterial ischemia. IOP have upgraded significantly in isolated obliterating atherosclerosis in ischemia stage 3a and have lowered--in stage 3b. In coexistent DM IOP is upgraded in ischemia stage 3b also.

Alterations in energy homeostasis to favour adipose tissue gain: A longitudinal study in healthy pregnant women

BACKGROUND

Pregnancy is associated with an increase in body fat; however, excessive gestational weight gain predisposes to significant maternal and neonatal morbidity and mortality. It remains unclear whether alterations in energy homeostasis have a major influence on fat storage.

AIMS

To evaluate longitudinal changes in body composition and energy metabolism in healthy pregnant women.

MATERIALS AND METHODS

Body composition, energy expenditure and energy intake were measured longitudinally in 26 women with singleton pregnancies at 12-14 weeks, 24-26 weeks and 34-36 weeks of gestation. Fat mass (FM) and lean body mass (LBM) were measured using bio-impedance analysis, total energy expenditure (TEE) using the Sensewear Armband and energy intake through a 3-day food recall diary.

RESULTS

Throughout pregnancy, all women remained healthy. Body weight increased by 10.8 ± 3.9 kg, from 67.3 ± 14.1 kg to 78.1 ± 13.8 kg from the first to the third trimester (P < 0.001). Body fat percentage increased by 4.5 ± 4.2% (P < 0.001). LBM also increased throughout pregnancy, by 3.9 ± 2.4 kg (P < 0.001). TEE increased significantly from the first to the third trimesters (9514 kJ/day to 10 263 kJ/day; P < 0.05). In contrast, energy expenditure due to physical activity, energy intake and macronutrient intake did not change significantly throughout pregnancy.

CONCLUSION

Healthy women increase FM during pregnancy despite slight increases in TEE and no change in energy intake. This suggests that energy storage efficiency improves during pregnancy, which may be related to alterations in gut microbiota and activation of anabolic pathways during pregnancy. Clarifying factors leading to this more efficient fat and energy storing state, and the role of the pregnancy-related changes in gut microbiota, may be important for managing gestational weight gain.

Lung Volume Reduction in Emphysema Improves Chest Wall Asynchrony

BACKGROUND

Lung volume reduction (LVR) techniques improve lung function in selected patients with emphysema, but the impact of LVR procedures on the asynchronous movement of different chest wall compartments, which is a feature of emphysema, is not known.

METHODS

We used optoelectronic plethysmography to assess the effect of surgical and bronchoscopic LVR on chest wall asynchrony. Twenty-six patients were assessed before and 3 months after LVR (surgical [n = 9] or bronchoscopic [n = 7]) or a sham/unsuccessful bronchoscopic treatment (control subjects, n = 10). Chest wall volumes were divided into six compartments (left and right of each of pulmonary ribcage [Vrc,p], abdominal ribcage [Vrc,a], and abdomen [Vab]) and phase shift angles (θ) calculated for the asynchrony between Vrc,p and Vrc,a (θRC), and between Vrc,a and Vab (θDIA).

RESULTS

Participants had an FEV₁ of 34.6 ± 18% predicted and a residual volume of 217.8 ± 46.0% predicted with significant chest wall asynchrony during quiet breathing at baseline (θRC, 31.3° ± 38.4°; and θDIA, -38.7° ± 36.3°). Between-group difference in the change in θRC and θDIA during quiet breathing following treatment was 44.3° (95% CI, -78 to -10.6; P = .003) and 34.5° (95% CI, 1.4 to 67.5; P = .007) toward 0° (representing perfect synchrony), respectively, favoring the LVR group. Changes in θRC and θDIA were statistically significant on the treated but not the untreated sides.

CONCLUSIONS

Successful LVR significantly reduces chest wall asynchrony in patients with emphysema.

Treatment of physiotherapy-refractory secondary upper limb lymphedema with vascularized lymph node transfer: A case report with clinical and bioimpedance analysis correlation

With radical treatment of cancer, lymphedema of limb has become a commonly faced adverse effect. The introduction of vascularized lymph node transfer (VLNT) has provided a possible treatment option for this troublesome condition. In this case report, we describe a 66-year-old lady who developed upper limb lymphedema after operation and radiotherapy for the cancer of her left breast. Her lymphedema did not improve despite wearing pressure garment and receiving six months of regular decongestive physiotherapy. VLNT was performed for this patient, the pre- and post-operative limb circumference and bioimpedance measurements were compared. After operation, the patient continued with her previous physiotherapy regimen. Complete resolution of pitting edema was demonstrated five months after VLNT. In addition, there was a marked improvement in both limb circumference and bioimpedance measurements. From this case report, VLNT appears to be a promising treatment option for secondary lymphedema. We suggest this case report can serve as a model for future studies.

[Diagnosis and treatment of achalasia cardiae]

Achalasia is a progressive oesophageal motility disorder of unstudied aetiology involving the smooth muscle layer of the oesophagus. Insufficient knowledge of the pathogenesis of achalasia and the lack of clear treatment approaches has led to an increase of advanced disease forms. Common clinical manifestations of the disease are: incomplete LES relaxation, non-specific initial manifestations and as a result late medical seeking. Occurrence of achalasia cardiae is significantly low, therefore it is important to analyse the available clinical data. The article presents an experience of treatment of 30 patients over the last 16 years of observation. The average age of patients was 50, 5 years; insignificant male predominance is noted. III or IV disease state was diagnosed in 86.7% of patients; this diagnosis was confirmed by esophagogastroduodenoscopy. In the group of 24 patients who underwent attempted endoscopic dilatation of the cardiae, most of the included patients with stage II and III disease. Immediate good and satisfactory results of endoscopic treatment were obtained in 20 patients (83.3%), in 4 cases (16.7%) developed recurrent disease.

Impact of cardiac rehabilitation on peripheral circulation as assessed by impedance plethysmography: a randomized clinical trial

BACKGROUND

It's known, controlled physical exercise which is a part of cardiac rehabilitation lead to positive changes in coronary circulation and contributes to minimizing other risk factors, such as lipid concentration in the blood or body weight as well as decreases the risk of another acute coronary disease. Monitoring cardiovascular activity is a necessary element of supervising the patient during cardiac rehabilitation. This supervision is primarily concerned with coronary circulation, bypassing the peripheral circulation which may seem like an important part of properly reacts to physical activity.

AIM

The aim of the study was to evaluate changes in the peripheral circulation in the calf, induced by controlled physical exercise performed within a standard rehabilitation procedure in patients with acute coronary disease, with the use of impedance plethysmography.

DESIGN

Clinical trial (CT).

MATERIALS SETTING

All the patients were referred to be cardiologically rehabilitated to the hospital in the Clinic of Internal Diseases and Cardiological Rehabilitation of the Medical University of Łodz not later than one month following the occurrence of acute coronary disease.

POPULATION

Forty-seven patients with acute coronary disease were divided into two study groups. Group I (N.=23) participated in a two-week and Group II in a four-week cardiac rehabilitation.

METHODS

Forty-seven patients participated in interval training on a cycle ergometer and exercise improving general physical state held five times a week. All the patients underwent impedance plethysmography test before and after the training session in order to evaluate peripheral circulation in lower limbs.

RESULTS

The authors of the study observed changes in plethysmographic parameters. After two weeks of performing physical exercise Group I demonstrated an increase in the following parameters: PSlope by 3.8%, PAmpl by 1.7%, CT by 3.3% and PT by 1% (p>0.05). With regards to Group II, the parameters increased respectively by: 23.8% (PSlope), 20.4% (PAmpl), 11.6% (CT) and 6.8% (PT) (p<0.05). The authors also noted a complete correlation between the results of the plethysmographic parameters and cardiac stroke volume (Pearson=1).

CONCLUSIONS

Findings of the studies confirm that cardiac rehabilitation improves blood flow in lower limbs vessels in patients with acute coronary disease. Impedance plethysmography allows for non-invasive monitoring of local blood flow and is a precise and repeated method of evaluating peripheral circulation in patients during cardiac rehabilitation.

CLINICAL REHABILITATION IMPACT

The results indicate the role of the length of the training time, which has a beneficial effect on the peripheral circulation of the lower limbs. That could help change the rehabilitation program in other rehabilitation clinic.

Children with cystic fibrosis have prolonged chemical clearance of acid reflux compared to symptomatic children without cystic fibrosis

OBJECTIVES

Few studies compare gastroesophageal reflux (GER) parameters of cystic fibrosis (CF) children and symptomatic non-CF children. We aimed to compare the impedance-pH (IMP-pH) parameters for these two groups and to test the hypothesis that prolonged acid exposure in CF patients is due to delayed chemical clearance (CC).

METHODS

IMP-pH tracings from 16 CF children (median 8.2 years) and 16 symptomatic non-CF children (median 8.3 years) were analyzed. Software was used to generate IMP-pH reports and parameter data were extracted. IMP-pH was used to calculate the mean CC for each patient.

RESULTS

pH studies showed no difference in acid GER (AGER) frequency (p = 0.587); however, mean AGER duration, duration of longest AGER, AGER index, and DeMeester scores were all significantly higher for CF patients. IMP showed no difference in GER frequency [neither acidic (p = 0.918) nor non-acidic (p = 0.277)], but total bolus clearance was more efficient in CF patients (p = 0.049). A larger percentage of total GER reached the proximal esophagus in non-CF children (p = 0.039). Analyses of two-phase AGER episodes showed that these events were more acidic (p = 0.003) and the CC phase was significantly prolonged in the CF cohort (p = 0.001).

CONCLUSIONS

Compared to symptomatic non-CF children, CF children do not have more frequent reflux. Actually, they have better bolus clearance efficiency following reflux and may even have better control over the number of GER episodes that reach the proximal esophagus. CC of AGER, however, is significantly prolonged in the CF cohort, likely due to hyperacidity of refluxed gastric contents.

[Gender differences in weather sensitivity of normal adult people registered on the rheoencephalogram and electroencephalogram]

In the real-life environment the subjectively unperceived reactivity of rheoencephalogram (REG) and electroencephalogram (EEG) to ordinary geophysical factors (i.e. wind, atmospheric pressure, relative humidity and temperature) is gender-dependent. Correlations between REG and EEG values and weather fluctuations are more frequent and stronger in men. Dependence of EEG rhythms on weather factors increases as the rhythmic activity within the delta-theta-beta range becomes more rapid. This pattern is particularly evident in men but not women. Reactivity of neurodynamic parameters in female REG and EEG is responsive to the ovarian-menstrual cycle. Almost all cases of cerebral weather sensitivity of women were objectified in the post-ovulatory period, whereas in the preovulatory period episodes of weather sensitivity were only singular.

[Variations of the volume and segmental blood flow in the upper extremity of the patents presenting with breast cancer treated with the application of various regimes of pneumatic compression]

Post-mastectomy lymphedema on the side of the surgical intervention is a major complication of radical therapy of breast cancer patients. Pneumatic compression (compression pump technology) of various types, modes and techniques is used for their rehabilitation. A total of 192 breast cancer patients with I-IV degree lymphedema were available for the examination in the present study. All of them were treated with the application of different modes of one- and multi-chambered pneumatic compression. Based on the results of aqueous and impedance plethysmography, the multi-chambered pneumatic compression was identified as the most effective methods for the purpose, with the pressure inside the chambers below 60-80 mm Hg and the duration of the treatment 45-60 min per day. It is recommended to perform three treatment courses each consisting of 15 procedures with the intervals of 3-6 months between them (depending on the severity of the edema).

Evaluation of gastroesophageal function and mechanisms underlying gastroesophageal reflux in infants and adults born with esophageal atresia

PURPOSE

To evaluate the mechanisms underlying gastroesophageal reflux (GER) following esophageal atresia (EA) repair and gastroesophageal function in infants and adults born with EA.

METHODS

Ten consecutive infants born with EA as well as 10 randomly selected adult EA patients were studied during their first postoperative follow-up visit and a purposely planned visit, respectively. A (13)C-octanoate breath test and esophageal pH-impedance-manometry study were performed. Mechanisms underlying GER and esophageal function were evaluated.

RESULTS

Transient lower esophageal sphincter relaxation (TLESR) was the most common mechanism underlying GER in infants and adults (66% and 62%, respectively). In 66% of all GER episodes, no clearing mechanism was initiated. On EFT, normal motility patterns were seen in six patients (four infants, two adults). One of these adults had normal motility overall (>80% of swallows). Most swallows (78.8%) were accompanied by abnormal motility patterns. Despite this observation, impedance showed normal bolus transit in 40.9% of swallows. Gastric emptying was delayed in 57.1% of infants and 22.2% of adults.

CONCLUSIONS

TLESR is the main mechanism underlying GER events in patients with EA. Most infants and adults have impaired motility, delayed bolus clearance, and delayed gastric emptying. However, normal motility patterns were seen in a minority of patients.

Sodium set-point in haemodialysis: is it what we see clinically?

BACKGROUND

Natraemia in haemodialysis (HD) patients is considered constant contrary to daily clinical observations. Its relationship with clinical parameters, dialysis parameters and body water (BW) distribution is not clear.

OBJECTIVES

The aims of this study were to know 1) the intraindividual variability of natraemia, 2) the relationship between natraemia and clinical and dialysis parameters and 3) the relationship between natraemia and BW distribution by bioimpedance.

MATERIAL AND METHOD

Observational retrospective study on 98 chronic HD patients. Clinical, HD and natraemia, glucose and bioimpedance data were collected.

RESULTS

We included 63 males and 35 females of 69.6 (21-91) years of age, with a follow-up of 23.2 (10) months. Variability: 1802 sodium measurements: mean natraemia 138 (3.2) mEq/l and corrected for glucose: 139.1 (3.6) mEq/l, p<.0001. Intraindividual coefficient of variation (CV) was 2% (0.8) (range 1-5.6%) and it correlated negatively with natraemia (r=-0.63, p<.0001). Clinical parameters: corrected natraemia was lower in diabetics than in non-diabetics 138 (2.4) compared with 139 (2) mEq/l, p<.003, CV 2.3 (0.9) compared with 1.9 (0.7)% (p<.01) and SD 3.2 (1.2) compared with 2.5 (0.9) mEq/l (p<.04). No differences according to gender, age, HD time, cardiac or liver disease, medication use, residual renal function or mortality were found. HD parameters: a positive relationship was found between natraemia and total dialysate conductivity and it was negative with interdialysis weight gain (IDG). - Bioimpedance: no relationship was found between natraemia and BW distribution.

CONCLUSIONS

Natraemia varies in each patient and is related positively with conductivity and negatively with IDG. In diabetics natraemia is lower and CV is higher. There is no relationship between natraemia and BW distribution.

[Association of cardiovascular system and endothelial dysfunction indicators in patients with hemorrhagic shock]

Endothelial dysfunction is a universal mechanism of pathogenesis of many critical conditions. Goal of the study was to assess a relation of cardiovascular system and endothelial dysfunction indicators in patients with hemorrhagic shock.

MATERIALS AND METHODS

17 patients with hemorrhagic shock 3 were involved in the study. All patients received infusion therapy, artificial lung ventilation after tracheal intubation and symptomatic treatment in prehospital period. Common volume of blood loose was 2900 +/- 200 mL. The patients received infusion, transfusion, inotrope, antibacterial, respiratory and symptomatic therapy in ICU after surgical treatment. Cardio-vascular system parameters were assessed by Tischenko method of integral reography. Number of red cells, hemoglobin, lactate, endotelin-1 and Wb-factor of venous blood were studied before surgery, in 12 and in 24 hours after. Morphological study of the omentumbiopsy was carried out.

RESULTS

Performed correlation analysis showed statistically significant relations of cardiovascular system and endothelial dysfunction indicators in patients with hemorrhagic shock. Endothelial dysfunction occurs in patients with hemorrhagic shock 3. The endothelial dysfunction correlates with parameters of cardio-vascular system and tissue perfusion.

Respiration and heart rate complexity: effects of age and gender assessed by band-limited transfer entropy

Aging and disease are accompanied with a reduction of complex variability in the temporal patterns of heart rate. This reduction has been attributed to a break down of the underlying regulatory feedback mechanisms that maintain a homeodynamic state. Previous work has established the utility of entropy as an index of disorder, for quantification of changes in heart rate complexity. However, questions remain regarding the origin of heart rate complexity and the mechanisms involved in its reduction with aging and disease. In this work we use a newly developed technique based on the concept of band-limited transfer entropy to assess the aging-related changes in contribution of respiration and blood pressure to entropy of heart rate at different frequency bands. Noninvasive measurements of heart beat interval, respiration, and systolic blood pressure were recorded from 20 young (21-34 years) and 20 older (68-85 years) healthy adults. Band-limited transfer entropy analysis revealed a reduction in high-frequency contribution of respiration to heart rate complexity (p<0.001) with normal aging, particularly in men. These results have the potential for dissecting the relative contributions of respiration and blood pressure-related reflexes to heart rate complexity and their degeneration with normal aging.

[Characteristic of hepatorenal perfusion in patients with acute appendicitis]

Analysis of hepatorenal perfusion was conducted in 44 patients, suffering an acute appendicitis. In 22 of them laparoscopic appendectomy was conducted, in 22--appendectomy, using a standard access in accordance with Volkovich-Dyakonov or Mac-Burney method. There was established more favourable impact of laparoscopic appendectomy conduction on hepatorenal postoperative perfusion, what is connected with lesser pain syndrome severity, influencing common hemodynamics, and more rapid elimination (or prophylaxis) of postoperative paralytic ileus, as well as better physical state of the patients.

Association between vasoconstriction during and following exposure to hand-transmitted vibration

OBJECTIVES

This study investigated whether reductions in finger blood flow (FBF) during and after vibration are similarly dependent on the magnitude and duration of the vibration.

METHODS

FBF on the left and right hand was measured every minute during, and for 1 h following, exposure of the right hand to one of three magnitudes of 125-Hz sinusoidal vibration (0, 22, or 88 ms(-2) rms) for one of two durations (7.5 or 15 min). Each of five experimental sessions was comprised of five periods: (i) no force and no vibration (5 min), (ii) 2-N force and no vibration (5 min), (iii) 2-N force and vibration (7.5 or 15 min), (iv) 2-N force and no vibration (5 min), and (v) no force and no vibration (60 min).

RESULTS

Vibration reduced FBF in the exposed and unexposed hands, both during and after vibration. With increased magnitude of vibration, there was increased vasoconstriction in all fingers during and after exposure, and longer recovery times after vibration exposure. With increased duration of vibration, there were no changes in vascular responses during exposure but increased vasoconstriction after exposure and prolonged recovery times. With the greater vibration magnitude, the reduction in FBF during exposure was correlated with the time taken to recover after exposure.

CONCLUSIONS

Subjects with greater reduction in blood flow during vibration exposure also have stronger and longer vasoconstriction during subsequent recovery. The correlation between vascular changes during and after vibration exposure suggests similar mechanisms control FBF during and after vibration exposure.

Diagnosis of deep venous thrombosis and pulmonary embolism

Venous thromboembolism manifests as deep venous thrombosis (DVT) or pulmonary embolism, and has a mortality rate of 6 to 12 percent. Well-validated clinical prediction rules are available to determine the pretest probability of DVT and pulmonary embolism. When the likelihood of DVT is low, a negative D-dimer assay result excludes DVT. Likewise, a low pretest probability with a negative D-dimer assay result excludes the diagnosis of pulmonary embolism. If the likelihood of DVT is intermediate to high, compression ultrasonography should be performed. Impedance plethysmography, contrast venography, and magnetic resonance venography are available to assess for DVT, but are not widely used. Pulmonary embolism is usually a consequence of DVT and is associated with greater mortality. Multidetector computed tomography angiography is the diagnostic test of choice when the technology is available and appropriate for the patient. It is warranted in patients who may have a pulmonary embolism and a positive D-dimer assay result, or in patients who have a high pretest probability of pulmonary embolism, regardless of D-dimer assay result. Ventilation-perfusion scanning is an acceptable alternative to computed tomography angiography in select settings. Pulmonary angiography is needed only when the clinical suspicion for pulmonary embolism remains high, even when less invasive study results are negative. In unstable emergent cases highly suspicious for pulmonary embolism, echocardiography may be used to evaluate for right ventricular dysfunction, which is indicative of but not diagnostic for pulmonary embolism.

[Impact of arterial stiffness on cardiovascular disease and hypoxia]

We performed an analysis of scientific studies about arterial stiffness impacting on cardiovascular diseases and special mechanisms of its developing. One of these mechanisms is hypoxie endothelial damage. Pulse pressure, aortic pulse wave velocity, the shape of the blood pressure curve, rheography, rheovasography are the methods for determinating arterial stiffness.

Effect of mode selection when using contact-electrode bioelectrical impedance analyzers to estimate percent body fat in young adults

AIM

When using bioelectrical impedance analysis (BIA) analyzers to assess body composition, a computer-programmed prediction equation referred to as a mode (i.e., standard STD or athletic ATH) must be selected prior to the assessment. This study examined the effect of mode selection on percent body fat (%BF) determined by leg-to-leg and segmental bioelectrical impedance analysis (LBIA; SBIA) in young adults.

METHODS

Ninety-two young adults (52 women; 40 men) had %BF estimated using LBIA (Tanita: TBF-300A) and SBIA (Tanita: BC-418) which was then compared to air displacement plethysmography (ADP). During the BIA assessment, %BF was determined using both the STD and ATH pre-programmed modes.

RESULTS

In the women, %BF (mean±SD) was significantly (P<0.001) underestimated by the ATH modes of LBIA (23.0±6.9%) and SBIA (23.4±6.2%) when compared to ADP (25.5±7.3%). In the men, the STD mode of LBIA (18.3±5%) overestimated %BF when compared to ADP (14.1±7%). All standard error of estimate and pure error values (range=3.8% to 6.3%) exceeded the recommended range for accuracy (<3.5%).

CONCLUSION

The STD mode produced mean %BF values most similar to ADP in the women, whereas the ATH mode did so in the men; a finding that was consistent for both analyzers. However, large individual prediction errors and wide confidence intervals were observed regardless of the mode selected or analyzer used for the assessment. As such, when precision is critical, the prediction equations programmed in the LBIA and SBIA analyzers examined in this study cannot be recommended to measure %BF on an individual basis.

[Regulation of blood circulation in the surgical correction of portal hypertension]

56 patients with portal hypertension were examined who underwent decompressive shunt surgery. Cardiorhytmography and integral rheography body were performed in different stages. In the late postoperative period, there were positive changes in the autonomic regulation of functions: reduced tension index and sympathetic influence on heart rhythm, increases the value of other indicators of heart rate variability. Due to an increase in heart rate and peripheral vascular resistance normalizes blood pressure while reducing the values of cardiac output. There is a further normalization of the reactivity of blood circulation: arterial pressure and vascular resistance during the functional test remained at a constant level of magnitude of shock and cardiac index significantly increased and then decreased to the level of the original values, which corresponds to the reaction apparently healthy. Disorders of regulation, state and reactivity of blood flow in portal hypertension, manifested: 1. Reduction of heart rate variability with a significant increase in sympathetic activity of autonomic nervous system. 2. Reduction of cardiac output and vascular resistance, heart rate, changes in physiological determination of hemodynamic parameters: Blood pressure is determined only by the vessel resistance. 3. Reduction of blood pressure in response to breath holding test.

[Some disorder features of blood circulation in lungs in older age influenza patients]

Patients aged 51-65 years with influenza develop circulatory disorders of the lung. Tone of the arteries of small and medium-caliber and venular vessels of the vascular bed of the lungs persistently reduced during the illness and a month after its start. The flow of venous blood from the vessels of the lungs disturbs: it is slow, difficult and becomes unstable. Such circulatory disorders in the lungs of influenza patients of older age groups appear during the illness and persist for a long time in the recovery period, which is a risk factor associated with complications of the respiratory system, not only during the illness, but after the disease.

A novel system for continuous peripheral arterial pressure-volume loop measurement

This study develops a system to obtain continuous blood pressure signal and impedance plethysmography (IPG) signal, simultaneously. Based on the principle of impedance measurement, the peripheral vessel volume change can be computed from the IPG signal. Equipped with simultaneous information of pressure and volume, a pressure-volume (PV) loop can be constructed. It is well known that the left ventricular pressure-volume loop contains a number of feature points indicating the performance of cardiac function. Therefore, in this study, the same principle is used to try to discuss the peripheral vessel pressure-volume loop. Ten volunteers were recruited for this study. Subjects went through the cold pressor test by immersing their left foot into ice water. Blood pressure signal and impedance changed were recorded using a custom-made system. The results illustrated that the pressure-volume loop, as it was expected, demonstrated a contraction phenomenon after stimulation in five out of ten subjects. The areas of those pressure-volume loops reduced as much as 70% in some subject. However, loop responses to stressors varied from subject to subject and the slope of the loop did not alter significantly. In conclusion, the proposed system is a potential way to measure and to investigate the compliance and characteristic of peripheral blood vessel.

[Standards of multimodal monitoring in obstetrical clinic]

Safety issues of anaesthesia care in obstetrics are extremely important, because they influence the possibility of reducing the complications in mothers, foetus and newborns. Monitoring of haemodynamics is a necessary part of anaesthesia care. A correct estimation of haemodynamics in pregnant with gestosis is possible only when analyzing the rates of peripheral resistance and a cardiac index. 72 pregnant patients with gestosis were examined, 48 of above had a moderate form. In latter group, a hypokinetic type of haemodynamics was revealed in 4% of patients, normokinetic type in 86% and a hyperkinetic type in 10%. In 24 patients with severe gestosis the distribution was as 82%, 18% and 0% respectively. Measuring the central haemodynamic parameters with a bio-impedance spectrometry allows to choose the hypotensive therapy in a more accurate way to ensure the control of its effectiveness, and to consider the need in early delivery in proper time when in aggravation of gestosis, providing better outcomes for women and children.

Assessment of respiratory mechanical properties with constant-phase models in healthy and COPD lungs

This study employs the concept of applying constant-phase models to input respiratory impedance data obtained with the non-invasive Forced Oscillation Technique (FOT) lung function test. Changes in respiratory mechanics from healthy and chronic obstructive pulmonary disease (COPD) diagnosed patients are observed with a four- and a five-parameter constant-phase model. Tissue damping (p<<0.01), tissue elastance (p<0.02) and tissue hysteresivity (p<<0.01) are calculated from the identified model parameters, providing significant separation between healthy and COPD groups. Limitations of the four-parameter constant-phase model are shown in relation to frequency-dependent impedance values within the range 4-48 Hz. The results clearly show that the five-parameter constant-phase model outperforms the four-parameter constant-phase model in this frequency range. The averaged error is 0.02 and 0.04 for healthy subjects in the five-parameter and four-parameter constant-phase models, respectively. The results show that the identified model values are sensitive to variations between healthy and COPD lungs.

[Preventive measures with low-intensity laser for workers exposed to physical exertion]

Studies covered 168 personal computer users, 98 jewelry female polishers, 64 assemblers of metallic ship frameworks. Various doses of laser rays in accordance with work conditions appeared effective for improving upper limbs microcirculation. The suggested method is based on effects of low-intensity laser irradiation.

Body composition determination by bioimpedance: an update

PURPOSE OF REVIEW

To review various methods for measuring body composition by bioimpedance and their limitations, as well as available impedance meters, including body fat analyzers for home use.

RECENT FINDINGS

Bioimpedance spectroscopy, which requires multifrequency impedance meters, is preferable for fluid volume measurements, especially extracellular fluid, whereas bioimpedance analysis at 50 kHz is more widely used for measuring fat-free mass. A method for using bioimpedance spectroscopy equations with 50 kHz impedance meters has been recently proposed and successfully tested. Low cost foot-to-foot impedance meters (body fat analyzers) with plantar electrodes on a body scale, that are easy and fast to use, have been compared with medical impedance meters and with dual X-ray absorptiometry measurements and found reasonably accurate, except for individuals with very low or high BMI.

SUMMARY

Body composition by bioimpedance is gaining acceptance in nutrition, hemodialysis, gerontology and sports medicine. Body fat analyzers that have been validated by comparison with dual x-ray absorptiometry could be useful to general practitioners, nutritionists and cardiologists.

Technical limitations in detection of gastroesophageal reflux in neonates

OBJECTIVE

Characterize the incidence and possible etiologies of acid reflux events detected by pH and not identified by multiple intraluminal impedance (MII) monitoring.

MATERIALS AND METHODS

Acid reflux events detected by pH but not identified by MII (pH-only) were documented in 80 preterm and 39 term infants. Reasons for failure of MII to detect these events were classified as failure to meet MII scoring criteria, presence of an air bolus, technical artifact, and no change in impedance. Events with no change in impedance were stratified to low impedance throughout the study (possible esophageal inflammation), transient decrease in pre-event impedance (presence of refluxate), occurrence <30 seconds of a preceding event, and no explanation.

RESULTS

A total of 2572 events were detected by pH, with 59% of events not identified by MII. A higher incidence of pH-only events occurred in preterm versus term infants (54 +/- 27% versus 42 +/- 23%, P = .025, respectively). Thirteen percent of pH-only events were missed due to MII scoring criteria, 12% due to technical artifact, 11% due to an air bolus, and 64% had no change in impedance. Of the 978 events with no change in impedance, 154 were associated with low impedance throughout the study, 430 with a transient decrease in pre-event impedance, and 175 were preceded by a reflux episode within 30 seconds.

CONCLUSIONS

There was a high incidence of acid reflux events detected by pH but not identified by MII. This occurred more often in the least mature infants, and we speculate that delayed esophageal fluid clearance is the major underlying mechanism.

Electrical impedance plethysmography technique in estimating pulmonary function status

An attempt has been made to study the appropriateness of electrical impedance plethysmography (EIP) in detecting pulmonary health status. A feasibility study was conducted on normal, obstructive and restrictive subjects aged between 20 and 60 years. Quantitative assessment of pulmonary function was made by way of both EIP and pulmonary function tests (PFT). Amongst the various EIP parameters, a statistically significant difference was observed for the respiratory band power, between normal (129.7) and obstructive (35.8) subjects, indicating that this EIP variable can be used to distinguish between the two pulmonary function states. A significant positive correlation was observed between a spirometry parameter, peak expiratory flow rate (PEFR), and an EIP parameter, respiratory amplitude (r = 0.372, p < 0.05), thereby indicating that EIP information by way of respiratory amplitude is comparable to that provided by PEFR. Hence, both respiratory amplitude and respiratory band power were seen to provide useful information on pulmonary health status.

Impedance of Goat Lens as a Function of Frequency at DC Voltages 0, 50, 100, 200 mV

Impedance characteristics of lens tissue has been studied using the AC impedance system (EG&G PARC, model 318) at different low voltage excitations using a Cole-Cole Plot. The extracellular resistance (Re), intracellular resistance (Ri), depressed angle (theta), total impedance (/Z/), and phase angle (phi) of the tissue were measured. The impedance locus between the real part (Z') and imaginary part (Z'') of the complex impedance of lens was examined at discrete frequencies ranging from 10 mHz to 10 Hz. A decrease in extra-cellular resistance (Re) and increase in distribution of the factor (alpha) of 56.8 KOmega, 48.1 KOmega, 32.8 KOmega, 13.4 KOmega, and 0.40, 0.43, 0.46, 0.53 were found at 0 mV, 50 mV, 100 mV, and 200 mV, respectively. The total impedance (/Z/) and phase angle (phi) were also evaluated and the observed frequency dependent for the frequency range was tested as a function of excitation voltage. An attempt has been made to explain the effect of voltage stress on lens impedance.