Bioelectrical impedance analysis predicts outcome in patients with suspected bacteremia

We expanded a previously described rule-based computerized method to recognize the sensory irritating effect of airborne chemicals. Using 2-chlorobenzylchloride (CBC) as a sensory irritant, characteristic modifications of the normal breathing pattern of exposed mice were evaluated by measuring the duration of braking (TB) after inspiration and the resulting decrease in breathing frequency. From the measurement of TB, each breath was then classified as normal (N) or sensory irritation (S). Using increasing exposure concentrations, the classification S increased from < or = 2% (equivalent to sham-exposure) to 100% within a narrow exposure concentration range. The potency of CBC was then evaluated by calculating the concentration necessary to produce 50% of the breaths classified as S, i.e., S50. This approach is easier to use than obtaining RD50 (decrease in respiratory frequency by 50%) when high exposure concentrations are difficult to achieve. Detection limits were also established for this bioassay and experiments were conducted to obtain a level of response just around these limits, in order to delineate the practicality of using this bioassay at low exposure concentrations. Using this approach, sensory irritation was the only effect induced by CBC at low exposure concentrations. However, bronchoconstriction and pulmonary irritation were superimposed on this effect at higher exposure concentrations.     

Bioelectrical impedance analysis of body composition in patients with pulmonary emphysema

In this study we utilized bioelectrical impedance analysis (BIA) to compare the body composition of 36 stable pulmonary emphysema (PE) patients with 19 healthy controls. We compared the PE patients and healthy controls in terms of fat-free mass (FFM) and body fat (BF) as percentages of ideal body weight (FFM/IBW, BF/IBW). FFM/IBW and BF/IBW were significantly lower in the PE patients than in the controls (75.0 +/- 9.8% vs. 85.2 +/- 7.3%, p < 0.001 and 11.8 +/- 6.4% vs. 16.7 +/- 7.7%, p < 0.05, respectively). We divided the PE patients into two subgroups according to FFM, then investigated the relationships between FFM and skeletal muscle strength, and between FFM and respiratory muscle strength. In patients with reduced FFM (FFM < 43.5 kg) grip strength as an index of skeletal muscle strength was significantly lower than in patients without reduced FFM (FFM > or = 43.5 kg) (25.7 +/- 7.8 kg vs. 36.2 +/- 7.2 kg, p < 0.005). As indexes of respiratory muscle strength, maximal expiratory pressure (PEmax) and maximal inspiratory pressure (PImax) were lower in the patients with reduced of FFM, but not to a statistically significant degree (49.6 +/- 20.8 cm H2O vs. 58.7 +/- 23.9 cm H2O and 40.5 +/- 19.2 cm H2O vs. 50.2 +/- 22.1 cm H2O, respectively). In the PE patients, FFM correlated closely with vital capacity (r = 0.528, p < 0.001), forced vital capacity (FVC) (r = 0.531, p < 0.001), FEV1.0 (r = 0.554, p < 0.001), FEV1.0/FVC (r = 0.467, p < 0.005), RV/TLC (r = -0.395, p < 0.05), DLco (r = 0.770, p < 0.001), and DLco/VA (r = 0.622, p < 0.001). However no correlation was observed between BF and any of the measures of lung function. The findings of our study suggest that FFM correlates with skeletal muscle strength, respiratory muscle strength and some measures of lung function in patients with PE, and that assessments of body composition are valuable to their clinical management.     

Bioelectrical impedance spectroscopy (BIS) in young children with acute and semi-acute hydration disorders: potentials and limitations

This study aimed to evaluate the feasibility and reliability of bioelectrical impedance spectroscopy in young children suffering of acute hydrational disorders. Whole body and segmental measurements were carried out in a group of 42 of children aged 4 to 147 months, using a BIS analyzer (Xitron 4000B). This phase of the study involved several hundred of BIS measurement, which showed the feasibility of using this technique in young children. Using the sweep mode and the modeling software provided for the manufacturer of the instrument, the resistance of the extracellular (RECW) and intracellular (RICW) compartment was calculated. Correlation coefficient (r) and technical error of measurement (TEM) were obtained from paired BIS measurements. RECW showed to be highly reproducible (r = 0.99), with a relatively low TEM (from 1 to 3.5%), across all segments. The reliability was markedly lower respect to RICW, which shows the potential application of BIS technique even in critically ill young child populations.     

Bioelectrical impedance techniques in medicine. Part I: Bioimpedance measurement. Second section: impedance spectrometry

Electrical impedance spectrometry is an important application field of bioimpedance measurements. After introducing the electrical properties of biological tissues, this part presents instrumental aspects and applications of electrical impedance spectrometry. The main instrumental constraints encountered in spectrometric electrical impedance measurements are reviewed, focusing on low-frequency applications. Examples of impedance cells and probes are presented and several instrumental setups operating in the frequency and time domain are described. Some examples of applications are presented, including in vitro characterization and modeling of normal tissues, in vitro and in vivo characterization of cancerous tissues, and assessment of tissue perfusion/ischemia levels.     

Migrating monopredominant arthritis in children of Assyrian ancestry

We describe an unusual form of arthritis affecting 3 Assyrian children to inspire a search for further cases to determine how unique it may be. After different patterns of onset, 3 of 4 children with arthritis from the Assyrian community in northern California had an unusual course of recurrent arthritis, predominantly in one joint at a time. There was rapid cartilage and bone destruction in involved joints. The 3 children are HLA-DR4. The 4th patient had a more typical childhood polyarticular course. Two of the first 3 patients had fever with attacks. None had rheumatoid factor, antinuclear antibody, or the HLA-B27 antigen. This unusual, severe, monopredominant but migrating arthritis appears to be particularly associated with Assyrian descent.     

Bioelectrical impedance analysis in human immunodeficiency virus-infected patients: comparison of single frequency with multifrequency, spectroscopy, and other novel approaches

Bioelectrical impedance (BIA), a prediction method for estimating body water compartments and body cell mass (BCM), is being increasingly used in studies of human immunodeficiency virus (HIV)-related wasting, but there are few validation studies of the method in this group. The aim of this study is to examine the relationship between impedance measurements and body water compartments in patients with advanced HIV disease, and to investigate whether the newer approaches of multifrequency BIA, BIA spectroscopy, logarithmic transformation using a parallel circuit model, and direct calculation from electrical theory offer any advantage over traditional single-frequency BIA. We measured total body water (TBW) by deuterium dilution and extracellular water by bromide dilution in 33 patients with advanced HIV disease. Intracellular water and BCM were calculated from these results. Impedance was measured over a range of frequencies using a multifrequency analyzer. The relationship between impedance index at various frequencies and body water compartments was assessed by correlation and linear regression. We found that impedance index at higher frequencies had a closer relationship to TBW (r = 0.86, standard error of the estimate [SEE] = 2.96 at 1000 kHz) and at lower frequencies a closer relationship to extracellular water (ECW) (r = 0.47, SEE = 3.13 at 0 kHz) than the traditional 50 kHz measurement (r = 0.84, SE = 3.11 for TBW; r = 0.44 SEE = 3.19 for ECW), but the differences were marginal and not statistically significant. None of the other novel approaches tested were significantly better than traditional single frequency measurement. The 50 kHz equation for BCM developed in this study [BCM (kg) = (0.360331 x Ht2/Z50) + (0.151123 x Wt)-2.95] may be useful to investigators using BIA for hIV-wasting studies.     

Nutritional and environmental risk factors for diarrhoeal diseases in Ecuadorian children

In the first part of this paper, the effects of single administration of nicotine on gastric motility of urethane-anesthetized rats are briefly summarized from our recently reported papers. Then, the effects of repeated administration of nicotine on the nicotine-induced changes in gastric motility and release of hypothalamic noradrenaline, in vitro, are described, with special references to up-regulation of nicotinic receptors. Nicotine 0.1 nmol administered into the dorsal motor nucleus of the vagus (DMV) elicited a dual change, a decrease followed by an increase in gastric motility. Intravenous administration of nicotine 300 nmol/kg decreased gastric motility. This decrease in gastric motility was inhibited by microinjection of hexamethonium into the DMV and was terminated by bilateral vagotomy. In animals pretreated with nicotine 200 nmol intracerebroventricularly (icv) administered once a day for 5 days, nicotine 100 nmol administered icv induced the decrease but not the increase in gastric motility. In conclusion, nicotine activates nicotinic receptors in the DMV and a resultant vagally-mediated dual change in gastric motility occurs. Furthermore, gastric inhibitory mechanisms in the DMV are susceptible to nicotine more than the excitatory mechanisms, and desensitization to nicotine occurs easily in the excitatory mechanisms.     

Characterization of mitochondrial DNA and Y-chromosome haplotypes in a Uruguayan population of African ancestry

We used a set of informative mtDNA and Y-chromosome-specific markers to determine the origin of maternal and paternal lineages in a sample of 41 Uruguayan black individuals. We found that 20 maternal lineages were African, 13 were Amerindian, and 5 were Caucasian. In three individuals we were unable to determine the ethnic origin of the mtDNA lineages. Of the 22 males analyzed we found 4 Y chromosomes of African origin, 5 of Caucasian origin, and 13 of undetermined ancestry. Our results suggest that mtDNA and Y-chromosome-specific DNA variants may be a useful tool in determining the level of mtDNA and Y chromosome ethnic introgression in a population of a given ethnic origin.     

Ethnicity and cardiovascular risk: variations in people of African ancestry and South Asian origin

Mortality from coronary heart disease (CHD), stroke and end-stage renal failure are high in South Asian migrants in the UK. This is associated with high prevalence of diabetes and hypertension. These seem to be manifestations of a metabolic syndrome with insulin resistance (hyperinsulinaemia) and central obesity (based on high waist-to-hip ratio rather than on conventional measures of body mass index). This is associated with sedentary lifestyle, high serum triglycerides and low HDL-cholesterol. Mortality from stroke and end-stage renal failure are high in black migrants to the UK (both Caribbeans and West Africans). However, CHD mortality is low in this group. This pattern of mortality is associated with high prevalence of hypertension and diabetes. This group tends to be obese (particularly women) according to conventional measures of body mass index and to have hyperinsulinaemia, low serum triglycerides and high HDL-cholesterol. Conventional risk factors such as cigarette smoking and hypercholesterolaemia are less prevalent in ethnic minority populations in the United Kingdom and unlikely to explain the differences seen between groups, although each risk factor is likely to contribute to the variation in vascular disease within each group. There is difficulty in reconciling the results of migration studies (eg, from rural to urban environments) pointing to major environmental influences on the changes in cardiovascular risk factors with the consistent pattern of disease of ethnic groups across the world and in subsequent generations, suggesting a certain degree of genetic susceptibility. Important environment-gene interplays might be underlying some of these processes. The detection and management of hypertension and diabetes are still unsatisfactory in inner city areas and show variations by ethnic origin. Strategies for the control of CHD and stroke adopted in European countries directed mostly to white populations may be inappropriate for ethnic minority populations.     

Body fatness and bioelectrical impedance in non-obese pre-menarcheal girls: comparison to anthropometry and evaluation of predictive equations

This study investigated the period of time that blood pressure (BP) should be measured at home in older patients in order to obtain steady BP values. Thirty-six men and 38 women (> or =60 years) were recruited at one family practice. At one office visit the family physician measured supine, sitting and standing BPs three times consecutively in each position. During 10 consecutive days, BP was measured at home five times daily. The supine and standing BPs were measured once in the morning and in the evening and the sitting BP once at noon. These home BP values were averaged over the first day (1-day), over the first 3 days (3-day) and all 10 days (10-day) of measurements. In both the supine (-5.1 mm Hg) and sitting (-3.8 mm Hg) positions the 10-day average systolic home BP was significantly lower than the corresponding office BP. The opposite was observed for the 10-day average standing home BP values (+7.3/+3.4 mm Hg). Comparison of the 3-day and 10-day average home BP values showed only a significantly lower 10-day than 3-day systolic BP level in the supine position (-1.1 mm Hg, 95% CI -1.9 to -0.2 mm Hg). Repeated measures ANOVA, showed a small but significant decrease over time only for the supine systolic home BP (-0.29 mm Hg per day, 95% CI -0.49 to -0.08 mm Hg per day). We conclude that in older subjects, 3 days of home measurements may suffice to obtain steady values for the sitting and standing BPs. A longer interval might be required for the supine BP.     

Bioelectrical impedance techniques in medicine. Part III: Impedance imaging. Second section: reconstruction algorithms

This section is devoted to the reconstruction algorithms published in the literature and developed for reconstructing the electrical conductivity and permittivity inside a body from measurements made on the body surface. These algorithms fall into two main categories. The first, based on linear approximations, are noniterative methods assuming that conductivity does not differ very much from a constant. Examples of noniterative methods are the Barber-Brown back-projection method and related methods, the Calderon's approach, the moment method, and one-step Newton methods. The second class of methods consists of iterative methods, which typically include output least squares for various functions. A related class includes the adaptive methods, in which the applied patterns of current are adjusted to get the best signal. A review of all these different alternatives is presented.     

Bioelectrical impedance techniques in medicine. Part I: Bioimpedance measurement. First section: general concepts

After a brief historical overview, the concept of electrical impedance is introduced as a principle of transduction calling attention to the possible mechanisms by which a physiological event may change impedance, i.e., by geometric, resistivity, and/or permittivity changes. Thereafter, since impedance measurements usually require the injection of current, its biological effects are discussed in order to establish the safety criteria. Finally, the elements found in an impedancimetric circuit and their respective nature are presented and described. The particular behavior of the biological impedance and the electrode/electrolyte interface appear immediately as strikingly important. The section ends with a bird's-eye view of the basic circuitry to measure impedance. Each subsection is closed by partial conclusions to underline the relevant concepts.     

Insonation and impedance analysis in graft surveillance

Seventy consecutive patients with infrainguinal bypass grafts entered a 1-year graft surveillance programme involving colour duplex scanning, direct graft insonation and computer-assisted impedance analysis. Graft patients with a positive duplex scan, high frequencies on graft insonation or an impedance value above 0.50 subsequently underwent arteriography. Sixteen patients were excluded before the initial surveillance visit. The 54 remaining patients with grafts (30 vein, 24 synthetic) underwent a total of 137 surveillance visits, with 21 grafts confirmed to be 'at risk'. The sensitivity of an impedance value above 0.55 in identifying these grafts was 86 per cent, rising to 95 per cent when combined with graft insonation. Duplex scanning did not identify any abnormalities in 11 grafts that were either shown by arteriography to be 'at risk' or occluded before arteriography. Impedance measurement and graft insonation are simple screening techniques with a high sensitivity (when combined), which identify 'at risk' infrainguinal grafts. Positive graft insonation or an impedance value over 0.55 will identify all 'at risk' vein grafts while minimizing the number of unnecessary arteriograms.     

Pure-tone audiometric and impedance measurements in school-aged children in Finland

While clinical reports indicate that significant relief of angina is achieved with transmyocardial laser revascularization (TMLR), the mechanisms of benefit are still a matter of considerable controversy. Studies in our laboratory, as well as in the laboratories of other investigators, have challenged the classic hypothesis that benefits are derived from blood flow through chronically patent channels. While several alternatives have been proposed, our work has focused on investigating the possibility that TMLR stimulates vascular growth in the region around the TMLR channels. We have performed studies looking at histologic markers of vascular growth (including vessel counting and cellular proliferation assays) in order to test this hypothesis, the results of which are reviewed. In brief, we find that TMLR markedly enhances myocardial vascular growth above what is seen normally in ischemic myocardium. We hypothesize that the underlying mechanism relates to liberation of growth factors by inflammatory cells, which are recruited in response to the laser induced myocardial injury. Clarification of whether this mechanism contributes to observed clinical benefits is of fundamental importance, since such understanding may suggest means of enhancing the process.     

Use of bioelectric impedance analysis (BIA) in children with alterations of body water distribution

Validation studies of bioelectric impedance analysis (BIA) were performed in children with obesity, Duchenne muscle dystrophy and juvenile rheumatoid arthritis. BIA allowed an accurate assessment of total body water in all groups (CV from 4.1 to 5.1%). However, the prediction of extracellular water by BIA was not always satisfactory (CV from 8.5 to 12.5%), being better in the groups of children with the lowest variability in body water distribution.     

Renal problems in black South African children

Black South African children have an increased prevalence of acute post-streptococcal glomerulonephritis, focal glomerulosclerosis, hepatitis B-associated membranous nephropathy, congenital syphilis, congenital nephrotic syndrome with Alport-like basement membrane changes and Takayasu's arteritis, but a paucity of reflux nephropathy, polycystic kidney disease and non-shigella-induced haemolytic uraemic syndrome. However, in recent years, the haemolytic uraemic syndrome has become more prevalent in black children; this is usually due to Shigella dysenteriae type 1, and could indicate a different emphasis in the pathogenic mechanism. Focal glomerulosclerosis is the commonest reason for renal failure requiring transplantation in black children with rapidly progressive glomerulonephritis (usually streptococcal induced) being second. Transplantation has been somewhat problematic with a scarcity of kidneys at times, many mismatches and poor compliance in the lower socio-economic groups. The association of tuberculosis with focal glomerulosclerosis and Takayasu's arteritis in black South African children is intriguing. The progression of focal glomerulosclerosis is accelerated in those patients with evidence of previous tuberculosis, and in Takayasu's arteritis the association is almost absolute as experienced locally, with the data suggesting an autoimmune reaction.     

Serum immunoglobulins in Black South African children

Serum immunoglobulin levels in Black children were estimated and the results analysed in 13 age ranges, from birth up to 15 years of age. Samples from children whose serum immunoglobulins were unlikely to be affected by their clinical condition were chosen for the analysis. The values measured were much higher when compared with conventionally accepted reference ranges in White children within the same age groups. Therefore, it is most important to interpret the results of immunoglobulin measurement within the range for the individual concerned.