Generalizability of extracellular-to-intracellular fluid ratio using bio-impedance spectroscopy

Changes in R0/R∞ ratio and membrane capacitance are associated with milk removal from the breast

Perceived low milk supply is a common reason for introducing supplementary feeds, which in turn serves to further diminish the milk supply. Current methods of measuring milk production and milk transfer from the breast to the infant are inaccessible to the mothers. There is a need for an inexpensive, portable device to enable mothers to measure milk transfer to either confirm their milk production is adequate or identify breastfeeding issues early. The aim of this study was to examine changes in bioimpedance spectroscopy associated with milk removal from the human lactating breast using an electric breast pump. Thirty lactating women participated in 2 research sessions performed in random order over 2 weeks. Milk flow rate and volume were measured during pumping. All mothers completed 24-hour milk profiles. Breasts were monitored using bioimpedance spectroscopy. Analysis was performed using linear mixed effects models to investigate the relationship between both proportional change in membrane capacitance (C_m) and R0/R∞ with milk removal. There was an inverse relationship between R0/R∞ and milk removed (p<0.001). A positive relationship was also observed between C_m and both volume of milk removed (P<0.001) and percentage of available milk removed (p<0.001). This study has shown that changes in bioimpedance are related to the volume of milk removed from the breast during pumping. This modality may hold promise for the measurement of the effectiveness of the breastfeeding infant in removing milk from the breast.

Adding "hemodynamic and fluid leads" to the ECG. Part I: the electrical estimation of BNP, chronic heart failure (CHF) and extracellular fluid (ECF) accumulation

OBJECTIVES

In primary care the diagnosis of CHF and ECF accumulation is no triviality. We aimed to predict plasma BNP, CHF and ECF accumulation with segmental impedance spectroscopy while using and extending the electrodes of the conventional electrocardiography.

METHODS

Three combined multiple electrodes were added to the 15 lead ECG for segmental impedance spectroscopy and for measuring the maximal rate of segmental fluid volume change with heart action at the thorax and the legs. The obtained signals were analyzed by partial correlation analyses in comparison with plasma BNP, CHF classes, ejection fraction by echocardiography and cardiac index by double gas re-breathing. 119 subjects (34 healthy volunteers, 50 patients with CHF, NYHA classes II to IV and 35 patients without CHF) were investigated.

RESULTS

The maximal rate of volume change with heart action at the thorax and at the legs, as well as the ECF/ICF ratio at the legs contribute equally and independently to the prediction of BNP and heart failure in an unknown test sample of 49 patients (multiple r=0.88, p<0.001). The ROC-curve for the predicted plasma BNP>400 pg/ml gave an AUC=0.93. The absence or the presence of heart failure could be predicted correctly by a binomial logistic regression in 92.9 and 87.5% of cases, respectively.

CONCLUSION

The methodology, which is based on inverse coupling of BNP release and of maximal blood acceleration and on sensitive detection of ECF overload, could enable the diagnosis of CHF with useful sensitivity and specificity while writing a routine-ECG.

Comparison of two bioimpedance spectroscopy techniques in the assessment of body fluid volumes

The present study aimed to compare the estimates of body liquid volumes performed by two bioimpedance spectrometry techniques. One based on a step response technique (BIS-PEB) and second one based on multifrequency Xitron Hydra 4200 equipment (Xitron Technologies, San Diego, CA, USA). The convenience sample was initially composed of 422 students from a military parachuting course of the Brazilian Army. From such sample 42 male students were randomly selected to be evaluated during three weeks. The anthropometrical characteristics of the sample can be summarized as: 25.18 +/- 4.10 years old; weight equals of 76.77 +/- 7.84 kg; height equals to 174.96 +/- 5.67 cm; body mass index (BMI) equal to 25.05 +/- 2.11 kg m(-2). Bland-Altman graphics were used to compare the two methods in what concerns to estimate of extracellular fluid (ECF), intracellular fluid (ICF), and total body water (TBW). One can observe that the estimates of the two techniques present a good correlation, especially in the case of ECF (r = 0.975). The present study indicates that BIS-PEB technique associated with De Lorenzo equation can supply noninvasive estimates of body fluid volumes comparable to Xitron Hydra 4200 equipment.

Effects of ventilation on reproducibility of bioimpedance spectroscopy fluid ratio measures

The aim of this study was to determine the score reproducibility of the observed extracellular-to-intracellular fluid (ECF/ICF) scores using generalizability theory across three ventilation conditions of the trunk and forearm segments. The test instrument employed was a Xitron Hydra ECF/ICF bioimpedance analyzer system Model 4200. Volunteer subjects were healthy North American males (n = 50) and females (n = 50), 18-71 years. Each segment was tested on a one-trial test, for each of the three ventilation conditions. The single trial was six continuous time measures, taken 5 s apart during a 30 s time period. The three ventilation conditions were the following: normal ventilation, regimented breathing and no ventilation. A two-facet, person-by-time, fully crossed design was used; all facets were treated as random. The ECF/ICF data for each segment were independently analyzed for each ventilation condition and each gender group. The findings were as follows. (1) The reproducibility of scores improved by using the forearm segment compared to the trunk segment, (2) breath holding improves the reproducibility of test scores compared to normal breathing on men's trunk scores, (3) breath holding was not superior to normal breathing on women's trunk scores.