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Reference values of the bioelectrical impedance vector in neonates in the first week after birth
Antonio Piccoli1, Vassilios Fanos, Licia Peruzzi
1Department of Medical and Surgical Sciences, University of Padova, Padova, Italy. apiccoli@unipd.it
Insights
This study establishes reference intervals for whole-body impedance vectors in healthy neonates, aiding in the assessment of infant body composition. These findings provide crucial data for understanding neonatal physiological development.
Area of Science:
- Physiology
- Biophysics
- Neonatal Medicine
Background:
- Whole-body impedance vector analysis is a valuable tool for assessing body composition.
- Establishing reference intervals is crucial for interpreting impedance data in specific populations.
- Neonatal body composition undergoes rapid changes in the first postnatal week.
Purpose of the Study:
- To determine reference, bivariate, and tolerance intervals for the whole-body impedance vector in healthy white neonates.
- To provide a basis for evaluating body composition in neonates using impedance vector analysis.
- To compare neonatal impedance vector data with those of children and adults.
Main Methods:
- An observational, cross-sectional study was conducted with 163 healthy white neonates (1-7 days old).
- Standard tetrapolar analysis at 50-kHz frequency was used to measure the impedance vector.
- Bivariate vector analysis employed the resistance-reactance (RXc) graph method, with data standardized by height.
Main Results:
- Age-specific 95% confidence intervals of mean vectors and 95%, 75%, and 50% tolerance intervals for individual measurements were established.
- Neonatal impedance vector distribution showed a progressive shortening from birth towards adult positions.
- Comparison with children and adults revealed distinct developmental trajectories in impedance vectors.
Conclusions:
- Reference bivariate tolerance intervals for the impedance vector in the first postnatal week were established for healthy white neonates.
- These established intervals facilitate the testing of impedance vectors in infants with altered body composition.
- Free software is available for utilizing these established reference intervals.
Objective:
To determine the reference, bivariate, tolerance intervals of the whole-body impedance vector for healthy white neonates, we performed an observational, cross-sectional study in two university hospitals.
Methods:
The impedance vector (standard, tetrapolar analysis at 50-kHz frequency) was measured in 163 consecutive subjects (87 boys and 76 girls) with postnatal ages of 1 to 7 d. Bivariate vector analysis was conducted with the resistance-reactance (RXc) graph method.
Results:
The age-specific 95% confidence intervals of mean vectors and the 95%, 75%, and 50% tolerance intervals for individual vector measurements were plotted using R and Xc components standardized by the subject's crown-to-heel length (height). Mean vectors from the groups (1, 2, and 3 to 7 d) with overlapping 95% confidence ellipses were considered representative of only one age class of 1 to 7 d. The impedance vector distribution of neonates also was compared with healthy white children (1014 boys and 1030 girls, age 2-15 y) and adult subjects (354 men and 372 women, age 15-85 y) from the same geographic area. There was a definite, progressive, vector shortening from birth, through ages 2 to 15 y, toward the adults' vector position.
Conclusions:
We established the reference, bivariate, 95%, 75%, and 50% tolerance intervals of the impedance vector in the first postnatal week for healthy white neonates, with which the vectors from infants with altered body composition can be tested (free software is available from apiccoli@ unipd.it).