Thoracic versus whole body bioimpedance measurements: the relation to hydration status and hypertension in peritoneal dialysis patients

摘要

The whole body bioimpedance technique is a highly promising non-invasive, reproducible, fast and inexpensive bed-side method for monitoring hydration status. Using segmental bioimpedance measurements, it is possible to obtain information about the fluid change in each body segment ( Song, Lee, Kim and Kim 1999 Perit. Dial. Int. 19 386 - 90). In this pilot study we have measured 25 male patients ( 30 - 65 yr, BMI 20 - 32 kg m(-2)) undergoing continuous ambulatory peritoneal dialysis ( CAPD). Tetrapolar impedance measurements were obtained using the right-side technique ( whole body), and a segmental impedance method focused in the thorax region. Blood pressure ( BP) measurements were taken manually with a sphygmomanometer. Patients were classified as either stable ( group 0) or unstable ( group 1) using clinical parameters of overall cardiovascular risk. The Mahalanobis distance ( dM(2)) was calculated for the mean blood pressure ( BPmean), and the impedance parameter R normalized by body height H for the right-side ( R-RS/H) and the thorax segment ( R-TH/H). Differences between groups were significant ( p < 0.0001) for R-TH/H and for BPmean, and less significant ( p = 0.016) for R-RS/H. Group 1 patients showed a small dM(2) as compared with a reference patient ( a critical patient with acute lung edema) with high BPmean and low values of R-TH/H and R-RS/H. Moreover, Group 0 patients showed a larger dM(2) with respect to the reference patient, with lower BPmean and higher values of R-TH/H and R-RS/H. All patients classified as unstable by clinical assessment were correctly classified using R-TH/H in conjunction with BPmean using dM(2). Segmental-monofrequency non-invasive bioimpedance of the thoracic region could provide a simple, objective non-invasive method of support for facilitating the clinical assessment of CAPD patients.