Simultaneous electrical online estimation of changes in blood hematocrit and temperature in cardiopulmonary bypass

AbstractTwo equations have been developed from multi-frequency measurements of blood impedanceZb for a simultaneous electrical online estimation of changes in blood hematocritΔH [%] and temperaturesΔT [K] in cardiopulmonary bypass (CPB).Zb of fixed blood volumes at varyingH andT were measured by an impedance analyzer and changes in blood conductivityσb and relative permittivityεb computed. Correlation analysis were based on changes inσb withH orT atf = 1 MHz whileH andT equations were developed by correlating changes inεb withH andT at dual frequencies off = 1 MHz andf = 10 MHz which best capture blood plasmaZp and red blood cell cytoplasmZcyt impedances respectively. Results show high correlations betweenσb andH (R2 = 0.987) orσb andT (R2 = 0.9959) indicating dependence of the electrical parameters of blood on itsH andT. Based on computedεb, changes in blood hematocritΔH and temperatureΔT at a given timet are estimated asΔH(t)  = 1.7298Δεb (f = 1 MHz) – 1.0669Δεb (f = 10 MHz) andΔT(t)  = -2.186Δεb (f = 1 MHz) + 2.13Δεb (f = 10 MHz). When applied to a CPB during a canine mitral valve plasty,ΔH andΔT had correlations ofR2 = 0.9992 andR2 = 0.966 againstH andT respectively as measured by conventional devices.
Source: Journal of Artificial Organs - Category: Transplant Surgery Source Type: research