Can bioimpedance spectroscopy (BIS) tell us about the form of lymphoedema?

Bioimpedance spectroscopy (BIS) has proved useful for the rapid accurate and quantification of lymphoedema. The underlying principle is that the impedance of a limb to an applied low frequency alternating electric current is inversely proportional to the quantity of extracellular fluid, including lymph. While many studies have shown a high degree of concordance between impedance and limb volume measurements, the question has often been asked: "How is this influenced by the form of lymphoedema?" Lymphoedema may present in various forms, e.g. primarily fluid, fibrotic etc. Broadly, these may be envisaged to represent a continuum from "purely" fluid through gel-like to a pseudo-membraneous tissue-like structure. BIS allows estima-tion of tissue capacitance which for biological structures is a characteristic of the cell membrane and tissue inter-faces. This study tested the hypothesis that membrane capacitance (Cm) would differentiate limbs with lym-phoedema from normal. Cm was measured (SFB3, Im-pediMed Ltd, Brisbane) for both arms of 116 women with no history of lymphoedema and 41 women with clinically affirmed unilateral post-mastectomy lymphoe-dema. Mean Cm for the controls were 4.2 +/- 1.7 nF (mean +/- SD) and 3.7 +/- 1.5 nF for the dominant and non-dominant arm respectively. Corresponding values were 4.1 +/- 3.7 nF and 6.2 +/- 7.1 nF for the unaffected and affected limbs re-spectively. While limb dominance significantly (

Red cell infusion but not saline is effective for volume expansion in preterm piglets

OnlinePubl first published 12Dec22Background: A common first-line treatment for supporting cardiovascular function in preterm infants is volume expansion using saline, but this does not improve outcomes. This study aimed to determine if volume expansion with saline increases blood volume, blood pressure and cerebral oxygenation; and if volume expansion with packed red blood cells (RBC) is more effective. We hypothesized that RBC infusion is more effective than saline for increasing blood volume and maintaining cardiovascular function and cerebral oxygenation. Methods: Five groups of preterm piglets (98/115d gestation) were infused with saline (10 or 20 mL/kg) or RBC (10 or 20 mL/kg) or no treatment. Blood volume, blood pressure, central venous pressure, heart rate, carotid flow, cerebral oxygenation, arterial pH, base excess, and lactate levels were assessed for 6 h after treatment started. Results: Both RBC groups had significant increases in blood volume, and improved measures of cardiovascular function, cerebral oxygenation and metabolic acidosis. Saline infusion did not increase blood volume or measures of cardiovascular function, cerebral oxygenation or metabolic acidosis. Conclusions: The results suggest that the deteriorating cardiovascular function in the hours after birth in preterm piglets, and possibly in premature babies, may be reversed or halted by more effective support of blood volume. Impact: Blood volume decreases after birth in preterm piglets and this decrease is associated with deteriorating cardiovascular function and cerebral oxygenation. Infusion of saline does not increase blood volume nor prevent deterioration in cardiovascular function. Infusion of packed red blood cells results in an increase in blood volume and improvements in cardiovascular function and cerebral oxygenation. Deteriorating cardiovascular function in the hours after birth in preterm piglets, and possibly in human preterm neonates, may be reversed or halted by more effective support of blood volume.Yvonne A. Eiby, Ian M. R. Wright, Michael J. Stark, Barbara E. Lingwoo

Time-frequency analysis of heart rate variability in neonatal piglets exposed to hypoxia

To determine whether the sympathetic nervous system plays any role in the inter-individual variation of cardiovascular response to hypoxia in newborns, neonatal heart rate variability (HRV) analysis was used to assess autonomic response during hypoxia in piglets. Due to the nonstationary nature of HRV signals and the inaccuracy in pre-defined neonatal HRV frequency bands using standard spectral methods, we applied time-frequency distribution analysis to assess neonatal HRV. Although sympathetic activity was initially enhanced to stimulate the cardiac compensation, it did not account for the variation of cardiovascular response since the power of low frequency component in HRV neither showed corresponding changes with the heart rate nor had any correlation with the brain injury. This may be attributed to immaturity of the neural pathway.Scopu

Detection of perinatal hypoxia using time-frequency analysis of heart rate variability signals

This paper presents a time-frequency approach to detect perinatal hypoxia by characterizing the nonstationary nature of heart rate variability (HRV) signals. Quadratic time-frequency distributions (TFDs) are used to represent the HRV signals. Six features based on the instantaneous frequency (IF) of the lower frequency components of HRV signals are selected to establish a classifier using support vector machine. The classifier is trained and tested using the signals recorded from a neonatal piglet model under a controlled hypoxic condition, which provides reliable annotations on the data. The method shows superior performance in the detection of hypoxic epochs with sensitivity (89.8%), specificity (100%) and total accuracy (94.9%) compared with that based on frequency domain features, indicating that nonstationarity should be taken into account for a more accurate assessment of the newborn status with possible hypoxia when analyzing HRV signals

Detection of perinatal hypoxia using time-frequency analysis of heart rate variability signals

This paper presents a time-frequency approach to detect perinatal hypoxia by characterizing the nonstationary nature of heart rate variability (HRV) signals. Quadratic time-frequency distributions (TFDs) are used to represent the HRV signals. Six features based on the instantaneous frequency (IF) of the lower frequency components of HRV signals are selected to establish a classifier using support vector machine. The classifier is trained and tested using the signals recorded from a neonatal piglet model under a controlled hypoxic condition, which provides reliable annotations on the data. The method shows superior performance in the detection of hypoxic epochs with sensitivity (89.8%), specificity (100%) and total accuracy (94.9%) compared with that based on frequency domain features, indicating that nonstationarity should be taken into account for a more accurate assessment of the newborn status with possible hypoxia when analyzing HRV signals.Scopu