Liquid Blood Phantoms to Validate NIRS Oximeters: Yeast Versus Nitrogen for Deoxygenation

Liquid blood phantoms are a tool to calibrate, test and compare near-infrared spectroscopy (NIRS) oximeters. They comprise a mixture of saline, blood and Intralipid, which is subsequently oxygenated and deoxygenated to assess the entire range of tissue oxygen saturation (StO) from 0% to 100%. The aim was to investigate two different deoxygenation methods: yeast versus nitrogen (N) bubbling. The phantom was oxygenated with pure O in both experiments, but deoxygenated by bubbling N in the first and by addition of yeast and glucose in the second experiment. A frequency domain NIRS instrument (OxiplexTS) was used as reference and to monitor changes in the reduced scattering coefficient (μ') of the phantom. Both deoxygenation methods yielded comparable StO values. The deoxygenation was slower by a factor 2.8 and μ' decreased faster when bubbling N. The constant bubbling of N mechanically stresses the Intralipid emulsion and causes a decrease in μ', probably due to aggregation of lipid droplets. Deoxygenation by N requires a more complex, air tight phantom. The gas flow cools the liquid and temperature needs to be monitored more closely. Consequently, we recommend using yeast for phantom deoxygenation

Complete classification of purely magnetic, non-rotating and non-accelerating perfect fluids

Recently the class of purely magnetic non-rotating dust spacetimes has been shown to be empty (Wylleman, Class. Quant. Grav. 23, 2727). It turns out that purely magnetic rotating dust models are subject to severe integrability conditions as well. One of the consequences of the present paper is that also rotating dust cannot be purely magnetic when it is of Petrov type D or when it has a vanishing spatial gradient of the energy density. For purely magnetic and non-rotating perfect fluids on the other hand, which have been fully classified earlier for Petrov type D (Lozanovski, Class. Quant. Grav. 19, 6377), the fluid is shown to be non-accelerating if and only if the spatial density gradient vanishes. Under these conditions, a new and algebraically general solution is found, which is unique up to a constant rescaling, which is spatially homogeneous of Bianchi type $VI_0$, has degenerate shear and is of Petrov type I($M^\infty)$ in the extended Arianrhod-McIntosh classification. The metric and the equation of state are explicitly constructed and properties of the model are briefly discussed. We finally situate it within the class of normal geodesic flows with degenerate shear tensor.Comment: 12 pages; introduction partly rewritten, notation made more clear, table of results adde

Diagnostic and predictive value of Doppler ultrasound for evaluation of the brain circulation in preterm infants: a systematic review

INTRODUCTION: Very and extremely preterm infants frequently have brain injury-related long-term neurodevelopmental problems. Altered perfusion, for example, seen in the context of a hemodynamically significant patent ductus arteriosus (PDA), has been linked to injury of the immature brain. However, a direct relation with outcome has not been reviewed systematically. METHODS: A systematic review was conducted to provide an overview of the value of different cerebral arterial blood flow parameters assessed by Doppler ultrasound, in relation to brain injury, to predict long-term neurodevelopmental outcome in preterm infants. RESULTS: In total, 23 studies were included. Because of heterogeneity of studies, a meta-analysis of results was not possible. All included studies on resistance index (RI) showed significantly higher values in subjects with a hemodynamically significant PDA. However, absolute differences in RI values were small. Studies using Doppler parameters to predict brain injury and long-term neurodevelopmental outcome were inconsistent. DISCUSSION: There is no clear evidence to support the routine determination of RI or other Doppler parameters in the cerebral arteries to predict brain injury and long-term neurodevelopmental outcome in the preterm infant. However, there is evidence that elevated RI can point to the presence of a hemodynamically significant PDA

Classical relativistic statistical mechanics: The case of a hot dilute plasma

Starting from predictive relativistic mechanics we develop a classical relativistic statistical mechanics. For a system of N particles, the basic distribution function depends, in addition to the 6N coordinates and velocities, on N times, instead of a single one as in the usual statistical mechanics. This generalized distribution function obeys N (instead of 1) continuity equations, which give rise to N Liouville equations in the case of a dilute plasma (i.e., to lowest, nonzero order in the charges). Hence, the Bogoliubov-Born-Green-Kirkwood-Yvon hierarchy for the reduced generalized distribution functions is derived. A relativistic Vlasov equation is obtained in this way. Thermal equilibrium is then considered for a dilute plasma. The calculation is explicitly worked out for a weakly relativistic plasma, up to order 1/c2, and known results are recovered

Sexuality in patients with asthma and COPD

SummarySexual quality of life was examined in 55 outpatients with chronic obstructive pulmonary disease (COPD) and asthma, using disease-specific questionnaires. Compared to an age- and sex-matched norm group, male patients with COPD reported a significantly lower sexual quality of life on all dimensions of the questionnaire. Female patients with COPD reported a lower frequency of sexual intimacy and lower sexual quality of life overall. Patients with asthma reported sexual quality-of-life scores that were somewhat better than COPD patients but worse than the healthy control group. Patients reported that they did not discuss sexual quality-of-life issues with their physician. Sexuality needs to be discussed by the health care provider in the consultation in order to improve quality of life of patients with chronic respiratory disorders

Predictive Role of F2-Isoprostanes as Biomarkers for Brain Damage after Neonatal Surgery.

OBJECTIVE: Neonates have a high risk of oxidative stress during anesthetic procedures. The predictive role of oxidative stress biomarkers on the occurrence of brain injury in the perioperative period has not been reported before. METHODS: A prospective cohort study of patients requiring major surgery in the neonatal period was conducted. Biomarker levels of nonprotein-bound iron (NPBI) in plasma and F2-isoprostane in plasma and urine before and after surgical intervention were determined. Brain injury was assessed using postoperative MRI. RESULTS: In total, 61 neonates were included, median gestational age at 39 weeks (range 31-42) and weight at 3000 grams (1400-4400). Mild to moderate brain lesions were found in 66%. Logistic regression analysis showed a significant difference between plasma NPBI in patients with nonparenchymal injury versus no brain injury: 1.34 umol/L was identified as correlation threshold for nonparenchymal injury (sensitivity 67%, specificity 91%). In the multivariable analysis, correcting for GA, no other significant relation was found with the oxidative stress biomarkers and risk factors. CONCLUSION: Oxidative stress seems to occur during anaesthesia in this cohort of neonates. Plasma nonprotein-bound iron showed to be associated with nonparenchymal injury after surgery, with values of 1.34 umol/L or higher. Risk factors should be elucidated in a more homogeneous patient group