A Hybrid Multi-Distance Phase and Broadband Spatially Resolved Spectrometer and Algorithm for Resolving Absolute Concentrations of Chromophores in the Near-Infrared Light Spectrum

For resolving absolute concentration of tissue chromophores in the human adult brain with near-infrared spectroscopy it is necessary to calculate the light scattering and absorption, at multiple wavelengths with some depth resolution. To achieve this we propose an instrumentation configuration that combines multi-distance frequency and broadband spectrometers to quantify chromophores in turbid media by using a hybrid spatially resolved algorithm. Preliminary results in solid phantoms as well as liquid dynamic homogeneous and inhomogeneous phantoms and in-vivo muscle measurements showed encouraging results

Effects of Endurance Exercise Training and Crataegus Extract WS® 1442 in Patients with Heart Failure with Preserved Ejection Fraction - A Randomized Controlled Trial

Impaired exercise capacity is the core symptom of heart failure with preserved ejection fraction (HFpEF). We assessed effects of exercise training and Crataegus extract WS 1442 in HFpEF and aimed to identify mechanisms of action in an exploratory trial (German Clinical Trials Register DRKS00000259). 140 sedentary HFpEF NYHA II patients on standard treatment received eight weeks of aerobic endurance training and half were randomized to WS 1442 900 mg/day. Symptoms, 2 km walking time (T2km), parameters of exercise tolerance, cardiac and vascular function, muscular efficiency and skeletal muscular haemoglobin oxygen saturation (SO2) measured during a treadmill protocol were captured at baseline and after eight weeks. Adverse events were recorded during the trial. Mechanisms of action were explored by correlation and path analyses of changes. Symptoms and exercise capacity improved with training, but correlations between improvements were low and path models were rejected. SO2 increased, decreased or undulated with increasing exercise intensity in individual patients and was not altered by training. WS 1442 improved T2km (-12.7% vs. -8.4%, p = 0.019), tended to improve symptoms and to pronounce SO2-decrease with increasing exercise, an indicator of oxygen utilisation. Endurance training and WS 1442 were safe and well tolerated in combination with standard drug treatment

Simultaneous imaging of cortical blood flow and haemoglobin concentration with LASCA and RGB reflectometry

© 2013 Springer Science+Business Media New York

Noninvasive cerebral blood flow monitoring by a dye bolus method: Separation of extra- and intracerebral absorption changes by frequency-domain spectroscopy

Tracking a bolus of contrast agent traveling through the cerebral vasculature provides a measure of the blood supply and the blood flow velocity in the respective cerebral tissue. This principle has been the basis for the first approaches in functional MR imaging and is of great value when investigating stroke and other vascularly compromised patients. While the bolus measurement is a standard procedure in clinical MR imaging, optical bolus tracking has not yet become a reliable protocol. Here optical absorption changes induced by bolus signals of the dye indocyanine- green are studied by near infrared spectroscopy on volunteers. The aim is to assess the latency and shape of the absorption change

Exposure to a combination of heat and hyperoxia during cycling at submaximal intensity does not alter thermoregulatory responses

In this study, we tested the hypothesis that breathing hyperoxic air (FinO2 = 0.40) while exercising in a hot environment exerts negative effects on the total tissue level of haemoglobin concentration (tHb); core (T-core) and skin (T-skin) temperatures; muscle activity; heart rate; blood concentration of lactate; pH; partial pressure of oxygen (PaO2) and carbon dioxide; arterial oxygen saturation (SaO2); and perceptual responses. Ten well-trained male athletes cycled at submaximal intensity at 21 degrees C or 33 degrees C in randomized order: first for 20 min while breathing normal air (FinO2 = 0.21) and then 10 min with FinO2 = 0.40 (HOX). At both temperatures, SaO2 and PaO2, but not tHb, were increased by HOX. Tskin and perception of exertion and thermal discomfort were higher at 33 degrees C than 21 degrees C (p < 0.01), but independent of FinO2. Tcore and muscle activity were the same under all conditions (p > 0.07). Blood lactate and heart rate were higher at 33 degrees C than 21 degrees C. In conclusion, during 30 min of submaximal cycling at 21 degrees C or 33 degrees C, T-core, T-skin and T-body, tHb, muscle activity and ratings of perceived exertion and thermal discomfort were the same under normoxic and hyperoxic conditions. Accordingly, breathing hyperoxic air (FinO2 = 0.40) did not affect thermoregulation under these conditions

Changes in cytochrome-oxidase oxidation in the occipital cortex during visual stimulation: Improvement in sensitivity by the determination of the wavelength dependence of the differential pathlength

In this study we assess changes in the hemoglobin oxygenation (oxy-Hb, deoxy-Hb) and the Cytochrome-C-Oxidase redox state (Cyt-ox) in the occipital cortex during visual stimulation by near infrared spectroscopy. For the calculation of changes in oxy-Hb, deoxy-Hb and Cyt-ox from attenuation data via a modified Beer-Lambert equation, the wavelength dependence of the differential pathlength factor (DPF), i.e. the ratio of the mean optical pathlength and the physical light-source-detector separation, has to be taken into account. The wavelength dependence of the DPF determines the crosstalk between the different concentrations and is therefore essential for a high sensitivity. Here a simple method is suggested to estimate the wavelength dependence of the DPF((lambda) ) from pulse induced attenuation changes measured on the head of adult humans. The essence is that the DPF is the ratio of the attenuation changes over absorption coefficient changes and the spectral form of the pulse correlated absorption coefficient change is proportional to the extinction coefficient of blood. Indicators for the validity of the DPF((lambda) ) derived for wavelengths between 700 and 970 nm are the stability of the calculated oxy-Hb, deoxy-Hb and Cyt-ox signals with variations of the wavelength range included for their calculation and its overall agreement with the data available from the literature. The DPF derived from pulse measurements was used for the analysis of attenuation data from cortical stimulations. We show that Cyt-ox in the occipital cortex of human subjects is transiently oxidized during visual stimulation. © (1998) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only

Neuronal activation induced changes in microcirculatory haemoglobin oxygenation: To dip or not to dip

A tight temporal and spatial relationship exists between neuronal activity, metabolism, and blood flow in the brain, and different temporal and spatial kinetics of oxygen consumption and blood flow lead to complex changes in regional cerebral haemoglobin oxygenation. Until now, it remains unclear whether neuronal activation leads to an early deoxygenation termed ‘initial dip’ preceding the rCBF response accompanied by hyperoxygenation. Although several studies have reported the ‘initial dip’, other studies did not confirm these findings, regardless of the species used. In an extensive series of experiments in anesthetized rats, we did not robustly find the dip using various modes of cortical O2-measurements. Our findings for the first time demonstrate that the appearance of an initial dip and its amplitude may be correlated to the kinetics of the rCBF response. In addition, we show that the mode of analysis of spectroscopic data critically affects results. In our experiments, the finding of an initial dip was sensitive to the mode of spectroscopic analysis. Advanced models of spectroscopic analysis, including differential pathlength correction, should become standard in optical imaging spectroscopy studies. We conclude that in the rodent the initial dip is not a robust phenomenon, the occurrence of which may depend on the level of baseline CBF and thus mean transit time