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We report the design of a tissue oxygen and temperature monitor. The non-inv asive, fibre based device monitors tissue haemoglobin (Hb) and oxygen saturation (SO 2 ) and is based on white-light reflectance spectroscopy.Visible light with wavelengths in the 500 – 650nm range is utilized . The spectroscopic algorithm takes into account the tissue scattering and melanin absorption for the calculation of tissue haemoglobin concentration and oxygen saturation. The monitor can probe superfi cial layers of tissue with a high spatial resolution (mm 3 ) and a high temporal resolution (40 Hz). It provides an accurate measurement with the accuracy of SO 2 at 2 % and high reliability with less than 2 % variation of continuous SO 2 measurement over 12 hours. It can also form a modular system when used in conjunction with a laser Doppler monitor, enabling simultaneous measure ments of Hb, SO 2 and blood flow. W e found experimentally that the influence of the source-detector separation on the haemoglobin parameters is small. his finding is discussed by Monte Carlo Tsimulations for the depth sensitivity profile. T he influence of probe pressure and the skin pigmentation on the measurement parameters are assessed before in vivo experiment al data is presented . T he co mbination with laser D oppler flowmetry demonstrates t he importance of a measurement of both the haemoglobin and the blood flow parameters for a full description of blood tissue perfusion. This is discussed in experimental data on human skin during cuff occlusion and after hyperemisation by a pharmacological cream. Strongcorrelation is observed between tissue oxygen (Hb and SO

We demonstrate the simultaneous mapping of haemoglobin oxygenation and blood flow changes of human skin and the exposed cortex in rats by broad-band reflectometry and laser speckle contrast analysis (LASCA). A hard- and software set-up is realized with a high temporal resolution achieved by techniques of multi- and manycore computing. Spatial and temporal resolved changes of haemoglobin oxygenation and blood flow in rats are observed in response to middle cerebral artery occlusion and cortical spreading depression.

We use near infrared spectroscopy (NIRS) for the non-invasive assessment of calf oxygenation during a new walking protocol in healthy subjects of different fitness levels. The protocol increases the exercise power by an increase of the skew rather than speed, and the incremental power steps are intermitted by a 30 s rest which serves for blood sampling. The NIRS measurement parameter of tissue oxygenation are discussed, and a high correlation of the oxygen saturation (tissue oxygenation index) difference between exercise and rest period with exercise power is observed. This difference parameter can be interpreted as strongly linked to blood flow rather than oxygenation. This finding is supported by comparison with spirometry data. The effect of training is discussed. The exercise protocol is suited for testing unfit, or older subjects and the data discussed here servers as a test for a larger trial with heart clinic patients.

We used spatially resolved near-infrared spectroscopy (SRS-NIRS) to assess calf and thigh muscle oxygenation during running on a motor-driven treadmill. Two protocols were used: An incremental speed protocol (velocity = 6 – 12 km/h, Δv = 2 km/h) was performed in 3 minute stages, while a pacing paradigm modulated step frequency alternatively (2.3 Hz [SLow]; 3.3 Hz [SHigh]) during a constant velocity for 2 minutes each. A SRS-NIRS broadband system (600 – 1000 nm) was used to measure total haemoglobin concentration and oxygen saturation (SO2). An accelerometer was placed on the hip joints to measure limb acceleration through the experiment. The data showed that the calf (SO2 58 to 42%) desaturated to a significantly lower level than the thigh (61 to 54%). During the pacing protocol, SO2 was significantly different between the SLow vs. SHigh trials. Additionally, physiological data as measured by spirometry were different between the SLow vs. SHigh pacing trials (VO2 (2563± 586 vs. 2503 ± 605 mL/min). Significant differences in VO2 at the same workload (speed) indicate alterations in mechanical efficiency. These data suggest that SRS broadband NIRS can be used to discern small changes in muscle oxygenation, making this device useful for metabolic exercise studies in addition to spirometry and movement monitoring by accelerometers.

Neurological impairments following cardio-pulmonary bypass (CPB) during open heart surgery can result from microembolism and ischaemia. Here we present results from monitoring cerebral hemodynamics during CPB with near infrared spatially resolved spectroscopy. In particular, the study has the objective (a) to monitor oxy- and deoxyhemoglobin concentrations (oxy-Hb, deoxy-Hb) and their changes during CPB surgery and (b) to develop and test algorithms for the calculation of these parameters from broad band spectroscopy. For this purpose a detection system was developed based on a lens imaging spectrograph designed to optimise sensitivity of recorded reflectance spectra for wavelengths between 600 and 1000 nm. Two independent detector channels for both cerebral hemispheres each with three source-detector distances are used. It is demonstrated that the system does record cerebral oxygenation parameters during CPB in infants with a significant decrease in oxygen saturation SO2 during cardiac arrest. The methodological focus is on an error estimation of the haemoglobin concentrations and separation of cerebral from skin signals. The depth sensitivity profile of the set-up is estimated with a layered structure model of tissue and Monte Carlo methods for the description of the photon propagation.

In a paradigm of transcallosal inhibition elicited by transcranial magnetic stimulation in humans we observe a decrease in oxy- and an increase in deoxy-hemoglobin in the motor cortex.

The current paper assesses the reliability of spatially resolved spectroscopy (SRS) for the assessment of oxygen saturation of muscle with a broad band, multi-channel system and validates it with time-resolved spectroscopy.