We found correlation between reduced scattering coefficient and total hemoglobin concentration measured on muscles by the frequency-domain spectroscopy during venous occlusion protocol. This can be a useful parameter, which can be employed in clinical studies.

Using near-infrared-spectroscopy a slow signal due to hemodynamic changes following brain activity is well characterized, while a fast signal is not enough investigated. With our frequency-domain-spectrometer and two different sensors we detected both signals.

We obtained maps of cerebral hemoglobin concentration changes by near-infrared spectroscopy during functional stimulation and physiological activity at rest. The correlation and phase shift between locations were characterized by phase portraits and the phase synchronization index.

We applied Near-Infrared Spectroscopy for the investigation of cerebral oxygenation during obstructive sleep apnea. We found a relatively large decrease in brain oxygenation during apnea and the peak of deoxygenation occurs after resumption of breathing.

We applied near-infrared spectroscopy (NIRS) to assess cerebral tissue oxygenation and hemodynamics in obstructive sleep apnea (OSA) sufferers and control volunteers. We designed NIRS sensors and applied measurement schemes that included certain polysomnography parameters, such as arterial hemoglobin oxygen saturation (SaO2), heart rate (HR), and respiratory signal (RS), together with NIRS parameters, such as oxy- ([O2Hb]), deoxy- ([HHb]), total hemoglobin ([tHb]) concentrations, and tissue hemoglobin oxygen saturation (SO2). Twenty-one volunteers (8 females, 13 males, age 22-74 years) participated in the study. Eight were OSA sufferers, while 13 constituted the control group. Measurements were conducted during breath holding exercises and 30-45 minute daytime naps. In comparing OSA subjects with controls during breath holding, a smaller increase or even a decrease in SO2, [O2Hb], and [tHb] and a simultaneous larger increase in [HHb], confirmed insufficiency of the circulatory compensatory mechanism that prevents brain tissue hypoxia. Changes in cerebral oxygenation and hemodynamics due to hypoxia during breath holding showed statistically significant differences (p<0.05) between control and OSA subjects and between non-snorers and OSA subjects (p<0.03 for Δ[O2Hb], Δ[HHb], Δ[tHb], and ΔSO2). NIRS provides the clinician with important, direct insight on the cerebral tissue oxygenation and hemodynamics related to the chronic intermittent hypoxia in OSA for potential identification of individuals at risk for cerebrovascular morbidity. © 2003 WebSciences.

Fast changes, in the range of milliseconds, in the optical properties of cerebral tissue are associated with brain activity and can be detected using non-invasive near-infrared spectroscopy (NIRS). These changes are assumed to be caused by changes in the light scattering properties of the neuronal tissue. The aim of this study was to develop highly sensitive data analysis algorithms to detect this fast signal, which is small compared with other physiological signals. A frequency-domain tissue oximeter, whose laser diodes were intensity modulated at 110 MHz, was used. The amplitude, mean intensity and phase of the modulated optical signal were measured at a sample rate of 96 Hz. The probe, consisting of four crossed source detector pairs was placed above the motor cortex, contralateral to the hand performing a tapping exercise consisting of alternating rest and tapping periods of 20 s each. An adaptive filter was used to remove the arterial pulsatility from the optical signals. Independent component analysis allowed further separation of a signal component containing the fast signal. In nine out of 14 subjects, a significant fast neuronal signal related to the finger tapping was found in the intensity signals. In the phase signals, indications of the fast signal were found in only two subjects.