Frontal cortical oxygenation changes during gravity-induced loss of consciousness in humans: a near-infrared spatially resolved spectroscopic study

2007 ◽  
Vol 103 (4) ◽  
pp. 1326-1331 ◽  
Author(s):  
Koichi Kurihara ◽  
Azusa Kikukawa ◽  
Asao Kobayashi ◽  
Toshio Nakadate
Keyword(s):  
High Performance ◽  
Near Infrared ◽  
Cerebral Oxygenation ◽  
Oxygenation Index ◽  
Loss Of Consciousness ◽  
Spatially Resolved ◽  
Hemoglobin Saturation ◽  
Significant Difference ◽  
Concentration Changes ◽  
Spatially Resolved Spectroscopy

Gravity (G)-induced loss of consciousness (G-LOC), which is presumably caused by a reduction of cerebral blood flow resulting in a decreased oxygen supply to the brain, is a major threat to pilots of high-performance fighter aircraft. The application of cerebral near-infrared spectroscopy (NIRS) to monitor gravity-induced cerebral oxygenation debt has generated concern over potential sources of extracranial contamination. The recently developed NIR spatially resolved spectroscopy (SRS-NIRS) has been confirmed to provide frontal cortical tissue hemoglobin saturation [tissue oxygenation index (TOI)]. In this study, we monitored the TOI and the standard NIRS measured chromophore concentration changes of oxygenated hemoglobin and deoxygenated hemoglobin in 141 healthy male pilots during various levels of +Gz (head-to-foot inertial forces) exposure to identify the differences between subjects who lose consciousness and those who do not during high +Gz exposure. Subjects were exposed to seven centrifuge profiles, with +Gz levels from 4 to 8 Gz and an onset rate from 0.1 to 6.0 Gz/s. The SRS-NIRS revealed an ∼15% decrease in the TOI in G-LOC. The present study also demonstrated the TOI to be a useful variable to evaluate the effect of the anti-G protection system. However, there was no significant difference found between conditions with and without G-LOC in subjects with terminated G exposure. Further studies that elucidate the mechanism(s) behind the wide variety of individual differences may be needed for a method of G-LOC prediction to be effectively realized.

Cerebral desaturation during exercise reversed by O2 supplementation

1999 ◽  
Vol 277 (3) ◽  
pp. H1045-H1052 ◽  
Author(s):  
H. B. Nielsen ◽  
R. Boushel ◽  
P. Madsen ◽  
N. H. Secher
Keyword(s):  
Infrared Spectroscopy ◽  
Near Infrared Spectroscopy ◽  
Near Infrared ◽  
Cerebral Oxygenation ◽  
Vastus Lateralis ◽  
Work Capacity ◽  
Vastus Lateralis Muscle ◽  
Double Blind ◽  
Hemoglobin Saturation ◽  
Concentration Changes

The combined effects of hyperventilation and arterial desaturation on cerebral oxygenation ([Formula: see text]) were determined using near-infrared spectroscopy. Eleven competitive oarsmen were evaluated during a 6-min maximal ergometer row. The study was randomized in a double-blind fashion with an inspired O2 fraction of 0.21 or 0.30 in a crossover design. During exercise with an inspired O2 fraction of 0.21, the arterial CO2 pressure (35 ± 1 mmHg; mean ± SE) and O2 pressure (77 ± 2 mmHg) as well as the hemoglobin saturation (91.9 ± 0.7%) were reduced ( P < 0.05).[Formula: see text] was reduced from 80 ± 2 to 63 ± 2% ( P < 0.05), and the near-infrared spectroscopy-determined concentration changes in deoxy- (ΔHb) and oxyhemoglobin (ΔHbO2) of the vastus lateralis muscle increased 22 ± 3 μM and decreased 14 ± 3 μM, respectively ( P < 0.05). Increasing the inspired O2fraction to 0.30 did not affect ventilation (174 ± 4 l/min), but arterial CO2 pressure (37 ± 2 mmHg), O2 pressure (165 ± 5 mmHg), and hemoglobin O2saturation (99 ± 0.1%) increased ( P < 0.05).[Formula: see text] remained close to the resting level during exercise (79 ± 2 vs. 81 ± 2%), and although the muscle ΔHb (18 ± 2 μM) and ΔHbO2 (−12 ± 3 μM) were similar to those established without O2 supplementation, work capacity increased from 389 ± 11 to 413 ± 10 W ( P < 0.05). These results indicate that an elevated inspiratory O2fraction increases exercise performance related to maintained cerebral oxygenation rather than to an effect on the working muscles.

Maintained cerebral oxygenation during maximal self-paced exercise in elite Kenyan runners

2015 ◽  
Vol 118 (2) ◽  
pp. 156-162 ◽  
Author(s):  
J. Santos-Concejero ◽  
F. Billaut ◽  
L. Grobler ◽  
J. Oliván ◽  
T. D. Noakes ◽  
...  
Keyword(s):  
Near Infrared ◽  
Ventilatory Threshold ◽  
Cerebral Oxygenation ◽  
Oxygenation Index ◽  
Time Trial ◽  
Stable Range ◽  
Long Distance ◽  
Speed Test ◽  
Long Distance Running ◽  
Concentration Changes

The purpose of this study was to analyze the cerebral oxygenation response to maximal self-paced and incremental exercise in elite Kenyan runners from the Kalenjin tribe. On two separate occasions, 15 elite Kenyan distance runners completed a 5-km time trial (TT) and a peak treadmill speed test (PTS). Changes in cerebral oxygenation were monitored via near-infrared spectroscopy through concentration changes in oxy- and deoxyhemoglobin (Δ[O2Hb] and Δ[HHb]), tissue oxygenation index (TOI), and total hemoglobin index (nTHI). During the 5-km TT (15.2 ± 0.2 min), cerebral oxygenation increased over the first half (increased Δ[O2Hb] and Δ[HHb]) and, thereafter, Δ[O2Hb] remained constant (effect size, ES = 0.33, small effect), whereas Δ[HHb] increased until the end of the trial ( P < 0.05, ES = 3.13, large effect). In contrast, during the PTS, from the speed corresponding to the second ventilatory threshold, Δ[O2Hb] decreased ( P < 0.05, ES = 1.51, large effect), whereas Δ[HHb] continued to increase progressively until exhaustion ( P < 0.05, ES = 1.22, large effect). Last, the TOI was higher during the PTS than during the 5-km TT ( P < 0.001, ES = 3.08; very large effect), whereas nTHI values were lower ( P < 0.001, ES = 2.36, large effect). This study shows that Kenyan runners from the Kalenjin tribe are able to maintain their cerebral oxygenation within a stable range during a self-paced maximal 5-km time trial, but not during an incremental maximal test. This may contribute to their long-distance running success.

scholarly journals Phantom testing of two clinical spatially-resolved NIRS instruments

2005 ◽  
Vol 19 (3) ◽  
pp. 165-169 ◽  
Author(s):  
A. J. Macnab ◽  
R. E. Gagnon
Keyword(s):  
Near Infrared ◽  
Cerebral Oxygenation ◽  
Full Range ◽  
Hemoglobin Concentration ◽  
Bone Thickness ◽  
Technical Design ◽  
Spatially Resolved ◽  
Hemoglobin Saturation ◽  
Oxygenation Status ◽  
Total Hemoglobin Concentration

We used a living biological phantom to evaluate whether previously observed clinical differences in data collection between two similar near infrared spectrophotometers were due to technical design differences. A Somanetics INVOS-5100 was compared to a Hamamatsu NIRO-300. Both express the ratio of oxygenated hemoglobin to total hemoglobin concentration as a percentage, and both are intended for monitoring cerebral oxygenation status at the bedside. The living phantom simulated different bone densities and contained a low haematocrit solution of blood, intra-lipid, and saline, to which was added grower's yeast to alter oxygenation status. Results: In all trials, oxygen saturation decreased from 100% to 0 % as the yeast consumed the available oxygen. In all trials the spectrometers were significantly correlated (range: r2=0.815 to 0.995, p2>0.232). The NIRO-300 indicated oxygenation change 1 minute after addition of yeast, whereas the INVOS-5100 showed change after 5 minutes. Simulated bone thickness had almost no effect upon the NIRO-300, but did affect the INVOS-5100. Conclusion: In this study, the spectrophotometers had similar results consistent with the technical design differences: the INVOS-5100 does not report hemoglobin saturation change above 95% or below 15% while the NIRO-300 reports the full range from 100% to 0%.

scholarly journals Use of near–infrared spectroscopy in the adult

1997 ◽  
Vol 352 (1354) ◽  
pp. 701-705 ◽  
Author(s):  
Peter J. Kirkpatrick
Keyword(s):  
Infrared Spectroscopy ◽  
Near Infrared Spectroscopy ◽  
Near Infrared ◽  
Cerebral Oxygenation ◽  
Haemoglobin Concentration ◽  
Potential Method ◽  
Adult Brain ◽  
Spatially Resolved ◽  
Clinical Scenarios ◽  
Spatially Resolved Spectroscopy

Adult near–infrared spectroscopy is a potential method for observing changes in cerebral oxygenation non–invasively. Access of light to the adult brain requires penetration through extracranial tissues; hence the detection of changes in cerebral chromophore concentration can only be achieved by using near–infrared spectroscopy in the reflectance–mode thereby adding variables which are difficult to control. These include the effects of variable anatomy, different intra–optode distances and the presence of an extra– to intracranial collateral blood supply. Although movements of oxygenated haemoglobin concentration following specific cerebral stimuli can be demonstrated, the challenge of separating changes which occur within the extracranial compartment from those occurring in the intracranial compartments remains. Our experience with near–infrared spectroscopy in the three adult clinical scenarios of carotid endarterectomy, head injury and carbon dioxide stress testing will be presented. The influence of extracranial contamination is demonstrated, as are the methods we have developed to help control for extracranial contamination. Provisional experience with spatially resolved spectroscopy technology will also be presented.

Cerebral Arterial and Venous Contributions to Tissue Oxygenation Index Measured Using Spatially Resolved Spectroscopy in Newborn Lambs

2010 ◽  
Vol 113 (6) ◽  
pp. 1385-1391 ◽  
Author(s):  
Flora Y. Wong ◽  
Theodora Alexiou ◽  
Thilini Samarasinghe ◽  
Vojta Brodecky ◽  
Adrian M. Walker
Keyword(s):  
Oxygen Saturation ◽  
Tissue Oxygenation ◽  
Volume Fraction ◽  
Cerebral Oxygenation ◽  
Oxygenation Index ◽  
Arterial Oxygen ◽  
Spatially Resolved ◽  
Tissue Oxygenation Index ◽  
Venous Volume ◽  
Spatially Resolved Spectroscopy

Background Bedside assessments of cerebral oxygenation are sought to monitor cerebral injury in patients undergoing intensive care. Spatially resolved spectroscopy measures tissue oxygenation index (TOI, %) which reflects mixed cerebral arterial and venous oxygenations. We aimed to evaluate arterial and venous components of TOI (cerebral arterial to venous volume ratio [A:V ratio]) in the newborn lamb brain using cerebral arterial and venous blood samples, and to investigate the impact of acute hypoxemia on the A:V ratio and TOI. Method Nine lambs were ventilated with varied inspired oxygen to generate arterial oxygen saturations between 25% and 100%. Cerebral arterial and venous oxygen saturations analyzed using cooximeter of arterial and superior sagittal sinus blood were used to estimate TOI (TOIcox), assuming cerebral A:V ratio of 25:75. TOIcox was compared with the TOI measured by spatially resolved spectroscopy (TOIsrs). Actual cerebral arterial and venous volume fractions were reestimated using TOIsrs = cerebral arterial volume fraction cerebral arterial oxygen saturation + cerebral venous volume fraction*cerebral venous oxygen saturation. Results Median (range) TOIsrs was 48.5% (32.0-64.1%), and TOIcox was 48.4% (13.7-74.4%), and the two were significantly correlated (R = 0.77). The mean difference between TOIsrs and TOIcox was 2.4% (limits of agreement ± 18.1%). The TOIsrs - TOIcox difference varied with oxygen saturations, with TOIsrs higher than TOIcox at low saturations, and lower at high saturations. Cerebral arterial volume fraction was 22.9-27.5% in normoxia and markedly increased in hypoxemia. Conclusion TOI corresponds with cerebral oxygenation. The variable agreement of TOIsrs with TOIcox may reflect changes in cerebral A:V ratio due to arterial oxygenation-related vasoreactivity.

Measuring The Tensile Strain of Wood By Visible And Near-Infrared Spatially Resolved Spectroscopy

2021 ◽  
Author(s):  
Ma Te ◽  
Tetsuya Inagaki ◽  
Masato Yoshida ◽  
Mayumi Ichino ◽  
Satoru Tsuchikawa
Keyword(s):  
Light Scattering ◽  
Prediction Accuracy ◽  
Tensile Strain ◽  
Near Infrared ◽  
Mean Squared Error ◽  
Calibration Model ◽  
Spatially Resolved ◽  
Squared Error ◽  
Stiffness Evaluation ◽  
Spatially Resolved Spectroscopy

Abstract Wood has various mechanical properties, so stiffness evaluation is critical for quality management. Using conventional strain gauges constantly is high cost, also challenging to measure precious wood materials due to the use of strong adhesive. This study demonstrates the correlation between light scattering changes inside the wood cell walls and tensile strain. A multifiber-based visible-near-infrared (Vis–NIR) spatially resolved spectroscopy (SRS) system was designed to rapidly and conventiently acquire such light scattering changes. For the preliminary experiment, samples with different thicknesses were measured to evaluate the influence of thickness. The differences in Vis–NIR SRS spectral data diminish with an increase in sample thickness, which suggests that the SRS method can successfully measure the whole strain (i.e., surface and inside) of wood samples. Then, for the primary experiment, 18 wood samples with the same thickness (2 mm) were tested to construct a strain calibration model. The prediction accuracy was characterized by a determination coefficient (R2) of 0.86 with a root mean squared error (RMSE) of 297.89 με for five-fold cross-validation; for test validation, The prediction accuracy was characterized by an R2 of 0.82 and an RMSE of 345.44 με.

scholarly journals T Tauri Binaries in Orion: Evidence for Accelerated and Synchronized Disk Evolution

2011 ◽  
Vol 7 (S282) ◽  
pp. 452-453 ◽  
Author(s):  
Sebastian Daemgen ◽  
Monika G. Petr-Gotzens ◽  
Serge Correia
Keyword(s):  
Accretion Disks ◽  
Near Infrared ◽  
Orion Nebula ◽  
Spatially Resolved ◽  
T Tauri ◽  
Significant Difference ◽  
Disk Evolution ◽  
The Individual ◽  
Gas Accretion

AbstractIn order to trace the role of binarity for disk evolution and hence planet formation, we started the currently largest spatially resolved near-infrared photometric and spectroscopic study of the inner dust and accretion disks of the individual components of 27 visual, 100–400 AU binaries in the Orion Nebula Cluster (ONC). We study the frequency of Brackett-γ (2.165μm) emitters to assess the frequency of accretion disk-bearing stars among the binaries of the ONC: only 34±9% of the binary components show signs of accretion and, hence, the presence of gaseous inner disks—less than the fraction of gas accretion disks among single stars of the ONC of ~50%. Additionally, we find a significant difference between binaries above and below 200 AU separation: no close systems with only one accreting component are found. The results suggest shortened disk lifetimes as well as synchronized disk evolution.

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