Near-infrared Spectrophotometry Research Articles

Regional Differences of Hemodynamics and Oxygenation in the Human Calf Muscle Detected with Near-Infrared Spectrophotometry

Measurements in muscle tissue are often performed at a selected single location over the muscle of interest. The hypothesis is that the values obtained reflect the status within the entire muscle or muscle group. This, however, may not be the case. The study was performed to investigate whether this hypothesis is true for hemodynamics and oxygenation in the healthy human calf muscle at rest. Hemoglobin flow, blood flow, oxygen consumption, and venous hemoglobin oxygen saturation were mapped at 22 locations in 30 legs of 15 healthy subjects (nine women, six men aged 26-37 years) simultaneously by using frequency-domain near-infrared spectrophotometry with a specially designed probe during venous occlusion. For all parameters, spatial heterogeneity was found between subjects and within individual legs. All parameters were highly significantly different when comparing proximal and distal regions. Differences were also found between medial and lateral regions. The global mean values (+/-standard deviation) over all measurements were as follows: hemoglobin flow, 1.27 micromol per 100 mL/min +/- 0.88; blood flow, 0.56 mL per 100 g/min +/- 0.38; oxygen consumption, 0.016 mL per 100 g/min +/- 0.011; and venous oxygen saturation, 77.6% +/- 5.9. The thickness of the overlying adipose tissue had an influence on the measurements and must be considered. Highly significant spatial heterogeneity of hemodynamics and oxygenation was found in the healthy human calf muscle.

INDICADORES DO METABOLISMO ENERGÉTICO NO PÓS-PARTO DE VACAS LEITEIRAS DE ALTA PRODUÇÃO E SUA RELAÇÃO COM A COMPOSIÇÃO DO LEITE

ilk synthesis is a challenge for energy metabolism lactation process requires a great quantity of gluconeogenic precursors for lactose synthesis. In early lactation period cows reduce dry matter ingestion and this situation lead to a negative energy balance (BEN) which is characterized by mobilization of lipid reserves. main objective of this work was to monitor biochemical energy indicators during postpartum period in high-yielding dairy cows and to evaluate possible relations of those metabolites with milk composition. The study was done with 110 multiparous Holstein Friesian dairy cows fed forage, hay, silage, concentrate and mineral supplement. Balancing of the diet was made through commercial software. The postpartum period that was evaluated by groups corresponded to 2, 5, 8 and 11 weeks of lactation, the same group and number of animals were evaluated during the winter and the summer. In the each period blood and milk samples were collected from seven animals group in five different herds. Non-esterified fatty acids (NEFA), beta-hydroxibutirate (BHB), glucose, triglycerydes and cholesterol were determined through colorimetric technique. Milk composition was determined by near infrared spectrophotometry (NIRS). Statistical analyses included correlation test, analysis of variance and Tukey´s means test. It was concluded that there is no statistical association between milk composition and energetic indicators. KEY-WORDS: Dairy cows, energetic metabolism, energy balance, milk composition.

Heart Rate and Muscle Oxygenation during Hyperbaric Hyperoxia

PURPOSE: Hyperbaric hyperoxia is known to increase oxygen concentration in arterial blood and tissue and also to decrease heart rate (HR). This study aimed to investigate the relation between muscle oxygenation and HR under the condition of hyperbaric hyperoxia (HBHO). METHODS: Three males and 4 females aged 27.1 ±4.7 yrs volunteered to participate in this investigation. Written informed consent was obtained from all subjects. They sat in the hyperbaric chamber for 60 min and breathed 1) air of normal pressure (1.0 ATA) for 10 min (baseline) and 2) 100% O2 of 1.3 ATA for 30 min. Between the two stages, the atmospheric pressure was gradually increased from 1.0 to 1.3 ATA for 10 min and decreased to 1.0 ATA for 10 min after the 2nd stage. Heart rate variability (HRV) and oxygenation of vastus lateralis were measured during each phase. Time domain (HR and SD of HRV) and frequency domain (LF/HF and HF/TOT, LF: low frequency power, HF: high frequency power, and TOT: total power) measures of HRV were calculated. The changes of oxyhemoglobin (deltaO2Hb), deoxyhemoglobin (deltaHHb) and total hemoglobin (deltacHb) as well as TOI (total oxygenation index: O2Hb/(O2Hb+HHb)) were evaluated using near-infrared spectrophotometry. Correlations between the changing rates for HRV measures and oxygenation related measures from baseline to HBHO were calculated. RESULTS: The decrease of HR and increase of TOI under HBHO were observed in all subjects. There was a significant positive correlation in the changing rates of HR and TOI. CONCLUSIONS: From the results of the present investigation, it can be said that lower oxygenation accompanied greater decrease of HR under HBHO. It might be due to individual differences in vasoconstriction which might occur in response to HBHO and which could induce the increase of venousreturn to the heart.

Inhalation of Ultrafine and Fine Particulate Matter Disrupts Systemic Vascular Function

This study investigated the effects of particulate matter (PM) with aerodynamic diameter 0.02–1 μm (noted as PM1) inhalation during exercise on conduit artery and microvascular function. Inhalation of internal combustion-derived PM is associated with cardiovascular mortality and morbidity. Direct action of PM on the vascular endothelium is likely, as a substantial fraction of ultrafine PM translocates from the alveoli to the circulatory system. Sixteen intercollegiate athletes performed 30 min of exercise while inhaling low or high PM1. Flow-mediated brachial artery dilation (FMD) using high-resolution ultrasonography with simultaneous measurements of forearm oxygen kinetics using near infrared spectrophotometry (NIRS) was done before and after exercise. Basal brachial artery vasoconstriction was found after high PM1 exercise (4.0%, 4.66 ± 0.609 to 4.47 ± 0.625 mm diameter; p = .0002), but not after low PM1 exercise (−0.3%, 4.66 ± 0.626 to 4.68 ± 0.613 mm diameter). FMD was impaired after high PM1 exercise (6.8 ± 3.58% for preexercise FMD and 0.30 ± 2.74% for postexercise FMD, p = .0001), but not after low PM1 exercise (6.6 ± 4.04% for preexercise FMD and 4.89 ± 4.42% for postexercise FMD). Reduction in forearm muscle reperfusion estimated by reoxygenation slope-to-baseline after 4 min cuff ischemia was observed for high PM1 exercise (55% vs. 3%, p = .0006); no difference was noted for low PM1 exercise. Brachial artery FMD was significantly correlated to muscle reoxygenation slope-to-baseline (r = .50, p = .005). Acute inhalation of high [PM1] typical of urban environments impairs both systemic conduit artery function and microcirculation. The observed decrease reoxygenation slope-to-baseline after cuff release is consistent with reduced blood flow in the muscle microvasculature.

Tissue oxygen saturation, measured by near-infrared spectroscopy, and its relationship to surgical-site infections

Surgical-site infections (SSIs) are common after major abdominal and groin bypass surgery. Tissue oxygen tension has been shown to predict these infections accurately. This study assessed whether a non-invasive measurement of tissue oxygenation, tissue oxygen saturation as measured by spectrophotometry, was as accurate. Fifty-nine patients having major abdominal or groin bypass surgery had tissue oxygen saturation measured by near-infrared spectrophotometry at the incision site and in the arm before operation, and at 12, 24 and 48 h after surgery. Masked outcome assessments for SSI were made at 7 and 30 days after operation. In this retrospective analysis, 17 patients (29 per cent) developed an SSI. At 12 h after operation there was a significant difference in tissue oxygen saturation at the surgical site between patients who developed an SSI and those who did not (mean(s.d.) 43.4(18.1) versus 55.8(22.0) per cent; P = 0.032). These oxygen saturation readings were found to be more specific and sensitive in predicting SSIs than the National Nosocomial Infection Surveillance system. There is a difference in postoperative surgical-site oxygen saturation between patients who subsequently develop SSIs and those who do not. Prediction of SSIs provides opportunities for intervention and prevention.

Near-infrared Spectro-photometry of Carbon Stars

Antarctica offers probably the best ground-based conditions for observing in the 1–3 μ m region, and may thus be considered as an alternative to Space for this domain. We examine the potential of integral-field spectro-photometry over wide areas of the sky in this wavelength range for the study of carbon stars, that seems promising. On the other hand, the conditions of transparency, background, and their short-time stability from Antarctic sites still need to be evaluated.

Visible and near-infrared spectrophotometry of the Deep Impact ejecta of Comet 9P/Tempel 1

We have obtained optical spectrophotometry of the evolution of Comet 9P/Tempel 1 after the impact of the Deep Impact probe, using the Supernova Integral Field Spectrograph (SNIFS) at the UH 2.2-m telescope, as well as simultaneous optical and infrared spectra using the Lick Visible-to-Near-Infrared Imaging Spectrograph (VNIRIS). The spatial distribution and temporal evolution of the “violet band” CN (0–0) emission and of the 630 nm [OI] emission was studied. We found that CN emission centered on the nucleus increased in the 2 h after impact, but that this CN emission was delayed compared to the light curve of dust-scattered sunlight. The CN emission also expanded faster than the cloud of scattering dust. The emission of [OI] at 630 nm rose similarly to the scattered light, but then remained nearly constant for several hours after impact. On the day following the impact, both CN and [OI] emission concentrated on the comet nucleus had returned nearly to pre-impact levels. We have also searched for differences in the scattering properties of the dust ejected by the impact compared to the dust released under normal conditions. Compared to the pre-impact state of the comet, we find evidence that the color of the comet was slightly bluer during the post-impact rise in brightness. Long after the impact, in the following nights, the comet colors returned to their pre-impact values. This can be explained by postulating a change to a smaller particle size distribution in the ejecta cloud, in agreement with the findings from mid-infrared observations, or by postulating a large fraction of clean ice particles, or by a combination of these two.

Visible and near-infrared spectrophotometry of the Deep Impact ejecta of Comet 9P/Tempel 1

We have obtained optical spectrophotometry of the evolution of Comet 9P/Tempel 1 after the impact of the Deep Impact probe, using the Supernova Integral Field Spectrograph (SNIFS) at the UH 2.2-m telescope, as well as simultaneous optical and infrared spectra using the Lick Visible-to-Near-Infrared Imaging Spectrograph (VNIRIS). The spatial distribution and temporal evolution of the “violet band” CN (0–0) emission and of the 630 nm [OI] emission was studied. We found that CN emission centered on the nucleus increased in the 2 h after impact, but that this CN emission was delayed compared to the light curve of dust-scattered sunlight. The CN emission also expanded faster than the cloud of scattering dust. The emission of [OI] at 630 nm rose similarly to the scattered light, but then remained nearly constant for several hours after impact. On the day following the impact, both CN and [OI] emission concentrated on the comet nucleus had returned nearly to pre-impact levels. We have also searched for differences in the scattering properties of the dust ejected by the impact compared to the dust released under normal conditions. Compared to the pre-impact state of the comet, we find evidence that the color of the comet was slightly bluer during the post-impact rise in brightness. Long after the impact, in the following nights, the comet colors returned to their pre-impact values. This can be explained by postulating a change to a smaller particle size distribution in the ejecta cloud, in agreement with the findings from mid-infrared observations, or by postulating a large fraction of clean ice particles, or by a combination of these two.

Correlation of transcutaneous hepatic near‐infrared spectroscopy readings with liver surface readings and perfusion parameters in a piglet endotoxemic shock model

To determine whether transcutaneous liver near-infrared spectrophotometry (NIRS) measurements correlate with NIRS measurements taken directly from the liver surface, and invasive blood flow measurements. Laparotomy was performed in 12 Yorkshire piglets, and ultrasound blood flow probes were placed on the hepatic artery and portal vein. Intravascular catheters were inserted into the hepatic and portal veins for intermittent blood sampling, and a pulmonary artery catheter was inserted via the jugular vein for cardiac output measurements. NIRS optodes were placed on skin overlying the liver and directly across the right hepatic lobe. Endotoxemic shock was induced by continuous infusion of Escherichia coli lipopolysaccharide O55:B5. Pearson's correlations were calculated between the NIRS readings and the perfusion parameters. After endotoxemic shock induction, liver blood flow, and oxygen delivery decreased significantly. There were statistically significant correlations between the transcutaneous and liver-surface NIRS readings for oxyhemoglobin, deoxyhemoglobin, and cytochrome c oxidase concentrations. There were similar significant correlations of the transcutaneous oxyhemoglobin with both the mixed venous and hepatic vein saturation, and mixed venous and hepatic vein lactate. Transcutaneous NIRS readings of the liver, in an endotoxemic shock model, correlate with NIRS readings taking directly from the liver surface, as well as with global and specific organ-perfusion parameters.

Cerebral blood flow and oxygenation during head-up tilt in patients with multiple system atrophy and healthy control subjects

To assess cerebral hemodynamics in patients with multiple system atrophy (MSA), cerebral blood flow and oxygenation were evaluated in 7 MSA patients and 9 healthy controls during a head-up tilt test (HUT) by means of transcranial Doppler ultrasonography and near-infrared spectrophotometry. In the MSA patients examined, the perfusion pressure reduction during HUT was marked, but severe reduction in blood flow velocity was prevented because of a decrease in cerebrovascular resistance. The MSA patients showed no severe reduction in cerebral oxygenation during HUT. These findings indicate that our MSA patients exhibited a compensatory cerebral vasodilatation response to orthostatic hypotension.

Inhalation of Ultrafine and Fine Particulate Matter Disrupts Systemic Vascular Function

Epidemiological evidence suggests that inhalation of internal combustion-derived particulate matter (PM) is associated with cardiovascular mortality and morbidity. Significant increases in emergency room visits for cardiac events during high PM episodes have been documented. Direct action of PM on the vascular endothelium is likely, as a substantial fraction of ultrafine PM translocates from the alveoli to the circulatory system. PURPOSE: To investigate effects of PM1 (PM with an aerodynamic diameter of 0.02–1 um) inhalation during exercise on conduit artery and microvascular function. METHODS: Sixteen intercollegiate athletes performed 30-min of exercise while inhaling low or high [PM1]. Flow-mediated brachial artery dilation (FMD) using high-resolution ultrasonography with simultaneous measurements of forearm oxygen kinetics using near infrared spectrophotometry (NIRS) was done before and after exercise. RESULTS: Basal brachial artery vasoconstriction was found after high [PM1] exercise (4.0%, 4.66±0.609 vs 4.47±0.625 mm diameter; P=0.0002), but not after low [PM1 exercise (−0.3%, 4.66±0.626 vs 4.68±0.613 mm diameter). FMD was impaired after high [PM1] exercise (6.8±3.58% for pre-exercise FMD vs 0.30±2.74% for postexercise FMD, P=0.0001), but not for low PM1 exercise (6.6±4.04% for pre-exercise FMD vs 4.89±4.42% for post-exercise FMD). Significant reduction in forearm muscle reperfusion estimated by reoxygenation slope to baseline after 3 min cuff ischemia was observed for high [PM1] exercise, while no difference was noted for low [PM1 exercise (55% vs 3%, P=0.0006). Brachial artery FMD response was related to muscle reoxygenation slope to baseline (R=0.50, P=0.005). CONCLUSION: Acute inhalation of high [PM1] typical of urban environments impairs both systemic conduit artery function and microcirculation. Decreased reoxygenation slope to baseline after cuff release is consistent with reduced blood flow in the muscle microvasculature. Supported by AHA 0455734U.

The postural reduction in middle cerebral artery blood velocity is not explained by PaCO2

In the normocapnic range, middle cerebral artery mean velocity (MCA Vmean) changes approximately 3.5% per mmHg carbon-dioxide tension in arterial blood (PaCO2) and a decrease in PaCO2 will reduce the cerebral blood flow by vasoconstriction (the CO2 reactivity of the brain). When standing up MCA Vmean and the end-tidal carbon-dioxide tension (PETCO2) decrease, suggesting that PaCO2 contributes to the reduction in MCA Vmean. In a fixed body position, PETCO2 tracks changes in the PaCO2 but when assuming the upright position, cardiac output (Q) decreases and its distribution over the lung changes, while ventilation (VE) increases suggesting that PETCO2 decreases more than PaCO2. This study evaluated whether the postural reduction in PaCO2 accounts for the postural decline in MCA Vmean). From the supine to the upright position, VE, Q, PETCO2, PaCO2, MCA Vmean, and the near-infrared spectrophotometry determined cerebral tissue oxygenation (CO2Hb) were followed in seven subjects. When standing up, MCA Vmean (from 65.3+/-3.8 to 54.6+/-3.3 cm s(-1) ; mean +/- SEM; P<0.05) and cO2Hb (-7.2+/-2.2 micromol l(-1) ; P<0.05) decreased. At the same time, the VE/Q ratio increased 49+/-14% (P<0.05) with the postural reduction in PETCO2 overestimating the decline in PaCO2 (-4.8+/-0.9 mmHg vs. -3.0+/-1.1 mmHg; P<0.05). When assuming the upright position, the postural decrease in MCA Vmean seems to be explained by the reduction in PETCO2 but the small decrease in PaCO2 makes it unlikely that the postural decrease in MCA Vmean can be accounted for by the cerebral CO2 reactivity alone.

Do GSM 900MHz signals affect cerebral blood circulation? A near-infrared spectrophotometry study

Effects of GSM 900MHz signals (EMF) typical for a handheld mobile phone on the cerebral blood circulation were investigated using near-infrared spectrophotometry (NIRS) in a three armed (12W/kg, 1.2W/kg, sham), double blind, randomized crossover trial in 16 healthy volunteers. During exposure we observed borderline significant short term responses of oxyhemoglobin and deoxyhemoglobin concentration, which correspond to a decrease of cerebral blood flow and volume and were smaller than regular physiological changes. Due to the relatively high number of statistical tests, these responses may be spurious and require further studies. There was no detectable dose-response relation or long term response within 20min. The detection limit was a fraction of the regular physiological changes elicited by functional activation. Compared to previous studies using PET, NIRS provides a much higher time resolution, which allowed investigating the short term effects efficiently, noninvasively, without the use of radioactive tracers and with high sensitivity.

Pulse glucometry: a new approach for noninvasive blood glucose measurement using instantaneous differential near-infrared spectrophotometry

We describe a new optical method for noninvasive blood glucose (BGL) measurement. Optical methods are confounded by basal optical properties of tissues, especially water and other biochemical species, and by the very small glucose signal. We address these problems by using fast spectrophotometric analysis in a finger, deriving 100 transmittance spectra per second, to resolve optical spectra (900 to 1700 nm) of blood volume pulsations throughout the cardiac cycle. Difference spectra are calculated from the pulsatile signals, thereby eliminating the effects of bone, other tissues, and nonpulsatile blood. A partial least squares (PLS) model is used with the measured spectral data to predict BGL levels. Using glucose tolerance tests in 27 healthy volunteers, periodic optical measurements were made simultaneously with collection of blood samples for in vitro glucose analysis. Altogether, 603 paired data sets were obtained in all subjects and two-thirds of the data or of the subjects randomly selected were used for the PLS calibration model and the rest for the prediction. Bland-Altman and error-grid analyses of the predicted and measured BGL levels indicated clinically acceptable accuracy. We conclude that the new method, named pulse glucometry, has adequate performance for safe, noninvasive estimation of BGL.

New multichannel near infrared spectrophotometry system for functional studies of the brain in adults and neonates

We have designed a versatile, multi-channel near-infrared spectrophotometry (NIRS) instrument for the purpose of mapping neuronal activation in the neonatal and adult brain in response to motor, tactile, and visual stimulation. The optical linearity, stability, and high signal to noise ratio (>70 dB) of the instrument were demonstrated using an in vitro validation procedure. In vivo measurements on the adult forearm were also performed. Changes in oxygenation, induced by arterial occlusion of the forearm, were recorded and were shown to compare well with measurements acquired using a conventional NIRS instrument. To demonstrate the capabilities of the instrument, functional measurements in adults and neonates were performed. The instrument exhibited the capability to differentiate with a spatial resolution in the order of cm, local activation patterns associated with a finger tapping sequence.

Maintained cerebral and skeletal muscle oxygenation during maximal exercise in patients with liver cirrhosis

In cirrhotic patients, insufficient redistribution of blood from splanchnic organs to the central circulation could limit blood supply to skeletal muscles and the brain during exercise. Eight cirrhotic patients performed incremental cycling to exhaustion (74 (49-123) W; median with range). Heart rate increased from 68 (62-88)beats/min at rest to 142 (116-163)beats/min, cardiac output from 5.1 (3.3-7.2) to 12.9 (8.5-15.9)l/min, and mean arterial pressure from 89 (75-104) to 115 (92-129)mmHg (P<0.05), while the indocyanine green elimination determined hepatosplanchnic blood flow declined from 0.97 (0.55-1.46) to 0.62 (0.36-1.06)l/min (P<0.05). As assessed by near-infrared spectrophotometry, cerebral oxygenation (NIRS) was 61% (48-85%) and increased to 72% (57-86%) during exercise (P<0.05). The NIRS determined oxygenation of the vastus lateralis muscle also increased: the concentrations of oxygenated haemoglobin by 5.9 (0.57-9.47)micromol/l, deoxygenated haemoglobin by 7.2 (1.8-12.0)micromol/l, and thus total haemoglobin by 12.1 (3.6-21.5)micromol/l (P<0.05). In patients with cirrhosis, exercise reduces hepatosplanchnic blood flow, while O(2) supply to muscle and brain appears to increase indicating that blood redistribution from splanchnic organs does not limit blood flow to working muscles and the brain.

Clinical NIRS of the urinary bladder – A demonstration case report

Urinary incontinence is a common affliction among people of all ages throughout the world. There are many causes of incontinence, treatment options are determined by the cause, and current diagnostic methods require urodynamic assessment, which involves urethral and rectal catheterization, which are uncomfortable and distasteful for patients. Since clinical near infrared spectrophotometry (NIRS) is a non‐invasive, rapid means of measuring tissue oxygenation status at the bedside, we examined whether NIRS could be useful as a diagnostic tool for bladder dysfunction. An adult patient attending an incontinence clinic for routine urodynamic testing also had NIRS data collection during the standard bladder filling regimen. NIRS optodes were placed on the skin of the intact abdomen over the supra pubic region. Changes in oxy and de‐oxy hemoglobin concentration and changes in cytochrome c oxidase net redox status via NIRS were collected at 6 Hz. The magnitudes of change that occurred during NIRS data collection are on the order of 0.5 µmol/l and the moments of change correspond to the subject′s reported sensations of bladder filling and emptying, and with conventional urodynamics. These observations suggest that NIRS may be a disruptive technology with a role to play in non‐invasive evaluation of bladder dysfunction in humans.

273 Near Infrared Spectrophotometry Detects the Neuronal Activation Induced by Tactile, Auditory and Visual Stimulation in term Neonates

Background: Near infrared spectrophotometry (NIRS) can be used to non-invasively measure changes in optical properties during functional activation. Because these changes originate from differences in optical properties between activated and non-activated neurons, the spatial localization and temporal resolution of this signal make it a promising tool for studying the time course of neuronal activity in localized brain areas. So far no normative data exist in neonates.Aim: 1. To detect neuronal activation and observe its time course in healthy term and preterm infants. 2. To get normative data in order to establish a NIRS optical encephalogram.Methods: The NIRS instrument consists of a measuring system, stimulation unit and sensors. To allow for mapping of different brain regions, 8 locations were analyzed simultaneously. The following stimulation tasks were performed: tactile (vibration motor), auditory (headphones), and visual (light emitting diodes). Four sensors were placed over either the C3 or C4 area (tactile), T3 or T4 area (auditory), or the occipital O1 area (visual). Left and right sides were alternately stimulated for 20s. Stimuli were pulsed using random on/off cycles ranging from 300 to 500ms. Each stimulation period was followed by 10 seconds of rest. Stimulation-rest cycles were repeated for a minimum of 10min. Novel adaptive spectral filters where applied to extract the neuronal signal form the optical intensity signal. A time triggered, folded average allowed isolation of the time course of the neuronal signal.Results: For tactile stimulation a total of 29 measurements in 16 neonates were recorded. For auditory stimulation a total of 27 measurements in 14 neonates, and for visual stimulation a total of 30 measurements in 10 neonates were recorded. Preliminary results indicate that visualization of the neuronal response to tactile stimulation was possible in 13 infants and to auditory stimulation in 11 infants. No clear signal could be observed during visual stimulation. The latter might be due to immaturity, as only the subcortical visual region is activated in term newborns.Conclusions: Our observations show that it is possible to detect neuronal activation from the optical NIRS signal in healthy term infants. The NIRS system thus, may provide an inexpensive tool for cerebral functional diagnostics in the neonatal intensive care unit.

Multichannel Monitoring of Cerebral Circulatory and Oxygenation Status Using Optical Topography during Deep Hypothermic Retrograde Cerebral Perfusion

In this study, we evaluated changes in the cerebral circulatory and oxygenation status during deep hypothermic total circulatory arrest (TCA) and retrograde cerebral perfusion (RCP) using optical topography, a form of multichannel near-infrared spectrophotometry, to monitor the broad area perfused by the middle cerebral artery. Seven patients underwent thoracic aortic surgery with TCA and RCP via the superior vena cava. Pressure-regulated RCP was performed under pH-stat. No postoperative neurologic complications occurred. Using optical topography, the relative changes in oxy-, deoxy-, and total hemoglobin (oxy-Hb, deoxy-Hb, total Hb) were simultaneously measured from 24 points in both hemispheres. Deoxy-Hb was used for evaluating the regional oxygenation status under RCR The values of deoxy-Hb at the beginning of RCP were regarded as the basal values, and the rate of increase in deoxy-Hb per minute (deoxy-Hb/min) was calculated at each site. Deoxy-Hb/min during TCA was also calculated. In every case, both oxy-Hb and total Hb decreased and deoxy-Hb increased during TCA. When RCP was initiated, the decrease in oxy-Hb and the increase in deoxy-Hb were attenuated. Deoxy-Hb/min was significantly lower under RCP than during TCA in all portions. There was no significant difference of deoxy-Hb/min between any portions during RCP Our results showed that the status of circulation and oxygenation might be uniform in the brain during RCP and better than that under TCA.

NIR spectrophotometry characterization of ITO electronic property changes at the interface with a PPV derivative

The electronic effects at polymer/indium tin oxide (ITO) interface play a crucial role in light-emitting devices as controlling charge injection. Near-infrared spectrophotometry has been used to characterize the modifications of the ITO electronic properties induced by the deposition of a PPV derivative. Near-infrared (NIR) spectra have been analyzed using Drude free electron theory providing information on the free carriers density and local conductivity. The optical analysis reveals a 10% reduction of the ITO free carrier concentration at the contact with the PPV derivative, which has been attributed to the formation of a polarization layer at the interface. Comparison has been done between polymer deposited directly on ITO or on ITO functionalized with a phosphonic acid layer (SAM) to improve the electronic/polymer interface. The NIR study indicates that charge transfers occur with the first deposited layer, providing confirmation of an interface effect.