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PubMed1990

Carbon dioxide-related changes in cerebral blood volume and cerebral blood flow in mechanically ventilated preterm neonates: comparison of near infrared spectrophotometry and 133Xenon clearance.

Carbon dioxide-induced changes in near infrared spectrophotometry recordings were compared with changes in cerebral blood flow estimated by 133Xenon clearance (global cerebral blood flow (infinity)) at serial measurements in 24 mechanically ventilated preterm infants (mean gestational age 30.2 wk). In all infants, three measurements were taken at different arterial carbon dioxide tension levels (mean 4.4 kPa, range 2.1-7.8) obtained by adjustment of the ventilator settings. Mean arterial blood pressure changed spontaneously, whereas arterial oxygen tension was kept within normal range. At all wavelengths (904, 845, 805, and 775 nm), the OD increased at higher arterial carbon dioxide tension levels, indicating cerebral vasodilation. This conclusion was supported by conversion of the data to changes in oxygenated and deoxygenated Hb concentration. A parallel increase in cerebral blood volume index and global cerebral blood flow (infinity) was found (p less than 0.0001). The oxygenation level of cytochrome aa3 increased with increases in oxygen delivery (p less than 0.0001). This observation, however, may have been artifactual due to cross-talk between the oxidized cytochrome aa3 and the oxygenated Hb signals, as these signals were closely interrelated in the present experimental design. We suggest that near infrared spectrophotometry may be used for estimation of the cerebral blood volume index/cerebral blood flow-CO2 reactivity within a wide range of arterial carbon dioxide tension. Knowledge of the light path length would put this estimation on a quantitative basis.

Birth Weight↗
PubMed2003

Determining of crystalline silica in respirable dust samples by infrared spectrophotometry in the presence of interferences.

Infrared Spectrophotometry (IR) is now widely used to determine crystalline silica in industrial dust samples. Though the IR method has many advantages when dealing with respirable dust samples, some serious analytical errors are often caused by interference minerals contamination. These minerals have a characteristic absorption band corresponding in position to the analytical peak for crystalline silica. In this paper, six typical interference minerals (Kaolinite, Mullite, Muscovite, Pyrophyllite, Montmorillonite and Amorphous silica) were pre-size controlled to respirable range and their infrared spectra were measured by means of an FT-IR with the well-known potassium bromide tablet technique. The effects of these interference minerals on the Japanese OEL or the administrative control level for respirable dust which depend on the silica content were calculated and expressed in figures. The measured absorption coefficients of the interference minerals and quartz were 1.36-6.98 Abs/mg and 24.46 Abs/mg, respectively. The absorption band height ratios of each interference minerals were also measured. Then the efficiency and applicability of two spectrum correction methods for the interference minerals, absorbance ratio method and difference spectrum method were examined by using artificially mixed samples (standard interference mineral + standard quartz). By comparing the quantifying results for the mixture samples, it was revealed that the interfered spectra were almost corrected successfully when using the difference spectrum method, whereas correction by the absorbance ratio method resulted in apparent negative errors. Furthermore, the difference spectrum method was proven to be superior to the absorbance ratio method in applicability.

Dust↗
PubMed1991

[Use of infrared spectrophotometry of bile for diagnosis of cholelithiasis and predicting the chemical composition of the concrements].

Infrared spectrophotometry was applied in bile investigation from 47 cholelithiasis, 53 acalculous chronic cholecystitis and 23 control subjects. A cholelithiasis--specific shift in the absorption band appeared in the range of 900-1150 cm-1. Bile calculi removed at surgery from 110 relevant patients and bile from them were exposed to infrared spectrophotometry. The authors derived a correlation between the shape of the absorption band for bile in the range of 1500-1800 cm-1 and chemical composition of the concrement.

Bile↗
PubMed1985

A noninvasive method for monitoring the effects of increased intracranial pressure with near infrared spectrophotometry.

Two experiments were conducted to assess the feasibility of near infrared spectrophotometry (niroscopy) to monitor directly the effects of increased intracranial pressure on brain metabolism. ICP was increased in cats by subarachnoid infusion of a "mock" CSF solution. Cytochrome a,a3 redox state, oxyhemoglobin, deoxyhemoglobin and cerebral blood flow were noninvasively and continuously monitored by niroscopy. The results of both experiments indicated that changes in ICP correlated with a reduction in cytochrome a,a3 redox state (p less than 0.01), a decrease in the quantity of oxyhemoglobin and cerebral flow (p less than 0.01) and an increase in deoxyhemoglobin. The study results suggest that niroscopy has the potential for providing noninvasive and continuous data for assessing brain metabolic activity. The correlations obtained with simultaneous measurements of intracranial pressure make this an attractive method for application to those at risk for increased intracranial pressure.

Animals↗
PubMed1993

[Monitoring of peripheral tissue oxygenation with near infrared spectrophotometry during abdominal or iliac aortic cross-clamping surgery].

Peripheral tissue oxygenation was monitored with near infrared spectrophotometry during abdominal or common iliac aortic cross-clamping surgery. Six patients who had abdominal aortic aneurysm (AAA) and eight patients who had aortic sclerotic occlusive disease (ASO) were studied. At the beginning of cross-clamping, oxyhemoglobin was decreasing and deoxyhemoglobin was increasing in all AAA patients. Average of 37 minutes following cross-clamping of abdominal aorta, both hemoglobin values were stabilized. On the other hand, changes in both hemoglobin values were delayed or missing in ASO patients. The results suggest that the duration from cross-clamping to stabilization is related to co-lateral blood flow. During operation, monitoring of peripheral blood flow with near infrared spectrophotometry is useful for detection of peripheral ischemia and for the estimation of postoperative local blood flow.

Aorta, Abdominal↗