International anesthesiology clinics
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Int Anesthesiol Clin · Jan 1987
ReviewTheory and development of fluorescence-based optochemical oxygen sensors: oxygen optodes.
As the preceding considerations concerning the physical and technical features of oxygen optodes have demonstrated, fluorescence-based optochemical oxygen sensors possess certain advantages and peculiarities compared to conventionally applied electrochemical sensors such as polarographic oxygen electrodes. First, in contrast to oxygen electrodes, oxygen measurements with oxygen optodes do not suffer from distortions caused by the reference electrodes. In addition, because of the polarographic process, platinum electrodes continuously consume oxygen, which falsifies the results, especially when small sample volumes or long-term measurements, or both, are involved, whereas the sensor layer of oxygen optodes must only be equilibrated. ⋯ Furthermore, the sensitivity of oxygen optodes can be tuned to the desired range of PO2 values, resulting in a higher resolution. Use of suitable polymer alloys as indicator matrices can even enhance oxygen sensitivity; therefore, the application of optodes for trace analysis of oxygen might be possible, especially with regard to the application of highly oxygen-sensitive phosphorescent indicators. Finally, owing to the reversibility of fluorescence quenching, monitoring of oxygen by fluorescence optical sensors allows a continuous and remote control of biomedical parameters as well as regulation of biotechnological processes.(ABSTRACT TRUNCATED AT 400 WORDS)
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The pulse oximeter estimates arterial hemoglobin saturation by measuring the light absorbance of pulsating vascular tissue at two wavelengths. The relationship between measured light absorbances and saturation was developed empirically and is built into the oximeter software. Studies in human volunteers have shown good performance of the device in healthy adults for saturations in the range of 70 to 100%. ⋯ The pulse oximeter is one of the most important advances in noninvasive monitoring because it provides a means of continuously and quickly assessing arterial blood oxygenation. It is easy to use and interpret, requires little setup time, and poses no additional risks to the patient. Pulse oximetry may soon be a standard of practice for routine monitoring in any clinical setting in which the patient is at risk of hypoxemia.
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SvO2 measurement by reflectance oximetry incorporated into a thermodilution catheter is a reliable method of assessing the adequacy of oxygen delivery and is currently the best method of continuously monitoring oxygen supply-demand relationships. The SvO2 measurement continuously monitors the tissue status of oxygenation. ⋯ SvO2 monitoring is of value in the critically ill cardiac and general surgical patients, not only during the surgical intervention but also in the postoperative period when managing derangements of ventilation and circulation. In our experience, continuous surveillance of the SvO2 currently is the best rapidly responsive indicator of cardiopulmonary function and oxygen transport.
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Int Anesthesiol Clin · Jan 1987
Review Comparative StudyCrystalloid versus colloid: is colloid worth the cost?