Adv Exp Med Biol
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The photon diffusion theory can yield quantitative estimation of tissue hemoglobin saturation, provided that the medium is homogeneous and that one calibration data is available. The error in detection of tissue OS of the gut mucosa ranged from 5 to 10% in oxygen saturation. In application to skin, the two-layer tissue model suggests that by properly designing the optical sensor and by appropriately selecting the illumination wavelengths, it is possible to capture mainly the light returning from the specific depth in tissue. ⋯ Once one point calibration is accomplished, reflectance changes thereafter due to changes in HbT and OST can be fairly accurately predicted by the photon diffusion theory in combination with linear analysis. Concerning separation of arterial and venous blood in tissue, the diastolic and systolic phases of the optical plethysmographic signal can be assumed to relate to venous or DC level, and to arterial or AC component. Since the four components, arterial and venous OS and Hb, are unknowns in the system, four equations or four wavelength measurements are required to sort out each effect.(ABSTRACT TRUNCATED AT 400 WORDS)
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Comparative Study Clinical Trial
Folinic acid (CF)/5-fluorouracil (FUra) combinations in advanced gastrointestinal carcinomas.
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Comparative Study
Pulse oximetry and transcutaneous oxygen tension for detection of hypoxemia in critically ill infants and children.
We tested the performance of transcutaneous oxygen monitoring (TcPO2) and pulse oximetry (tcSaO2) in detecting hypoxia in critically ill neonatal and pediatric patients. In 54 patients (178 data sets) with a mean age of 2.4 years (range 1 to 19 years), arterial saturation (SaO2) ranged from 9.5 to 100%, and arterial oxygen tension (PaO2) from 16.4 to 128 mmHg. Linear correlation analysis of pulse oximetry vs measured SaO2 revealed an r value of 0.95 (p less than 0.001) with an equation of y = 21.1 + 0.749x, while PaO2 vs tcPO2 showed a correlation coefficient of r = 0.95 (p less than 0.001) with an equation of y = -1.04 + 0.876x. ⋯ Pulse oximetry was reliable at values above 65%, but was inaccurate and overestimated the arterial SaO2 at lower values. TcPO2 tended to underestimate the arterial value with increasing PaO2. Pulse oximetry had the best sensitivity to specificity ratio for hypoxia between 65 and 90% SaO2; for tcPO2 the best results were obtained between 35 and 55 mmHg PaO2.