A "pulse oximeter" operates by using light and a photocell tomeasure oxygen saturation in arterial blood. The transmission oflight energy as it passes through a solution of light-absorbingmolecules is described by the Beer-Lambert law, given below, whichgives the decrease in intensity I in terms of the distance L thelight has traveled through a fluid with a concentration C of thelight-absorbing molecule.
I = I010-eCL or log10(I / I0) = -eCL
The quantity e is called the extinction coefficient, and its valuedepends on the frequency of the light. (It has units of m2/mol.)Assume the extinction coefficient for 660-nm light passing througha solution of oxygenated hemoglobin is identical to the coefficientfor 940-nm light passing through deoxygenated hemoglobin. Alsoassume also that 940-nm light has zero absorption (e = 0) inoxygenated hemoglobin and 660 nm light has zero absorption indeoxygenated hemoglobin. If 30% of the energy of the red source and79% of the infrared energy is transmitted through the blood, whatis the fraction of hemoglobin that is oxygenated?
%???
A "pulse oximeter" operates by using light and a photocell tomeasure oxygen saturation in arterial blood. The transmission oflight energy as it passes through a solution of light-absorbingmolecules is described by the Beer-Lambert law, given below, whichgives the decrease in intensity I in terms of the distance L thelight has traveled through a fluid with a concentration C of thelight-absorbing molecule.
I = I010-eCL or log10(I / I0) = -eCL
The quantity e is called the extinction coefficient, and its valuedepends on the frequency of the light. (It has units of m2/mol.)Assume the extinction coefficient for 660-nm light passing througha solution of oxygenated hemoglobin is identical to the coefficientfor 940-nm light passing through deoxygenated hemoglobin. Alsoassume also that 940-nm light has zero absorption (e = 0) inoxygenated hemoglobin and 660 nm light has zero absorption indeoxygenated hemoglobin. If 30% of the energy of the red source and79% of the infrared energy is transmitted through the blood, whatis the fraction of hemoglobin that is oxygenated?
%???
