OBJECTIVE :
1. Find oxygen saturation formula
PROCEDURE :
- 1. The oxygen saturation is defined, as SaO2 (SPO2) and s a function of the concentration of the two forms of hemoglobin in the blood:
- The peak follower algorithm uses the differentiated Lowpass output sequence from the IR sensor as its input. The idea is to allow the Peak variable to follow these differentiated peaks and decay at a very slow rate. It works much like a filter capacitor in a power supply. It attempts to follow the peaks and decays very slowly producing an envelope that can be used to time the heartwave that is produce by the IR signal. This IR signal was chosen because its amplitude is greater that that of the RED source and it doesn’t vary as much as the RED sensor does.
- The peak follower is used to time the period of the heart wave and also set up a period for the RMS calculation of the AC portion of the signal. In the T1 handler, the AC signal is calculated by taking the difference between the Filtered Sensor output and the DC level (from the DC tracking algorithm). For example, the AC signal from the RED sensor is:
Rdiff = Rfilt – R_DC;
The RMS value is calculated for each sample of the Rdiff and accumulated using the statement:
Rsum = RDiff*RDiff + Rsum;
After the period is detected, the RMS value is calculated and Rsum set back to 0:
Rms = sqrt(Rsum/period);
Rsum = 0;
Once the RMS value is calculated, the SPO2 is calculated by finding the ratio R;
R = Rrms/RDC / Irrms/IRDC
Then,