@@ -68,3 +68,5 @@ A few paths exist that may be worth pursuing, given the aforementioned concerns:
- Develop a calibration system that can be easily manufactured and deployed based on fundamental principles, i.e. one that does not need to be _itself_ calibrated. One could build a spinning hollow clear plastic wheel with two chambers and controlled thickness, with the chambers filled with various concentrations of a solution whose absorption spectrum closely matches that of blood at a given oxygenation level. The wheel would be spun to simulate the heartbeat, and different wheels would represent different SpO<sub>2</sub> values. The solution could be accurately mixed using basic laboratory equipment, such as a scale or a pipette.
- Design an automated calibration system that uses a camera and optical character recognition to gather SpO<sub>2</sub> values from a commercial or clinical instrument and build a calibration table for the low-cost device while it is simultaneously clipped to the patient. Caregivers could "train" the low-cost device prior to patient discharge so they can self-monitor for flare-ups or subsequent respiratory ailments.
- Develop a methodology for cheaply and accurately characterizing LEDs and other components in the low-cost sensor, so that a master calibration file from a clinical study can be propagated to other devices as is done by traditional manufacturers.
In all cases, a reasonable first step is to design and prototype a sensor with sufficient performance to measure $`R`$, the O<sub>2</sub>Hb / Hb ratio discussed above.
