Why does the OxiFirst system use the 735-nm wavelength?
The 735nm wavelength light was selected for the red LED to improve the fetal pulse oximetry system’s performance at low oxygen saturations. The use of the 735-nm wavelength, when paired with 890 nm, results in a dramatically better balance between the two signals at the lower saturations typically seen in fetuses. Oxygen saturation readings become significantly less sensitive to normal physiological variations, such as tissue blood volume and pressure.1,2 At high oxygen saturations (>85%), such as those typically seen in adult pulse oximetry, signal absorption by the tissue at 660 nm is well matched to that at 890 nm, and the conventional choice of wavelengths is generally superior to those chosen for fetal monitoring.
