Can methylene blue affect pulse oximeter readings?
Vital dyes, such as methylene blue, can cause erroneously low pulse oximetry readings due to absorption of light at 660 nm or 940 nm; however, these effects tend to be transient and resolve rapidly as the dyes are diluted and metabolized. Methylene blue has the greatest impact compared to other vital dyes as it absorbs significantly at 670 nm.
Ralston AC, Webb RK, Runciman WB. Potential errors in pulse oximetry. III: Effects of interferences, dyes, dyshaemoglobins and other pigments. Anaesthesia. 1991 Apr;46(4):291-5. doi: 10.1111/j.1365-2044.1991.tb11501.x. PMID: 2024749
Posted in Question Of The Day