The effect of henna paste on oxygen saturation reading obtained by pulse oximetry.

A controlled study was designed to examine the effect of red and black henna on the measurement of oxygen saturation by pulse oximetry. Fifty adult normal female volunteers had their left thumb coloured with red henna (40) or black henna (10). The uncoloured right thumb was used as a control. All measurements were done under room temperature, and the same pulse oximeter was used in all volunteers. In the red henna group there was no difference on oximetry reading between right and left thumb. In contrast, the thumb coloured with black henna gave no reading when compared to the uncoloured right thumb. On the basis of this study, pulse oximetry is not limited by red henna while black henna has a potential of causing major error in the measurement of oxygen saturation by pulse oximetry. In these cases we recommend to use ear oximetry for accurate measurement of oxygen saturation.