Effect of henna (mehndi) on pulse oximetry reading

Abstract

Introduction: Pulse oximetry is a frequently used and a non-invasive method for monitoring oxygen saturation in blood. It estimates arterial hemoglobin saturation by measuring the light absorbance of pulsating vascular tissue at two wavelengths which can be altered by various factors. Numerous factors could lead to inaccuracy or ambiguous information about oxygen saturation and might result in unwanted procedures. In many cultures, women decorate their fingernails and feet with henna. The purpose of this study was to determine the effect of henna on the measurement of oxygen saturation. Methods: 100 healthy females with a mean age of 19±1.0 years with normal oxygen saturation at room air were included into the study. Individuals with cardiovascular disorders like congenital heart disease, heart failure, any respiratory diseases were excluded from the study. Henna was applied to all the participants on the distal phalanx of left index finger (test) of the individuals and kept for 2 hours whereas right index finger was left empty as control. After 2 hours of application, henna was scrapped off from left finger. Oxygen saturation in addition to radial pulse was determined on both tested and control finger. Similarly, oxygen saturation and radial pulse was again determined on 2nd day as well as on the 7th day of application of henna on both tested and control finger and were statistically compared. Results: Our results revealed no alteration in radial pulse after henna application even after 07th day (p value more than 0.05 in all the cases). However, a change in oxygen saturation was observed after 2 hours of application of henna till 07th day. Nonetheless, it must be emphasized that an increase of saturation of this minor magnitude (average 0.67%) does not translate into a clinically important change. Conclusion: Application of natural henna does not cause any major error in measurement of oxygen saturation in young healthy individuals. Keywords: Oxygen saturation, Pulse oximetry, Henna, Monitoring, Errors