Nail polish and pulse oximetry
To the Editor!
We have read the original contribution by Sutcu Cicek et al.  with high interest regarding the effect of nail polish and henna on pulse oximetry readings. In their study, these authors report on the influence of both factors in 33 normoxic healthy females. Although the study is interesting, it has significant limitations, which must be addressed. To our surprise, the authors state, it is not proven that nail polish effects the accuracy of pulse oximeters . However, several randomized, controlled trials with both healthy persons and critically ill patients report on the effect of nail polish on oxygen saturation measured by pulse oximetry [2, 3, 4]. Interestingly, some of these studies have been cited by the authors themselves. Sample size calculation prior to beginning of a trial is obligate to determine the significance of results. Unfortunately, in this trial an adequate mathematical sample size calculation was obviously waived. Therefore, results of the present study cannot be interpreted regarding both the statistical significance and the clinical relevance. To determine pulse oximetry accuracy, intermittent arterial blood gas analyses (ABGA) are essential . However, accuracy in the present study was only determined by consecutive pulse oximeter measurements over a specific duration, which may alter pulse oximetry readings. A major limitation of the present study is that accuracy is not analyzed in the present study although it is most important in patients who have nail polish applied, e.g. to identify hypoxia. The authors only report on mean values (given in percent) but omit to verify their measurements, e.g. with ABGA. Additionally, the presented results also lack standard deviation (SD). Independently, one may assume that the presented differences (max. 1,25%) are not clinically relevant, which is in congruency to other publications [2, 3, 4]. In the present trial one may therefore speculate the differences identified might be due to slightly alternating oxygen saturation values in spontaneously breathing persons. In conclusion, the present study does not add significant new data for nail polish to the present knowledge.
 Sutcu Cicek H, Gumus S, Deniz O, Yildiz S, Acikel CH, Cakir E, Tozkoparan E, Ucar E, Bilgic H. Effect of nail polish and henna on oxygen saturation determined by pulse oximetry in healthy young adult females. Emerg Med J. 2010 Oct 5. [Epub ahead of print]
 Cote CJ, Goldstein EA, Fuchsman WH, et al. The effect of nail polish on pulse oximetry. Anesth Analg 1988;67:683
 Hinkelbein J, Genzwuerker HV, Sogl R, Fiedler F. Effect of nail polish on oxygen saturation determined by pulse oximetry in critically ill patients. Resuscitation. 2007 Jan;72(1):82-91
 Rodden AM, Spicer L, Diaz VA, Steyer TE. Does fingernail polish affect pulse oximeter readings? Intensive Crit Care Nurs. 2007 Feb;23(1):51-5.
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