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Review of: Hinkelbein J, Genzwuerker HV, Sogl R, et al: "Effect of nail polish on oxygen saturation determined by pulse oximetry in critically ill patients." Resuscitation. 72(1):82-91, 2007.
The Science
Pulse oximetry has been around for many years, and when they first came out, we were all taught to remove the patient's nail polish to improve the accuracy of the reading. The authors of this study undertook an experiment to determine whether or not the presence of nail polish affects the reading.
They applied nine shades of nail polish to the fingers of patients in the critical care unit who also had arterial lines established. They then compared the oxygen saturation level with that obtained from direct analysis of arterial blood samples.
They found that black, purple, and dark blue resulted in the greatest deviation from the arterial measurement, but it was less than 2%, which is within the margin of error for the device as stated by the manufacturer. If the probe was rotated 90 degrees and applied side-ways on the finger, the effect of the darker colors was eliminated.
When there was a discrepancy between the pulse oximeter and measured levels, the pulse oximeter tended to underestimate the oxygen saturation.
Their conclusion was that the presence of nail polish did not significantly affect the reading, and that routine removal of nail polish is not necessary.
The Street
It is amazing that there are so many things we do in EMS that we simply have not applied any type of scientific scrutiny to. We have all had the unpleasant experience of opening nail polish removal packets to get rid of every bit of polish, only to find the reading is normal.
According to these researchers, this practice is not necessary. However, there are some limitations to this study that needed to be examined. All of their patients were white, normotensive and not hypoxic. They only tested one model of oximeter, the Seimans Nellcor device that emits two wavelengths of light. What, if any, effect these variables would have on the result are not known and should prompt additional research.
Before reading this study, I had never heard of rotating the probe to get a better reading. Those that have done this tell me that sometimes they don't get a good pulse wave indication with normal positioning, but that if the probe is rotated, the pulse wave improves and provides a reading.
