Pulse oximetry has revolutionized noninvasive oxygen saturation (Spo2) monitoring. It is not an uncommon belief that fingernail polish may affect the accuracy of pulse oximetry. Indeed, Coteé and coworkers
also found that a blue color fingernail polish decreased Spo2 from 97 to 87%.
We undertook this study to determine whether measurement of Spo2 by a newer and widely used model of pulse oximeter (Biox 3740; Ohmeda; Louisville, CO) is affected by various fingernail polish colors. Ten different colors of Wet ‘n’ Wild (Pavion; Nyack-on-the-Hudson, NY) fingernail polish were used: red, yellow, dark blue, green, black, purple, fuchsia, light blue, brown, and white. In seven healthy subjects, each finger of the left hand was painted with a fingernail polish while the fingers on the right hand remained unpainted. Three readings were taken from each finger with the probe in the standard position (top-to-bottom, Fig 1, top, A) and in a side-to-side position (Fig 1, bottom, B).
The procedure was repeated with the next set of five colors after removal of the original set of colors. Combined measurements from the seven subjects were averaged, SEM calculated, and statistical significance determined by analysis of variance.
As shown in Figure 1, top, A, there was a small but consistent decrease of Spo2 with all the painted fingernails when the probe was in the top-to-bottom position. However, only the black or brown fingernails showed a small but statistically significant decrease in Spo2 when compared with their corresponding unpainted nails; for the black painted and corresponding unpainted fingernails, the means ± SEM were 93.9 ± 0.94% and 95.9 ± 0.06%, respectively (p < 0.05). For the brown painted and corresponding unpainted fingernails, the means ± SEM were 95.1 ± 0.46% and 97.0 ± 0.31%, respectively (p < 0.05). In contrast, when the probe was placed in the side-to-side position, there were no significant differences between painted and unpainted fingernails (Fig 1, bottom, B).
In summary, there was a small decrease in Spo2 (by approximately 2%) in fingernails painted with either brown or black fingernail polish when measured with the probe in the top-to-bottom position. However, placing the probe in a side-to-side position precluded any minor effects fingernail polishes may have on Spo2 and so may obviate the need to remove fingernail polish.