Artificial acrylic finger nails may alter pulse oximetry measurement

SummaryIntroductionPulse oximetry is the most common technique to monitor oxygen saturation (SpO2) during intensive care therapy. However, intermittent co-oximetry is still the “gold standard” (SaO2). Besides acrylic nails, numerous other factors have been reported to interfere with pulse oximetry. Data of measurements with artificial finger nails are not sufficiently published.Materials and methodsA prospective clinical-experimental trial in mechanically ventilated and critically ill patients of an ICU was performed. Patients were randomly assigned to either group S (S: Siemens pulse oximeter) or group P (P: Philips pulse oximeter) prior to the measurements. SpO2 was determined in each patient three times alternately in standard (NSpO2) and sideways position at the natural nail (N90SpO2). For the reference measurements oxygen saturation was measured by means of a haemoximeter (co-oximetry). Thereafter, SpO2 was obtained at the acrylic finger nail in the same way (ASpO2 and A90SpO2). Bias was calculated as ΔS = NSpO2 − SaO2 and ΔS = ASpO2 − SaO2. Accuracy (mean difference) and precision (standard deviation) were used to determine the measurement discrepancy. P < 0.05 was considered significant.ResultsAccuracy and precision without acrylic nails applied were comparable to SaO2 in both groups (n.s.). With acrylic nails applied a bias of ΔS = −1.1 ± 3.14% for group S (P = 0.00522) and a bias of ΔS = +0.8 ± 3.04% for group P was calculated (n.s.).ConclusionAcrylic finger nails may impair the measurement of oxygen saturation depending on the pulse oximeter used and may cause significant inaccuracy. Hence, removal of artificial acrylic finger nails may be helpful to assure an accurate and precise measurement with pulse oximetry.