Introduction: Pulse oximetry is the most common technique to monitor oxygen saturation (SpO(2)) during intensive care therapy. However, intermittent co-oximetry is still the "gold standard" (SaO(2)). 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 methods: A 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. SpO(2) was determined in each patient three times alternately in standard ((N)SpO(2)) and sideways position at the natural nail ((N90)SpO(2)). For the reference measurements oxygen saturation was measured by means of a haemoximeter (co-oximetry). Thereafter, SpO(2) was obtained at the acrylic finger nail in the same way ((A)SpO(2) and (A90)SpO(2)). Bias was calculated as DeltaS=(N)SpO(2)-SaO(2) and DeltaS=(A)SpO(2)-SaO(2). Accuracy (mean difference) and precision (standard deviation) were used to determine the measurement discrepancy. P<0.05 was considered significant.
Results: Accuracy and precision without acrylic nails applied were comparable to SaO(2) in both groups (n.s.). With acrylic nails applied a bias of DeltaS=-1.1+/-3.14% for group S (P=0.00522) and a bias of DeltaS=+0.8+/-3.04% for group P was calculated (n.s.).
Conclusion: Acrylic 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.