Accuracy of pulse oximetry in pigmented patients.

Abstract

OBJECTIVE: Prospective assessment of the accuracy of three pulse oximeters and two probe sites in darkly pigmented critically ill patients under clinical conditions. PATIENTS AND METHODS: One hundred consecutive, darkly pigmented critically ill adult patients with arterial lines in situ were studied. Patients were excluded if the haemoglobin concentration was less than 7 g/dl and carboxyhaemoglobin or methaemoglobin levels exceeded 2%. Pigmentation was objectively quantified with a portable EEL reflectance spectrophotometer (Evans Electroselenium Company, Diffusion Systems Limited, London). Reflectance was measured at nine wavelengths. RESULTS: The degree of pigmentation as measured by percentage reflectance closely matched that of a control group of black Africans from a pigmentation study. The limits of agreement (2.6% to 5.8%), precision and bias values between pulse oximeter and co-oximeter readings fell within a narrow range. The 95% confidence intervals of the limits of agreement reflected a small variation in the difference between pulse oximeter and co-oximeter readings. These small differences were not clinically significant in the pigmented patients who were enrolled in the study. CONCLUSION: The accuracy of pulse oximetry is not adversely affected by skin pigmentation, and it remains a useful oxygenation monitoring device in darkly pigmented patients.