[Usefulness of pulse oximetry in respiratory diseases]

The aim of the present study was to verify the usefulness and the limits of the pulse oximeter (po) in the management of patients with pulmonary disease. To this end oxyhemoglobin saturation measured with the po (SpO2) in 81 outpatients (mean age 67.7 +/- 12.7 years) was compared to oxyhemoglobin saturation calculated from a Radiometer computerized system (ScO2) and measured with a Co-oximeter (SaO2), considered as a reference value. Both SpO2 values and ScO2 values were, in average, significantly higher than SaO2 values (p < 0.001). In a multiple stepwise regression analysis, carboxyhemoglobin was the determinant of both SaO2-SpO2 and SaO2-ScO2 differences. The relationship between SpO2 values and the arterial gas data revealed that a wide range of PaO2 and PaCO2 values could be related to a narrow range of SpO2 values showing a clear variability of PaO2 and PaCO2 for the same value of SpO2. These findings seem to indicate that the po can be regarded as a simple, non-invasive, and non-expensive method to measure the oxyhemoglobin saturation with a sufficient reliability. The SpO2 values could be used in the management and follow-up of patients with hypoxemia, but SpO2 values could be misleading in presence of hypercapnia and/or hemoglobinopathies.