Introduction

In clinical practice, non-invasive techniques are used to measure peripheral oxygen saturation (SpO2). The most used zones to measure it are the fingers and the earlobe.

Aims and objectives

The objective of the study was to evaluate the correlation and concordance of arterial oxygen saturation (SaO2) measured by radial arterial blood gases and pulse oximetry according to the anatomical location and the device used.

Materials and methods

Diagnostic precision study in patients scheduled for regular follow-up for arterial blood gases. The SpO2 was obtained with the Nellcor N550® and Covidien Nellcor Bedside® pulse oximeters simultaneously with obtaining the blood gases. To evaluate the correlation, the Spearman coefficient was used and for concordance the Bland-Altman graphs and the analysis by intraclass correlation coefficients (ICC) were carried out.

Results

51 patients were included, 47% male, with a mean age of 70.2±2 years. The highest correlation was obtained with pulse oximetry measured on the finger by Nellcor N550® (Spearman's Rho = 0.74, p = 0.0001) and the lowest with the Covidien Nellcor Bedside® pulse oximeter measured on the ear (Spearman's Rho = 0.7, p = 0.0001). According to the Bland-Altman graph, the highest concordance was that of the Nellcor N550® device placed on the finger (-3.42; 4.77%). The rest of the graphs are presented in the image 1. The ICCs showed the same trend, the results are shown in the table 1.

Conclusions

The measurement with the highest correlation and concordance was obtained with the Nellcor N550® measured on the finger. Ear measurement tends to overestimate SpO2.