Comparison of pulseoximetry oxygen saturation and arterial oxygen saturation in open heart intensive care unit

Pulseoximetry is widely used in the critical care setting, currently used to
guide therapeutic interventions. Few studies have evaluated the accuracy of SPO2 (pulseoximetry
oxygen saturation) in intensive care unit after cardiac surgery. Our objective
was to compare pulseoximetry with arterial oxygen saturation (SaO2) during clinical
routine in such patients, and to examine the effect of mild acidosis on this relationship.
Methods: In an observational prospective study 80 patients were evaluated in intensive
care unit after cardiac surgery. SPO2 was recorded and compared with SaO2 obtained
by blood gas analysis. One or serial arterial blood gas analyses (ABGs) were performed
via a radial artery line while a reliable pulseoximeter signal was present. One hundred
thirty seven samples were collected and for each blood gas analyses, SaO2 and SPO2 we
recorded.
Results: O2 saturation as a marker of peripheral perfusion was measured by Pulseoximetry
(SPO2). The mean difference between arterial oxygen saturation and pulseoximetry
oxygen saturation was 0.12%±1.6%. A total of 137 paired readings demonstrated good
correlation (r=0.754; P<0.0001) between changes in SPO2 and those in SaO2 in samples
with normal hemoglobin. Also in forty seven samples with mild acidosis, paired
readings demonstrated good correlation (r=0.799; P<0.0001) and the mean difference
between SaO2 and SPO2 was 0.05%±1.5%.
Conclusion: Data showed that in patients with stable hemodynamic and good signal
quality, changes in pulseoximetry oxygen saturation reliably predict equivalent changes
in arterial oxygen saturation. Mild acidosis doesn’t alter the relation between SPO2 and
SaO2 to any clinically important extent. In conclusion, the pulse oximeter is useful to
monitor oxygen saturation in patients with stable hemodynamic.