BACKGROUND AND OBJECTIVES: Peripheral oxy-hemoglobin saturation (SpO2) is commonly used to guide ventilator settings. SpO2 values equal to, or higher than 96% are necessary to assure arterial oxy-hemoglobin saturation (SaO2) higher than 90% in intensive care patients. This study aimed to determine SpO2 - SaO2 gap and to establish the lowest SpO2 associated to SaO2 values equal to, or higher than 90%. METHODS: Participated in this prospective study 120 adult patients of both genders submitted to general anesthesia and mechanical ventilation or under intensive care. Arterial blood samples were obtained by arterial puncture or central line aspiration using the anaerobic technique and heparin-containing syringes. Samples were analyzed immediately after collection. SpO2 was measured during collection with the pulse oximeter placed on the opposite second finger and using arterial pulse dichroic wave as the adequacy parameter. RESULTS: Two hundred and twenty-eight samples were analyzed. The difference between SpO2 and SaO2 ranged between -7.10% and 15.2%, being -0.20% ± 2.02% the mean difference (bias). SpO2-SaO2 higher than 4.04% (two standard deviations of the difference) was observed in 4.72% of samples. Graphical analysis of the lowest SpO2 to assure an SaO2 higher than 90% has shown that only SpO2 values equal to, or higher than 99% were not associated to SaO2 values below 90%. CONCLUSIONS: Although SpO2-SaO2 gap remaining between plus or minus 5% for 97% of the samples, only SpO2 values higher than 99% excluded patients with SaO2 values below 90%.
MONITORING; VENTILATION
