The pulse oximeter: A non-invasive monitor of oxygenation during thoracic surgery

The pulse oximeter continuously and non-invasively measures arterial saturation. The objective of the current study was to assess the value of this monitor during thoracic surgery with one-lung ventilation. A total of 108 pulse oximeter saturation readings (SaO₂[O]) were compared with PaO₂ and calculated saturation (SaO₂[C]) values. Hypoxia (PaO₂ <70 mmHg) always resulted in a SaO₂(O) value below 95%. For the detection of hypoxia, the pulse oximeter had a sensitivity of 100%, a specificity of 91% and a predictability of 70%. The correlation between SaO₂(C) and SaO₂(O) was good (r = 0.895). In the samples with a PaO₂ below 100 mmHg the correlation between SaO₂(C) and SaO₂(O) was significantly better when the temperature was at least 36° C (r = 0.956 vs. r = 0.706; p < 0.005) or when the cardiac index was greater than 2.5 l/min/m² (r = 0.896 vs. r = 0.417; p < 0.01).