A clinical evaluation of pulse oximetry during thoracic surgery

To evaluate the utility of pulse oximetry for monitoring oxygenation during thoracic surgery, pulse oximeter oxygen saturation (SpO₂) values from the Nellcor N-100 (Nellcor Inc, Haywood, CA) and Novametrix model 500 (Medical Systems Inc, Wallingford, CT) were compared with simultaneous arterial saturation values (SaO₂) in 20 patients. A total of 255 matched observations were recorded, and the data were divided for statistical analysis into preinduction of anesthesia and postinduction groups. The preinduction group showed a good correlation between SpO₂ and (SaO₂) values, with both pulse oximeters consistently overestimating the Sao, However, once anesthesia was induced, there was no longer any correlation for either of the pulse oximeters versus simultaneous (SaO₂) values, although on average, the SpO₂ values were significantly higher than the corresponding SaO₂ values. It was concluded that pulse oximetry is useful in following trends of oxygenation in patients with preexisting lung pathology undergoing thoracic surgery, but it cannot replace arterial blood gas sampling for the intraoperative management of respiratory function.