Oxygen saturation monitoring in experimental surgery: A comparison of pulse oximetry and arterial blood gas measurement

Experimental surgery in animal models often requires prolonged periods of general anesthesia. Animals undergoing these procedures may have difficulty maintaining normal ventilation and oxygenation and therefore may require physiologic monitoring and endotracheal intubation to avoid hypoxia that could adversely affect the results of the investigation. Monitoring has traditionally included measurements of PaO₂, PCO₂, pH, and oxygen saturation calculated from arterial blood. Endotracheal intubation and placement of arterial catheters necessary for the intraoperative collection of specimens for blood gas analysis are labor-intensive and time-consuming. In this study, rats undergoing thoracic laminectomy as part of a study on spinal cord injury were monitored by noninvasive pulse oximetry, with a reflectance transducer placed on the skin/fur of the neck overlying the cervical carotid artery. Comparison of these data with intermittent arterial blood gas measurements in the same animals indicated >90% concordance with the pulse oximetry values. We also determined the fraction of inspired oxygen (FiO₂) that, delivered via facemask, can achieve at least the minimal normal oxygen saturation (SaO₂) of 90%. These findings suggest that physiologic monitoring during experimental rodent surgery can be substantially simplified by pulse oximetry and by delivery of oxygen via facemask, eliminating the need for arterial blood gas determinations or endotracheal intubation.