Usefulness of the pulse oximeter as a respiratory monitor during intravenous sedation.

During intravenous sedation, the pulse oximeter was applied as a respiratory monitor to 17 patients (Physical status classification of the American Society of Anesthesiologists, Class I-II) who were to have oral surgical operations, and the changes in arterial saturation of oxygen (SaO2) was observed consecutively. SaO2 dropped after administration of sedative agents in each case; there was some individual variation. Respiratory depression during sedation was evaluated from arterial blood gas analysis. The reduction in SaO2 caused by surgical manipulations was also noted. Furthermore, arterial partial pressures of oxygen (PaO2) and saturation calculated from PaO2 (SAT) measured from blood gas analysis were compared with SaO2 measured by the pulse oximeter. Both PaO2 and SAT correlated well with SaO2. The differences between SAT and SaO2 exceeded the range of error (+/- 2%) in many cases after the administration of sedative agents. These results suggest that the pulse oximeter is useful as a respiratory monitor during oral surgery. However, the pulse oximeter gives incorrect SaO2 readings in the presence of abnormal hemoglobin due to medication with nitrites or smoking habit.