Journal of oral and maxillofacial surgery : official journal of the American Association of Oral and Maxillofacial Surgeons
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J. Oral Maxillofac. Surg. · Jan 1987
Use of capnography and transcutaneous oxygen monitoring during outpatient general anesthesia for oral surgery.
The combination of the capnograph (respired CO2 monitor) and the transcutaneous oxygen monitor was evaluated as a non-invasive system for monitoring of respiratory function in 10 ASA class I patients undergoing ultralight general anesthesia for removal of third molars. Capnography proved to be a sensitive and accurate method for detecting apnea and airway obstruction using the continuous display of the CO2 waveform. All episodes of apnea or obstruction were immediately detected as the respired CO2 level fell to zero baseline. ⋯ During steady-state conditions of respiration, transcutaneous oxygen tensions (PtcO2) correlated well with simultaneously measured PaO2 (r = 0.93). However, during any period when oxygenation was rapidly changing (step increase in FIO2, step decrease in FIO2, or apnea) the PtcO2 lagged behind changes in PaO2 even after a five-minute equilibration period, thereby not accurately reflecting the true state of oxygenation. Consequently, the transcutaneous oxygen monitor does not appear to be optimal as a respiratory monitor in the setting of ultralight general anesthesia where rapid, critical changes in oxygenation must be detected without delay.