Human Performance Effects of Decreased Cerebral Tissue Oxygen Saturation Inducedby Various Levels of Mixed Oxygen/Nitrogen

摘要

Non-invasive measures of arterial oxygen saturation (SaO2) and regional cerebraloxygen saturation (rSO2) were recorded as hypoxic subjects' (N-11) performances were measured on a computer-based cognitive task. One objective was to correlate changes in rSO2 (Somanetics INOS 3100 cerebral oximeter) to changes to SaO2 (Nellco N-200 pulse oximeter). Each subject was instrumented with a cerebral oxysensor, a Nellcor RS-10 oxysensor and EEG electrodes for P300 evoked potential measurement. A Sternberg single-stimulus visual task was to evaluate performance. Hypoxic SaO2 levels of 90%, 80% and 70% were randomized across subjects, and attained using gas mixtures consisting of 12.8%, 11.8% and 10.9% oxygen corresponding to altitudes of 13,000, 15,000 and 17,000 feet. rS02 correlated with the downward trends of SaO2 during desaturation but showed slower return to normal, correlating with failure of subject CNS function to return to normal. There were significant differences in saturation and performance parameters between the 90% target mix and the others, but no consistent difference between the 80% and 70% mixes. CNS deficiencies persisted even though Sa02 had returned to normal.