Early detection of hypoxia-induced cognitive impairment using the king-devick test

Introduction: Hypoxic incapacitation continues to be a significant threat to safety and operations at high altitude. Noninvasive neurocognitive performance testing is desirable to identify presymptomatic cognitive impairment, affording operators at altitude a tool to quantify their performance and safety. Methods: There were 25 subjects enrolled in this study. Cognitive performance was assessed by using the King-Devick (K-D) test. The performance of the subjects on the K-D test was measured in normoxia followed by hypoxia (8% O 2 equivalent to 7101 m) and then again in normoxia. Results: K-D test completion time in hypoxia for 3 min was significantly longer than the Baseline Test (54.5±12.4 s hypoxic vs. 46.3 ± 10.4 s baseline). Upon returning to normoxia the completion time was significantly shorter than in hypoxia (47.6 ± 10.6 s post test vs. 54.5 ± 12.4 s hypoxic). There was no statistically significant difference between baseline test and post test times, indicating that all subjects returned to their normoxic baseline levels. S_pO₂ decreased from 98 ± 0.9% to 80 ± 7.8% after 3 min on hypoxic gas. During the hypoxic K-D test, S_pO₂ decreased further to 75.8 ± 8.3%. Conclusions: In this study the K-D test has been shown to be an effective neurocognitive test to detect hypoxic impairment at early presymptomatic stages. The K-D test may also be used to afford a reassessment of traditional measures used to determine hypoxic reserve time.