Narcotic Nitrogen Effects Persist after a Simulated Deep Dive.

: Scuba divers often experience persistent inert gas narcosis (IGN) even after surfacing. This study aimed to test the hypothesis that breathing oxygen (O) before surfacing can reduce postdive IGN. : A group of 58 experienced divers underwent a 5 min dive at a depth of 50 m in a multi-place hyperbaric chamber. They were decompressed using air (air group). Another group of 28 divers (O group) breathed 100% O during the end of decompression. Prior to and after the dive, all participants performed the Sharpened Romberg test (SRT) and a modified tweezers test. : In the air group, the number of positive SRT results increased postdive (47% vs. 67%), indicating a greater impairment in the vestibular system (Cohen's d = 0.41). In the O group, the percentage of positive SRT results remained constant at 68% both before and after the dive. In terms of the modified tweezers test, the air group showed no significant change in the number of picked beads (40 ± 9 vs. 39 ± 7), while the O group demonstrated an increase (36 ± 7 vs. 44 ± 10) (Cohen's d = 0.34). : The results reveal that the SRT revealed a negative effect of nitrogen (N) on the vestibular system in the air group. The increased number of beads picked in the O group can be attributed to the learning effect, which was hindered in the air group. Consistent with our hypothesis, breathing O during decompression appears to reduce postdive IGN.