Germonpre
Some evidence that reducing the inspired nitrogen partial pressure during diving improves both cognition and fatigue during and after a simulated dive.
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Clinical bottom line: 1. Breathing oxygen enriched air resulted in better mathematical and trail-making test results for 30 minutes after a simulated dive. |
Citation/s:1. Germonpre P, Balestra C, Hemelryck W, Buzzacott P, Lafère P. Objective vs. subjective evaluation of cognitive performance during 0.4-MPa dives breathing air or nitrox. Aerospace medicine and human performance. 2017 May 1;88(5):469-75
Lead author's name and fax: Corresponding auth: Pierre Lafere pierre.lafere@chu.brest.fr
Three-part Clinical Question:For divers, does breathing enriched air nitrox, compared to air, result in improved cognitive performance while under water?
Search Terms: Cognition; Inert gas narcosis; safety
The Study:Double-blinded concealed randomised crossover controlled trial with intention-to-treat.
The Study Patients: Healthy adult trained divers, selected to be between 30 and 40 years, non-smokers of normal weight.
Control group (N = 8; 8 analysed): A compressed air dry dive in a compression chamber to 4 ATA (30 msw) for 22 minutes followed by a linear decompression.
Experimental group (N = 8; 8 analysed): As above but breathing 40% oxygen in nitrogen.
The Evidence:
Measure |
Air Group |
EANx Group |
Difference |
95% CI | ||
Mean |
SD |
Mean |
SD | |||
|
Time to completion of mathematical processing task at depth. (ms) |
1616 |
612 |
1523 |
694 |
93 |
-459,033 to 459,219 |
|
Time to completion of math processing task 30 mins after surfacing (ms)* |
1858 |
58 |
1495 |
639 |
363 |
-220.402 to 221,128 |
|
Fatigue at surfacing (% increase from baseline VAS)* |
135 |
50 |
103 |
50 |
32 |
-2,649 to 2,713 |
|
Fatigue at 30 minutes post dive (% increase from baseline VAS)* |
161 |
120 |
158 |
40 |
3 |
-8.577 to 8,583 |
*Reported in paper as statistically significant differences
Comments:
1. Blinded, crossover design. No evidence of a sample size calculation.
2. Formal testing suggested the divers could not distinguish between breathing gases.
3. Simulated (dry) diving may not fully reflect the situation when submerged in water.
4. The most remarkable finding is the persistence of differences between groups for at least 30 minutes after surfacing. Possible implications for the mechanism of inert gas narcosis.
Appraised by:Mike Bennett m.bennett@unsw.edu.au; Monday, 26 July 2021
Kill or Update By: July 2024
