Brebeck
Nitrox breathing did not significantly improve bubble scores after a dive, nor was improved cognition evident during the dive.
Clinical bottom line:
|
1. Weak evidence there were fewer bubbles after breathing nitrox. 2. Non-random evidence of more bubbles in female divers 3. No clear improvement in cognition with nitrox. |
Citation/s:1. Brebeck AK, Deussen A, Range U, Balestra C, Cleveland S, Schipke JD. Beneficial effect of enriched air nitrox on bubble formation during scuba diving. An open-water study. Journal of sports sciences. 2018 Mar 19;36(6):605-12. 2. Brebeck AK, Deussen A, Schmitz-Peiffer H, Range U, Balestra C, Cleveland S, Schipke JD. Effects of oxygen-enriched air on cognitive performance during SCUBA-diving–an open-water study. Research in sports medicine. 2017 Jul 3;25(3):345-56.
Lead author's name and fax: Anne-Kathrin Brebeck. Contact Jochen Schipke j.schipke@gmx.org
Three-part Clinical Question:For scuba diving, does breathing an oxygen reduced air mix compared to air result in fewer detectable venous bubbles after diving and better cognition during the dive?
Search Terms: Venous gas embolism; doppler; decompression
The Study:Double-blinded concealed randomised controlled trial with intention-to-treat.
The Study Patients: Adult volunteer divers
Control group (N = 54; 54 analysed): Air breathing during a standard dive to 24 msw for 62 minutes
Experimental group (N = 54; 54 analysed): Enriched air breathing of 28% oxygen (nitrox28) for the same dive.
The Evidence:
Outcome |
Time to Outcome |
Air group |
Nitrox group |
Relative risk reduction |
Absolute risk reduction |
NNT |
Bubble free after dive |
60 mins |
0.11 |
0.07 |
36% |
0.04 |
25 |
95% CIs: |
-97% to 211% |
-0.07 to 0.15 |
NNT = 15 to INF NNH = 7 to INF | |||
Number of errors in number connection test |
0.28 |
0.17 |
40% |
0.11 |
9 | |
95% CIs: |
-16% to 96% |
-0.04 to 0.27 |
NNT = 4 to INF NNH = 22 to INF | |||
Measure |
Air Group |
HBOT Group |
Difference |
95% CI | ||
Mean |
SD |
Mean |
SD | |||
|
Pooled bubble numbers per minute |
30 |
32 |
16 |
16 |
14 |
-230.1 to 258.1 |
|
Number connection test (secs) |
87 |
30.3 |
85.5 |
26.7 |
1.50 |
-309.6 to 312.6 |
Non-Event Outcomes |
Time to outcome |
Air group |
Nitrox group |
P-value |
|
Correct items remembered (short-term) |
30 seconds |
7.5 (4 to 12) |
8.0 (4 to 13) |
0.26 |
Comments:
1. All dives conducted as pairs and 38 were female.
2. Trial powered for one-sided statistical testing for a 25% reduction in subclavian bubbles with nitrox. The figure for that comparison is not given.
3. The authors exhaustively analyzed the data for differences between vein sites and time with few important differences noted.
4. There were more bubbles detected in males than females.
5. The authors report in the abstract, but not in results that "more bubbles were
counted in the air-group than in the air28-group (pooled vein: early: 1845 vs. 948; P = 0.047. One may get the feeling the authors are stretching for meaning here.
5. Cognitive testing done at depth. Air group made more mistakes connecting the numbers
Appraised by: Michael Bennett m.bennett@unsw.edu.au ; Monday, 13 April 2020 + 28 August 2020
Kill or Update By:April 2022
