Recompression breathing 100% oxygen at six metres suppressed venous bubble counts after diving compared to 100% oxygen breathing at 1 ATA.

Clinical Bottom Line:
  1. 1. In-water recompression on oxygen at 1.6 ATA is more effective than oxygen breathing at 1 ATA in reducing venous bubble counts.
  2. 2. In-water recompression on oxygen might prevent decompression illness following high-risk dives or omitted decompression.

Citation:1. Blatteau, J-E, J-M Pontier. Effect of in-water recompression with oxygen to 6 msw versus normobaric oxygen breathing on bubble formation in divers. European journal of applied physiology 2009; 106(5):691-695.

Three-part Question:
Is in-water recompression breathing oxygen at 6msw more effective than normobaric oxygen in reducing post-dive venous circulating bubbles?

Search Terms:
DCS, recompression, normobaric oxygen

The Study:
Non-blinded randomized crossover trial with intention to treat
The study patients: 19 healthy military divers did three randomly ordered dives: one control dive (no specific intervention) and two intervention groups given oxygen within 10 minutes of surfacing. Doppler bubble detection done at 40, 60 and 80 min after surfacing.
Control group (N = 19; 19 analysed): 30 metre air dive for 30 minutes with a 9 minute stop at 3 metres. No specific intervention.
Experimental group (N = 19; 19 analysed): Same air dive. Two active groups: 1) normobaric oxygen breathing for 30 minutes, beginning 10 minutes after surfacing; 2) 1.6 ATA oxygen breathing by immersion on 100% oxygen for same time.

The Evidence:

Outcome
Control Group
Experimental Group
Difference
95% CI
Mean
SD
Mean
SD
KISS for control versus 1 ATA oxygen
25.53
18.92
8.52
13.27
17.01
6.26 to 27.76
KISS for control versus 1.6 ATA oxygen
25.53
18.92
0.23
0.46
25.30
16.50 to 34.11
KISS for 1 ATA versus 1.6 ATA oxygen
8.52
13.27
0.23
0.46
8.29
2.11 to 14.47

Comments:
1.) Spencer gradings were not analysed. Despite the authors statement, KISS results were not given as mean and standard deviation. Friedman test not applied as stated.
2.) No sample size calculation but statistical significance evident so a moot point. Text and tables do not fully agree.

Appraised by: Tobias Cibis, Mike Bennett, HBOEvidence Working Group, Sydney, 22.07.2016





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