Risberg
No reduction in detectable venous bubbles in volunteer hyperbaric attendants with nitrox breathing or increased 100% oxygen breathing periods.
| 1. There were no important differences in the grade or frequency of venous bubbles detected between the three arms of the study. ** 2. There was no measured advantage to any of the three experimental profiles. |
- Citation/s:
1. Risberg J, Englund M, Aanderud L, Eftedal O, Flook V, Thorsen E. Venous gas embolism in chamber attendants after hyperbaric exposure. Undersea and Hyperbaric Medicine 2004;31(4):417-429.
Lead author's name and fax: Jan Risberg no contact given
- Three-part Clinical Question: For attendants during hyperbaric oxygen treatment sessions, does modification of the breathing gas, compared to air breathing, reduce the degree of venous bubbling associated?
Search Terms: Doppler bubble detection; decompression stress; occupational diving
- The Study: Double-blinded concealed randomised controlled trial with intention-to-treat.
The Study Patients: Volunteer females employed at the participating centres. Volunteers acted as their own controls.
Control group (N = 9; 9 analysed): Compression to 2.4 ATA over 15 minutes, followed by 95 minutes breathing air, then five minutes on 100% oxygen before decompression on 100% oxygen over seven minutes (routine group).
Experimental group (N = 10; 10 analysed): Two experimental groups. The same profile but with 10 minutes on 100% oxygen at 2.4 ATA and during the decompression over 14 minutes (revised group); and a third group that breathed 40.5% oxygen for three 30 minute periods at 2.4 ATA, but no 100% oxygen periods (Nitrox group).
- The Evidence:
| Outcome | Time to Outcome | Control group | Combined experimental groups | Relative risk reduction | Absolute risk reduction | NNT |
| VGE present after exposure (proportion) | 15 minutes | 0.67 | 0.80 | -20% | -0.13 | -8 |
| ^ | 95% CIs: | -79% to 39% | -0.53 to 0.26 | NNT 4 to INF; NNH 2 to INF |
- Comments:
1. Very small study of only 10 subjects. 2. The usefulness of using VGE detection to quantify decompression stress in this population is unclear. 3. Using a mathematical model, the authors calculated that the routine, revised and nitrox series would release 2.1, 1.3 and 1.6 µl gas/ml blood into the bubbles in the central venous blood. 4. The authors switched to monoplace chambers for routine treatment following this investigation
Appraised by: Mike Bennett m.bennett@unsw.edu.au; Tuesday, 6 December 2016
Kill or Update By: December 2021
