Ribicic
50% oxygen breathing during decompression, but not 99% oxygen breathing, was associated with significantly reduced flow-mediated dilatation in the brachial artery.
Clinical bottom line
|
1. 99% oxygen decompression reduced the bubble numbers after provocation |
Citation/s:1.Ribicic IŠ, Valic M, Božic J, Obad A, Glavaš D, Glavicic I, Valic Z. Influence of oxygen enriched gases during decompression on bubble formation and endothelial function in self-contained underwater breathing apparatus diving: a randomized controlled study. Croatian medical journal. 2019 Jun;60(3):265.
Three-part Clinical Question:For rebreather divers, does altering the proportion of oxygen in the breathing gas result in any differences in venous bubbling or endothelial function?
Search Terms: Rebreather; nitrrox; venous gas embolism
The Study:Non-blinded randomised controlled trial with intention-to-treat.
The Study Patients: Fit adult experienced divers with no significant comorbidities or history of decompression illness.
Control group (N = 10; 10 analysed): Air dive to 45msw with V-planner calculated decompression stops on air for a total dive time of 65 minutes.
Experimental group (N = 10; 10 analysed): Same bottom time and depth but V-planner calculated decompression stops with 50% oxygen (from 21 msw, total dive time 45 mins) and 99% oxygen (from 6 msw and total dive time 43 mons).
The Evidence:
Measure |
Air Group |
50% oxygen Group |
Difference |
95% CI | ||
Mean |
SD |
Mean |
SD | |||
|
Flow mediated vasodilatation (%) at 30 mins |
8.14 |
3.61 |
3.62 |
5.57 |
4.5 |
-16.2 to 25.2 |
Non-Event Outcomes |
Time to outcome/s |
Control group |
Experimental group |
P-value |
|
Bubble Grade after provocation with cough (Eftedal and Brubakk score) |
30 mins |
3 |
1 |
0.026 |
Comments:
1. Ten individuals did the three dives in a random order with one day off between each dive.
2. Brachial arterial flow mediated dilatation (FMD) was measured using % dilatation after a five minute occlusion of flow.
3, Bubble grade data analysed by Friedman repeated measures analysis of variance.
4. FMD difference was statistically significant between 50% oxygen and either of the other two conditions by two way repeated measures ANOVA with Tukey test, P=0.03 in the paper.
5. The FMD was expected to decrease further with 99% oxygen than 50% oxygen so this finding is surprising.
Appraised by:Mike Bennett m.bennett@unsw.edu.au; Monday, 21 December 2020
Kill or Update By: December 2022
