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Enriched Air Nitrox Breathing Reduces Venous Gas Bubbles after Simulated SCUBA Diving: A Double-Blind Cross-Over Randomized Trial.

Souday V, Koning NJ, Perez B, Grelon F, Mercat A, Boer C, Seegers V, Radermacher P, Asfar P - PLoS ONE (2016)

Bottom Line: Weak correlations were observed between bubble scores and age or body mass index, respectively.When using similar diving profiles and avoiding oxygen toxicity limits, EAN increases safety of diving as compared to compressed air breathing.ISRCTN 31681480.

View Article: PubMed Central - PubMed

Affiliation: Department of Medical Intensive Care and Hyperbaric Medicine, University Hospital, Angers, France.

ABSTRACT

Objective: To test the hypothesis whether enriched air nitrox (EAN) breathing during simulated diving reduces decompression stress when compared to compressed air breathing as assessed by intravascular bubble formation after decompression.

Methods: Human volunteers underwent a first simulated dive breathing compressed air to include subjects prone to post-decompression venous gas bubbling. Twelve subjects prone to bubbling underwent a double-blind, randomized, cross-over trial including one simulated dive breathing compressed air, and one dive breathing EAN (36% O2) in a hyperbaric chamber, with identical diving profiles (28 msw for 55 minutes). Intravascular bubble formation was assessed after decompression using pulmonary artery pulsed Doppler.

Results: Twelve subjects showing high bubble production were included for the cross-over trial, and all completed the experimental protocol. In the randomized protocol, EAN significantly reduced the bubble score at all time points (cumulative bubble scores: 1 [0-3.5] vs. 8 [4.5-10]; P < 0.001). Three decompression incidents, all presenting as cutaneous itching, occurred in the air versus zero in the EAN group (P = 0.217). Weak correlations were observed between bubble scores and age or body mass index, respectively.

Conclusion: EAN breathing markedly reduces venous gas bubble emboli after decompression in volunteers selected for susceptibility for intravascular bubble formation. When using similar diving profiles and avoiding oxygen toxicity limits, EAN increases safety of diving as compared to compressed air breathing.

Trial registration: ISRCTN 31681480.

No MeSH data available.


Related in: MedlinePlus

Intravascular bubble scores.Intravascular bubble scores at T0 (Panel A), T30 (Panel B), T60 (Panel C) and T90 (Panel D) for all individuals undergoing both air and enriched air nitrox dives. All panels were tested with Wilcoxon tests adjusted for multiple comparisons by the Hochberg method.
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pone.0154761.g003: Intravascular bubble scores.Intravascular bubble scores at T0 (Panel A), T30 (Panel B), T60 (Panel C) and T90 (Panel D) for all individuals undergoing both air and enriched air nitrox dives. All panels were tested with Wilcoxon tests adjusted for multiple comparisons by the Hochberg method.

Mentions: Fig 3 shows the individual pulmonary artery bubble scores for the randomized dives immediately (Panel A) as well as 30 (Panel B), 60 minutes (Panel C), and 90 minutes (Panel D) post decompression. EAN breathing markedly reduced the number of bubbles at all time points, the maximum difference being present at 30 (0 [0–1] vs. 2 [1–3]; P = 0.008), 60 (0 [0–1] vs. 2 [1–3]; P = 0.008), and 90 minutes post-decompression (0 [0–1] vs. 2 [1.25–3]; P = 0.008). Consequently, EAN lowered the total bubble load following decompression as assessed by the sum of the four consecutive bubble scores (1 [0–3.25] vs. 8 [4.75–9.5]; P = 0.008). A Koch rank test for grouped and repeated measures over the four time points showed a significant difference between groups (P = 0.0062; Fig 4).


Enriched Air Nitrox Breathing Reduces Venous Gas Bubbles after Simulated SCUBA Diving: A Double-Blind Cross-Over Randomized Trial.

Souday V, Koning NJ, Perez B, Grelon F, Mercat A, Boer C, Seegers V, Radermacher P, Asfar P - PLoS ONE (2016)

Intravascular bubble scores.Intravascular bubble scores at T0 (Panel A), T30 (Panel B), T60 (Panel C) and T90 (Panel D) for all individuals undergoing both air and enriched air nitrox dives. All panels were tested with Wilcoxon tests adjusted for multiple comparisons by the Hochberg method.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4862661&req=5

pone.0154761.g003: Intravascular bubble scores.Intravascular bubble scores at T0 (Panel A), T30 (Panel B), T60 (Panel C) and T90 (Panel D) for all individuals undergoing both air and enriched air nitrox dives. All panels were tested with Wilcoxon tests adjusted for multiple comparisons by the Hochberg method.
Mentions: Fig 3 shows the individual pulmonary artery bubble scores for the randomized dives immediately (Panel A) as well as 30 (Panel B), 60 minutes (Panel C), and 90 minutes (Panel D) post decompression. EAN breathing markedly reduced the number of bubbles at all time points, the maximum difference being present at 30 (0 [0–1] vs. 2 [1–3]; P = 0.008), 60 (0 [0–1] vs. 2 [1–3]; P = 0.008), and 90 minutes post-decompression (0 [0–1] vs. 2 [1.25–3]; P = 0.008). Consequently, EAN lowered the total bubble load following decompression as assessed by the sum of the four consecutive bubble scores (1 [0–3.25] vs. 8 [4.75–9.5]; P = 0.008). A Koch rank test for grouped and repeated measures over the four time points showed a significant difference between groups (P = 0.0062; Fig 4).

Bottom Line: Weak correlations were observed between bubble scores and age or body mass index, respectively.When using similar diving profiles and avoiding oxygen toxicity limits, EAN increases safety of diving as compared to compressed air breathing.ISRCTN 31681480.

View Article: PubMed Central - PubMed

Affiliation: Department of Medical Intensive Care and Hyperbaric Medicine, University Hospital, Angers, France.

ABSTRACT

Objective: To test the hypothesis whether enriched air nitrox (EAN) breathing during simulated diving reduces decompression stress when compared to compressed air breathing as assessed by intravascular bubble formation after decompression.

Methods: Human volunteers underwent a first simulated dive breathing compressed air to include subjects prone to post-decompression venous gas bubbling. Twelve subjects prone to bubbling underwent a double-blind, randomized, cross-over trial including one simulated dive breathing compressed air, and one dive breathing EAN (36% O2) in a hyperbaric chamber, with identical diving profiles (28 msw for 55 minutes). Intravascular bubble formation was assessed after decompression using pulmonary artery pulsed Doppler.

Results: Twelve subjects showing high bubble production were included for the cross-over trial, and all completed the experimental protocol. In the randomized protocol, EAN significantly reduced the bubble score at all time points (cumulative bubble scores: 1 [0-3.5] vs. 8 [4.5-10]; P < 0.001). Three decompression incidents, all presenting as cutaneous itching, occurred in the air versus zero in the EAN group (P = 0.217). Weak correlations were observed between bubble scores and age or body mass index, respectively.

Conclusion: EAN breathing markedly reduces venous gas bubble emboli after decompression in volunteers selected for susceptibility for intravascular bubble formation. When using similar diving profiles and avoiding oxygen toxicity limits, EAN increases safety of diving as compared to compressed air breathing.

Trial registration: ISRCTN 31681480.

No MeSH data available.


Related in: MedlinePlus