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Physiology of repeated mixed gas 100-m wreck dives using a closed-circuit rebreather: a field bubble study
Balestra, C.; Guerrero, F.; Theunissen, S.; Germonpré, P.; Lafère, P. (2022). Physiology of repeated mixed gas 100-m wreck dives using a closed-circuit rebreather: a field bubble study. Europ. J. Appl. Physiol. 122(2): 515-522. https://dx.doi.org/10.1007/s00421-021-04856-5
In: European Journal of Applied Physiology. Springer: Berlin. ISSN 1439-6319; e-ISSN 1439-6327, more
Peer reviewed article  

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Keyword
    Marine/Coastal
Author keywords
    Bubble detection; Bubbles; Decompression; Technical diving; Risk assessment; Echocardiography; Diving; Doppler; CCR

Authors  Top 
  • Balestra, C., more
  • Guerrero, F.
  • Theunissen, S., more

Abstract

    Purpose

    Data regarding decompression stress after deep closed-circuit rebreather (CCR) dives are scarce. This study aimed to monitor technical divers during a wreck diving expedition and provide an insight in venous gas emboli (VGE) dynamics.

    Methods

    Diving practices of ten technical divers were observed. They performed a series of three consecutive daily dives around 100 m. VGE counts were measured 30 and 60 min after surfacing by both cardiac echography and subclavian Doppler graded according to categorical scores (Eftedal–Brubakk and Spencer scale, respectively) that were converted to simplified bubble grading system (BGS) for the purpose of analysis. Total body weight and fluids shift using bioimpedancemetry were also collected pre- and post-dive.

    Results

    Depth-time profiles of the 30 recorded man-dives were 97.3 ± 26.4 msw [range: 54–136] with a runtime of 160 ± 65 min [range: 59–270]. No clinical decompression sickness (DCS) was detected. The echographic frame-based bubble count par cardiac cycle was 14 ± 13 at 30 min and 13 ± 13 at 60 min. There is no statistical difference neither between dives, nor between time of measurements (P = 0.07). However, regardless of the level of conservatism used, a high incidence of high-grade VGE was detected. Doppler recordings with the O’dive were highly correlated with echographic recordings (Spearman r of 0.81, P = 0.008).

    Conclusion

    Although preliminary, the present observation related to real CCR deep dives questions the precedence of decompression algorithm over individual risk factors and pleads for an individual approach of decompression.


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