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Publications

Journal Article Comparative Study Ppublish 1 citation

PubMed: 42834697 DOI: 10.14814/phy2.71129

Heliox versus trimix in closed-circuit rebreather diving: A comparative study of pulmonary and decompression stress in male divers.

Physiol Rep 14(19):e71129

Authors: Emmanuel Gouin, Jérémy Orsat, Emmanuel Dugrenot, Rhiannon J Brenner, Géraldine Leman, Eléonore Bettacchioli, Michael Theron, Marie-Agnès Giroux-Metges, Erwan L'Her, François Guerrero

Affiliations

  • Univ Brest, Laboratory ORPHY EA 4324, IBSAM, Brest, France.
  • Anesthesiology, Perioperative and Intensive Care Units, CHU La Cavale Blanche, Brest, France.
  • Divers Alert Network, Durham, North Carolina, USA.
  • Lampe Joint Department of Biomedical Engineering, The University of North Carolina and North Carolina State University, Chapel Hill, North Carolina, USA.
  • Subaquatic Operational Research Team (ERRSO), Military Institute of Biomedical Research (IRBA), Toulon, France.
  • Univ Brest, Laboratory ORPHY EA 4324, IBSAM, Brest, France. Divers Alert Network, Durham, North Carolina, USA.
  • Immunology and Immunotherapy Laboratory, CHU Morvan, Brest, France.
  • Univ Brest, LBAI UMR 1227, Inserm, Brest, France.
  • Lung Function Unit, CHU La Cavale Blanche, Brest, France.
  • Medical Intensive Care Unit, CHU La Cavale Blanche, Brest, France.
  • Univ Brest, Laboratory LaTIM UMR 1101, Inserm, Brest, France.

Abstract

Closed-circuit rebreather (CCR) and helium-based breathing mixtures are widely used in technical diving. This study compared the effects of Heliox and Trimix on pulmonary function and decompression stress during CCR dives. Nineteen divers performed a standardized dive (50 ± 3 msw, 147 ± 10 min) using Heliox (16% O 2/84% He; n = 9) or Trimix (16% O 2/32% He/52% N 2; n = 10). Pre- and post-dive venous gas emboli (VGE), pulmonary function, lung ultrasound, heart rate variability, and inflammatory parameters were assessed. VGE were detected in all Heliox divers but in only 50% of Trimix divers. Heliox exhibited higher VGE counts 45 min post-dive than Trimix (12 [IQR 3-32] vs. 0 [IQR 0-6], p = 0.03); this difference disappeared by 90 min. No clinically significant pulmonary function changes were observed. Lung diffusion capacity decreased moderately regardless of breathing gas (-6% ± 7%). Lung ultrasound revealed minor transient B-line changes. Dive induced mild inflammatory responses, including neutrophilia and increased MRP8/14 in both groups. Heliox divers also showed transient complement activation alongside increased circulating platelets. CCR dives induced limited pulmonary stress, without gas-dependent differences. Although Heliox may promote a higher post-dive VGE burden and inflammatory responses, the relationship between these physiological effects and decompression sickness risk remains uncertain.

MeSH

Respiration, Stress, Physiological, Decompression, Diving