title: Exhaled nitric oxide concentration and decompression-induced bubble formation: An index of decompression severity in humans?
abstract: BACKGROUND
  Previous studies have highlighted a decreased exhaled nitric oxide concentration (FE NO) in divers after hyperbaric exposure in a dry chamber or following a wet dive. The underlying mechanisms of this decrease remain however unknown. The aim of this study was to quantify the separate effects of submersion, hyperbaric hyperoxia exposure and decompression-induced bubble formation on FE NO after a wet dive.
  
  
  METHODS
  Healthy experienced divers (n=31) were assigned to either (i) a group making a scuba-air dive (Air dive), (ii) a group with a shallow oxygen dive protocol (Oxygen dive) or (iii) a group making a deep dive breathing a trimix gas mixture (deep-dive). Bubble signals were graded with the KISS score. Before and after each dive FE NO values were measured using a hand-held electrochemical analyzer.
  
  
  RESULTS
  There was no change in post-dive values of FE NO values (expressed in ppb=parts per billion) in the Air dive group (15.1 ± 3.6 ppb vs. 14.3 ± 4.7 ppb, n=9, p=0.32). There was a significant decrease in post-dive values of FE NO in the Oxygen dive group (15.6 ± 6 ppb vs. 11.7 ± 4.7 ppb, n=9, p=0.009). There was an even more pronounced decrease in the deep dive group (16.4 ± 6.6 ppb vs. 9.4 ± 3.5 ppb, n=13, p<0.001) and a significant correlation between KISS bubble score >0 (n=13) and percentage decrease in post-dive FE NO values (r=-0.53, p=0.03).
  
  
  CONCLUSIONS
  Submersion and hyperbaric hyperoxia exposure cannot account entirely for these results suggesting the possibility that, in combination, one effect magnifies the other. A main finding of the present study is a significant relationship between reduction in exhaled NO concentration and dive-induced bubble formation. We postulate that exhaled NO concentration could be a useful index of decompression severity in healthy human divers.
authors.affiliation: Diving and Hyperbaric Department, French Navy Diving School, BP 311, 83800 Toulon, France.
authors.forename: J-M
authors.initials: JM
authors.lastname: Pontier
authors.affiliation: ORPHY Laboratory, PHYPODE Project, Université de Bretagne Occidentale, Brest, France; School of Sports Science, Exercise and Health, The University of Western Australia, Crawley, Western Australia 6009, Australia.
authors.forename: P
authors.initials: P
authors.lastname: Buzzacott
authors.affiliation: Assistance Publique Hôpitaux de Marseille AP-HM, 13000 Marseille, France.
authors.forename: J
authors.initials: J
authors.lastname: Nastorg
authors.affiliation: Assistance Publique-Hôpitaux de Paris, Université Paris Descartes, Hôpital Cochin, Service de Physiologie-Explorations Fonctionnelles, Paris, France.
authors.forename: A T
authors.initials: AT
authors.lastname: Dinh-Xuan
authors.affiliation: ORPHY Laboratory, PHYPODE Project, Université de Bretagne Occidentale, Brest, France. Electronic address: lambrechtskate@hotmail.com.
authors.forename: K
authors.initials: K
authors.lastname: Lambrechts
mesh_terms: D000328:Adult; D001944:Breath Tests; D003664:Decompression; D004242:Diving / Q000502:physiology*; D045853:Exhalation / Q000502:physiology*; D006801:Humans; D018496:Hyperoxia / Q000378:metabolism; D008297:Male; D009569:Nitric Oxide / Q000378:metabolism*; D010100:Oxygen / Q000378:metabolism; D055815:Young Adult
chemical_list: D009569:Nitric Oxide; D010100:Oxygen
keywords: Bubble formation; Decompression sickness; Exhaled nitric oxide; Hyperbaria; Hyperoxia; KISS score; Scuba diving