title: Effects of successive air and trimix dives on human cardiovascular function.
abstract: BACKGROUND
  The use of trimix (a mixture of oxygen, helium, and nitrogen) has significantly increased among the diver population. However, data indicating how trimix dives at most common depths affect the cardiovascular function are sparse. The purpose of this study was to investigate the cardiovascular effects of trimix dives and compare them with air dives and to determine whether the repetition of dives in successive days affects their extent.
  
  
  METHODS
  Nine professional divers performed four dives in consecutive days where the dive depth was progressively increased to the maximum of 55 m. Divers used air in the first dive, nitrox 25 in the second, and trimix 20/30 in the third and fourth dives. Echocardiography was performed before and after each dive.
  
  
  RESULTS
  After each dive, a significantly decreased left ventricular ejection fraction and fractional shortening and an increased end-systolic volume without a change in end-diastolic volume were found, indicating a depressed systolic function of the left side of the heart. Assessment of the ratio between pulmonary artery acceleration time and right ventricular ejection time (used as an indicator of pulmonary artery pressure (PAP)) revealed an increase in PAP after all the dives. No physiologically relevant cumulative effects of the multiple dives or signs of acclimatization were found.
  
  
  CONCLUSIONS
  The current study shows that the cardiovascular effects of trimix dives do not differ from those of the dives with compressed air. However, it suggests that even a very safe and conservative trimix diving profile exerts significant cardiovascular effects.
authors.affiliation: Department of Physiology, University of Split School of Medicine, Split, Croatia.
authors.forename: Jasna
authors.initials: J
authors.lastname: Marinovic
authors.forename: Marko
authors.initials: M
authors.lastname: Ljubkovic
authors.forename: Ante
authors.initials: A
authors.lastname: Obad
authors.forename: Darija
authors.initials: D
authors.lastname: Bakovic
authors.forename: Toni
authors.initials: T
authors.lastname: Breskovic
authors.forename: Zeljko
authors.initials: Z
authors.lastname: Dujic
mesh_terms: D000328:Adult; D001794:Blood Pressure / Q000502:physiology; D002320:Cardiovascular Physiological Phenomena / Q000187:drug effects*; D004242:Diving / Q000502:physiology*; D004452:Echocardiography; D006371:Helium / Q000494:pharmacology*; D006801:Humans; D008875:Middle Aged; D009584:Nitrogen / Q000494:pharmacology*; D010100:Oxygen / Q000494:pharmacology*; D055815:Young Adult
chemical_list: D006371:Helium; C045257:trimix; D009584:Nitrogen; D010100:Oxygen