title: The effects of increased pressure, variation in inspired gases and the use of a mask during dry chamber dives on salivary cortisol in professional divers.
abstract: BACKGROUND
  Stress activates the hypothalamic-pituitary-adrenal axis resulting in measurable changes in hormone levels in blood or saliva in humans. We aimed to find out if professional divers expressed any change in salivary cortisol levels during a simulated dive to 608 kPa (50 metres' sea water) in a hyperbaric chamber. Furthermore, we investigated the effect of wearing a mask or modifying the breathing gas during decompression.
  
  
  METHODS
  We investigated 89 Navy and Coast Guard male divers. The divers were randomised into three groups for decompression by inspired gas and the use of a mask. The saliva samples were collected before and approximately 3 minutes after the hyperbaric test.
  
  
  RESULTS
  Salivary cortisol levels decreased from a mean (SD) of 16.0 (8.1) mmol per L pre-dive to 10.3 (5.0) mmol per L post-dive (P < 0.01). Cortisol values did not relate to the anthropometric and physical fitness characteristics of the divers or to increased pressure, variation in inspired gases or the use of a mask. The individual variation in cortisol values was large.
  
  
  CONCLUSIONS
  This finding is in line with previous studies demonstrating large individual variations in salivary cortisol. Our findings suggest that professional divers are well adapted to these hyperbaric conditions. However, there continues to be a need to identify divers sensitive to stress caused by diving and the hyperbaric environment.
authors.affiliation: Diving Medical Centre, Centre for Military Medicine, Kirkkonummi, Finland and Department of Physiology, University of Helsinki, Finland. SLK, PL5, FIN-02471 Upinniemi, Finland. Phone: +358-(0)299-581-551, E-mail: janne.tikkinen@mil.fi.
authors.forename: Janne
authors.initials: J
authors.lastname: Tikkinen
authors.forename: Ari
authors.initials: A
authors.lastname: Hirvonen
authors.forename: Kai
authors.initials: K
authors.lastname: Parkkola
authors.forename: Martti A
authors.initials: MA
authors.lastname: Siimes
mesh_terms: D003664:Decompression; D004242:Diving; D005740:Gases; D006801:Humans; D006854:Hydrocortisone / Q000097:blood; D007030:Hypothalamo-Hypophyseal System; D008397:Masks; D010913:Pituitary-Adrenal System
chemical_list: D005740:Gases; D006854:Hydrocortisone