ABSTRACT
We investigated the effects on cerebral blood flow (CBF) of pure oxygen breathing exposure during dives in a group of professional divers, in both the normobaric (NBO) and the hyperbaric oxygen (HBO) breathing conditions. Using single photon emission computerized tomography (SPECT) and Tc-99m hexamethylpropylenamine oxime (HM-PAO), we studied 10 young divers and six normal volunteers. Divers were studied by SPECT in the NBO and HBO conditions, in two different sessions. The HBO state was obtained in a hyperbaric chamber at 2.8 ATA for 15 min. By ANOVA, we did not observe any significant difference in CBF distribution between controls and divers in both NBO and HBO conditions. By individual analysis, divers showed a decreased CBF in a total of 33 regions of interest (ROIs) during NBO and 46 ROIs during HBO with respect to control values. In particular, two divers showed a remarkable increase in the number of hypoperfused ROIs during HBO (+7 and +5 ROIs, respectively). Pure oxygen breathing exposure in young divers is associated with a patchy distribution of brain areas of hypoperfusion. This phenomenon is more pronounced in the HBO state than in the NBO state. Further studies on CBF are needed to help identify divers potentially prone to harmful oxygen effects.
Subject(s)
Brain/metabolism , Diving/physiology , Hyperbaric Oxygenation , Oxygen/administration & dosage , Tomography, Emission-Computed, Single-Photon , Adult , Brain/diagnostic imaging , Cerebrovascular Circulation/physiology , Humans , MaleABSTRACT
Considering previous studies on EEG brain mapping in the course of saturation dives, the authors studied the same standards of EEG performance during the compression phase of a saturation dive reaching -250 m. An increase of theta and beta rhythms was observed, especially in the midline anterior regions of the brain, during the entire compression period, while an increase of delta activity was noted only at -100 m. These results confirm our hypothesis that the compression profile is physiologically correct, because the EEG modifications decreased during the stay at maximum depth.
