Oxidative balance in scuba divers

Underwater immersion may mimic hyperbaric conditions finally favouring some unwanted effects such as oxidative stress, which has been defined as an unbalance between pro-oxidative and antioxidant processes (1). However, although many observations suggest that inhaled oxygen under hyperbaric treatment may increase total oxidant status in humans (2), however no conclusive data are now available in apnea and self-contained underwater breathing apparatus (scuba) divers (3). The aim of this study was to evaluate globally oxidative balance in apnea and scuba divers in different immersions. Four apparently healthy professional divers, one apnea diver and three scuba divers were recruited. The athletes observed the appropriate programs of the immersion and the correct decompression time. Blood samples were collected from forearm vein before and after diving in three different immersions performed in three different days. Immediately after collecting the samples, oxidative balance was evaluated by performing on a dedicated photometer (FREE system) the Carratelli’s panel (Diacron International s. r. l., Grosseto, Italy) (4), which includes total oxidant status measurement by means of d-ROMs test (normal range 250 to 300 CARR U, where 1 CARR U is equivalent to 23.51 mol/L hydrogen peroxide) (5), serum ferric reducing activity quantification by means of BAP test (optimal value > 2200 mol/L reduced iron) (6) and serum total antioxidant barrier to hypochlorous induced oxidation by means of OXY-adsorbent test (optimal value >350 mmol HClO/L sample) (7). The results were expressed as mean ± SD. The comparison among data was performed by using the Student’s t Test. The differences were considered statistically significant for p<0.05. When the results of the tests before immersion were compared with that after immersion, in the apnea diver total oxidative balance did not change. In the scuba divers, d-ROMs test values remained unchanged (382.44±84.73 CARR U vs. 385.89±78.20 CARR U, respectively, p=0.77), while BAP test results significantly increased (2217,11±288,45 mol/L vs. 2413.56±362.93 mol/L reduced iron, respectively p=0.009) as well as OXY-adsorbent test values (461.44±56.28 mmol/L vs. 517.33 ± 81.80 mmol/L, respectively, p= 0.01). When the results of each diver were considered separately, before vs. after immersion, d-ROMs test result significantly increased only in one scuba. The herein reported evidence show that in apnea diver(s) repeated immersions do not change significantly oxidative balance; however no further general conclusions can be made because only one man was tested and this man showed an impaired oxidative balance at baseline. Most significantly, scuba divers showed after repeated immersion a significant increase of serum antioxidant capacity, as measured by means of both BAP test and OXY-adsorbent test; this datum, although preliminary, is in agreement with previous studies (3, 8, 9) and suggest that hyperbaric-like conditions may activate antioxidant defences in the light of the possible increase of oxidant threats. The Carratelli’s panel showed useful in the global assessment of oxidative stress in apnea and scuba diving who may be considered at risk for oxidative stress. Further studies should be performed in order to confirm the findings of this preliminary report.