As we have been studying oxygen for 250 years

Background: Military deep divers experience extreme environmental stressors, particularly with prolonged diving. Alterations such as hyperbaric conditions and variable O ₂ levels can prompt systemic/local oxidative stress (OxS) and elevated nitric oxide (NO ^. ) post-dive release, heightening the risk of inflammation and cardiovascular events. Yet, deep diving (e.g. saturation diving) can also lead to cognitive impairment, whose mechanisms remain largely elusive but relevant to determine. Methods: Three Deep Divers (Italian Navy-Comsubin), with an average age of 31.00 ± 2.64 years, carried out a technical surface-supplied bounce diving in open water (-89m) in the Mediterranean Sea. From them, we collected saliva and urine samples before diving (T0), after deep diving followed by water-surface decompression (T1), and after complete subemersion (T2). To assess for pro-inflammatory and stress conditions, we evaluated reactive oxygen species (ROS) production, DNA oxidation (8-OHdG), total antioxidant capacity (TAC), nitric oxide (NO ^. ) oxidation products, and the levels of interleukin-6, cortisol, brain-derived neurotrophic factor (BDNF), dopamine, and glutamate. Results: At T1, ROS production increased (+ 121%) and continued to increase just to T2, coupled to a continuous rise in 8-OHdG, and a contemporary decline in TAC. Simultaneously, cortisol levels increased while those of dopamine decreased (-27%). BDNF levels were also sizably elevated (+ 175%). Conversely, no changes in pro-inflammatory markers and NO concentrations were evident. Conclusions: Oxidative stress and neurotransmitter increase and/or decrease (according to biomarkers evaluated) occur post-deep diving, suggesting preventative strategies to mitigate cognitive impairment.

Background: Intermittent Hypoxic–Hyperoxic Training (IHHT) induces physiological adaptations. While its efficacy in athletic performance remains debated, IHHT improves health markers in pathological and geriatric populations. This Exploratory Pilot Study aimed to explore the safety and feasibility of two IHHT protocols through preliminary responses. Methods: Twelve healthy volunteers completed a 4-week intervention (two sessions/week, 45 min/session) combining IHHT simultaneously during low-intensity exercise. The study compared a Training Group (TG: 30 min hypoxia, 7.5 min normoxia, 7.5 min hyperoxia) with a Conditioning Group (CG: 15 min hypoxia, 22.5 min normoxia, 7.5 min hyperoxia). Outcomes assessed included cardiorespiratory parameters, Acute Mountain Sickness symptoms, Perceived Exertion, a comprehensive biochemical panel, systemic inflammation, oxidative stress, and renal status. Results: Both protocols were well-tolerated. The TG exhibited significantly greater oxygen desaturation than the CG (p = 0.048). Moreover, the CG demonstrated a significantly attenuated increase in Interleukin-6 (p = 0.021) compared to the TG. Additionally, preliminary variations highlighted an interesting reduction in lipid parameters (TC, LDL, and Apo A1/B ratios) in both groups, although these did not reach statistical significance after FDR correction. Conclusions: While both protocols proved feasible and safe, a more balanced hyperoxic-to-hypoxic exposure (CG) showed better acute physiological tolerability, attenuating cardiovascular strain and mitigating systemic pro-inflammatory responses compared to the unbalanced exposure (TG). Finally, the preliminary variations observed in lipid parameters provide a rationale that warrants further controlled investigations.