Return to an extreme environment exposure after pulmonary infection: SCUBA diving as a model?

The human body implements several adaptive mechanisms to perform in extreme environments. Increasingly, individuals return to such conditions after pulmonary infections, raising concerns about potential long-term respiratory consequences. This study aims to investigate the return to SCUBA diving after pulmonary infection, using COVID-19 as a model to provide evidence for safe reintegration into extreme environments, with a focus on vascular, oxidative and vascular stress. Twenty-three expert SCUBA divers who had symptomatic COVID-19 (SARS-CoV-2 Alpha variant) were enrolled as studied group (COV-19). None required intensive care, but all showed signs of lung inflammation. A control group (CTR) included nine male divers. They performed three dives at increasing depths (-10, -20, and -40 m). Lung function, nitric oxide derivatives (NOx), exhaled FeNO, oxidative stress biomarkers such as reactive oxygen species (ROS), 8-isoprostante, total antioxidant capacity (TAC) and TAC main components (albumin and uric acid), inflammatory response indicators including interleukin-6 (IL-6), IL-1beta, and tumor necrosis factor-alpha (TNF-alpha) and glycocalyx indexes were measured before and after each dive. No differences in FeNO, NOx, or lung function were observed between groups. However, COV-19 divers showed higher ROS, 8-isoprostane, IL-6, IL-1β, and TNF-α than the CTR divers, suggesting persistent inflammatory alterations. TAC remained unchanged. Significant differences emerged in glycocalyx markers. These results suggest an overall return to normal adaptation to diving after pulmonary infection. However, persistent inflammatory differences highlight the need for caution and personalized evaluation based on disease severity and recovery.