Recreational technical diving and its effects on respiration and working capacity.

Aim Oxidative stress is increased in recreational technical diving. In an explorative retrograde study we investigated the hypothesis that, (1) repetitive, multi-day dives with oxygen-enriched breathing gases will have an impact on physiological measures, (2) negative effects can be assessed within one week post-dive. Study Design Exploratory retrospective crossover study. Setting Open-water study. Participants Ten healthy experienced technical divers. Interventions Repetitive dives with oxygen-enriched breathing gases during a 5-days diving trip to the Adriatic Sea (Croatia). Outcome Measures Basic measures of medical examination, electrocardiography, echocardiography, body plethysmography, and spiroergometry. Results The divers (32±8 years; mean±SD) performed 11±4 dives. Static and dynamic pulmonary measures were slightly decreased after the trip. On the bicycle ergometer, arterial oxygen partial pressure (pO2) remained almost unchanged from rest to 300 W before the trip (87.5±7.9 vs 85.4±9.7 mmHg) it decreased after the trip (90.4 ±7.2 vs 81.8±8.2 mmHg; p<0.05). Peak oxygen uptake (at 300 W) was decreased after the trip (45.1±9.9 vs 41.7±9.8 ml/min; p<0.05). In parallel, the aerobic threshold was decreased (234±43 vs 186±39 W; p<0.05). Conclusions Pulmonary injury is not detected at rest but at substantial physical load on the bicycle. Even after maximum one week, pO2 at 300 W was decreased together with the pulmonary O2 uptake, thus decreasing the aerobic threshold. In conclusion: (1) Multi-day, repetitive tech dives seem to induce - at least transient - pulmonary injury. (2) Pauses during a diving trip or more conservative diving are recommended. (3) A major physiological study on open-water divers can be performed by one single medical practice with an adequately equipped laboratory. [ABSTRACT FROM AUTHOR]