[Respiratory changes in deep diving].

Deep diving refers to saturation diving to a depth of more than 180 m (1.9 MPa ambient pressure). In the 1990s diving to 400 m may be necessary on the Norwegian continental shelf. The safety margins are narrow and at such depths the respiratory system is subject to great strain. Respiratory resistance increases and the dynamic lung volumes are reduced as the pressure increases due to enhanced gas density. Helium is used together with oxygen as breathing gas and the lower density partly normalises the dynamic lung volumes. The respiratory system imposes clear limitations on the intensity and duration of physical work during deep diving. We lack systematic studies of lung mechanics, gas exchange and respiratory regulation in the different phases of deep dives. Demonstration of possible chronic occupational respiratory diseases connected to diving is dependent on follow-up over a long time.