Final answer:
In extremis refers to a critical medical state where patients require immediate intervention, such as those with severe Decompression Sickness (DCS) who experience joint pain, headaches, and vision issues. Treatment includes pure oxygen and the use of a hyperbaric chamber to safely repressurize the body and dilute nitrogen in the blood.
Step-by-step explanation:
The term 'in extremis' refers to patients who are at a high risk of death without immediate medical intervention. In the context of DCS, or Decompression Sickness, the most common symptoms are pain in the joints, headaches, and disturbances of vision. The immediate treatment for very severe DCS, which may lead to death if untreated, is the administration of pure oxygen, followed by relocation to a hyperbaric chamber.
The hyperbaric chamber is crucial in treating DCS as it repressurizes the body at a controlled pace, preventing a rapid decrease in pressure which can be harmful. Inside the chamber, the increased pressure allows for a higher concentration of oxygen in the blood. This dilutes the nitrogen levels, which is beneficial because oxygen is easier for the body to tolerate being out of solution.