(bă-rĭs′ĭ-tĭ)
[Pronunciation]

The relative pressure, density, or concentration of a gas or a solution.
Hyperbaric solutions have an increased density relative to a reference substance (e.g., hyperbaric oxygen has a greater oxygen concentration than the air we normally breathe). Hypobaric solutions are less concentrated than a reference solution (e.g., an injected drug can be made hypobaric relative to serum or plasma by diluting it with sterile water).