Hyperbaric: Pertaining to gas pressures greater than 1 atmosphere* of pressure. Also pertaining to solutions that are more dense than the medium to which they are added. The term "hyperbaric" is derived from Greek roots: "hyper-" meaning high, beyond, excessive, above normal + "baros" meaning weight.
Hyperbaric oxygenation is an increased amount of oxygen in organs and tissues resulting from the administration of oxygen in a compression chamber at an ambient pressure greater than 1 atmosphere* of pressure.
Hyperbaric solutions in spinal anesthesia are solutions that have a density greater than that of spinal fluid.
*An atmosphere is a unit of pressure taken to be the standard pressure of the earth's atmosphere at sea level. An atmosphere is equal to the pressure of a column of mercury 760 mm high and expressed as 101.325 kilopascals (1.01325 × 105 newtons per square meter), or about 14.7 pounds per square inch.