Altitude<unk> or hypobaric<unk> is the reduction in ambient pressure below the normal range of sea level atmospheric pressure. Altitude<unk> is the natural consequence of unprotected elevation to altitude, while hypobaric<unk> is due to intentional or unintentional release of pressurisation of a pressure suit or pressurised compartment, vehicle or habitat, and may be controlled or uncontrolled, or the reduction of pressure in a hypobaric chamber. Altitude<unk> may occur as a<unk> from saturation at a lower altitude, or as<unk> from an excursion to a lower altitude, in the case of people living at high altitude, making a short duration trip to low altitude, and returning.<unk> has physical effects on gas filled spaces and on liquids, particularly when they contain dissolved gases. Physiological effects of<unk> are due to these physical effects and the consequential effects on the living tissues, mostly as a result of the formation and growth of bubbles, and the expansion of gas filled spaces. Formation and growth of bubbles due to reduced pressure can be due to reduction in solubility of dissolved gases as described by Henry's Law, with nucleation and growth of bubbles in supersaturated liquids, or due to boiling of liquids when the pressure is reduced below the vapour pressure for the temperature of the liquid. There are three principal physiological effects arising from<unk> at altitude: *<unk> illness, which includes *<unk> sickness due to bubble formation in the tissues similar to those caused by<unk> after exposure to pressures higher than sea level atmospheric pressure. There is little evidence of altitude<unk> sickness occurring among healthy individuals at altitudes below , but it can occur at lower altitudes in underwater divers with sufficient residual inert gas tissue loading after recent divers. * Barotrauma caused by the over-expansion of gas-filled spaces. * Altitude sickness, also known as acute mountain sickness (AMS), altitude illness, hypobaropathy, or soroche, is a pathological effect of high altitude on humans, caused by acute exposure to low partial pressure of oxygen and respiratory alkalosis arising from low partial pressure of blood carbon dioxide caused by hyperventilation. Abrupt excursions from sea level to altitudes above without oxygen prebreathing may induce venous gas bubbles, with a 5% probability of symptoms developing at about , at which altitude there is over 50% probability of venous bubbles. By the incidence of venous bubbles exceeds 70%, with a 55% incidence of DCS. These effects may be prevented or delayed by more gradual<unk> or by flushing some of the nitrogen from the tissues before<unk> by prebreathing a high percentage of oxygen before and during<unk>
Decompression 
Perfusion
Infiltration analgesia
Corticotomy
Massage
Infusion therapy
Diaphragm pacing
Rewarming shock