What is "decompression"

decompression \decompression\ n.

1. the process of experiencing decompression; the act or process of relieving or reducing pressure.

   Syn: decompressing.

2. the reduction of atmospheric pressure experienced by divers rising from deep water to the surface, thus reducing the concentration of dissolved atmospheric gases in the blood; -- especially applied to a gradual reduction of such pressure.

3. the process, analogous to sense 2, undergone by divers in a decompression chamber, in which an artificially high atmospheric pressure is gradually lowered to normal pressure.

4. a return to a normal, more relaxed state after a period of intense stress, psychological pressure, or urgent activity; -- of people.

5. (Computers) the process of converting digitally encoded data from a more compact (compressed) form to its original, larger size.

   Note: The process of compression and decompression may completely recover all of the original data (called lossless compression), or may lose some of the original data in order to achieve higher degress of compression (lossy compression). The latter is used especially with images or video data, which may be of very large size relative to text, and for which small changes may be imperceptible to the human eye. The JPEG data compression format is a lossy format.

1905, from de- + compression.

n. 1 The process of decompressing. 2 The restoration to atmospheric pressure of a person who has spent time under higher pressure (such as a diver) 3 (context medicine English) The relief of pressure on a body part by surgery

1. n. restoring compressed information to its normal form for use or display [ant: compression]

2. relieving pressure [syn: decompressing] [ant: compression]

Decompression has several meanings:

• Data decompression, the action of reversing data compression
• Decompression (altitude). the reduction of pressure and the related physiological effects due to increase in altitude or other equivalent reduction of ambient pressure below normal atmospheric pressure
• Decompression (comics), in comic book storytelling, is the stylistic choice to tell a story mainly by visuals, with few words
• Decompression (diving), the reduction in pressure and the process of allowing dissolved inert gases to be eliminated from the tissues during ascent from a dive. Also relating to decompression (diving):
  • Decompression algorithm, one of several algorithms used to compute decompression tables, or the decompression status of a diver in real-time using a dive computer, and for dive planning. These include:
    • Buhlmann decompression algorithm
    • Reduced gradient bubble model
    • Thalmann algorithm
    • Varying Permeability Model
  • Decompression buoy, a buoy that marks a diver's position when doing decompression stops
  • Decompression chamber, a pressurizable chamber used to prevent and/or treat decompression sickness
  • Decompression computer, also called a Dive computer or decompression meter, a device used by a scuba diver to measure the time and depth of a dive and compute a safe ascent profile.
  • Decompression practice, Techniques and procedures for decompression used by underwater divers
  • Decompression tables, Printed tabulated decompression schedules used to plan diving decompression
  • Decompression trapeze, a horizontal bar or bars suspended at the depth of intended decompression stops by buoys
  • Decompression sickness decompression sickness as a hazard in Scuba diving
  • Ratio decompression, A method for estimating a decompression schedule for a given set of breathing gases, based on time at depth.
• Decompression party, a party that occurs after an event or a party to unwind after a stressful period
• Decompression (physics), the release of pressure and the opposition of physical compression
• Decompression sickness, a condition arising from the formation and growth of bubbles of gas within the tissues of the body during and after depressurization
• Decompression theory, The study and modelling of physiological effects of decompression, including the development and testing of decompression algorithms
• Decompression (surgery), a procedure used to reduce pressure on a compressed structure, such as spinal decompression
• "Decompression" (The Outer Limits), an episode of the American television fiction series The Outer Limits
• Herniated disc decompression, a form of treatment for Spinal disc herniation, employed by chiropractors
• History of decompression research and development, History of R&D related to diving and altitude decompression
• Uncontrolled decompression, catastrophic reduction of pressure in accidents involving pressure vessels such as aircraft

In comics, decompression is a stylistic storytelling choice characterized by a strong emphasis on visuals or character interaction, which, in turn, usually leads to slower-moving plots.

The style is often used with widescreen comics.

"Decompression" is the 13th episode of season six of The Outer Limits. It first aired on July 30, 2000.

In physics, decompression refers to a reduction of pressure or compression, and to some extent to the consequences of a reduction of pressure. Decompression has the most obvious consequences when applied to gases or to liquids containing dissolved gases.

In medicine, Decompression refers to the removal or repositioning of any structure compressing any other structure.

Common examples include decompressive craniectomy (removal of part of the scull to relieve pressure on the brain), and spinal decompression to relieve pressure on nerve roots.

The decompression of a diver is the reduction in ambient pressure experienced during ascent from depth. It is also the process of elimination of dissolved inert gases from the diver's body, which occurs during the ascent, during pauses in the ascent known as decompression stops, and after surfacing until the gas concentrations reach equilibrium. Divers breathing gas at ambient pressure need to ascend at a rate determined by their exposure to pressure and the breathing gas in use. A diver who only breathes gas at atmospheric pressure when free-diving or snorkelling will not usually need to decompress, Divers using an atmospheric diving suit do not need to decompress as they are never exposed to high ambient pressure.

When a diver descends in the water the hydrostatic pressure, and therefore the ambient pressure, rises. Because breathing gas is supplied at ambient pressure, some of this gas dissolves into the diver's blood and is transferred by the blood to other tissues. Inert gas such as nitrogen or helium continues to be taken up until the gas dissolved in the diver is in a state of equilibrium with the breathing gas in the diver's lungs, at which point the diver is saturated for that depth and breathing mixture, or the depth, and therefore the pressure, is changed. During ascent, the ambient pressure is reduced, and at some stage the inert gases dissolved in any given tissue will be at a higher concentration than the equilibrium state and start to diffuse out again. If the pressure reduction is sufficient, excess gas may form bubbles, which may lead to decompression sickness, a possibly debilitating or life-threatening condition. It is essential that divers manage their decompression to avoid excessive bubble formation and decompression sickness. A mismanaged decompression usually results from reducing the ambient pressure too quickly for the amount of gas in solution to be eliminated safely. These bubbles may block arterial blood supply to tissues or directly cause tissue damage. If the decompression is effective, the asymptomatic venous microbubbles present after most dives are eliminated from the diver's body in the alveolar capillary beds of the lungs. If they are not given enough time, or more bubbles are created than can be eliminated safely, the bubbles grow in size and number causing the symptoms and injuries of decompression sickness. The immediate goal of controlled decompression is to avoid development of symptoms of bubble formation in the tissues of the diver, and the long-term goal is to avoid complications due to sub-clinical decompression injury.

The mechanisms of bubble formation and the damage bubbles cause has been the subject of medical research for a considerable time and several hypotheses have been advanced and tested. Tables and algorithms for predicting the outcome of decompression schedules for specified hyperbaric exposures have been proposed, tested and used, and in many cases, superseded. Although constantly refined and generally considered acceptably reliable, the actual outcome for any individual diver remains slightly unpredictable. Although decompression retains some risk, this is now generally considered acceptable for dives within the well tested range of normal recreational and professional diving. Nevertheless, all currently popular decompression procedures advise a 'safety stop' additional to any stops required by the algorithm, usually of about three to five minutes at , even on an otherwise continuous no-stop ascent.

Decompression may be continuous or staged. A staged decompression is interrupted by decompression stops at calculated depth intervals, but the entire ascent is actually part of the decompression and the ascent rate is critical to harmless elimination of inert gas. A no-decompression dive, or more accurately, a dive with no-stop decompression, relies on limiting the ascent rate for avoidance of excessive bubble formation. The elapsed time at surface pressure immediately after a dive is also an important part of decompression and can be thought of as the last decompression stop of a dive. It can take up to 24 hours for the body to return to its normal atmospheric levels of inert gas saturation after a dive. When time is spent on the surface between dives this is known as the "surface interval" and is considered when calculating decompression requirements for the subsequent dive.

Decompression (altitude) refers to the reduction in ambient pressure due to ascent above sea level. Decompression has physical effects on gas filled spaces and on liquids, particularly when they contain dissolved gases. Physiological effects of decompression 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 as described by Henry's Law, nucleation and growth of bubbles in supersaturated liquids and boiling of liquids when the pressure is reduced below the vapour pressure for the temperature of the liquid.

Altitude decompression may be a natural consequence of unprotected elevation to altitude, or due to intentional or unintentional release of pressurisation of a pressure suit or pressurised compartment, vehicle or habitat, and may be controlled or uncontrolled.

There are three principal physiological effects arising from decompression at altitude:

1. Decompression illness, which includes decompression sickness due to bubble formation in the tissues similar to those caused by decompression after exposure to pressures higher than sea level atmospheric pressure. There is little evidence of altitude decompression occurring among healthy individuals at altitudes below .
2. Barotrauma caused by the over-expansion of gas-filled spaces
3. Altitude sickness, also known as acute mountain sickness (AMS), altitude illness, hypobaropathy, the altitude bends, or soroche, is a pathological effect of high altitude on humans, caused by acute exposure to low partial pressure of oxygen and blood alkalosis arising from the low partial pressure of carbon dioxide at high altitude.