Altitude-induced decompression sickness Guide, Meaning , Facts, Information and Description
Decompression sicknessDecompression sickness (DCS) describes a condition characterized by a variety of symptoms resulting from exposure to low barometric pressures that cause inert gases (mainly nitrogen), normally dissolved in body fluids and tissues, to come out of physical solution and form bubbles. DCS can occur during exposure to altitude (altitude DCS) or during ascent from depth (mining or diving). The first documented cases of DCS (Caisson Disease) were reported in 1841 by a mining engineer who observed the occurrence of pain and muscle cramps among coal miners exposed to air-pressurized mine shafts designed to keep water out. The first description of a case resulting from diving activities while wearing a pressurized hard hat was reported in 1869.
Altitude DCS became a commonly observed problem associated with high-altitude
balloon and aircraft flights in the 1930s. In present-day aviation, technology
allows civilian aircraft (commercial and private) to fly higher and faster than
ever before. Though modern aircraft are safer and more reliable, occupants are
still subject to the stresses of high altitude flight-and the unique problems
that go with these lofty heights. A century and one-half after the first DCS
case was described, our understanding of DCS has improved, and a body of
knowledge has accumulated; however, this problem is far from being solved.
Altitude DCS still represents a risk to the occupants of modern aircraft.
According to Henry's Law, when the pressure of a gas over a liquid is decreased,
the amount of gas dissolved in that liquid will also decrease. One of the best
practical demonstrations of this law is offered by opening a soft drink. When
the cap is removed from the bottle, gas is heard escaping, and bubbles can be
seen forming in the soda. This is carbon dioxide gas coming out of solution as a
result of sudden exposure to lower barometric pressure. Similarly, nitrogen is
an inert gas normally stored throughout the human body (tissues and fluids) in
physical solution. When the body is exposed to decreased barometric pressures
(as in flying an unpressurized aircraft to altitude, or during a rapid
decompression), the nitrogen dissolved in the body comes out of solution. If the
nitrogen is forced to leave the solution too rapidly, bubbles form in different
areas of the body, causing a variety of signs and symptoms. The most common
symptom is joint pain, which is known as "the bends."
Although bubbles can form anywhere in the body, the most frequently targeted
anatomic locations are the shoulders, elbows, knees, and ankles.
Table 1 lists the different DCS types with their corresponding bubble
formation sites and their most common symptoms. "The bends'' (joint pain)
account for about 60 to 70% of all altitude DCS cases, with the shoulder being
the most common site. Neurologic manifestations are present in about 10 to 15%
of all DCS cases with headache and visual disturbances being the most common
symptoms. "The chokes" are very infrequent and occur in less than 2%
of all DCS cases. Skin manifestations are present in about 10 to 15% of all DCS
cases.ALTITUDE-INDUCED DECOMPRESSION SICKNESS
Tiny Bubbles
Trouble Sites
| DCS Type | Bubble Location | Signs & Symptoms (Clinical Manifestations) |
|---|---|---|
| BENDS | Mostly large joints of the body (elbows, shoulders, hip, wrists, knees,ankles) | * Localized deep pain, ranging from mild (a "niggle") to excruciating. Sometimes a dull ache, but rarely a sharp pain.
|
| NEUROLOGIC | Brain | * Confustion or memory loss
|
| Spinal Cord | * Abnormal sensations such as burning, stinging, and tingling around the lower chest and back
| |
| Peripheral Nerves | * Urinary and rectal incontinence
| |
| CHOKES | Lungs | * Burning deep chest pain (under the sternum)
|
| SKIN BENDS | Skin | * Itching usually around the ears, face, neck arms, and upper torso
|
There is no specific altitude that can be considered an absolute altitude
exposure threshold, below which it can be assured that no one will develop
altitude DCS. However, there is very little evidence of altitude DCS occurring
among healthy individuals at altitudes below 18,000 ft. who have not been SCUBA
(Self Contained Underwater Breathing Apparatus) diving. Individual exposures to
altitudes between 18,000 ft. and 25,000 ft. have shown a low occurrence of
altitude DCS. Most cases of altitude DCS occur among individuals exposed to
altitudes of 25,000 ft. or higher. A US Air Force study of altitude DCS cases
reported that only 13% occurred below 25,000 ft. The higher the altitude of
exposure, the greater the risk of developing altitude DCS. It is important to
clarify that although exposures to incremental altitudes above 18,000 ft. show
an incremental risk of altitude DCS, they do not show a direct relationship with
the severity of the various types of DCS (see Table 1).
Repetitive exposures to altitudes above 18,000 ft. within a short period of
time (a few hrs.) also increase the risk of developing altitude DCS.
The faster the rate of ascent to altitude, the greater the risk of developing
altitude DCS. An individual exposed to a rapid decompression (high rate of
ascent) above 18,000 ft. has a greater- risk of altitude DCS than being exposed
to the same altitude but at a lower rate of ascent.
The longer the duration of the exposure to altitudes of 18,000 ft. and above,
the greater the risk of altitude DCS.
There are some reports indicating a higher risk of altitude DCS with
increasing age.
There is some indication that recent joint or limb injuries may predispose
individuals to developing "the bends."
There is some evidence suggesting that individual exposure to very cold
ambient temperatures may increase the risk of altitude DCS.
Typically, a person who has a high body fat content is at greater risk of
altitude DCS. Due to poor blood supply, nitrogen is stored in greater amounts in
fat tissues. Although fat represents only 15% of an adult normal body, it stores
over half of the total amount of nitrogen (about 1 liter) normally dissolved in
the body.
When a person is physically active while flying at altitudes above 18,000
ft., there is greater risk of altitude DCS.
The after-effects of alcohol consumption increase the susceptibility to DCS.
SCUBA diving requires breathing air under high pressure. Under these conditions,
there is a significant increase in the amount of nitrogen dissolved in the body
(body nitrogen saturation). The deeper the SCUBA dive, the greater the rate of
body nitrogen saturation. Furthermore, SCUBA diving in high elevations (mountain
lakes), at any given depth, results in greater body nitrogen saturation when
compared to SCUBA diving at sea level at the same depth. Following SCUBA diving,
if not enough time is allowed to eliminate the excess nitrogen stored in the
body, altitude DCS can occur during exposure to altitudes as low as 5,000 ft. or
less.
This is an Article on Altitude-induced decompression sickness. Page Contains Information, Facts Details or Explanation Guide About Altitude-induced decompression sickness PREDISPOSING FACTORS
Altitude
Repetitive Exposures
Rate of Ascent
Time at Altitude
Age
Previous Injury
Ambient Temperature
Body Type
Exercise
Alcohol Consumption
Scuba Diving Before Flying
WHAT TO DO WHEN ALTITUDE DCS OCCURS
THINGS TO REMEMBER