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Decompression Illnesses:
A Side By Side Comparison of Decompression Sickness and
Pulmonary Barotrauma
Let's get the disclaimer out of the way first: Since I
am not a doctor, the information on this page should not be used as the basis of
any medical treatment or even a semi-professional diagnosis. Much information
was gleaned from: DiveCon: Dive Control Specialist Manual. Concept
Systems, 1993.
Why did I build this page? Well, I was working on my SSI DiveCon rating, and one
of the chapters is on Physiology. The similarities in the symptoms of
Decompression Sickness and the various forms of Pulmonary Barotrauma (or Lung
Expansion Injury) can lead to some confusion (particularly in the cases where
Decompression Sickness results in bubble formation in the blood stream, which
would almost certainly, in my semi-educated opinion, resemble AGE). As a general
rule, one does not really need to know which is which; in both cases, First Aid
involves the administration of 100% O2 to the victim. However, in
order to assist EMT and Medical Personnel with treatment, an educated guess can
be made if the noticeable differences are learned.
| Definition and Cause |
| |
Decompression Sickness |
Pulmonary Barotrauma |
| Definition/Cause |
As compressed air is breathed under pressure, the nitrogen
in the air (which makes up roughly 80% of the air we breathe) is absorbed
into the blood stream and body tissues. The longer a diver stays at a
given depth, the more nitrogen will saturate the diver's blood stream.
This rate of saturation is affected by many things, including physical
condition of the diver, age, dehydration, temperature of the water, and
over exertion at depth.
Failure to decompress (either by ascending too quickly or failing to stop
at a given depth for enough time to allow off-gassing of nitrogen) can
cause the nitrogen to form bubbles in the body tissues. There are two
types of DCS:
- Type I: Symptoms are not Central Nervous System related; see
"Pain" and "Skin Signs" below
- Type II: Involves the Central Nervous System
|
Also termed "Lung Expansion Injury," it is when
compressed air that is trapped in the lungs expands beyond the lungs
capacity to hold it, and the air escapes into the body. Causes can include
holding one's breath (or other 'respiratory pauses' such as sneezing or
coughing) during an ascent, previous lung problems, colds ... anything
that traps air in the lungs, or changes the pressure rapidly during a time
when the diver cannot exhale (i.e., being around 10 feet deep and inhaling
as a large wave passes over head). There four main types of Barotrauma:
- Arterial Gas Embolism (AGE): Air escapes into the bloodstream
- Pneumothorax: Air gets trapped between the lung and the inside of
the chest cavity
- Mediastinal Emphysema: Air builds up around the heart
- Subcutaneous Emphysema: Air builds up in the skin, usually under the
neck
|
| Caveats |
When Nitrogen bubbles (DCS) form within the blood stream, it
is, for all intents and purposes, equivalent to Arterial Gas Embolism.
Although AGE is sometimes defined in books as "Air escaping from the
lungs into the blood stream," this (in some folks' opinions) is a
misnomer, as Nitrogen bubbles can form directly in the blood stream, and
cause symptoms identical (or nearly identical, depending on who you ask)
to a "Lung Expansion Injury" that involves air going into the
blood stream. |
| Symptoms |
| Pain |
Deep throbbing pain, usually in the joints (but sometimes
in other body tissues, such as the muscles). With DCS, it will almost
always be tissue related. |
Depends on the type of barotrauma experienced:
- Pain in or near the heart is caused by AGE (air in the bloodstream
enters the heart) or by Mediastinal Emphysema (air is in the pocket
around the heart)
- Pain in other areas of the chest would suggest Pneumothorax
|
| Skin Signs |
Itchy or burning skin, possibly with some discoloration ...
basically, a rash |
Subcutaneous Emphysema results in noticeable bubbles under
the skin. The skin may audibly crackle to the touch. Though not usually
life threatening, a doctor should be consulted ... immediately if the
amount of trapped air is large. |
| Fatigue or Shortness of Breath |
Usually a sign of a "Type II" DCS occurrence,
where the Central Nervous System is affected (most commonly, the spinal
cord itself). Shortness of breath not being the issue for DCS so much as
fatigue in general, my uneducated guess would more be an interpretation of
some of the effects of a combination of other symptoms. |
All barotrauma discussed here, except for Subcutaneous
Emphysema, can cause breathing problems, either due to restricted blood
flow, or air trapped in areas that put pressure on the lungs. Both
restricted blood flow and breathing problems can result in fatigue. |
| Loss of Sensation |
Another "Type II" indication, I believe it starts
in the extremities and progresses from there. |
Although not usually a symptom of AGE, a semi-educated
guess would leave me to believe that the restricted blood flow could lead
to tingly feelings or numbness in some areas. |
| Paralysis |
Again, since "Type II" DCS involves the CNS,
partial, progressing to total, paralysis can result. |
Not usually an indicator of barotrauma. |
| Muscular Weakness |
Independent of fatigue in general, this could (I would
guess) signal the formation of bubbles in muscle tissue, or occur prior to
the onset of actual paralysis. |
Not usually an indicator of barotrauma. |
| Unconsciousness |
It would be my guess that it can occur more suddenly,
should the bubbles form near the brain. |
When a result of AGE, blood flow to the brain can be
blocked, resulting in what would appear to be a stroke. |
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