ecompression sickness (DCS) is a syndrome that follows the reduction in environmental pressure massively or rapidly enough to cause the formation of bubbles from gases already dissolved within body tissues.
It represents one of the many man made illnesses, though its exact nature is still not fully understood.
In compressed gas diving, DCS happens if:
1-The elimination of the inert gas cannot adequately parallel the rate of reduction of external pressure (as in the case of fast ascents).
2-The amount of residual inert gas at the end of a particular dive (or dives) is high enough to create bubbles - supersaturation. (as in the case of missing a decompression stop).
3-Accumulation of the inert gas in the body due to repeated diving for a few days (inert gas load)
DCS is differentiated into 2 types:
Type I DCS can be presented in one of these forms:
1- Extreme fatigue.
2- Skin rash
3-Joint pain (limb bend or musculoskeletal pain-only symptoms)
4- Lymphatic Symptoms (where localized swelling and pain occurs in the area drained by involved lymph glands).
Type II DCS
Where the nervous system, the inner ear or cardio-pulmonary systems are involved producing serious signs and symptoms.
DCS can present itself in a variety of symptoms and signs, which pose diagnostic problems for the non-experienced officer. Amongst these symptoms:
Skin rash - Joint pain - Back pain - Itching - Dizziness - Chest pain - Girdle pain - Paralysis - Hearing problems like ringing in the ears - Tingling - Urination difficulty - Memory changes - Nausea, vomiting - Extreme fatigue - Visual disturbances - Balance problems - Speech problems - Shortness of breath - Cognitive deterioration.
It is important to establish whether symptoms are diving related, and a good procedure is to:
1. Refer back to the dive profiles of the last few dives (depth and exposure times), and consider any unusual events happening during these dives like: emergency or fast ascents, omitted stops, YO -YO like profiles, reversed profile(s), multiple ascents, cold temperatures or strenuous exposure etc.
2. Pay attention to Inert Gas Load (in case of repeated diving days).
3. Overview the individual factors involved such as:
sometimes misdiagnosed as DCS.
So encourage your divers to drink rehydration salts together with water.
II. Age: altered blood flow due to atherosclerosis associated with age increases the risk of DCS.
III. Sex: some literature suggests an increased incidence in females due to the redistribution of the body fluids due to hormonal changes during different stages of menstruation, but it is still under study.
IV. Obesity: is a point of controversy:
Some authors accuse fat tissue of being a contributing factor (having a great affinity to nitrogen thus increasing
the nitrogen load in case of repeat diving days), whilst others believe in its action as a good reservoir for nitrogen in cases of short, deep single exposures.
V. High Serum Cholesterol levels can enhance bubble formation by rendering the blood more viscous.
VI. Improper training of equipment usage (mainly the BCD).
VII. Overconfident attitude in a poorly educated or a well trained diver.
VIII. Any underlying condition that hampers the anatomy of the body (like scarring), can form a bubble trap due to the alteration in local tissue perfusion and gas elimination.
E.g. a previous joint, spine or brain injury or affection, also any previous episode of DCI.
IX. Increased carbon dioxide tension due to exertion or increased breathing resistance because of faulty equipment, which increase nitrogen loading.
*Dive computers:
They do allow divers to spend more time under water than conventional tables as they compute time and depth input minute by minute against the tables and calculate inert gas absorption and elimination in a number of theoretical body tissues continuously to credit the diver for multi-level dives.
But amongst disadvantages of dive computers are:
-They do not take all factors into consideration like: water temperature, age, body figure, dehydration or exertion.
-They have a high incidence of faults in computing inert gas load in successive diving days and failure during underwater exposure.
-It is practically impossible to override them without being aware of it due to divers' unfamiliarity or lack of warning features of some computers.
In fact diving computers are responsible for a good number of DCS cases in sport diving.
Any symptoms or signs which cannot be explained and develop after a dive should be regarded as Decompression Sickness until proved otherwise.
The first and most significant aid is to plan for safe dives including accident management and plans for evacuation to the nearest recompression facility.
Dive leaders should stick to safety rules and regulations regarding depths, dive tables, repetitive dives, medical statements and checks for divers, individual and age consideration of the guests and fulfillment of the Instructor/Student - Guide /Diver ratio as stated by different organizations.
Dive leaders should co-operate with chamber personnel by doing what is asked of them, being honest in all of their answers to questions and having understanding and appreciation for chamber personnel and consultants. These people are trying to be helpful and they also have stress due to the tasks associated with their function during the course of treatment itself.
I. Dehydration: is one of the major predisposing factors in the occurrence of DCS as dehydration renders the blood more viscous than normal, which reduces perfusion of tissues and thus the elimination of inert gas.
Dehydration can happen as a result of :
1. Inadequate fluid intake.
2. Drinking dehydrating agents like alcohol and coffee.
3. Dehydrating conditions as diarrhea and vomiting.
Note that:
1. During diving there is a continuous fluid loss due to perspiration, dry gas breathing and immersion that increases urine formation.
2. Advising divers to drink a lot of water in tropical areas or in the summer without adequate salt intake leads to dilution of body electrolytes with the consequent symptoms of dizziness, weakness, nausea and vomiting that is sometimes misdiagnosed as DCS.,...etc.
By: Dr. Hossam Nasef
