Pathogenesis, Symptoms, Prophylaxis of Decompression (Caisson) Sickness

It is often encountered in divers.

Pathogenesis

· On diving to the depth the pressure of gases as well as solubility of gases in blood increase.

· On quick rising of a diver from the depth, or decompression of a plane cabin in the upper layers of atmosphere the pressure of gases sharply falls and solubility of gases in blood decreases.

· Nitrogen slowly diffuses through a pulmonary-alveolar membrane and is excreted in blood and tissues in a form of bubbles which diameter depends on depth, i.e. the difference of pressure on depth and on surface.

Thus a gas (nitrogen) vascular embolism occurs.

Other gases, such as oxygen, CO2, helium quickly diffuse through membrane and do not form bubbles.

Symptomatology

The following degrees of severity of the disease are distinguished:

· A mild degree of the disease (the diameter of bubbles is very small) results in embolism of only capillaries causing numbness and pain of fingers and toes, headaches.

· A moderate degree of disease is manifested by sharp pains in extremities, headaches, pains and inflation of intestines.

· A severe degree leads to embolism of large vessels in the CNS (lesion of the vital centers), coronary vessels, pulmonary artery and cardiac arrest.

Prophylaxis

· A gradual stepped rise to the surface

· Substitution of nitrogen by other inert gas — helium

· Usage of altitude chamber after rising to the surface

Carbon Dioxide СО2

The content of CO2 in atmosphere is 0.03-0.04%. It is excreted in nature at breathing of biota, processes of burning, etc. Constancy of CO2 in atmosphere is maintained due to its assimilation by plants, absorption by sea and fresh-water reservoirs.

CO2 acts on the man and animals as a physiological irritator of the respiratory center. At increased concentrations of CO2 in organism acidosis, disturbances of the CNS occur.

Effect of Various СО2 Concentrations on Organism

Table 30

СО2 concentration, %	Biological effect
0.05 — 0.1	The appreciable dilatation of peripheric vessels
0.5	Change of EEG, increase of respiratory depth
1.0	Acidosis starts
1.0 — 2.0	Decrease of work capacity, toxic effect on CNS
2.0 — 3.0	Expressed irritation of respiratory center and CNS
10.0 — 12.0	Loss of consciousness and death

 

Maximal Permissible Concentration of СО2 in the Air of Closed Premises

In the air of any room the maximal permissible concentration of СО2 is 0.1 % (It was established by Pettencofer in the 19th century). Substantiation of MPC: CO2 is a parameter of air cleanliness and efficiency of ventilation — at growth of СО2 over 0.1 % the increase of concentration of toxic and microbe air pollutants takes place, which can have a harmful effect on a human organism.

Air Ventilation, Parameters of its Efficiency

The aim of ventilation is to change air in a room. Ventilation is subdivided into the following kinds:

· Natural (through windows, doors, window leaves) –due to difference of temperatures or speed of air movement;

· Artificial — with the help of ventilators (input ventilation, extract ventilation, combined extract and input ventilation).

· Mixed — a combined natural and artificial ventilation

Parameters of ventilation efficiency are the following:

· Content of СО2 in the air is up to 0.1 %;

· Air changes per hour (for habitable rooms it should be 0.5-1, in kitchens — 2-3, in cinema halls — 5-6);

· Air exchange capacity for 1 person per hour — 20-30 m3.

Table 31

Standards of Ventilation for Different Premises

Kind of premise	Air changes per hour	Air change capacity per 1 person
Habitable rooms	0.5 — 1	20 — 30 m3
Kitchens, laboratories	2 — 3	-“-
Operating room	5 — 6 (with conditioning 8 –10)	-“-
Cinema hall	5 — 6	-“-

 

Ecological and Hygienic Estimation of Anthropogenic Atmosphere          Pollution

The modern mankind lives in conditions of constant and growing anthropogenic pollution of biosphere.

Thus, special danger is presented by pollution of atmosphere:

v It is polluted more than other objects of the environment;

v Pollutants in the air are more dangerous than those in water, foodstuffs and soil because:

Ø The area of lungs penetrated with vessels is big (120 m2 in adult), that is why at once a big concentration of pollutant in blood is formed;

Ø Blood from the lungs by-passing liver is carried around the whole organism, thus a neutralizing function of the liver is reduced.

According to prognosis of UNEP (Program of the United Nations on the environment protection), Washington Science Academy, the pollution of biosphere, including atmosphere, by stable and toxic substances (heavy metals, pesticides, dioxines, etc.), having a tendency to increase in the nearest years, constitutes a real threat of global ecological catastrophe for mankind.