Decompression sickness the

If they return to atmospheric pressure too rapidly, large bubbles of nitrogen gas will form in their blood and cause a potentially lethal condition known as the bends or decompression sickness. The diver must enter a hyperbaric (high pressure) chambers to redissolve the nitrogen back into the blood. 

In 1966 experimental studies were initiated on the susceptibility of anaesthetized hamsters to decompression insult, attempting to utilize existing pharmacokinetic and toxicological modeling techniques to characterize the role of the inert gas in producing decompression sickness. The hamster model consisted of three discrete elements. First, a mass transfer model had to be developed that would describe the uptake,... 

Figure 2. Generalized mass transfer model for the hamster The model consists of n tissues, 1 of which play a role in initiating decompression sickness. The first few tissues equilibrate with the rapidly circulating blood and have a high water content. The slower tissues may be characterized by two compartments coupled by inert gas diffusion.

The health hazards of work in compressed air and diving are decompression sickness ( the bends ) and aseptic bone necrosis ( bone rot ). Both these illnesses can have long-term effects varying from slight impairment of mobility to severe disablement. The protective measures, including decompression procedures, are laid down in the Work in Compressed Air Special Regulations and these should be observed in conjunction with the medical code of practice for work in compressed air. 

If a diver ascends too quickly, the lungs cannot remove the nitrogen fast enough. Gas bubbles form in the blood, causing decompression sickness. Decompression sickness is also known as "the bends," because one of its symptoms is an inability to bend the joints. 

Both decompression sickness and air embolism can be treated by placing the victim in a hyperbaric chamber. Hyper ... 

D.M. LeMessurier, Supersaturation and preformed nuclei in the etiology of decompression sickness, paper presented at the Second International Meeting on Aerospace Medicine, Melbourne, 1972 (unpublished). 

Y. Mano and J.S. D Arrigo, The relationship between CO2 levels and decompression sickness implications for disease prevention, Aviat. Space Environ. Med. 49 (1978) 349-355. 

J. How, A. Vijayan and T.M. Wong, Acute decompression sickness in compressed air workers exposed to pressures below 1 bar in the Singapore Mass Rapid Transit project, Singapore Med. J. 31 (1990) 104-110. 

A detailed knowledge of the predominant physicochemical/biochemical mechanism by which gas microbubbles are stabilized in aqueous media is of practical importance to numerous and varied fields acoustic and hydrodynamic cavitation, commercial oil recovery, hydraulic and ocean engineering, waste-water treatment, chemical oceanography, meteorology, marine biology, food technology, echocardiography, and the continual medical problem of decompression sickness. Many of these applications... 

Under current Navy policy, when a submarine fire occurs, the crew is instructed to put on emergency air breathing devices (EABs) to prevent smoke inhalation and toxic gas exposure. When a large number of crew members use EABs, expired air increases the pressure inside the submarine, which can increase the chance of decompression sickness. Minimizing the use of EABs to prevent... 

FIGURE 1-1 Relationship between the depth of the disabled submarine, the internal pressure of the submarine, and the percentage of the crew members likely to suffer from decompression sickness. Abbreviations DCS, decompression sickness DISSUB, disabled submarine fsw, feet seawater. Source Parker et al. 2000. Reprinted with permission from Aviation Space and Environmental Medicine, copyright 2000, Aerospace Medical Association, Alexandria, Virginia. 

Contraindications. Any closed, distendable air-filled space expands dm-ing administration of nitrous oxide, which moves into it from the blood. It is therefore contraindicated in patients with demonstrable collections of air in the pleural, pericardial or peritoneal spaces intestinal obstruction arterial air embolism decompression sickness severe chronic obstructive airway disease emphysema. Nitrous oxide will cause pressure changes in closed, noncompliant spaces such as the middle ear, nasal sinuses, and the eye. 

The bends first recorded in 1841, is also known as decompression sickness. It is a very serious and potentially lethal condition. The bends occurs when there is a rapid and great change in blood pressure. Deep sea divers are especially vulnerable to this painful and sometimes fatal condition. There is a higher pressure environment under vast amounts of water such as in a sea or ocean. 

Air embolism is not synonymous with nor a manifestation of decompression sickness. It refers specifically to air embolization of cerebral vessels subsequent to the rupture of lung parenchyma by expanding gases. Air embolism should not be confused with the bubble formation that occurs in the circulatory system and tissues in decompression sickness vide infra). 

There are various factors that predispose to decompression sickness. Some of these are obesity, age, exercise, and CO2 accumulation. In general, older individuals are more susceptible to decompression sickness than younger persons this is apparently related to the status of the circulatory system. Increased physical activity results in more rapid saturation of the tissues per unit time than in a resting individual. This increased rate of tissue saturation is due to the increased rate of ventilation and circulation resulting in more rapid transport of nitrogen to the tissues. Due to their very rapid circulation and ventilation, small animals are more resistant than man to decompression sickness. Blinks et al. (B28) found that increased CO2 tension in the tissues lowers the threshold for bubble formation. Although the mechanism of this phenomenon is not known, there is reason to suspect that it may be due to the high solubility and diffusibility of carbon dioxide (H5). 

Other factors, such as temperature, water balance, and drugs, may affect the susceptibility to decompression sickness. Results were inconclusive (C24, G27). 

The symptoms of decompression sickness include bends (local pain), skin rashes, itching, neurological disturbances (scotomata, hemianopsia, diplopia, paresis, paralysis, abnormal reflexes, dysesthesia, aphasia, vertigo), respiratory distress ( chokes )> nausea, and shock (neurocirculatory... 

For virtually all cases of decompression sickness, save perhaps neurocirculatory collapse which may require oxygenation and blood transfusions, (B41, C19) the most expeditious therapy is recompression. Afflicted indi-... 

---