Decompression sickness

Decompression sickness (DCS), also known as diver's disease, aerobullosis,the bends,or caisson disease, is an uncommon diving-related decompression illness that can be an acute neurological emergency typically occurring in deep sea divers.

Clinical presentation

Decompression sickness can be further clinically subdivided into:

• type I: arthralgia, skin marbling (cutis marmorata), small patchy haemorrhages, and lymphatic obstruction

  • the antalgic posture and gait caused by arthralgia gives rise to the colloquial term 'the bends'

• type II: neurological (brain and/or spinal cord), inner ears, and/or lungs

Pathology

Nitrogen gas bubbles can cause neurovascular infarction of the brain and spinal cord leading to neurological deficits. There are various theories to explain this, which hypothesise between arterial occlusion, venous infarction and cellular nitrogen toxicity.

Location

The white matter tracts of the spinal cord and brain are predominantly affected due to their high myelin content ³. Cord Cord lesions are more common than brain lesions. In the spinal cord, there is a predilection for the thoracic cord segments to be affected, thought to be secondary to more nitrogen accumulating in the lateral and posterior columns where there is higher fat content and also the relatively low blood flow compared to the cervical and lumbar segments.

Complications

• bone infarction

• spinal cord infarct

Radiographic features

MRI

Radiological changes are seen in early stages in MRI, including both dorsal column white matter, as well as grey matter T2 hyperintense changes. This suggest both arterial and venous infarction mediating the neurological deficits ⁶. There may also be an accumulation of nitrogen bubbles in marrow fat. However, normal MRI of the cord does not rule out the diagnosis ³.

There is also insufficient evidence to suggest the presence of MRI changes in predicting neurological complications from DCS. But it is worth noting that despite this, the United States Navy Diving Manual and the Association of Diving Contractors International recommend that with MRI abnormalities, the patient may not return to diving due to the increased risk of having more severe complications ⁴.

Treatment and prognosis

The usual treatment for DCS is rehydration, 100% oxygen via a non-rebreather mask, and most importantly, recompression therapy in a hyperbaric facility.

History and etymology

The disease was first formally described by physician Andrew H Smith in 1873 during the building of the Brooklyn Bridge in New York, when. He published observations of symptoms in workers was working in air-tight divewho emerged too quickly from pressurised underwater chambers named caissons (hence, coining the name caissonterm 'caisson disease)' ⁵. The bends refers to the spinal degenerative changes and joint pain associated with repeatsymptomatic posture of those suffering from rapid decompression sickness, which resembled the Grecian Bend, a stooped fashionable posture from the 1820's ⁵.

See also

• decompression illness