Decompression Sickness during Construction of the Dartford Tunnel

Abstract

A clinical, radiological and statistical survey has been made of decompression sickness during the construction of the Dartford Tunnel. Over a period of two years, 1,200 men were employed on eight-hour shifts at pressures up to 28 pounds per square inch (p.s.i.). There were 689 cases of decompression sickness out of 122,000 compressions, an incidence of 0-56%.The majority of cases (94-9 %) were simple "bends". The remainder (5 1 %) exhibited signs and symptoms other than pain and were more serious. All cases were successfully treated and no fatality or permanent disability occurred. In two serious cases, cysts in the lungs were discovered. It is suggested that these gave rise to air embolism when the subjects were decompressed, and pulmonary changes may contribute more than hitherto believed to the pathogenesis of bends. Some other clinical features are described, including "skin-mottling" and an association between bends and the site of an injury. The bends rate is higher for the back shift (3 p.m. to 11 p.m.) and the night shift (11 p.m. to 7 a.m.) than for the day shift. In the treatment of decompression sickness it appears to be more satisfactory to use the minimum pressure required for relief of symptoms followed by slow decompression with occasional "soaks", than to attempt to drive the causative bubbles into solution with high pressures.During the contract the decompression tables recently prescribed by the Ministry of Labour were used. Evidence was obtained that they could be made safer, and that the two main assumptions on which they are based (that sickness will not occur at pressures below 18 p.s.i., and that a man saturates in four hours) may be incorrect. It is desirable to test tables based on 15 p.s.i. and eighthour saturation. The existence of acclimatization to pressure was confirmed; it is such that the bends rate may fall in two to three weeks to 011% of the incidence on the first day of exposure. Acclimatization is lost again, with a "half-time" of about seven days, if a man is away from work.A study of bone damage in compressed air work has been started. In certain radiographs, abnormalities have been seen which may represent an early stage of caisson disease of bone.The new tunnel between Kent and Essex under the Thames at Dartford is part of a four miles road link between A2, the London-Rochester road, and A13, the Barking-Southend road. It is situated 14 piiles down river from the Blackwall Tunnel, until now the most easterly point at which it has been possible to cross the Thames by road. The river at Dartford is half a mile wide, so that the total length of the tunnel, including the sloping approaches at each end, will be approximately one mile. The tunnel lies about 20 ft. below the existing bed of the river in strata which consist of soft blue peaty clay overlying gravel which in turn overlies solid chalk. The preliminary pilot tunnel was completed in 1938, and the present contract for the full tunnel was let in 1956. It has an internal diameter of 28 ft. 2 in. and will accommodate tw...

Mechanisms and Risks of Decompression

“…A report on the construction of the Dartford tunnel was the first publication to classify DCS as type 1 or type 2. 130 In this paper, type 1 DCS was described in 650 men with pain in and around the joints, and type 2 was described in 35 men who had symptoms other than pain or who had abnormal physical signs. Two men with lung cysts were considered to have type 2 DCS, although the disease described appears to have been AGE.…”

“…130 Men with type 2 injuries were forbidden from further employment in compressed air. A report on the construction of the Dartford tunnel was the first publication to classify DCS as type 1 or type 2.…”

Cutis Marmorata skin decompression sickness is a manifestation of brainstem bubble embolization, not of local skin bubbles

“…The first classification, although scientifically less correct, is still widely used in pre-clinical practice because it allows a simple, be it not entirely correct, link to a therapeutic decision tree [3][4][5].…”

Neurological effects of deep diving

“…DCS has been categorized as type 1 (with musculoskeletal, skin or lymphatic symptoms, or fatigue) and type 2 (neurologic or cardiorespiratory or audiovestibular symptoms or shock) [36]. It is now recognized that DCS is a systemic disease and that the differentiation between Type I and Type II disease is artificial.…”