[Research on the incidence of decompression sickness in compressed air works. The development of its recent five years' study].

Compressed air works have been used as the safest construction work for the basic underground or underwater compressed shield or caisson works in Japan; however, the workers who were exposed to the compressed fields must have put themselves at risk of decompression sickness. Decompression sickness is generally considered to be due to the bubble effects and the bubbles originate from the supersaturated gas dissolved in the blood and other tissues. The standard decompression schedule by the Ministry of Labor has been practically applied at the end of compressed air works, and the laborers decompress slowly from the bottom pressure to the surface according to the schedule. It is difficult to completely prevent the sickness and the average percentage of contracting "bends," using the Japanese standard decompression schedule, is considered to be 0.54%. But previous papers reported higher incidences from 1.42 to 3.3% or more. We have continued an actual investigation on the incidence, and the number of the exposed trials amounted to nearly a hundred thousand. These data were compared between recent five years' group and before. Eventually, it was ascertained that the incidence has been significantly decreased in the recent five years; however, greater care in occupational safety control is still needed.