Relationship between CO2 levels and decompression sickness: implications for disease prevention

Extensive data concerning the incidence of decompression sickness among workers participating in the deepest caisson operation in Japan to date have been collected and analyzed for the period April through August, 1976. When the bottom pressure was between 3.0 and 3.2 ATA, the incidence of decompression sickness was 3.05%; subsequently, the incidence was only 0.96% between 3.2 and 3.4 ATA. The man lock (i.e., decompression chamber) had never been ventilated during the former group of decompressions and the level of CO2 had ranged between 1.8 and 2.3% (v/v); in the latter group of decompressions, the CO2 level ranged between 0.3 and 0.8% with ventilation. All other conditions, including the decompression table used, were the same. Moreover, based upon the nature of the muscular activity required of the caisson workers just prior to decompression, their most common site of affliction was found to lie within the body region where the highest tissue tensions of CO2 would be expected during decompression.