Evaluation of decompression tables by Doppler technique in caisson work in The Netherlands.

INTRODUCTION Hyperbaric work was conducted for constructing an underground tramway in the Netherlands. A total of 11,647 exposures were conducted in 41,957 hours. For these working conditions specifically developed oxygen decompression tables were used. METHODS Fifteen workers were submitted to Doppler monitoring after caisson work at a depth at 12 msw. Measurements were done according to the Canadian DCIEM protocol. For bubble grading the Kisman-Masurel 12-points ordinal scale (0-IV) was used. RESULTS Bubbles were detected in 17 of the 38 examinations. The highest grade (III-) was found in four measurements. At rest the grading was never higher than I+. Two hours after decompression the grading was remarkably higher than after one hour. CONCLUSIONS Bubble scores were relatively low, although the maximum grading probably is not reached within two hours after decompression. It may be concluded that the oxygen decompression tables used, were reliable under these heavy working conditions. At group level, decompression stress can be evaluated by Doppler monitoring. In order to reduce health hazard of employees, use of oxygen during decompression in caisson work should be embodied in the occupational standard.