QinetiQ was tasked by Morgan Est plc to provide Doppler technicians to monitor venous gas emboli (VGE) in compressed air tunnel workers from the Belfast Sewer Project. This report, presents an analysis of Doppler data, with reference to pre-existing information on Doppler monitoring of compressed air tunnel workers. QinetiQ Doppler technicians conducted the monitoring according to an approved ethical protocol. The pressure for the compressed air work exposures ranged from 0.67 to 1.8 bar gauge, with 21 work shifts monitored. Data were obtained from 65 Doppler monitoring sessions conducted on 17 individuals. Monitoring began at 30 minutes post decompression, and continued at intervals for up to three hours. Compliance with attendance at monitoring sessions was varied, depending on other work commitments and the willingness of the workers. Resting and movement Doppler scores were recorded, which covered the full range (Kisman Masurel score 0 – 4) of possible scores. Thirty-six of the 65 Doppler monitoring sessions (55%) demonstrated resting Grade III or higher VGE. Resting VGE loads were significantly lower for exposure to pressures <1.0 bar gauge than for exposure to 1.8 bar gauge decompressing on Swanscombe Oxygen Decompression Table line 9.
This report and the work it describes were funded by the Health and Safety Executive (HSE). Its contents, including any opinions and/or conclusions expressed, are those of the authors alone and do not necessarily reflect HSE policy.
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