The rate of decompression sickness in scientific diving at the Australian Institute of Marine Science (Townsville) 1996 to 2001

Abstract

Objectives: To detail the rate of decompression sickness (DCS) in and describe the pattem of scientific diving according to the Canadian Defence and Civil Institute of Environmental Medicine (DCIEM) decompression tables, and project the impact of the AS/NZS Scientific Diving Standard (AS/NZS 2299.2:2002) on dive profiles at the Australian Institute of Marine Science (AIMS), Townsville.

Methods: Data have been collected for all scientific diving conducted at AIMS according to the DCIEM tables from October 1996 to December 2001. Details of location, date, time in and out, bottom time, effective bottom time (bottom time calculated according to residual nitrogen from previous dives), maximum depth, repetitive group and factor, and surface interval were recorded via the dive work sheels.

Results: The data from 14,944 dives were analysed. The total bottom time for all dives was 13,033 hours. No cases of DCS were reported this period for a DCS rate of zero (exact binomial 95% confidence interval 0 to 30) cases per 100,000 dive hours. More than half (58.0%; n = 8,669) of all dives were conducted more than two hours' travel time from a recompression chamber. Two thirds of dives were conducted at the rate of two (35.8%; n = 5,352) or three (31.4%; n = 4,698) dives per diver per day. The median depth of dives was 10 metres' sea water with a median effective bottom time of 1 :00 hr (interquartile range 0:40-1:21 hours), One quarter (25.1%; n = 3,241) of dives would have exceeded the maximum repetitive group limits if they were conducted according to AS/NZS 2299.2:2002.

Conclusions: The results of this analysis demonstrate that the rate of DCS in multi-day scientific diving conducted according to the DCIEM tables is low, regardless of maximum dive depth and travel time from recompression chamber support. The observed DCS rates at AIMS provide evidence that the repetitive group limits of AS/NZS 2299.2:2002 are restrictive for the purposes of scientific diving and require modification.