A comparison between compressed air and Nitrox gas for recreational scuba divers to 18 msw

It has been hypothesised that Nitrox may actually be a safer gas for shallower dives (above 30 msw), as the gas may lessen the risk of decompression illness.

Grant ID: T-2010-018-BLAKE-NITROX

Lay Summary

The Emergency department at the Townsville Hospital sees the largest no of emergency patients with decompression illness due both tertiary referral and the proximity of the great barrier reef. Decompression illness is the commonest form of diving related emergency requiring emergency management. It is thought that nitrogen bubbles become trapped in the body as the gas expands upon ascent of the diver to the surface. Divers breathe from a scuba tank for the duration of the dive. Normally they would breathe compressed air for the shallower recreational dives (up to 30 metres of sea water (msw)). Divers have found that in order to dive for longer periods underwater they can use Nitrox (a gas with a higher oxygen content than compressed air and therefore less nitrogen), from their scuba cylinder. Nitrox gas is used extensively by the navy and commercial sector; and the majority of the work on the safety profile is done on navy schedule dives. It has been hypothesized that Nitrox may actually be a safer gas for shallower dives (above 30 msw), as the gas may lessen the risk of decompression illness.

In this study we aim to detect bubbles present in the body after a dive. After a standard dive it is common to have some bubbles detected using Doppler ultrasound in the heart and major vessels. Intravascular bubbles are not indicative of decompression illness, but are valuable markers of the extent of decompression stress experienced. We aim to compare the quantity of bubbles detected for a group of health volunteers breathing either compressed air, or Nitrox gas ( Enriched Air Nitrox x36 (EANx36 )– a widely available recreational nitrox gas mix) to 18 msw (281.3 kPa) for 50 minutes in both a hyperbaric chamber, and in a dive at sea.
As recreational diving is now enabling a wide cross section of the community to participate, every effort to determine safe practices and minimizing the risks of decompression illness needs to be fully examined.

Leveraged Funds

- $7,629.00 from Townsville Hospital PPTH Fund


Amount Awarded


Grant Scheme


Principal Investigator:
Dr Denise Blake

Co Investigators:
Julia Bruce-Thomson
Lawrence Brown

Associate Investigators:
Mr Peter Bisaro
Cory Van Der Broek


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