Are you an Auckland based diver, or live near Auckland, New Zealand? Are you available on Saturday 19th or Sunday 20th July 2014? Do you dive a rebreather or are thinking of becoming a rebreather diver? If you answer ‘yes’ to these questions, Dr Simon Mitchell and Dr Neal Pollock need your help. They are conducting a Carbon Dioxide (CO2) Prebreathe Study and need volunteers to assist in this incredibly useful research.
We are delighted to report that the findings from this study will be announced at EUROTEK.2014 in September.
What is the purpose of this research?
Rebreathers which recycle exhaled gas after removing carbon dioxide (CO2) are becoming increasingly popular in recreational diving because they offer advantages such as the conservation of breathing gas. However, they are more complex than normal scuba equipment, and there is potential for operator error in their use. These errors may lead to accidents and death. Several of these potential operator errors relate to the use of the CO2 absorbent (or the CO2 “scrubber”). If there is failure of CO2 removal from the expired breath, the diver will re-inhale CO2 and this may result in hypercapnia (commonly referred to as CO2 toxicity). Rebreather divers are taught about this during their rebreather dive training. CO2 toxicity may cause progressive shortness of breath, headache, anxiety, panic, and ultimately unconsciousness. In addition, CO2 toxicity enhances the adverse effects or toxicity of other gases such as nitrogen and oxygen. There have been many deaths during the use of rebreathers in which CO2 toxicity is thought to have contributed, though this is often difficult to prove.
The absorbent material used in CO2 scrubbers must be replaced periodically. Related errors include failing to replace the absorbent material, incorrect packing of the absorbent material into the scrubber canister, and incorrect installation of the canister in the rebreather (or forgetting to install it entirely). Most rebreather units do not monitor CO2, and so rebreather divers are taught to conduct a 5 minute “pre-breathe” of their unit just before entering the water. A prebreathe involves preparing the unit for diving, and then sitting quietly breathing on the rebreather loop. If the CO2 scrubber is absent or faulty the diver will rebreathe CO2 and, in theory, should notice the early symptoms of CO2 toxicity such as shortness of breath or headache.
Divers assume that symptoms of CO2 toxicity will occur reliably and be noted during a 5 minute prebreathe. However, this has never been formally tested. This study aims to measure the proportion of subjects who can identify the absence of an effective scrubber during a 5 minute prebreathe on a rebreather circuit. The detection of a partial scrubber failure may also be evaluated.
If you want to be part of this important study please email PADI Course Director Pete Mesley as soon as possible to get booked in. You will be needed for no more than 2 hours during the course of the weekend.
Photo Credit: Jason Brown / BARDOPhotographic