I recently took part in a discussion about pre-dive checklists and the need to create the environment where divers can question others if checklists are not done, or contain the actions/information required. One of the reasons cited for not doing the checklist was “that is why we get trained to deal with anything underwater”, and whilst some training is very robust, it is much better to prevent an incident from occurring than deal with the outcomes where it might not be possible to manage the escalation, especially if you are at depth.
The image shows a risk management model called the ‘Bow Tie Model’. On the left are the causes and potential barriers to prevent the incident from occurring, in the centre is the incident itself, and on the right are the mitigations which can minimise the escalation which creates the adverse consequence. I have used the example of an Out of Gas (OOG) scenario to show how both sides of the tie can prevent the incident from ending in a fatality.
As you can see, there are a number of activities which can be used to minimise the occurrence of the OOG from occurring. e.g. checklists which include checking gas contents, deployment and restow of hose to show it can be used in the event of an OOG, gas planning, gas monitoring and training. After the OOG has happened (not all the barriers on the left worked), then the right hand side shows what you can do to prevent a fatality from occurring. e.g. air share, CESA or alternative source.
Whilst all of the post-event actions require a level of training to allow them to be completed effectively and efficiently (this is where the “we can deal with anything” training helps), it is more efficient to prevent the incident from occurring in the first place. Furthermore, if you are dealing with something on the right, your ability to monitor barriers on the left is going to be diminished.
Just because you have conducted hundreds of dives where nothing has gone wrong when the controls on the left weren’t in place, it doesn’t mean that the mitigating controls on the right are going to be able to ‘save you’. It takes a layered approach to make sure that you can beat Murphy, unfortunately there are just too many permutations to take a single system approach to mitigate everything.
The following Bowtie was added following the publication of an article I wrote for the Divers Safety and Aquatic Medicine Magazine on an OOG incident and shows how teamwork can sit on both sides of the ‘event’