This question has been asked many times. The simple answer is safety. The majority of divers know the effects of narcosis and how it can impaire our judgement in making descisions, sometime life threatening.

The Recreational Trimix course is designed for those that want the benefits of reduced levels of narcosis but don’t necessarily want to dive deep. Some divers may feel that 30msw is a deep dive and the limit of their personal expectation of where they want to take their diving. Recreational Trimix allows them to safely dive within their personal limit and reduce the perceived level of narcosis. A helium based mix can improve the divers enjoyment of 30m dives and ensure that should circumstances arise where they need a clear head that they are able to react accordingly.

Many training agencies now recommend the use of Trimix for dives beyond 30m and some locations now require a Trimix ticket if divers are to venture beyond 30m. Deep Air is perceived as dangerous and as training agencies move away from such practices we should see more divers wanting to utilize a weak trimix to enable them to dive with increased levels of safety.

Inert gas narcosis has been documented at depths as shallow as 20msw- therefore adding helium to the mix can assist some divers in overcoming this problem. Helium also has the advantage of being less dense and therefore reducing the breathing resistance and level of Co2 build up- all things that a diver should be concerned with when diving.

garysrecandtech offer the IANTD Deep Diver course as a basic introduction to technical diving i.e. Twinsets, decommpression diving though many students are electing to either Recreational or Advanced Recreational Trimix.

Deep air used to be the only solution before Trimix training become available. Nowadays there are better options for divers wishing to go beyond 30m. For many inert gas narcosis becomes an issue beyond 30m and although divers believe that they can develop a resistance to narcosis, in truth this is more fiction than fact. Regular deep air divers can get used to dealing with the reduction in mental capacity but the sad fact is that when they need to react to a potentially dangerous situation then inert gas narcosis can prevent them reacting quickly and correctly. Whilst training and basic muscle memory can help the air diver, a diver on a Trimix will always be better able to react due to the reduced level of narcosis.

Some agencies continue to offer deep air diver training without the requirement for the use of a twinset. If a diver calculates their own level of air consumption it soon becomes apparent that 3ltr ponies are insufficient to safely get a diver back to the surface should something go wrong with their air supply. Air consumption can rise to 100 litres per minute under duress, and sustained rates in excess of 35 litres per minute have been recorded. A typical pony has a total capacity of 600 litres and at 40 msw (5 bar), the diver could be using 175 litres per minute whilst at depth. During the ascent the diver could maintain 35 litres per minute and in that event have insufficient air remaining to safely reach the surface. Using a twinset would enable the diver to enjoy a larger gas reserve if observing rule of thirds or minimum gas levels. Additional using Trimix would enable our diver to react more appropriately and seek the assistance of his team or rectify the problem.

With the availability of Trimix courses and training then today there is little need for deep air diving in the Uk. Granted in isolated areas without the benefit of Helium it may remain the only solution but in the UK divers are steadily moving toward the safer options of Trimix for recreational and technical diving beyond 30 msw.

The 5 minute neuro exam is designed to spot any potential problems and also take a baseline of thier condition should they need treatment.

Information regarding the injured diver's neurological status will be useful to the chamber in not only deciding the initial course of treatment but also in the effectiveness of treatment.

The 5 Minute Neuro Exam is easy to learn and can be done by individuals with no medical experience. Perform as much of the exam as possible, but do not let it interfere with evacuation to medical treatment.

Perform the following steps in order, and record the time and results.

You can buy plastic slates with this on or you can print out the following, laminate it and keep it in your log binder or dive bag.

5 Minute Neuro Exam

DON'T FORGET TO RECORD THE RESULTS!

1. Orientation
- Does the diver know his/her own name and age?
- Does the diver know the present location?
- Does the diver know what time, day, year it is?

Note: Even though a diver appears alert, the answers to these questions may reveal confusion. Do not omit them.

2. Eyes
- Have the diver count the number of fingers you display, using two or three different numbers.
- Check each eye separately and then together.
- Have the diver identify a distant object.
- Tell the diver to hold head still, or you gently hold it still, while placing your other hand about 18 inches/0.5 meters in front of the face. Ask the diver to follow your hand. Now move your hand up and down, then side to side. The diver's eyes should follow your hand and should not jerk to one side and return.
- Check that the pupils are equal in size.

3. Face
- Ask the diver to purse the lips. Look carefully to see that both sides of the face have the same expression.
- Ask the diver to grit the teeth. Feel the jaw muscles to confirm that they are contracted equally.
- Instruct the diver to close the eyes while you lightly touch your fingertips across the forehead and face to be sure sensation is present and the same everywhere.

4. Hearing
- Hearing can be evaluated by holding your hand about 2 feet/0.6 meters from the diver's ear and rubbing your thumb and finger together.
- Check both ears moving your hand closer until the diver hears it.
- Check several times and compare with your own hearing.

Note: If the surroundings are noisy, the test is difficult to evaluate. Ask bystanders to be quiet and to turn off unneeded machinery.

5. Swallowing Reflex
- Instruct the diver to swallow while you watch the "Adam's apple" to be sure it moves up and down.

6. Tongue
- Instruct the diver to stick out the tongue. It should come out straight in the middle of the mouth without deviating to either side.

7. Muscle Strength
- Instruct the diver to shrug shoulders while you bear down on them to observe for equal muscle strength.
- Check diver's arms by bringing the elbows up level with the shoulders, hands level with the arms and touching the chest. Instruct the diver to resist while you pull the arms away, push them back, up and down. The strength should be approximately equal in both arms in each direction.
- Check leg strength by having the diver lie flat and raise and lower the legs while you resist the movement.

8. Sensory Perception
- Check on both sides by touching lightly as was done on the face. Start at the top of the body and compare sides while moving downwards to cover the entire body.

Note: The diver's eyes should be closed during this procedure. The diver should confirm the sensation in each area before you move to another area.

9. Balance and Coordination

Note: Be prepared to protect the diver from injury when performing this test.

- First, have the diver walk heel to toe along a straight line while looking straight ahead.
- Have her walk both forward and backward for 10 feet or so. Note whether her movements are smooth and if she can maintain her balance without having to look down or hold onto something.
- Next, have the diver stand up with feet together and close eyes and hold the arms straight out in front of her with the palms up. The diver should be able to maintain balance if the platform is stable. Your arms should be around, but not touching, the diver. Be prepared to catch the diver who starts to fall.
- Check coordination by having the diver move an index finger back and forth rapidly between the diver's nose and your finger held approximately 18 inches/0.5 meters from the diver's face. The diver should be able to do this, even if you move your finger to different positions.
- Have the diver lie down and instruct him to slide the heel of one foot down the shin of his other leg, while keeping his eyes closed. The diver should be able to move his foot smoothly along his shin, without jagged, side-to-side movements.
- Check these tests on both right and left sides and observe carefully for unusual clumsiness on either side.

Important Notes:

Tests 1,7, and 9 are the most important and should be given priority if not all tests can be performed.

The diver's condition may prevent the performance of one or more of these tests. Record any omitted test and the reason. If any of the tests are not normal, injury to the central nervous system should be suspected.

The tests should be repeated at 30- to 60-minute intervals while awaiting assistance in order to determine if any change occurs. Report the results to the emergency medical personnel responding to the call.

Good diving safety habits would include practicing this examination on normal divers to become proficient in the test.

DON'T FORGET TO RECORD THE RESULTS!