If you have dived during the colder months while wearing a wet suit, you may have experienced loss of feeling in your hands and feet, and what is called an ‘ice-cream headache’ around the upper forehead area. When you try and undo your regulator from your cylinder, your fingers have lost feeling and you use your hands like claws. Warming up in a vehicle with the heater running can be painful for a while until your circulation returns to normal. It is interesting that during the winter we willingly experience this shut down by the body because we enjoy diving so much.
If we look at what is happening we quickly realise that what we are experiencing is a safety response by the brain when the body gets cold. Millions of people experience extreme cold in this world, The wise ones dress for the temperature so they lose as little body temperature as possible. Ideally, we should seek shelter and warmth before we get cold enough to lose circulation. When the body starts to lose temperature, the brain will restrict the flow of blood to the extremities such as our arms, hands, legs and our feet. The flow of warm blood is restricted to our brain and vital organs.
When we begin our dive, our circulation is fully functioning. As we descend, the nitrogen absorbed in our bodies will compress and that space will be taken up by more nitrogen from each breath we take. Once we have reached our dive depth, our nitrogen levels within our fast tissue will quickly reach saturation, while our slower tissue will take longer towards saturation. As we continue with our dive in cold water, our body temperature will drop and the circulation to our extremities will slow.
As we ascend, the pressure around us will reduce and the absorbed nitrogen gas will normally be safely removed during our slow ascent and safety stop. If we are cold, that process will not happen normally as our lack of circulation will prevent the release of nitrogen gas into our blood meaning that gas will form into bubbles which will remain trapped in our tissue. That can lead to decompression sickness or the Bends!
A drysuit is one excellent way of making your winter dives safer. A drysuit is designed to keep you DRY. It has seals around the wrists and neck and separate hood and gloves. Everything other than your head and hands are dry. Under the suit you would wear an undergarment, thinner during summer and thicker during winter. The undergarment traps a layer of air and that is what you heat to keep your body warm. Besides being safer, it takes 20% less energy to heat a body in a drysuit than it does in a wetsuit. Undergarments like ‘Fourth Element’ also wick any moisture, such as sweat, away from the skin to the outer layer of the garment.
During the drysuit dive you will maintain the circulation in your arms and legs, so your head and hands stay warm as well. Dry gloves are an option if you have circulation problems with your hands and thicker hoods are available. More importantly, on ascent, nitrogen in your tissue will release normally from your tissue into your blood and out safely through your lungs. The side benefit of a safe drysuit dive is you will also be warm and comfortable!