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Your planned bottom time has come to an end. You start to head for the surface. What happens to the body as you ascend?
As you start to ascend the partial pressures of your breathing gas decreases which causes off gassing to start in your fast tissues and slows the on-gassing process in your slow tissues. The inert gases are pumped through the body to the lungs where through diffusion and respiration the gas is exhaled.
Thirty percent of adults are estimated to have patent foramen ovale (PFO) whereby the blood can bypass the lungs and recirculate through the arterial system thereby increasing the risk of decompression sickness.
As you continue to ascend the air pressure in your middle ear increases and the air tries to escape. The air escapes through Eustachian tubes and into your mouth from which the air is exhaled. If your Eustachian tubes are clogged your experience may be different with the risk of a squeeze or even alternobaric vertigo. Alternobaric vertigo is where one ear depressurizes but the other doesn’t, fooling the brain into vertigo.
You continue to off-gas and your ears depressurize as you continue to ascend. At the same time the degree of dehydration in the body increases. Each breath of cold, dry inspired air takes moisture and heat from the body. If you are on a closed circuit rebreather (CCR) you can managed these losses more readily. A lack of moisture and heat in the respiratory tract can affect you and make it harder to breathe. In the human body the changes in the respiratory tract affecting breathing are generally made worse by smoking, cold temperatures and low humidity.
You reach the surface. Your body continues to re-establish your inert gas balance, equilibrium and state of hydration on the surface. This can take minutes, hours or days, depending on the dive(s) or diver. The ability of the body to adapt allows us to visit this underwater world of intrigue.
Read our blog article What happens to my body as I descend?.
The original article ‘The Body - Ascending’ by Derek Covington was published in the September 2014 edition of Tech Diving Mag is available here.