The greatest effect of scuba diving on the lungs, indeed on the human body as a whole, is pressure. To experience the world below the water, your lungs must be healthy to deal with the changing pressure.
What Happens to Lungs When Diving?
The human body works well in the environment it lives in. Air is not heavy, so changes in altitude do not drastically alter the squeezing against our bodies. Water, on the other hand, can be quite heavy, and changes in depth quickly increase or decrease pressure on our bodies. In fact, every 33 feet of depth in water increases the pressure on our bodies by one atmosphere. An atmosphere is the pressure compressing our bodies when standing on the beach at sea level.
Human Lung
You can picture the lung as a sack and inside that sack there are lots of little sacks. Inside the lungs are passages called bronchi, which branch off to smaller passages called bronchioles, which lead to alveolar sacs. The alveolar sacs have very thin walls and are where oxygen is transferred to the bloodstream. Because they are essentially hollow spaces, they are susceptible to the effects of changes in pressure to the body. While the chest cavity is protected by the rib cage, uncontrolled or incorrect breathing can cause significant damage to the lungs.
Descending
As the body gets deeper in water, pressure increases on the body, squeezing the tissue, organs and cavities in the body. Lungs actually get smaller the deeper you go. Scuba diving gear actually compensates for the external pressure by injecting more air into the body with each inhale. Thus breathing will still feel normal at any depth. However, body tissues and organs retain the nitrogen in air when they are under pressure, so rapid and deep breathing will put more more nitrogen in the bloodstream. This can lead to a condition called nitrogen narcosis, which will feel like having too much to drink; including compromised decision-making abilities.
Ascending
The reverse process occurs when ascending to the surface. Because the scuba equipment has compensated for the water pressure and put more air into the lungs, breath-holding while ascending can cause the lungs to over-expand and rupture. This is especially true of the thin-walled alveoli, which if ruptured will lead to bleeding in the lungs. Tissue and organs release the nitrogen they stored back into the bloodstream which is delivered to the lungs for expulsion. Ascending too quickly does not give the body time to deliver nitrogen to the lungs; this leads to the creation of nitrogen bubbles in the bloodstream, tissues and organs, a painful and potentially life-threatening condition called the bends.
Overall Health And Diving
The bodies overall health is very important to ensure safe scuba diving. Obviously, activities that include smoking will compromise the lungs' ability to function properly while diving. Weight and cardiovascular health also effect the efficiency of the lungs and can impact the body's performance in dealing with water pressure. So good health can help you enjoy the new world that lies under the ocean's surface.
