NAUI Master Scuba Diver 110 Diving Physiology your red blood cells. A small amount of oxygen dissolves in your blood plasma (the part of your blood without cells), but it is your red blood cells that pick up the most oxygen for the ride around your body. Hemoglobin enables your red blood cells to carry much more oxygen than they could carry without the hemoglobin. Four oxygen molecules loosely attach to each hemoglobin to form oxyhemoglobin, which carries about 98% of the oxygen in your blood. A hemoglobin molecule with four oxygen molecules bound to it looks red, while a hemoglobin molecule without bound oxygen molecules is so dark red that it looks blue. This is why your oxygenated (arterial) blood looks red and your deoxygenated (venous) blood looks blue. It is also why, if all of your blood is deoxygenating from a serious injury or disease process, all of you can look blue. Hemoglobin also combines with a small amount of carbon dioxide to make carbaminohemoglobin and can combine with carbon monoxide (CO) to make trouble, discussed later. From your lungs, oxygenated blood goes not to your body but directly to the left side of your heart. It is the left side of your heart that pumps blood through muscular vessels called arteries to your body. Your arteries branch to smaller and smaller arterioles until blood reaches your network of tissue capillaries - nearly 100,000 kilometers (60,000 miles) of tiny canals where you feed, clean, repair, and defend your cells, and exchange oxygen and carbon dioxide to stay alive. Oxygen diffuses from your blood to your tissues. Your body uses some of the oxygen but not all. At rest you use little oxygen. That is why mouth to mouth resuscitation can work. The air you breathe out contains enough oxygen to be used again. To put that in numbers, you breathe in about 21% oxygen, or about one-fifth of the air, and breathe out about 17% at rest, or about onesixth. When you exercise, your body needs more oxygen, so your cells extract more of the oxygen your blood provides. Average exercise increases the rate of oxygen supplied to your active tissues by about 10 times. That means that the exercise is about 10 times more work for your body as just sitting still. Heavy exercise can increase it to around 20 times, depending on how much aerobic capacity you have. Aerobically fit people can extract much more oxygen when exercising, and so they can do much more exercise. The better aerobic shape you are in, the more work your body can do without reaching your maximum oxygen carrying capability. World-class athletes have been recorded to reach over 30 times their resting rate; quite an achievement. Breathing in more oxygen won’t increase your ability to extract more oxygen. Only regular aerobic exercise will make the changes in your body that you need to do that. Read about how to do this in the section “Fitness for Diving.” Carbon dioxide diffuses from your cells into the blood in your capillaries. Your capillaries join your venules, which join your veins to bring leftover oxygen and the carbon dioxide you produce back to your heart. The right side of your heart collects this “used” blood and pumps it to your lungs. Your lungs get rid of the carbon dioxide, pick up new oxygen, and send filtered, oxygenated blood back to your left heart. The story starts all over when your left heart pumps this “fresh” blood to everywhere in your body through your arterial system. You have about 500 milliliters (one pint) of blood for every six and a half kilograms or so of body weight (14 pounds). The left side of your heart has the hard job of pumping all this blood to your entire body, so it is larger and more muscular than the right side of your heart. It is also the side that gets the most trouble, if you’re going to have heart trouble. The medical section discusses heart trouble in more detail. A little bit of used blood gets shunted back to your body, from the blood supply that partially feeds your lung and heart cells. But normally, oxygenated filtered blood and “used” blood don’t meet very much. That works well, because you do not want much “used” blood going back to your body. In diving, you also do not want many bubbles, formed from the decompression process in your veins, going back to your body or to your brain through your arteries. One way old and new blood can meet is through a hole joining the two sides of your heart. A patent foramen ovale (PFO) is an oval opening between the right and left sides of the upper chambers of your heart, called atria. (In Latin, foramen means opening, and ovalis
20047TC
To see the actual publication please follow the link above