NAUI Scuba Diver 112 Diving Science Verify What You Have Learned Review the following questions about squeezes and blocks: 16. Which air spaces in your body are affected by changes in pressure? ____________________________ ____________________________ ____________________________ ____________________________ 17. What problems might occur if you attempted to dive with a cold? ____________________________ ____________________________ 18. If you feel pressure on your face when descending, you should ____________________________. 19. When the pressure outside an air space is greater than the pressure in an air space, you have a condition called a ____________________________. 20. What are three consequences of ignoring an ear squeeze? ____________________________ ____________________________ ____________________________ ____________________________ 21. What is the most likely cause of a sinus squeeze?_______________________ 22. Which type of squeeze is the easiest to prevent? ____________________________ 23. When the pressure inside an air space is greater than the outside pressure, you have a condition known as a ____________. THE ANATOMY OF YOUR LUNGS Your lungs are inside large cavities within your chest. When you breathe in, they inflate, and when you exhale, they deflate. Your lungs consist of millions of tiny air sacs, called alveoli. The alveoli are surrounded by capillaries, which are tiny blood vessels (figure 4-27). Lung Overexpansion Injuries Whenever you breathe compressed air under pressure, you are exposed to the risk of a lung overexpansion injury. These injuries are rare and most divers never experience them, but they are life threatening and you must understand their causes and how to prevent and deal with them. Under normal conditions, as you ascend, you breathe in and out in a relaxed manner. You exhale the compressed air from your lungs before it can expand as a result of the decreasing pressure. If you hold your breath, you can suffer a serious lung injury. With your airway closed, the air expanding in your lungs will cause the alveoli to rupture soon after they reach their full volume. There is no sensation of discomfort that warns you when this rupture is about to occur. This type of accident most commonly occurs when divers panic under water and make a rapid ascent holding their breath. One cause is running out of air. It is instinctive to hold your breath when you cannot breathe under water. You must train yourself to exhale in any situation that would force you to ascend with no air to breathe. A lung overexpansion injury can occur in as little as 1.1 meters (4 feet) of water and is actually most likely to occur in shallow depths. You must understand the importance of not holding your breath at any time while under water. If a lung overexpansion injury occurs, it is extremely serious and can be fatal. You might think it would be a good idea to keep your lung volume as low as possible by forcefully blowing out all the air you can during an ascent. In reality, forcing air out during an ascent is not the best thing to do. Some small airways in your lungs can collapse when your lung volume is too low and the air trapped behind the collapse can expand and cause alveoli to
19116TC
To see the actual publication please follow the link above