Chapter 4- Diving Physiology Diving Physiology 109 increases your ventilatory drive, but to a smaller extent than high CO2 level. Breathing rate can rise during emotional stress such as fear.) Several factors can slow your respiration. Low CO2 from hyperventilation reduces your drive to breathe, sometimes so much that you can become unconscious. More on this is in the section on Hyperventilation. Your breathing rate slows during relaxation, some phases of sleep, and during the stupor of watching certain television shows. Work of breathing and high partial pressure of oxygen, both found in some diving situations, decreases rate, and are related to carbon dioxide toxicity, discussed further in that section. So your lungs breathe in and out, in and out, and exchange oxygen and carbon dioxide. They also have several other interesting functions. One is to filter all kinds of dust, bacteria, and particles that sweep through them all the time. In one experiment, lungs filtered out small glass beads injected into the blood stream. Lungs also efficiently filter out gas bubbles after diving. Such filtering keeps bubbles, in most cases, from going back to your heart and being pumped from there to the rest of your body. Too many bubbles can overwhelm your lungs ability to filter them. You will see how this is a problem in the sections on Decompression and Arterial Gas Embolism. Circulation After you do all this breathing, oxygen still needs to get to the rest of you from your alveolar capillaries (figure 4-4). Your blood is the ferryboat. Blood stays busy with many functions. It travels through your body, teeming with cells and proteins, food and water, disease fighters, and repair kits. This section focuses on blood’s role in bringing you oxygen. Your blood is mostly water, but water doesn’t dissolve oxygen very well. Your blood solves that problem by packaging a red protein molecule called hemoglobin inside Vein Abdomen Gas Exchange in the Lungs Bloodstream Gas Exchange in the Tissues Air Arterial (Outgoing) Venous (Incoming) Body Tissue Tissue CO2 O2 O2 CO2 FIGURE 4-4. CIRCULATION AND RESPIRATION.
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