Diving Physiology A Bonus from the 440 Staff Not in your Textbook Pressures Depth P atm P mm Hg 0 1 33 2 67 3 100 4 200 7 300 10 Vol 760 1520 2280 3040 5320 7600 1L 0 5 0 33 0 25 0 14 0 10 Partial Pressures of Gases in Air Gas 0 33 100 200 Air O2 N2 2280 640 2400 5320 1120 4200 760 160 600 1520 320 1200 Free Dive Limitations Alveolar pressures are not isolated from atmosphere As depth increases P across chest wall increases Depths below 100 result in the BIG SQUEEZE SCUBA Function of Regulator Deliver same volume of gas per minute as at sea level However 1L of gas now occupies less volume depending upon depth Must purge breathing tubes As depth increases air supply lasts less time Pgas dissolved in plasma and body fluids depends upon P of that gas As depth and P increases so does gas dissolved in blood Suddenly decrease P gas comes out of solution the Bends Decompression To combat the bends decompression is required Slow release of gases from body fluids due to stepwise decrease of pressure Decompression tables Time and depth Decompression after 1 hour at 200 10 min 50 17 min 40 19 min 30 50 min 20 84 min 10 Total Time 3 hours Gases at High Pressure Nitrogen Narcosis or Rapture of the Deep CO2 narcosis O2 toxicity due to free radicals at PO2 1520 mm Hg nausea twitching disturbed vision disorientation dizziness coma Solutions Replace N2 with inert gas Helium Remove CO2 with increased air flow as depth increases Increased depth decreases air supply time e g 1 hour tank lasts 1 4 hr at 100 Diving Mammals How can a Whale dive for 1 hour a Weddell seal for 15 minutes and a Peking duck for 5 minutes How long can you hold your breath Physiological Adaptations Hematocrit No Hemoglobin 1 5X increase Myoglobin 7X increase Tidal volume 80 of lung volume exhale before a dive prevents the bends O2 consumption decreases during a dive Cardiac Output decreases to 20 of that at rest on surface Vasoconstriction of major arteries Blood flow to skeletal muscles reduced to almost 0 Reflex bradycardia temperature dependent all mammals can be learned Sphincter on posterior vena cava decrease CO Delivers blood to critical Summary Selective delivery of blood O2 to CNS heart Prevent CO2 from reaching CNS Decreased O2 consumption Increased O2 stores in blood and muscle
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