Problem
Suzy is a 14 year old with pulmonary fibrosis. This disease causes progressive scarring of the lungs and therefore, reduced inspiratory volumes and chronic hypoxemia. Suzy is very inquisitive. Due to her disease, she knows that when she breathes in, her lungs help to bring oxygen into her blood, and when she breathes out, she gets rid of carbon dioxide from her blood. At her appointment today, you note that she has cyanosis (blue coloration) and clubbing in her fingers and toes - symptoms of hypoxemia. When Suzy asks why her fingers and toes look the way they do, you tell her that she is not getting enough oxygen to them. This answer does not satisfy Suzy! She then asks:
I. "How EXACTLY does oxygen get into my blood and carbon dioxide get out of my blood when I breathe?" (How do I oxygenate my blood?)
II. "And how does the oxygen get from my blood into my toes and fingers so they won't turn blue?" (How do I oxygenate my tissues?)
Be thorough (or Suzy will just keep asking "how...why?" She is annoying like that!)
For both I and II: Be sure you describe the events in the correct sequence. Your answer should include the how each gas's partial pressure affects its diffusion, and the chemical reactions that occur within the blood during gas exchange.
III. Concerned, the doctor asks you to determine Suzy's inspiratory reserve volume (IRV). Using a spirometer, you measure her tidal volume (TV) at 100 mL, expiatory reserve volume (ERV) at 800 mL, and her vital capacity (VC) at 1100 mL. What is her inspiratory reserve volume?
IV. Finally, you treat Suzy by giving oxygen via a mask. Explain why this would be helpful in oxygenating her blood even though her inspiratory volumes are reduced.