Gas Exchange and Transport Quiz 3.txt

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Gas Exchange and Transport Quiz 3.txt
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2012-02-04 18:49:00
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Crafton Hills College RESP 135 Gas Exchange Transport Quiz
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Crafton Hills College RESP 135 Gas Exchange and Transport Quiz 3
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  1. What are the differences between the mechanisms by which oxygen and carbon dioxide are transported in the blood?
    • Blood carries oxygen in two forms:
    • 1. dissolved in the plasma and erythrocyte intracellular fluid
    • 2. combined with hemoglobin in the red blood cell (RBC): MAJORITY IS CARRIED HERE!

    • Gaseous oxygen diffuses into the blood and dissolves in the plasma and erythrocyte fluid
    • Most blood oxygen is transported in chemical combination with hemoglobin (Hb) in the erythrocytes
  2. How do you calculate dissolved oxygen in the plasma?
    • Dissolved oxygen (ml/dl) = PO2 X 0.003
    • 0.003 is the solubility coefficient of oxygen at 1 mmHg in 100ml of plasma
  3. Describe and calculate oxygen carrying capacity of hemoglobin.
    • In whole blood, each gram of Hb can carry about 1.34 ml of oxygen.
    • Average Hb is about 15 g/dl
    • To compute the oxygen-carrying capacity of the blood we use the following formula:
    • 1.34 ml/g X Hb = Hb O2 carrying capacity
    • 1.34 ml/g X 15 g/dl = 20.1ml/dl
  4. Define and compute oxygen saturation of hemoglobin.
    • Saturation is a measure of the amount of available hemoglobin that is actually carrying oxygen.
    • It is content (HbO2) divided by capacity (total hemoglobin) expressed as a percentage.
    • SaO2 = [HbO2]___ x 100
    • Total Hb

    • Example: Total Hb = 15 g/dl and HbO2 = 7.5g/dl
    • SaO2 (%) = 7.5____ X 100 = 50%
    • 15
    • This hemoglobin is 50% saturated so it is only carrying half its oxygen
  5. What is the relationship of HbO2 and PO2 and the oxygen dissociation curve?
    • Hb saturation with oxygen varies with changes in PO2
    • Below 60mmHg, the curve steepens. Here, a small drop in PO2 causes a large drop in SaO2 indicating a lessening affinity for oxygen
  6. How do you calculate total oxygen content of the blood?
    • Must have three variables; (1) PO2, (2) total hemoglobin content (g/dl), and (3) hemoglobin saturation.
    • CxO2 = (0.003 X PxO2) + (Hbtot x 1.34 X SxO2)
    • CaO2 = (0.003 X 100) + 15 X 1.34 X 0.97
    • CaO2 = (0.3) + (19.5)
    • CaO2 = 19.8 ml/dl
  7. What is normal arterial SaO2?
    97 %
  8. What is normal venous SvO2?
    75%
  9. What values occur at loading point for oxygen to hemoglobin occur?
    PaO2 of 100 mmHg and SaO2 of 97%
  10. What values occur at unloading point for oxygen to hemoglobin occur?
    PvO2 of 40 mmHg and SvO2 of 73%
  11. What is the normal arterial-venous oxygen content difference and what is its significance?
    • 4-8, or 5 ml/dl and is the amount of oxygen given up by every 100 mls of blood on each pass through the tissues
    • The C(a-v)O2 indicates the amount of oxygen removed in relation to blood flow
  12. What are normal values for oxygen content of arterial and venous blood?
    • Combined O2 (1.34 x 15 X SO2) 19.5 14.7
    • Dissolved O2(PO2 X 0.003) 0.3 0.1
    • Total O2 content 19.8 14.8 (difference of 5)
  13. What is Fick's equation for calculating cardiac output?
    • Qt = VO2______
    • C(a-v)O2 X 10

    • Qt is cardiac output (L/min)
    • VO2 is whole-body consumption (ml/min)
    • C(a-v)O2 is the arteriovenous oxygen contents difference (ml/dl)
    • 10 converts ml/dl to ml/L

    • Using a normal VO2 of 250 ml/min and a normal C(a-v)O2 of 5 ml/dl you can calculate the cardiac output:
    • Qt = VO2___
    • C(a-v)O2 X 10
    • Qt = 250 ml/min________
    • 5 ml/dl X 10
    • Qt = 250 ml/min________
    • 50 ml/L
    • Qt = 5.0 L/min
  14. What is normal VO2 value and normal C(a-v)o2?
    250 ml/min; 5 ml/dl
  15. What is the Significance of the C(a-v)O2?
    If the oxygen consumption remains constant, a decrease in cardiac output will increase the C(a-v)O2 and if the cardiac output rises, the C(a-v)O2 will fall proportionately.
  16. What are the factors affecting oxygen loading and unloading?
    • blood pH,
    • body temperature,
    • erythrocyte concentration of certain organic phosphates (2,3 DPG),
    • Hb structure variations
    • Other substances combining with Hb (ex. carboxyhemoglobin)
  17. How does a low pH (acidity) shift the oxyhemoglobin dissasociation curve and what happens from that shift?
    • Right;
    • When the curve shifts to the right, the % Hb sat for a given PO2 falls (decreased affinity for oxygen)
  18. How does a high pH (alkalinity) shift the oxyhemoglobin dissasociation curve and what happens from that shift?
    • Left;
    • As the curve shifts to the left, the % Hb sat for a given PO2 rises (increased affinity of Hb for oxygen).
  19. What is the Bohr effect?
    alters the position of the HbO2 dissociation curve due to changes in blood pH. These changes enhance oxygen loading in the lungs and oxygen unloading in the tissues. As blood in the tissues picks up CO2, pH falls, the curve shifts to the right. With lower affinity for oxygen, Hb more readily gives up its oxygen to the tissues. Venous blood returning to the lungs, pH goes up to 7.40 and shifts the HbO2 curve back to the left to aid loading at the lungs.
  20. How does a drop in body temperature affect the HbO2 curve, oxygen affinity, and oxygen loading/unloading?
    Left; increases affinity; decreased unloading
  21. How does an increase in body temperature affect the HbO2 curve, oxygen affinity, and oxygen loading/unloading?
    Right; decreases affinity; increased unloading
  22. What is P50?
    • the partial pressure of oxygen at which the Hb is 50% saturated, at 7.40 pH
    • Normal P50 is about 27 (26.6)mmHg
  23. Where is 2,3-diphosphoglycerate (2,3-DPG) found, and what does it do?
    found in the red blood cells. It stabilizes the deoxygenated Hb molecule, reducing its affinity for oxygen. Without 2,3-DPG normal oxygen unloading would be impossible
  24. What does an increased 2,3-DPG cause and what causes an increase in it?
    • shifts the HbO2 curve to the right, increased oxygen unloading or decreased affinity of Hb for oxygen
    • Things that cause it:
    • alkalosis
    • chronic hypoxemia
    • anemia
  25. What does a decreased 2,3-DPG cause and what causes a decrease in it?
    • shift the curve to the left, increased affinity of Hb for oxygen (loading)
    • What causes this:
    • acidosis
    • banked blood-(stored blood)
  26. What does increased P50 mean?
    the curve is shifted to the right, increased unloading, decreased affinity of Hb for O2.
  27. What does decreased P50 mean?
    the curve is shifted to the left, increased affinity of Hb for O2 and decreased unloading
  28. How many different abnormal hemoglobins are there and what percents are usually found in a healthy individual?
    120; 15-40%
  29. What causes methemoglobinemia and what are common symptoms?
    nitrite poisioning; Blood looks brownish in color, and skin color is grayish
  30. How much stronger is the affinity for CO than Oxygen?
    200 times
  31. Where does HbCO shift the HbO2 curve and how do we treat it?
    • Left (harder unloading);
    • increasing oxygen concentration to decrease the half life of CO and to supersaturate the plasma to keep oxygen going to the tissues. Hyperbaric oxygen (HBO) is recommended for use, usually with patients of 25% or greater HbCO
  32. What things will shift the HbO2 curve to the right?
    • low pH (acidity)
    • increase in body temperature
    • increased 2,3-DPG
    • increased P50
  33. What things will shift the HbO2 curve to the left?
    • high pH (alkalinity)
    • decrease in body temperature
    • decrease 2,3-DPG
    • decreased P50
    • HbCO
  34. What things cause a decrease for affinity of O2?
    • low pH (acidity)
    • increase in body temperature
    • increased 2,3-DPG
    • increased P50
  35. What things cause a increase for affinity of O2?
    • high pH (alkalinity)
    • decrease in body temperature
    • decrease 2,3-DPG
    • decreased P50
  36. Does oxygen affinity for Hb and oxygen unloading/loading increase/decrease in the same or opposite directions?
    Opposite, if one is increase, the other will be decreased

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