Resp1- Resp Phys 4

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  1. For gas exchange to be efficient, __________ must match ___________.
    alveolar perfusion (Q.); alveolar ventilation (V.A)
  2. Regional changes in __(3)__ in disease can cause marked ventilation/perfusion mismatch, leading to... (2)
    lung compliance, airway resistance, and vascular resistance; ventilated alveoli with no blood supply or blood flowing through unventilated alveoli.
  3. Alveolar ventilation without perfusion (Q=0).
    dead space ventilation
  4. Perfusion without alveolar ventilation (V.A=0).
    right to left shunt- arterial blood does not come into contact with alveolus containing fresh gas
  5. ____________ is the most common cause of hypoxemia (reduced systemic Pa O2).
    Ventilation/perfusion mismatch
  6. Perfusion is better in the ________ portions of the lungs; ventilation is better in the _________ portions of the lungs.
    lower; upper
  7. What local reflexes are present in lung that can limit ventilation/perfusion mismatching? (2)
    hypoxic vasoconstriction and hypocapnic (state of reduced CO2 in the blood) bronchoconstriction
  8. What is hypoxic vasoconstriction?
    localized hypoventilation (reduced airflow to alveoli), reducing local PA O2--> causes vasoconstriction of pulmonary arteriole supplying that alveolus, redirecting blood flow towards better-ventilated areas of the lungs
  9. What is hypocapnic bronchoconstriction?
    occurs when airways are exposed to gas with lower than normal PA CO2 (b/c there is no movement of CO2 from blood to alveoli when no perfusion is occurring)--> leads to local bronchoconstriction to redirect airflow toward better-perfused lung regions
  10. What are the 2 forms of O2 carried in blood?
    combined with hemoglobin (measured as %oxyHb or %saturation), dissolved in plasma (measured as PO2- ABG)
  11. O2 content of arterial blood (Ca O2) is the sum of...
    oxyHb and amount of dissolve O2
  12. What are the 2 forms of hemoglobin?
    oxyhemoglobin (HbO2- oxidized Fe+++), deoxyhemoglobin (Hb- reduced Fe++)

    O2 + Hb ⇋ HbO2
  13. What is Hb saturation? What is its main determinant?
    fraction of all Hb that is oxyHb; mainly determined by Pa O2 (b/c the higher the arterial PO2, the more oxygen there is, the more can be taken up by Hb)
  14. The total amount of O2 carried by hemoglobin depends on... (2)
    Hb saturation (which depends on Pa O2) and [Hb] in blood
  15. Loss of Hb due to anemia reduces... (2)
    amount of O2 carried and O2 saturation
  16. Why isn't an oxygen-hemoglobin dissociation curve a linear relationship?
    reaction of the first Hb subunit with O2 FACILITATES reaction of the next with O2 [causes altered conformation by freeing up subsequent Hb subunits]
  17. Describe the oxygen-hemoglobin dissociation curve, and how it is affected by differing PO2 values.
    at low PO2, there is a steep curve (so with small increases in PO2, there are major increases in %oxyHb); at high PO2, the curve is plateaued
  18. At low PO2, how is oxygen-Hb affected?
    O2 and Hb rapidly combine/dissociate (need to be able to rapidly release it to the tissues)
  19. At PO2 above 60mmHg, how is oxygen-Hb affected?
    further increases in PO2 produce only a small increase in %oxyHb saturation
  20. In a normal mammal, hyperventilation or supplemental O2 add __________ O2 to blood because...
    • very little additional; Hb is 100% saturated at 100mmHg so above this, cannot carry more.
    • [HOWEVER, if delivery of air to lungs is impaired by disease, supplemental O2 will considerably increase O2 in blood]
  21. What dictates Pa O2? What does not?
    O2 diffusion from alveolus is only governed by O2 dissolved in plasma; O2 bound to Hb DOES NOT contribute to Pa O2
  22. Even though oxyHb does NOT contribute to Pa O2, it helps determine the total amount of O2 that diffuses across the alveolus because...
    Hb is an O2 sink--> O2 diffuses from alveolar air to plasma--> plasma PO2 increases, promoting O2 diffusion into RBCs--> increased RBC PO2 promotes O2 binding to Hb--> effectively lowering dissolved O2, leading to a decreased Pa O2--> that causes an increased gradient for O2 diffusion into plasma
  23. Plasma PO2 does not reach PA O2 until...
    all Hb is saturated.
  24. How does the Hb sink exchange O2 in the tissues?
    Tissue PO2 is lower than systemic PaO2--> O2 diffuses from plasma to interstitial fluid--> IF PO2 increases, which promotes O2 diffusion into cells --> lowers PO2 of IF, promoting diffusion of O2 from plasma--> decrease in plasma PO2--> dissolved O2 diffuses from RBC to plasma--> facilitates dissociation of Hb and O2 [overall consequence is transfer of O2 from Hb to plasma to IF to cells by diffusion]
  25. At any given PO2, Hb saturation is modified by... (4)
    blood PCO2, blood [H+], blood temperature, 2,3-DPG
  26. An increase in blood PCO2 shifts the oxyHb dissociation curve to the ____________.
    right (Hb decreased affinity for O2- more easily delivered to the tissues)
  27. An increase in blood [H+] shifts the oxyHb dissociation curve to the ____________.
    right(Hb decreased affinity for O2- more easily delivered to the tissues)
  28. An increase in blood temperature shifts the oxyHb dissociation curve to the ____________.
    right(Hb decreased affinity for O2- more easily delivered to the tissues)
  29. An increase in 2,3-DPG shifts the oxyHb dissociation curve to the ____________.
    right(Hb decreased affinity for O2- more easily delivered to the tissues)
  30. How does altered metabolism and increased production of CO2 alter affinity of Hb for O2?
    CO2 and H+ combine with globin and alter the conformation of Hb, decreasing its affinity for O2
  31. How does altered metabolism and increased blood temperature alter affinity of Hb for O2?
    increase temp alters conformation of Hb, decreasing affinity for O2
  32. How does altered metabolism and DPG production by glycolysis alter affinity of Hb for O2?
    DPG binds reversibly to Hb, reducing its affinity for O2
  33. What is Henry's Law?
    amount of gas dissolves in a liquid at equilibrium is directly proportional to the partial pressure of the gas with which the liquid is in equilibrium [at equilibrium, partial pressure of gas in liquid and gas phases are identical]
  34. When PO2 is higher in gas phase than liquid phase, O2 will _____________ until equilibrium is reached.
    diffuse into liquid [henry's law]
  35. The concentration of a gas in plasma depends on... (2)
    its partial pressure, its solubility in plasma
  36. __________ solubility of a gas in plasma means greater concentration at any given partial pressure.
  37. If plasma is exposed to 2 gases of differing solubility but the same partial pressure, at equilibrium, ....
    both will have identical partial pressure in the liquid but differing concentrations in the liquid [CO2 is way more soluble than O2- if there's the same partial pressure of each, the conc of CO2 will be way higher]
  38. Quantity of dissolved O2 in blood depends on... (2)
    solubility, partial pressure
  39. Quantity of combined O2 (oxyHb) in blood depends on... (4)
    amount of Hb in blood, carrying capacity of Hb, PO2 in blood, shape of the oxyHb dissociation curve
  40. The O2 content of arterial blood (Ca O2) is the sum of ____________; this is important because...
    dissolves O2 and Hb-bound O2; since Hb is 98% saturated at 100mmHg PO2, O2 supplementation will primarily result in an increase in dissolved O2 (which is insignificant int he grand're not doing much)
  41. The rate of O2 delivery to the tissues (Da O2) depends on.... (3)
    metabolic needs of tissues, heart rate, stroke volume
  42. Cyanosis results from...
    excess amount of deoxyHb in skin blood vessels (esp. mucous membranes); usually due to an impairment in ventilation (rarely problems with Hb itself).
  43. Why don't you get cyanosis with anemia?
    b/c there is less Hb, so all the Hb that is there is saturated with O2 and therefore red
  44. Why is there a greater flow of CO2 than O2 across the alveolus despite a smaller difference in the pressure gradient?
    because CO2 is so much more soluble
  45. What happens to CO2 in blood? (3)
    small amount carried dissolved in the plasma, most of it is converted to bicarb by erythrocytes, some forms carbamino-Hb
  46. As PCO2 increases in blood, the oxy-Hb dissociation curve shifts to the ________ because...
    right (decreased Hb affinity for O2-easier to deliver O2 to tissues); there is a need for increased oxygen delivery.
  47. Hypoventilation results in a relative _________ in Pa CO2, leading to an increase in _______, _________ arterial pH, and ___________.
    increase; [H+]; lower; respiratory acidosis
  48. Hyperventilation results in a relative _________ in Pa CO2, leading to a decrease in _______, _________ arterial pH, and ___________.
    decrease; [H+]; increased; respiratory alkalosis
  49. In exercising muscle, more O2 is consumed, therefore...
    tissue PO2 falls, increasing the diffusion gradient from blood to tissue and increasing the dissociation of Hb-O2.
  50. What is the difference b/w hypoxemia and hypoxia?
    hypoxemia is low Pa O2, while hypoxia is O2 deficiency at the tissue level; hypoxemia is a cause of hypoxia, but it si not the only cause
  51. What are causes of hypoxia? (4)
    hypoxemia, anemia, ischemia, histotoxicity
  52. What is histotoxicity?
    inability of tissue to utilize O2, even though O2 is being delivered at a normal rate (ex. cyanide poisoning, Vit B deficiency)
  53. What are causes of hypoxemia? (5)
    low atmospheric or inspired oxygen (fire, improper anesthesia), hypoventilation, impaired diffusion, vascular shunt, V/Q mismatch (most common)
  54. What are potential causes of hypoventilation, leading to hypoxemia? (3)
    defects i neurologic mechanisms of ventilation, thoracic cage abnormalities, upper airway obstruction
  55. With hypoxemia due to hypoventilation, reduced Pa O2 is ALWAYS accompanied by ________.
    elevated Pa CO2
  56. With hypoxemia caused by a vascular shunt, _________ does not increase because...
    Pa CO2; hypoxemia stimulates increased ventilation.
  57. What are the effects of severe tissue hypoxia?
    cell death
  58. Mild hypoxia results in... (2)
    depressed mental activity (maybe coma), reduced work capacity of muscles
  59. O2 therapy for hypoxia is effective for... (3)
    atmospheric hypoxia (high altitude), hypoventilation  due to increased airway resistance, hypoventilation due to pulmonary edema
  60. O2 therapy for hypoxia is ineffective for... (2)
    hypoxia caused by reduced O2 transport by blood or resulting from inadequate tissue O2 utilization
  61. What are the compensatory mechanisms for acclimation to high altitude? (3)
    peripheral chemoreceptors stimulate ventilation (at low PaO2), kidneys release erythropoietin in response to hypoxemia, increased DPG synthesis (reduced affinity b/w Hb and O2)
  62. Hypercapnia usually only occurs in association with hypoxia caused by... (2)
    hypoventilation or circulatory deficiency.
  63. Hypercapnia is NOT associated with...
    reduce atmospheric oxygen, anemia, poisoning of oxidative enzymes (b/c no CO2 even being produced in these circumstances), increased alveolar perfusion distance (CO2 is still diffusible enough to equilibrate)
  64. What are clinical signs of respiratory compromise? (11)
    lethargy/exercise intolerance, increased f or VT, altered posture, open-mouthed breathing, cyanosis, noisy breathing, excessive nasal secretions, loss of symmetry, cough, sneeze, fever
Card Set
Resp1- Resp Phys 4
vetmed resp1
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