Kaplanpulmphysio.txt

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arimoses
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120506
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Kaplanpulmphysio.txt
Updated:
2011-12-03 19:02:43
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Kaplan physiology
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Pulmonary physiology
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  1. What are the lung volumes as seen on spirometry?
    • Tidal Volume (Vt): 500mL, normal amount of gas that enters or leaves in a single respiratory cycle
    • Functional Residual Capacity (FRC): 2700mL, volume of gas left in lungs at end of Vt (passive expiration)
    • Inspiratory capacity (IC): 4000mL, volume of gas that can be inspired from FRC
    • Inspiratory Reserve Volume (IRV): 3500mL, volume of gas that can be additionaly inhaled after normal inspiration
    • Expiratory Reserve Volume (ERV): 1500mL, volume of gas that can be additionaly exhaled after normal expiration
    • Residual Volume (RV): 1200mL, amount of gas left in lungs after maximal expiration
    • Vital Capacity (VC): 5500mL, maximal volume that can be expired after maximal inspiration
    • Total Lung Capacity (TLC): 6700mL, total amount of gas in lungs after maximal inspiration.
  2. Draw a mental spirometry lung volume curve?
    Do it.
  3. What cannot be measured using spirometry, what is used instead?
    • Residual Volume (RV), or anything containing RV (TLC, FRC)
    • Helium dilution
    • plethysmography.
  4. What is total ventilation?
    Total ventilation (ve)= Vt x RR.
  5. Where does anatomic dead space end, what is a good way to approximate anatomic dead space?
    • Terminal bronchioles
    • Persons weight in pounds (i.e. 150lbs = 150mL dead space).
  6. What constitutes alveolar dead space?
    Alveoli containing air but without blood flow in surrounding capillaries.
  7. What is the physiologic dead space?
    Total dead space: anatomical + alveolar dead space.
  8. What is alveolar ventilation?
    • Alveolar ventilation (Va) = (Vt-Vd) x RR
    • Vt: Tidal volume
    • Vd: Dead space.
  9. What is the difference between increasing depth of breathing versus rate of breathing?
    • Increasing depth: increases actual alveolar ventilation because dead space does not change
    • Increasing rate: more ventilation of dead space.
  10. What is the major muscle of inspiration?
    • Diaphragm
    • Chest wall second.
  11. What is the major muscle of expiration?
    • Resting conditions: passive process, relaxation of inspiratory muscles
    • Active expiration: Abdominal muscles.
  12. What are the two main forces acting on the lung?
    • Recoil: acts to collapse lung
    • Intrapleural pressure: usually subatmospheric (negative pressure), acts to expand the lung (or collapse when positive pressure).
  13. What happens to systemic venous return and R ventricular output with inspiration?
    Both are increased.
  14. What happens to venous return to L heart and L ventricular output in inspiration?
    Both are decreased.
  15. What is the reflex increase in heart rate with inspiration (sinus arrythmia)?
    Expansion of R atrium -> drop in BP -> reflex increase in HR.
  16. What does a valsalve maneuver do?
    • Increase intrapleural pressure
    • Increase central venous pressure
    • Decrease venous return.
  17. What is the point of PEEP?
    • PEEP: positive end expiratory pressure
    • prevents collapse of small alveoli (atelectasis).
  18. What are the changes that occur with a simple pneumothorax?
    • Intrapleural pressure increases
    • Lung recoil decreses (lung collapses)
    • Chest wall expands.
  19. Tension pneumothorax most commonly occurs in?
    Patients on positive-pressure ventilator.
  20. What is compliance?
    dP/dV.
  21. What happens to compliance as lungs inflate?
    Decreases.
  22. Very compliant lungs have decreased?
    Recoil.
  23. Stiff lungs have increased?
    Recoil.
  24. What are the two components of lung recoil?
    • Lung Tissue: collagen and elastin fibers, larger lungs have greater recoil
    • Surface Tension: Greatest component of recoil.
  25. How does the law of LaPlace involve two different sized alveoli?
    • If wall tension is the same in both alveoli, the smaller alveolus will have greater pressure
    • i.e. more likely to collapse.
  26. What are the three main functions of surfactant?
    • Lowers surface tension: lowers lung recoil, increases compliance
    • Lowers surface tension more in smaller alveoli: decreases tendency for atelectasis
    • Decreases capilllary filtration pressure: Decreases negative intrathoracic pressure.
  27. What is the cause of infant respiratory distress syndrome, another name?
    • Deficiency of surfactant
    • Hyaline Membrane Disease.
  28. What are the two main causes of adult respiratory distress syndrome (ARDS)?
    • Sepsis: injury to endothelial capillary membrane by neutrophils
    • Gastric Aspirations: direct injury to lung epithelium.
  29. What are the three main symptoms of ARDS?
    • Increased lung recoil, decreased compliance
    • Atelectasis
    • Pulmonary edema.
  30. Resistance of an airway equals?
    Resistance= 1/radius^4.
  31. What bronchi represent most of the airway resistance?
    First and second.
  32. What produces bronchoconstriction?
    Parasympathetic nerve stimulation.
  33. What produces bronchodilation?
    Circulating catecholamines.
  34. What is normal FEV1/FVC?
    80%.
  35. What characterizes obstructive pulmonary disease, what is it measured as?
    • Increase in airway resistance
    • Decreased expiratory flow rates
    • FEV1/FVC: 50%.
  36. What characterizes restrictive pulmonary disease, what is it measured as?
    • Inrease in lung recoil, decreased compliance
    • Most lung volumes decreased, especially FRC, RV
    • FEV1/FVC: 88%.
  37. How do you calculate the partial pressure of a gas?
    • Pgas = Patm x Fgas
    • Pgas: partial pressure of gas
    • Fgas: concentration of gas
    • Patm: atmospheric pressure.
  38. How do you calculate the partial pressure of an inspired gas?
    PIgas= Fgas x (Patm-PH2O).
  39. What does partial pressure of water (PH2O) depend on?
    • Temperature only
    • at 37 C: 47 mm Hg.
  40. What is the normal Alveolar-arterial (A-a) gradient?
    5-10 mm Hg.
  41. What two factors affect alveolar PCO2 (PACO2)?
    • Metabolic production of CO2: constant under normal circumstances
    • Alveolar ventilation: inversely related to PACO2.
  42. What is the equation showing factors that affect Alveolar PO2 (PAO2)?
    • PAO2 = (Patm-47)FIO2 x PACO2/R
    • R: Respiratory exchange ration = o.8.
  43. What factors affect diffusion of a gas between alveoli and capillaries (gas exchange)?
    • Fick Law of Diffusion
    • Vgas= A/T x D x (P1-P2)
    • Vgas: rate of gas diffusion
    • A: surface area of lung
    • T: Thickness of membrane
    • P1-P2: Pressure gradient.
  44. What are the two terms to describe dynamics of substance transfer b/w capillaries and interstitium?
    • Perfusion-limited: the substance equalizes
    • Diffision-limited: the substance does not equalize.
  45. What is a classic, always diffusion limited substance?
    Carbon Monoxide (CO).
  46. What is a normal CO uptake?
    25 mL/min.
  47. What is the normal carrying capacity for O2?
    • 20% volume
    • .2mL O2/1 mL blood.
  48. What shifts the O2-Hb curve to the left?
    • Increased CO2 (Bohr Effect)
    • Increased H+ (decreased pH)
    • Increased 2,3-DPG
    • Increased Temperature.
  49. What shifts the O2-Hb curve to the right?
    • Everything opposite as left
    • Fetal Hemoglobin (HbF)
    • Stored blood (loss of 2,3-DPG).
  50. About 90% of CO2 is carried as?
    Plasma Bicarbonate (H2CO3).
  51. What enzyme is needed to convert CO2 into bicarbonate, where is it found?
    • Carbonic anhydrase
    • Insede red cell
    • CO2 + H2O -> H2CO3 -> H+ + HCO3-.
  52. What is the main drive for ventilation under normal conditions?
    CO2 (H+) on central chemoreceptors.
  53. Where are the central chemoreceptors found, what do they sense?
    • Close to surface of medulla
    • CSF H+: CO2 freely crosses BBB, bicarbonate dissociates -> H+.
  54. What are the two peripheral receptors and afferent nerves?
    • Carotid bodies: Carotid sinus, Glossopharyngeal nerve IX -- most important
    • Aortic bodies: Aortic arch, Vagus nerve X.
  55. What do the peripheral receptors respond to?
    PO2 in very hypoxic situations.
  56. Which receptors adapt, which do not?
    • Central chemoreceptors adapt
    • Peripheral do not.
  57. What nerve communicates the medulla (breathing center) to the diaphragm?
    Phrenic nerve.
  58. A lesion at what levels would preveng diaphragmatic breathing?
    Complete C1 or C2.
  59. What is Apneustic breathing?
    • Prolonged inspiration with shortened expiration
    • Lesion in caudal pons.
  60. What is Biot's breathing?
    • Alternating apnea with periods of identical depth breaths
    • Seen in increased intracranial pressure and midbrain lesions.
  61. What is Cheyne-Stokes breathing?
    • Alternating apnea with periods of "crescendo-decrescendo" depth breaths
    • Seen in infants and sleep, also some midbrain lesions.
  62. What are four causes of hypoxemia?
    • Hypoventilation
    • Diffusion Impairment
    • Pulmonary (right to left) shunt
    • Ventilation-perfusion mismatch.
  63. What happens to the A-a gradient with hypoventilation?
    • No change
    • Decrease of PO2 equal in all compartments (Alveolar, end capillary, systemic arterial).
  64. What does an A-a gradient greater than 10 usually signify?
    Diffusion impairment.
  65. What is a clue of a pulmonary shunt?
    Failure to correct hypoxemia with supplemental oxygen.
  66. Which alveoli recieve more ventilation, apex or base?
    • Base: higher compliance (less inflated at rest)
    • Apex have more negative pressure -> more inflated at rest -> lower compliance.
  67. What is the ideal ventilation/perfusion (V/Q) ratio, what does it mean when it is lower, higher?
    • V/Q: 0.8, pH= 7.4
    • V/Q < 0.8: underventilated, pH <7.4
    • V/Q > 0.8: overventilated, pH > 7.4.

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