chapter 10

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selenityhyperion
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73053
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chapter 10
Updated:
2011-03-15 09:24:03
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ventilation chapter
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Chapter 10 in Egan's - Ventilation
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  1. Define Ventilation
    the process of moving air between the environment and the alveoli
  2. define respiration
    the process of gas exchange between the alveoli and pulmonary capillary blood
  3. define transpulmonary pressure gradient
    pressure difference btwn the alveoli and the plural pressure
  4. define transairway pressure
    the pressure difference between the alveoli and the entrance of the airway
  5. define transthoracic pressure
    the pressure difference btwn the alveoli and the body surface
  6. what are the 3 pressure gradients responsible for gas movement and lung inflation?
    trans: pulmonary, airway, thoracic
  7. What 2 pressure gradients are the same?
    Transairway and Transthoracic
  8. why must pressure gradients exist?
    for spontaneous ventilation to occur
  9. what is pleural pressure at rest
    subatmospheric
  10. What is the process of inspiration during NORMAL breathing
    diaphragm and external intercostal muscles contract > Ribcage lifts > volume of pleural space increases > (the increase in volume causes a decrease in pleural pressure per Boyle's Law) > Transpulmonary pressure gradient increases > alveoli expand and their volume increases > alveolar pressure becomes subatmospheric > transairway pressure gradient increases > air flows from the airway entrances to the alveoli until muscular effort ceases and the transairway pressure equalizes
  11. process of expiration during NORMAL breathing?
    Diaphragm relaxes and rib cage recoils > plueral space and volume decrease > pleural pressure increases > transpulmonary pressure gradiant narrows (lessens) > alveoli recoil > alveolar space decreases > alveolar pressure becomes supraatmospheric > transairway pressure gradient widens (increases) > air flows out of the lungs until back into the resting state (transairway pressure gradient equalizes)
  12. what are the forces opposing ventilaion of the lung?
    elastic forces ( tissue retraction, ST in alveoli, static forces nor affected by airflow) and non-elastic frictional forces (RAW and tissue movement during breathing)
  13. define surface tension
    tension created at the liquid air interface
  14. define compliance
    the measure of distendability of the lung
  15. define elasticity
    the ability of the lung to return to a normal shape after being stretched
  16. how is ST produced?
    by the cohesive forces of a liquid that attracts the polar liquid molecules away from the interface
  17. What effect does ST have on the lungs?
    draws them inward, causing them to recoil
  18. how does the body combat ST
    with surfactant
  19. define surfactant
    a phospholipid that places itself between the liquid molecules, causing a decrease in cohesive bonding
  20. Is the surfactant layer thicker or thinner in a smaller SA than a greater SA? Why?
    thicker to offset increase ST
  21. What is lung complaince?
    the measure of distendability of the lung
  22. what is the formula for lung Compliance?
    • CL = dV/dP mL/cmH2O
    • V = tidal volume
    • P = transpulmonary pressure gradient
  23. What is the compliance of the lungs and chest wall?
    200 mL/cmH2O and 200 mL/cmH2O
  24. what is the total compliance?
    compliange of lung + compliance of thorax
  25. what is the normal total compliance
    100 mL/cmH2O
  26. what effect does the pressure of surfactant in the alveoli have on compliance? Why?
    increased (less ST so more stretching can be done)
  27. what would happen to compliance in a lung that loses its elastic fibers?
    increase
  28. what effect does increased compliance have on elasticity? why?
    since the lungs would expand more easily by recoil with more difficulty the elasticity would decrease
  29. what effect would decreased compliance have on elasticity? y?
    causes the lungs to distend with difficculty so an increased elasticity

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