RS Lec 4

Question 1

lung compliance (def.) - (3)

Answer 1

• measure of the elastic properties of lungs
• measure of how easily the lungs can expand
• magnitude of change in lung volume produced by change in transpulmonary pressure (slope in P-V curve)

Question 2

two types of lung compliance

Answer 2

• static compliance

- dynamic compliance

Question 3

static compliance (def.)

Answer 3

-lung compliance during periods of no gas flow (during inspiratory/expiratory pause)

Question 4

static compliance determined by

Answer 4

-P/V slope measured at FRC (end of expiratory effort)

Question 5

dynamic compliance (def.)

Answer 5

-lung compliance during periods of gas flow (inspiration, when Ptp changes)

Question 6

dynamic compliance reflects

Answer 6

-lung stiffness, airway resistance

Question 7

dynamic compliance decreases when (2)

Answer 7

lung stiffness/airway resistance increase

Question 8

dynamic compliance & static compliance relationship

Answer 8

-dynamic compliance is less than/equal to static lung compliance

Question 9

pressure-volume relationship (1. Stable VL)

Answer 9

-at low lung volumes, difficult to pop open airways, rising Ptp little effect on lung volume

Question 10

pressure-volume relationship (2. Opening of airways)

Answer 10

-first increases in lung volume open proximal airways, recruitment of other airways

Question 11

pressure-volume relationship (3. expansion of airways)

Answer 11

-all airways are open, Pip is more negative by chest wall expansions, increases V (linear)

Question 12

pressure-volume relationship (4. limit airway inflation)

Answer 12

-at high lung volumes, lung compliance decreases

Question 13

hysteresis

Answer 13

-difference between inflation + deflation compliance paths

Question 14

greater pressure difference (lung compliance)

Answer 14

-needed to open airway than keep from closing

Question 15

lung compliance determined by (2)

Answer 15

• elastic components of lungs + airway tissue (elastin + collagen)
• surface tension at air-water interface in alveoli

Question 16

location of elastic components of airways

Answer 16

-alveolar walls, around vessels, bronchi

Question 17

elastic behaviour determined by

Answer 17

-geometrical arrangements, not typically elongation of fibers

Question 18

collagen (twine) characteristics (3)

Answer 18

• high tensile strength
• inextensible
• stiff (low compliance)

Question 19

elastin (weak spring) characteristics (3)

Answer 19

• low tensile strength
• extensible
• spring- high compliance

Question 20

emphysema (def.)

Answer 20

-floppy lungs due to elastin destruction + alveolar wall destruction

Question 21

emphysema effects (3)

Answer 21

• increased compliance, less elastic recoil
• little Ptp changes, large changes in lung volume
• time to fill increased

Question 22

pulmonary fibrosis (def.)

Answer 22

-collagen deposition in alveolar walls in response to injury, silica dust, asbestosis

Question 23

pulmonary fibrosis effects (2)

Answer 23

• reduction in lung compliance (stiff lungs)

- large Ptp needed for little changes in Lung volume

Question 24

Surface tension (amount for elastic recoil)

Answer 24

-2/3 of elastic recoil of lungs, decreases lung compliance

Question 25

surface tension (def.)

Answer 25

• water molecules at surface attracted to each other

- measure of attracting forces pulling surface molecules together

Question 26

surface tension is seen at

Answer 26

-air-fluid boundaries (hydrogen bonding of water molecules)

Question 27

effect of surface tension

Answer 27

-cause the surface to maintain as small an area as possible

Question 28

saline-filled lung

Answer 28

-surface tension eliminates= small Ptp changes large increase lung volume

Question 29

alveolar collapse due

Answer 29

-ST created inward recoil

Question 30

increased pressure needed to balance

Answer 30

-surface tension, reduces tendency to collapse

Question 31

laplace’s equation

Answer 31

P=2T/r
T- surface tension (c0nstant)
r - radius
P - pressure

Question 32

smaller alveolar radius —>

Answer 32

-greater pressure needed to keep the bubble inflated

Question 33

smaller alveoli collapse

Answer 33

into the large ones, T is constant, pressure greater in the smaller bubbles

Question 34

surfactant produced by

Answer 34

-type II alveolar cells

Question 35

surfactant action (3)

Answer 35

• lowers the surface tension of the lining
• stabilize alveoli collapse
• increase lung compliance, easier to expand lungs

Question 36

surfactant made of (molecules) (5)

Answer 36

• phospholipids:
• dipalmitoyl-phosphatidylcholine (DPPC),
• phosphatidyl-choline
• surfactant apoproteins, Ca2+ ions

Question 37

surfactant properties

Answer 37

-hydrophobic & hydrophilic properties:

enable air-water interface,decreases the density of water molecules, reduces attraction between H20

Question 38

thickness of surfactant relationship with surface area

Answer 38

• thickness decreases with increasing SA,

- cause increase ST as radius increases

Question 39

surface tension remains (regardless of radius/size in lungs)

Answer 39

constant, equalize pressures in alveoli of different sizes (no differences in pressure gradient between small/larger alveoli)

Question 40

surfactant produced during

Answer 40

-last week of gestation

Question 41

IRDS

Answer 41

• infant respiratory distress syndrome

- lack of surfactant

Question 42

ventilation (upright lung)

Answer 42

-largest at bottom lung

Question 43

ventilation (upside down)

Answer 43

-largest at top lung

Question 44

ventilation (back)

Answer 44

-largest at back of lungs

Question 45

weight of lungs increase P at bottom effect on Pip

Answer 45

makes Pip less negative, Ptp decrease- able to expand more

Question 46

Alveoli at bottom

Answer 46

• starting more deflated, can expand more

- bottom regions of lung receive a larger portion of air