Ventilation/Mechanics III

Question 1

Surface Tension in lungs from?

Answer 1

H2O molecules on alveolar walls ->
attracted to other H2O ->
generates collapsing force

Question 2

Collapsing force is related to radius how?

Answer 2

inversely

Question 3

Laplace’s Law eqn

Answer 3

P = 2T/r

P = inward (collapsing) pressure
T = surface tension force
r = radius of alveolar

Question 4

Small alveoli empty into?

Answer 4

larger alveoli

Question 5

Atelectasis is?

Answer 5

alveolar collapse
(tele = far, tasis = stretching)

Question 6

Atelectasis opposed by? (2)

Answer 6

1) alveolar surfactant (disrupts interaction w/ H2O)

2) interdependence of alveoli (support ea other)

Question 7

Surfactant made of? (3)

Answer 7

phospholipid (DPPC)
lipids
proteins

Question 8

Surfactant made by?

Answer 8

Type II alveolar epithelial cells

Question 9

Hyaline Membrane Disease is?

Answer 9

infant respiratory distress synd:
premature infants,
alveoli collapse completely,
low surfactant makes difficult to reinflate

Question 10

Premature Infants surfactant levels?

Answer 10

< 24 wks = none

> 35 wks = sufficient

Question 11

Surfactant role in surface tension?

Answer 11

equalizes (reduces) surface tension forces in large and small alveoli

↑ compliance
↓ collapse of small alveoli
↓ gas discharge from small to large alveoli

Question 12

[Surfactant] is high where?

Answer 12

small alveoli

Question 13

[Surfactant] is related to T (surf tension) how?

Answer 13

inversely

Question 14

Alveolar collapse inhibited by? (2)

Answer 14

1) surfactant

2) surrounding alveoli (tendency for each to collapse cancel ea other out)

Question 15

Work of breathing is?

Answer 15

work req’d to move lung and chest wall

Question 16

Work calculated how?

Answer 16

pressure x vol

Question 17

Work of breating req’s what % of resting metabolic rate?

Answer 17

2-3%

Question 18

Total Work =

Answer 18

elastic work + resistance work

Question 19

Elastic work is?

Answer 19

work needed to expand lung:

65% of total

Question 20

Elastic work dependent on? (3)

Answer 20

1) surface tension
2) elastic elements in lung
3) lung vol (↑ as vol ↑)

Question 21

Resistance work (Raw) is?

Answer 21

work needed to move air through airways (overcome airway resistance):
35% of total

Question 22

Resistant work dependent on? (2)

Answer 22

1) AIRWAY DIAMETER (1/r^4)
2) flow of velocity
(↑ velocity -> ↑ turbulance -> ↑ work)

Question 23

ºVair (Air flow thru airway) =

Answer 23

(Palv - Pmouth)/Raw

Palv = alveoli air pressure
Pmouth = mouth air pressure

Question 24

Raw =

Answer 24

Raw = 8ηl/πr^4

Question 25

Airway resistance (AWR) related to lung vol how?

Answer 25

inversely: AWR ↓ as lung vol ↑ due to radial traction forces expanding the airway

Question 26

Radial Traction Forces (RTF) are?

Answer 26

force of alveoli supporting ea other

Question 27

RTF affected by obstructive dx how?

Answer 27

RTF ↓ | emphysema: tissue destruction so not available to support

Question 28

RTF responds to ↑ lung vol how?

Answer 28

RTF ↑

Question 29

RTF affected by restrictive dx how?

Answer 29

RTF ↑ | fibrosis: tissues held firmly by fibers

Question 30

Obstructive Disease affects airway how? (3)

Answer 30

1) excess secretions 2) thickening of airway wall (edema or hypertrophy) 3) destruction of lung parenchyma (loss of radial traction)

Question 31

COPD flow/volume curves look like?

Answer 31

volume ↓ | flow rate ↓ w/ scooped out on down slope of expiratory curve (middle volumes)

Question 32

Why do COPD pt's purse lips to breathe?

Answer 32

on exhalation, ↑ air pressure -> | ↓ premature collapse