B4.023 - Mechanisms of Ventilation

Question 1

what are the 4 components of respiration

Answer 1

Ventilation

Alveolo-capillary diffusion

blood gas transport

capillary-cell diffusion

Question 2

for ventilation to occur what 2 things have to happen

Answer 2

1. create airflow 2. stretch the lungs

Question 3

what is PTp

Answer 3

Transpleual pressure =Palv - Ppl ~ change in volume/compliance

Question 4

what is PPl

Answer 4

pressure in pleural space, usually negative to help lungs expand

Question 5

what are the opposing tendencies of thorax and lungs

Answer 5

thorax tends to expand lungs tend to recoil these opposing forces create a subatmospheric pressure in thoracic cavity

Question 6

what is transpulmonary pressure

Answer 6

pressure needed to keep lungs open

Question 7

what do each of these lines represent

Answer 7

Question 8

why does pleural pressure drop as you inspire

Answer 8

because the lungs are opening and volume is increasing, and tendency of lungs to recoil is increasing dropping pleural pressure

Question 9

what is happening in the red

Answer 9

forced exhalation and inhalation

Question 10

what does this represent in a lung

Answer 10

increased resistance

Question 11

what does this represent in the lung

Answer 11

decreased compliance

Question 12

in any given lung a higher volume means what

Answer 12

you have a higher PTp

Question 13

higher flow means what

Answer 13

higher resistance

Question 14

to have an increase in flow what else has to increase

Answer 14

difference between Patm and Palv has to increase

Question 15

at all times in the lung PB - Ppl = what

Answer 15

(PB-Palv) + (Palv-Ppl)

Question 16

what happens when you breath in and then pause mid breath

Answer 16

Ppl drops, flow stops, volume stays the same, Palv is 0

PTP STAYS THE SAME!!!

Question 17

What happens to lung pressures in the case of a stiff lung

Answer 17

flow stays the same

Ppl has to decrease a lot more

higher Ptp

Question 18

what happens to lung pressures in the case of increased airway resistance

Answer 18

alveolar and plaural pressures drop so Ptp stays the same

Question 19

how do you measure compliance

Answer 19

Pulmonary compliance = change in lung volume / change in Ptp

Question 20

what is the change in lung compliance if Ppl changes to -10

Answer 20

compliance goes up

from 2500/10 –> 2500/5

lung is easy to inflate but hard to compress

Question 21

what does the slope of this line represent

Answer 21

compliance

Question 22

what are 2 main factors of elastic properties of lung

Answer 22

elastic fibers in lung - tether and stretching

surface tension

Question 23

in the setting of emphysema what happens

Answer 23

you lose elastic fibers which make the lungs more compliant but harder to deflate

rubber band –> celofane bage

Question 24

what is laplaces law

Answer 24

pressure needed to keep alveoli open is inversely related to radius of alveoli

P=2ST/radius

Question 25

what happens if two differently sized alveoli are connected

Answer 25

the smaller will collapse into the larger one as lung volume becomes smaller during forced expiration. the tendency of alveoli to collapse increases

Question 26

what is surfactant

Answer 26

a lipoprotein that acts as a detergent, lowers ST lowering pressure needed to keep alvioli open

Question 27

what happens to effective concenatration of surfactant as radius decreases

Answer 27

it increases, works better in smaller alveoli

Question 28

what happens if there is insufficient surfactant?

Answer 28

1. decreased compliance 2. atelectasis 3. pulmonary edema

Question 29

where is the site of highest airway resistance

Answer 29

nose

Question 30

what accounts for 10% of total resistance in airways

Answer 30

airways \<1mm diameter

Question 31

how do you calculate total airway resistance

Answer 31

PB-Palv/airflow

Question 32

indentify each component of this graph

Answer 32

Question 33

what is TV

Answer 33

tidal volume, how you breath normally

Question 34

what is TLC

Answer 34

max inspiration volume

Question 35

what is IRV

Answer 35

inspiratory reserve volume, amount of air above TV you can breath in

Question 36

what is ERV

Answer 36

expiratory reserve volume, amount of air you can exhale other than RV and under what you normally exhale (TV)

Question 37

what is RV usually in percentage

Answer 37

20%

Question 38

what is VC

Answer 38

total amount you can exhale from max inspiration except residual volume

Question 39

what is FRC

Answer 39

volume in lungs at end of normal expiration

Question 40

what is normal FEV1/FVC

Answer 40

.7-.8

Question 41

what is forced vital capacity

Answer 41

most you can exhale

Question 42

what is FEV1

Answer 42

amount you can exhale in 1 second

Question 43

What does this graph represent

Answer 43

Question 44

what do a, b, c correspond to in this graph

Answer 44

a = highest effort b = normal c = least effort

Question 45

what is the value of the flow volume loop

Answer 45

demostrates effort dependent and independent states of expiration

Question 46

what does effort independent mean on flow volume loops

Answer 46

no matter how hard you expire you cant change slope of line

Question 47

why cant you change the slope of effort independent portion of flow volume loops

Answer 47

greater flow = greater resistance the alveoli sustains increased pressure due to diaphragm relaxation, with maximal effort youre contracting lungs fast as possible and the pressure is increasing, so is pleural pressure. This intra thoracic pressure increase narrows alveolar pressures and increases resistance

Question 48

what is dynamic airway compression

Answer 48

inherent aspect of lungs that slows flow and increases resistance responsible for effort independent portion of volume flow loop When you forcefully contract lungs to exhale the alveolar and pleural pressures both increase significantly, this increases pressure on airways and increases resistance

Question 49

what do lines a and b respresent

Answer 49

a. normal airway resistance b. moderate increase in airway resistance

Question 50

what does line c represent here

Answer 50

severe increase in resistance Note: increased residual volume bc you cant exhale as much as you normally would

Question 51

what are some mechanisms of increased airway resistance (pathology)

Answer 51

Contraction of BSM: Asthsma narrowing of airway lumen: chronic bronchitis loss of elastic recoil : ephysema

Question 52

equation for resistance

Answer 52

resistance = PB-Palv/airflow

Question 53

equation for compliance

Answer 53

compliance = change in volume/change in Palv - PPl