Mechanics of Breathing II

Question 1

during inspiration pressure?

Answer 1

intrapleural pressure drops

Question 2

during expiration pressure?

Answer 2

intrapleural pressure increases

Question 3

transmural pressure?

Answer 3

Ptm = alveolar pressure - intrapleural pressure

Question 4

driving pressure?

Answer 4

pressure change from one end of tube to the other

deltaP = V x R

Question 5

laminar flow

Answer 5

P ~ V

Question 6

turbulent flow

Answer 6

P ~ V-squared

Question 7

reynolds number

Answer 7

Re = 2rvd / n

Question 8

end pressure in laminar vs. turbulent?

Answer 8

greater drop in pressure turbulent vs laminar flow

end pressure turbulent < laminar

Question 9

higher velocity of flow?

Answer 9

less pressure

Question 10

resistance = ?

Answer 10

R = (P1-P2) / flow

constant irrespective of flow

1/ r to the 4th

Question 11

turbulent flow

Answer 11

resistance increases with flow rate

Question 12

resistance in lung?

Answer 12

increases in 5-7 generations then drops off

• increase in airways in parallel - cross sectional area increases
• have lower resistance

Question 13

velocity of gas in lung?

Answer 13

highest in trachea (turbulent)
decreases as you go along airway

laminar flow in smaller airways (moving slower)

Question 14

two types of resistance in lung?

Answer 14

airway and tissue

Question 15

tissue resistance

Answer 15

overcome for lung to inflate

-85% of total resistance

Question 16

factors determining cross sectional area of airways

Answer 16

lung volume
lung elasticity
bronchial smooth muscle tone

Question 17

airway resistance and lung volume?

Answer 17

resistance decreases as lung volume increases

Question 18

patient with obstructive lung disease?

Answer 18

breathe at higher lung volumes to decrease airway resistance

ex/ barrel chested in emphysema

Question 19

bronchoconstrictors

Answer 19

medium sized airways (bronchioles)

PNS (ACh and methacholine)
histamine
irritants (cigarettes)

Question 20

bronchodilators

Answer 20

SNS (NE on beta-2 receptors)
beta-2 agonists (isoproterenol and albuterol)
increased P-CO2 in bronchioles

Question 21

parasympathetic on lungs?

Answer 21

bronchoconstriction

Question 22

sympathetic on lungs?

Answer 22

bronchodilation

Question 23

quiet respiration?

Answer 23

transmural pressure remains positive

Question 24

forced expiration?

Answer 24

engage expiratory muscles raises intrapleural pressure which is often positive

Question 25

intrapleural pressure exceeds airway pressure?

Answer 25

transmural is negative

-airways will collapse unless supported by smooth muscle or cartilage

Question 26

extra effort?

Answer 26

leads to compression of alveolus

no increase in flow

Question 27

dynamic airway compression

Answer 27

during forced expiration

• loss of pressure occurs as gas moves from alveolus to mouth
• increasing resistance and velocity
• transition from laminar to turbulent flow

Question 28

forced expiration

Answer 28

dramatic increase in intrapleural pressure

transmural pressure becomes negative (airways close)

Question 29

airway compression driving force?

Answer 29

difference between alveolar pressure and pleural pressure

Question 30

elastic recoil pressure?

Answer 30

difference between alveolar and pleural pressure

Question 31

flow volume loop and emphysema

Answer 31

not much change with inspiration curve

• during expiration, decreased flow-volume loop
• due to airway closure (air trapping)

bronchodilator - expiratory curve will increase

Question 32

obstructive FEV/FVC relationship?

Answer 32

decreased ratio

Question 33

restrictive FEV/FVC releationship?

Answer 33

increased ratio

Question 34

FEV/FVC?

Answer 34

FEV - forced expiratory volume (in 1 second)

FVC - forced vital capacity

Question 35

work of breathing for restrictive?

Answer 35

increased elastic resistance

-around 20 breath is comfortable (rapid)

Question 36

work of breathing for obstructive?

Answer 36

increased airflow resistance

-around 10 breaths is comfortable (slower)

Question 37

airway resistance

Answer 37

decreases with increased volume

Question 38

airways in parallel?

Answer 38

decreases resistance

Question 39

obstructive lung disease?

Answer 39

airflow limitations at early point when compared to normal subjects