Dynamics Resistance to Flow

Question 1

what is flow equal to?

Answer 1

change in pressure divided by resistance….think about it more pressure pushing helps but more resistance makes it harder to go down

Question 2

in laminar flow, what provides resistance?

Answer 2

the walls of the tube

Question 3

in laminar flow, what is the change in pressure proportional to?

Answer 3

the velocity of flow

Question 4

in turbulent flow, what is the change in pressure proportional to?

Answer 4

the velocity of flow squared

Question 5

what parts of the respiratory tract have turbulent flow?

Answer 5

the trachea and mainstem bronchi

Question 6

what parts of the respiratory tract have transitional flow?

Answer 6

most of the bronchial tree

Question 7

what parts of the respiratory tract have laminar flow? why is this?

Answer 7

the small airways…bc the cross sectional area is so high

Question 8

what is the relationship between resistance and radius of the tube?

Answer 8

resistance is inversely proportional to radius to the 4th power…halving the radius raises the resistance to the 16th

Question 9

does cross sectional area increase or decrease as you move down the respiratory tract?

Answer 9

INCREASE

Question 10

does resistance increase or decrease with expiration? what about inspiration?

Answer 10

resistance increases during expiration and decreases during inspiraition

increase due to smaller radius in small airways
decrease due to increasing radius in small airways

Question 11

on a flow volume loop, when a forced exhalation occurs…explain what the curve looks like and why it is this shape?

Answer 11

the curve is initially sharply increasing then it peaks and has a smaller decreasing slope because the airways are getting more resistance and recoil is running the show not muscles

Question 12

describe how the alveolus pressure changes as you begin forced expiration and transition from end inspiration

Answer 12

the pressure raises from 0 to about 30 and is driving the air out

Question 13

what happens when the intrapleural pressure overcomes the pressure in the airways during expiration?

Answer 13

the airways collapse

Question 14

what causes the decrease in pressure during expiration? what can this cause?

Answer 14

resistance of the airways as they are becoming smaller is increasing…this can lead to airway collapse if pressure becomes smaller than intrapleural pressure

Question 15

what are the two phases of forced expiration?

Answer 15

effort dependent and effort independent

Question 16

in effort dependent forced expiration, where does the pressure of intrapleural cavity overcome the pressure in the airways?

Answer 16

this is in bronchus/trachea so you do not get collapse in effort dependent forced expiration

Question 17

in effort independent forced expiration, where does the intrapleural cavity pressure overcome the pressure in the airway? what happens?

Answer 17

this is in the smaller airways like bronchioles and can lead to airway collapse…the resistance of the small vessels is dropping the pressure faster and leads to their collapse

Question 18

what is the driving force of expelling air in effort independent phase?

Answer 18

elastic force of the lung

Question 19

why are alveoli tethered to small airways?

Answer 19

they help keep them open during expiration and avoid collapsing

Question 20

do obstructive lung breathers breath at higher or lower than normal volumes?

Answer 20

higher volumes to help overcome the resistance of the tightened airways

Question 21

do restrictive lung breathers breath at higher or lower than normal volumes?

Answer 21

breath at lower volumes because of less recoil

Question 22

do obstructive or restrictive flow/volume curves have a scooped out appearance during expiration? why?

Answer 22

obstructive…because airways are collapsing so much quicker due to the increased resistance

Question 23

what is the FEV?

Answer 23

forced expiratory volume in 1 second

Question 24

what is the FVC?

Answer 24

forced vital capacity

Question 25

what is FEV/FVC?

Answer 25

this is the percentage of the forced vital capacity that one can expel in forced expiration

Question 26

what is the normal value for FEV/FVC?

Answer 26

80%..some say 70% (4/5L)

Question 27

is the FEV/FVC higher or lower in obstructive lung disease?

Answer 27

lower…because of the quick collapse of airways

40%

Question 28

is the FEV/FVC higher or lower in restrictive lung disease?

Answer 28

higher…close to 90%

but this is less volume relatively

Question 29

what is the FEF25-75 value representative of in forced expiration?

Answer 29

middle 50% of the FEV

more refelctive of the smaller airways

Question 30

why are the small airways called the silent zone when it comes to obstructive pulmonary disease?

Answer 30

because they barely contribute to the overall resistance of the flow…the flow experiences most of its resistance in the upper airways

Question 31

in forced expiration, how high can you raise intrapleural pressure?

Answer 31

close to 100 cmH2O

Question 32

do restrictive and obstructive lungs have higher or lower maximum flow rates than

Answer 32

lower