Dynamics: Resistance to Air Flow

Question 1

airway caliber changes during

Answer 1

• the breathing cycle

Question 2

resistance is dependent upon

Answer 2

• radius of airway

- airflow pattern

Question 3

is resistance constant?

Answer 3

• no

Question 4

what is airflow pattern determined by

Answer 4

• flow rates

Question 5

describe laminar flow

Answer 5

• parabolic flow pattern

- center moving faster than near tube walls

Question 6

pressure drop in laminar flow

Answer 6

• directly proportional to flow rate

Question 7

describe turbulent flow

Answer 7

• vortices and eddies that increase reaction of fluid with tube wall
• consumes energy

Question 8

pressure drop in turbulent flow

Answer 8

• proportional to square of flow rate

Question 9

describe transitional flow

Answer 9

• intermediate state with elements of both laminar and turbulent flow
• eddies present at constrictions or branch points

Question 10

flow if pressure difference doubled in turbulent flow

Answer 10

• flow will be less than doubled

- it will be the square route of the doubled pressure difference

Question 11

where in the lungs do we find turbulent airflow

Answer 11

• trachea
• maintstem bronchi
• large diameter structures

Question 12

where in the lungs do we find transitional airflow

Answer 12

• most of bronchial tree

Question 13

where in the lungs do we find laminar airflow

Answer 13

• small airways like the normal bronchioles

Question 14

the pressure difference driving airflow is highest where (in regards to type of flow)

and lowest where

Answer 14

• where flow is turbulent

- lowest where flow is laminar

Question 15

resistance compared to radius in a tube under laminar flow conditions

Answer 15

• resistance inversely proportional to 4th power of the radius

Question 16

relationship of flow to tube length

Answer 16

• inverse

Question 17

relationship of resistance to tube length

Answer 17

• directly proportional

Question 18

resistance to flow is highly dependent on

Answer 18

• airway generation

Question 19

the exponential increase in airway number and cross sectional area results in

Answer 19

• decrease in aggregate airway resistance

Question 20

the highest resistance in the lung is present in

Answer 20

• segmental bronchi

Question 21

during the final stages of gas exchange in the respiratory zone, gas molecule move more by

Answer 21

• diffusion than bulk flow

Question 22

why are small airways considered the “silent zone”

Answer 22

• contribute minimally to lung resistance

- disease in these areas must become well advanced before it is easily detected

Question 23

airway caliber and resistance during inspiration

Answer 23

• airway caliber increases

- resistance drops

Question 24

airway caliber and resistance during expiration

Answer 24

• airway caliber decreases

- resistance increases

Question 25

where is total lung capacity located on the flow-volume loop?

Answer 25

- left most point

Question 26

where is residual volume located on the flow-volume loop?

Answer 26

- right most point

Question 27

at the beginning of expiration, airflow out of the lung is ________ upon the force of expiration

Answer 27

- dependent

Question 28

after a certain amount of time of expiration, airflow out of the lung is __________ upon the force of expiration

Answer 28

- independent

Question 29

effort independent phase of forced expiration due to

Answer 29

- dynamic compression of non-cartilaginous airways at lower lung volumes when airway radius is smaller and resistance is greater

Question 30

flow during inspiration on the flow-volume loop is

Answer 30

- symmetrical

Question 31

maximal inspiratory flow develops where on the flow-volume loop

Answer 31

- halfway between RV and TLC

Question 32

FRC represents

Answer 32

- the point where the outward recoil of the chest counterbalances the elastic recoil of the lung

Question 33

the net result of increased airway resistance is that

Answer 33

- pressure drop within airway from alveolus towards mouth becomes much steeper

Question 34

equal pressure point on effort dependent expiration

Answer 34

- located inside larger cartilaginous airways

Question 35

equal pressure point on effort independent expiration

Answer 35

- lofted in non-cartilaginous collapsable airways

Question 36

when pressure inside the floppy, noncartilaginous airway becomes lower than pressure in surrounding lung what happens

Answer 36

- choke points develop that collapse the airway

Question 37

airflow that is effort independent is driven mainly by

Answer 37

- elastic recoil of the lung

Question 38

what is the equal pressure point

Answer 38

- the point where pressure inside the airway is equal to pressure in the lung tissue

Question 39

from the equal pressure point towards the mouth as pressure inside the airways continues to drop

Answer 39

- there is now a negative transmural pressure that tries to collapse the airway

Question 40

why do the non-cartilaginous airways not totally collapse during effort independent phase of forced expiration

Answer 40

- the walls of alveoli that diminish help hold alveolar ducts and small airways open - alveolar interdependence

Question 41

coping strategies in obstructive lung disease

Answer 41

- exhale slowly - breathe at high lung volumes - create a back pressure via pursed lips

Question 42

why do people with obstructive lung disease exhale slowly

Answer 42

- lower pleural pressures | - minimize tendency for small airway collapse

Question 43

why do people with obstructive lung disease breathe at high lung volumes

Answer 43

- increases airway diameter | - lowers resistance

Question 44

why do people with obstructive lung disease purse the lips

Answer 44

- build up back pressure to hold small airways open

Question 45

_____ are lower in both obstructive and restrictive lung disease

Answer 45

- peak flows

Question 46

obstructive flow volume curves have a ________ appearance

Answer 46

- scooped out

Question 47

why do obstructive flow volume curves have a scooped out appearance

Answer 47

- airways are dynamically compressed earlier in expiration and at higher lung volumes

Question 48

what is FEV1

Answer 48

- volume of air expired in first second of max expiration

Question 49

normal value of FEV1 as a percent of forced vital capacity

Answer 49

- > 80%

Question 50

FEF25-75% represents

Answer 50

- flow during middle half of expiration - airflows through small airways - effort independent phase

Question 51

FEV1 in patients with obstructive disease

Answer 51

- low

Question 52

FEV1/FVC in patients with obstructive disease

Answer 52

- low

Question 53

FEV! in patients with restrictive disease

Answer 53

- low

Question 54

FEV1/FVC in patients with restrictive disease

Answer 54

- super normal

Question 55

super normal values of FEV1/FVC in conjunction with lower FVC indicate

Answer 55

- reduced lung compliance | - lung is stiffer which makes it harder to fill but easier to empty

Question 56

spirometry adjusted for

Answer 56

- age - race - height - sex

Question 57

peak flow how it is measured

Answer 57

- how fast air is coming in or out | - measured in liters/second