Resistance to Air Flow

Question 1

Airflow in the trachea and bronchi is (laminar or turbulent)

Answer 1

Turbulent

Question 2

Airflow in the small airways (bronchioles) is (laminar or turbulent)

Answer 2

Laminar

Question 3

If you half the radius of an airway, the resistance changes how?

Answer 3

Resistance increases 16x (greater contact with walls) (inversely proportional to the 4th power)

Question 4

Resistance is inversely proportionally to the ______ power of the radius

Answer 4

4th

Question 5

Total airway resistance is highest in the…

Answer 5

Segmental bronchi

Question 6

Total airway resistance decreases as you go towards ______

Answer 6

alveoli (may be individually smaller, but have tremendous total cross-sectional area)

Question 7

Resistance to airflow is increased during (expiration or inspiration)

Answer 7

Expiration

Question 8

Why is flow rate asymmetrical during expiration?

Answer 8

Flow rate is high at high lung volumes, but declines rapidly as the lung empties and airways are compressed (effort independent limitation)

Question 9

What does effort-independent mean in context to expiration?

Answer 9

With forced expiration, there is a point where more force can’t increase flow rate because you begin to compress airways

Question 10

What prevents non-cartilaginous airways from completely collapsing during the effort-independent phase of forced expiration?

Answer 10

alveolar interdependence and tethering of small airways by alveolar walls (synergistically keeping each other open)

Question 11

An example of a pulmonary disease characterized by the destruction of lung tissue, and thus decreased alveolar interdependence and tethers

Answer 11

Emphysema

Question 12

Coping strategies for obstructive lung diseases (to help prevent airway collapse)

Answer 12

1. Exhale slowly (airflow is less turbulent therfore less resistance)
2. Breath at high lung volumes (keeps the airway more open)
3. Create backpressure via pursed lips (keeps the airway more open)

Question 13

Obstructive flow-volume curves have what kind of appearance?

Answer 13

“scooped out” (premature collapse of airway)

Question 14

Common test/measurement for pulmonary function

Answer 14

Spirometry

Question 15

the volume of air expired in the 1st second of a maximal expiration

Answer 15

Forced Expiratory Volume 1 (FEV1)

Question 16

rate of flow during the middle portion of the expiration; has greater representation for air flow through the small airways, as flow is entering the effort independent phase of expiration

Answer 16

FEF 25-75%

Question 17

Why do patients with obstructive lung disease have a low FEV1 value?

Answer 17

their lungs have low elastic recoil and small airways lack tethers and/or are occluded by mucus plugging and edema. As a result, small airway collapse occurs early

Question 18

During the effort-independent phase of forced expiration, air flow is driven mainly by…

Answer 18

elastic recoil of the lung

Question 19

Minute Ventilation = ?

Answer 19

Tidal volume x Resp. Rate

Question 20

Airflow in airways is analogous to the flow of electrical current but is more complex because of three reasons:

Answer 20

1. Airway diameter shrinks with each generation but dichotomous branching pattern increases airway number and cross sectional area.
2. Airway caliber (diameter) changes as the lung inflates and deflates.
3. Resistance is dependent on the radius and the airflow pattern.

Question 21

Resistance depends on the airflow because the interaction of the flowing gas with the tube wall consumes energy and cause _________ down the length of the tube.

Answer 21

pressure drop

Question 22

Under laminar flow conditions, the pressure drop is ___________ to flow rate

Answer 22

directly proportional

Question 23

Under turbulent flow conditions, the pressure drop is _________ to _______ of flow rate

Answer 23

directly proportional; square

Question 24

Airflow in the bronchial tree (branching point) is

Answer 24

transitional

Question 25

Flow rate is largely determined by

Answer 25

resistance

Question 26

Resistance is largely determined by

Answer 26

radius

Question 27

Resistance to airflow is critically determined by

Answer 27

airway caliber

• which is NOT static!

Question 28

Poiseuille’s Law only applies to what airflow pattern?

Answer 28

laminar

Question 29

How much resistance do small airways contribute to the overall lung resistance?

Answer 29

very small

Question 30

Bronchioles and small airways are called _________ since disease must become well advanced before it is detected.

Answer 30

silent zone

Question 31

________ are lower in both obstructive & restrictive lung disease.

Answer 31

peak flows

Question 32

Restrictive flow-volume curves do not have “scooped out” appearance, why?

Answer 32

FRC decreases due to fibrosis but elastic coil is still intact, the effort independent phase of later expiration is normal.

Question 33

What is the normal FEV1 in healthy young adults?

Answer 33

generally >80%

Question 34

Why do patients with restrictive lung disease have a low FEV1 value?

Answer 34

their lungs have reduced compliance, making them harder to fill and easier to empty

*smaller amount of air in lung to begin expiration with

Question 35

Why do patients with restrictive lung disease have a normal FEV1/FVC ratio?

Answer 35

Since both of their FEV1 and FVC are low but their difference is small, the ratio looks normal.