5.3 - Lung Compliance and Elastance

Question 1

Define lung compliance

Answer 1

change in lung volume produced by a change in pressure

Question 2

TRUE OR FALSE:

The lower the lung compliance, the harder it is to expand the lungs (inhalation)

Answer 2

TRUE

Question 3

People with low lung compliance breath ____ and _______

Answer 3

shallowly and rapidly

Question 4

What are restrictive lung diseases?

Answer 4

pathological conditions that affect lung compliance

Question 5

List some restrictive lung diseases

Answer 5

fibrotic lung disease

New-Born Respiratory Distress Syndrome (NRDS)

Question 6

What causes fibrotic lung disease?

Answer 6

chronic inhalation of asbestos, silicon, coal, dust

Question 7

What is the effect of fibrotic lung disease?

Answer 7

build up of scar tissue in lungs: lowers compliance, makes it harder to breathe

Question 8

Where does the majority of the resistance to stretch come from within the lungs?

Answer 8

from surface tension within the lungs

Question 9

What causes the NRDS?

Answer 9

inadequate surfactant production

Question 10

TRUE OR FALSE:

surfactant synthesis becomes adequate at 12 weeks of gestation

Answer 10

FALSE

at 34 weeks of gestation

Question 11

Define lung elastance

Answer 11

the speed at which the lungs return to resting volume after being stretched

Question 12

What happens when lung elastance is low?

Answer 12

expiration must be active as lungs will not return to resting volume passively

Question 13

What happens during emphysema?

Answer 13

• elastin fibres in lung are destroyed
• lung have high compliance and low elastance
• breathing in is easy, breathing out is hard and forced

Question 14

What is primarily determined by airway diameter?

Answer 14

airway resistance

Question 15

What increases the resistance of the airways?

Answer 15

mucus accumulation from allergies/infections

Question 16

What are factors that affect bronchiole diameter?

Answer 16

nervous system, hormones, paracrines

Question 17

What are some things that can cause bronchiodilation and bronchioconstriction?

Answer 17

bronchiodilation: CO2
bronchioconstriction: histamine, severe allergic reaction

Question 18

Bronchioconstriction is primarily controlled by _____

Answer 18

parasympathetic neurons, no significant sympathetic innervation

Question 19

hormonal control of bronchioles is done primarily by _____ to cause ____

Answer 19

circulating epinephrine via adrenal medulla acting on b2 receptors in smooth muscle of bronchioles to cause bronchiodilation

Question 20

What does pulmonary function assess?

Answer 20

the amount of air someone can move during quiet breating and maximal breathing effort

Question 21

What is a spirometer? What can be diagnosed using it?

Answer 21

instrument used to measure movement of air during breathing

asthma, emphysema, chronic bronchitis

Question 22

List and define the 4 lung volumes that can be measured as air moves during breathing

Answer 22

tidal volume (TV)
- volume of air moved in single/normal inspiration or expiration

Inspiratory Reserve Volume (IRV)
- MAXIMUM of air that can be inspired above VT

Expiratory Reserve Volume (ERV)
- MAX air that can be expired after normal expiration

Residual Volume (RV)
- ammount of air left after maximal expiration

Question 23

The sum of 2 or more lung volumes is called a capacity. List and define the 2 capacities:

Answer 23

vital capacity: VC
- maximum amount of air that can be voluntarily moved in or out of the lungs
VC = IRV + ERV + IRV

Total Lung Capacity (TLC)
- TLC = vital capacity + RV

Question 24

How is the minute volume calculated?

Answer 24

MV (ml/min) = VT (mL/breath) X respiratory rate (breaths/min)

Question 25

What is the anatomical dead space in the airways?

Answer 25

• no gas exchange

- trachea, brochi, bronchioles

Question 26

How is alveolar volume calculated?

Answer 26

alveolar volume = VT - dead space

Question 27

What is the effectiveness of ventilation determined by?

Answer 27

rate and depth of breathing

Question 28

What is alveolar ventilation?

Answer 28

the amount of air reaching the alveoli per minute

Question 29

TRUE OR FALSE:

Alveolar ventilation is a more accurate indicator of the efficiency of ventilation

Answer 29

TRUE

Question 30

How is alveolar ventilation calculated?

Answer 30

alveolar ventilation = alveolar volume X ventilation rate

Question 31

How is the efficiency of gas exchange maximized?

Answer 31

the body attempts to match the airflow to alveolar blood flow

Question 32

How does decrease in tissue PO2 result in vasoconstriction of the arteriole?

Answer 32

depends on local control exerted by O2 levels in the interstitial fluid around arteriole surrounding alveoli
- ventilation of alveoli in an area of lung decreases, tissue O2 also decreases, blood diverted away from this area