Mechanics of breathing

Question 1

Resistance

Answer 1

An opposing force that acts to reduce the flow of a gas or fluid through a conduit

Question 2

The variable factors within the airway

Answer 2

Cross sectional area of the airway lumen

Airflow pattern

Question 3

Hagen Poiseuille equation describes

Answer 3

relationship between resistance and the various properties of ariways and airflow

Question 4

What is the resistance in the Haigen Poiseuille equation

Answer 4

Inversely proportional to cross sectional radius raised to power of 4

Question 5

Decrease in radius

Answer 5

Produce a large increase in resistance

Question 6

What pathological features can impact the cross sectional area of the airway lumen

Answer 6

Contraction of airway smooth muscle
Excessive mucus secretion
Oedema/swelling of airway tissue
Damage to the integrity of the airways structure

Question 7

Effect of reducing the size of the lumen

Answer 7

Increase airway resistance

Decrease airflow

Question 8

When does turbulence occur

Answer 8

High velocities of airflow are achieved

If there is a sudden decrease in luminal area such as obstructed airways

Question 9

Airway patency

Answer 9

State of being open or unobstructed

Question 10

Loss of patency

Answer 10

Closing/obstruction

Question 11

What maintains the open structure of airways

Answer 11

Elastic fibres within wall of airway and radial traction

Question 12

Transpulmonary pressure

Answer 12

Difference between pressure within the alveoli and intrapleural space
Determines level of force acting to expand or compress lungs

Question 13

During inspiration

Answer 13

Increasing levels of negative intrapleural pressure are generated as lung volume increases due to elastic properties of lung tissue

Question 14

Lung compliance

Answer 14

• Relationship between the change in lung volume produced by a change in transpulmonary pressure
• Describes how easily the lungs can be distended

Question 15

Higher lung compliance

Answer 15

less elastic recoil = less force required to inflate = increase volume change per pressure change

Question 16

Lower compliance

Answer 16

more elastic recoil = more force required to inflate = decrease volume change per pressure change

Question 17

Compliance

Answer 17

Change in volume/change in pressure

Gradient of curve

Question 18

Diseases that lower compliance

Answer 18

(Affect chest wall mechanics)
Scoliosis
Muscular dystrophy
Obesity
(affect elastin fibres)
Fibrosis
(Affect surface tension)
NRDS - Neonatal respiratory distress syndrome

Question 19

Diseases that increase compliance

Answer 19

(Affect elastin fibres)
COPD
Emphysema

Question 20

Surface tension

Answer 20

Arises due to the strength of hydrogen bonds between water molecules - cause a collapsing force - generate pressure

Question 21

Relationship between the pressure and radius

Answer 21

Inversely proportional - smaller = generate pressure greater pressure

Question 22

Pulmonary surfactant function

Answer 22

• Prevent smaller alveoli collapsing into larger alveoli due to pressure gradients
• disrupt attractive forces between water molecules, reducing surface tension
• prevent alveolar oedema - excessive fluid being pulled from capillaries

Question 23

Pulmonary surfactant structure

Answer 23

Phospholipoprotein - secreted by type II pneumocytes
Amphipathic - hydrophilic head, hydrophobic tail
Position themselves at air-liquid interface

Question 24

As alveolar size increases

Answer 24

Concentration of surfactant at interface decreases

Question 25

Net effect of pulmonary surfactant

Answer 25

Surface tension increases with increasing alveolar surface area
Air will move from large alveolar to small ones

Question 26

NRDS

Answer 26

Occurs in infants born prematurely. Produce insufficient levels of pulmonary surfactant

Question 27

NRDS results in respiratory failure due to

Answer 27

alveoli collapsing
Decreasing lung compliance
alveolar oedema reducing gas exchange

Question 28

Treatment for NRDS

Answer 28

Artificial surfactant

Glucocoritcoids