Factors that affect R to flow

Question 1

Formula for flow

Answer 1

Pressure/Resistace

Question 2

6 factors affecting R to flow

Answer 2

1. Diameter
2. Velocity
3. Anatomy
4. Lung vol
5. Inspiration
6. Expiration

Question 3

3 conditions flow depends on

Answer 3

1. Whether flow is laminar or turbulent
2. Airway dimension
3. Viscosity of gas

Question 4

Poiseuille’s Law

Answer 4

R = 8nl/πr⁴

Decreasing the radius by a factor of 2 increases the resistance by a factor of 16

Question 5

Is there turbulent or laminar flow in airways of children

Answer 5

turbulent

Question 6

What happens to larger airways during forced expiration

Answer 6

Compression of larger airways

Question 7

When will airways collapse

Answer 7

When transmural pressure (P difference across airways) becomes -ve (inside-outside), airways will collapse

Question 8

Where is the most resistance

Answer 8

Upper bronchi (5-7)

Question 9

What does airway branching result in

Answer 9

Many smaller airways all in parallel => reduced R

Question 10

Where is the highest total R in the resp tract

Answer 10

Trachea and larger bronchi (due to the huge no. of bronchioles and alveoli - in parallel)

Question 11

Relationship between lung volume and airway resistance

Answer 11

Not a linear relationship

Question 12

Impact of increasing lung volume above FRC on:

1. R
2. Airway diameter

Answer 12

1. Decreased R
2. Increased airway diameter

Question 13

Impact of decreasing lung vol below FRC to RV on:

1. Airway R
2. Airway diameter
3. Small airways

Answer 13

1. Increase airway R
2. Decrease airway diameter
3. Small sirways may close completely

Question 14

What does bronchial SM contraction involve

Answer 14

Parasympathetic (vagal) and ACh

irritant reflexes

Question 15

What does bronchial SM relaxation involve

Answer 15

Activation of adrenergic receptors

Adrenaline

Isoprenaline

B2 adrenergic agonists