Respiratory 2

Question 1

What are the dynamic factors influencing breathing?

Answer 1

• Resistance
• Flow
• Turbulence

Question 2

What is Poiseuille’s Law?

Answer 2

Flow=ΔP/R

P=Pressure
R (resistance) = 8ηl/πr⁴

Question 3

Where in the airway is the most resistance?

Answer 3

Upper airway (generation 0)

Question 4

What are the factors that determine reisitance?

Answer 4

• Lung volume and branching
• Bronchiolar smooth muscle tone
• Density and viscosity of gases (affected by altitude)

Question 5

What makes bronchiolar smooth muscle contract, decreasing the radius of tube?

Answer 5

• Parasympathetic activity
• Ach
• Irritants (allergens, smoke)
• Decreased alveolar PCO2

Question 6

What makes bronchiolar smooth muscle relax, increasing the radius of tube?

Answer 6

• Sympathetic activity
• Pulmonary stretch
• NorAdr
• Adr

Question 7

What causes the airway to collapse in asthma?

Answer 7

• Allergic inflammation of the airways =
• Hyper-reactivity of airway smooth muscle contraction
• Bronchial smooth muscle thickening
• Bronchial smooth muscle is more abundant In asthmatics and contracts constricting the airway

Question 8

What raises upper airway resistance?

Answer 8

Contraction of para-bronchial smooth muscle

Question 9

What is laminar flow?

Answer 9

When the gas molecules flow parallel to the walls of the vessel

Question 10

What is turbulent flow?

Answer 10

When the gas molecules do no flow parallel to the walls of the vessel, instead colliding
(becomes turbulent above 2000 Reynolds number)

Question 11

What happens to airway resistance during inhalation?

Answer 11

Airway resistance falls as gas flow and lung volume increases
-As the lung expands, the increasing tension in the alveolar walls pulls conducting airways open.

Question 12

Why is it important for the upper airway to have a high resistance during exhalation?

Answer 12

To help to keep airway pressure high to maximise gas movement out of the alveoli
-Aids clearance from alveoli

Question 13

What characterises COPD

Answer 13

Increased resistance to airflow
They have 
-Alveolar destruction
-Reduced SA
-Reduced elasticity

Question 14

What is the work of breathing ?

Answer 14

Overcoming elastic and non-elastic resistances

Question 15

What is the work of breathing in inspiration?

Answer 15

• Energy input required to overcome elastic component

- Energy input required to overcome surface tension

Question 16

What is the work of breathing in exhalation?

Answer 16

-Energy input to overcome airway and tissue resistance

Question 17

What is resistance?

Answer 17

8ηl/πr⁴