P L6 - Resp. mechanics

Question 1

What are the factors that influence compliance?

Answer 1

1. lung volume
2. elasticity
3. surface tension

Question 2

Compliance is _______ to lung volume

Answer 2

proportional

Question 3

At FRC what is the airway pressure equal to?

Answer 3

Airway pressure = atmospheric pressure = 0 mmHg

Question 4

Respiratory resistance arises from? Which is the more dominant resistance force?

Answer 4

• Tissue resistance (20%)
• Frictional resistance due to air flowing thru the airways (80%)

Question 5

Factors affecting airway resistance?

Answer 5

• Airway calibre
• Airway generation
• Airway profile
• Lung vol.

Question 6

What system (autonomic/somatic) moderates the airway calibre?

Answer 6

autonomic

Question 7

which part of the ANS causes the following:
- Increase in airway caliber (bronchodilation)
- Decrease in airway caliber (bronchoconstriction)

Answer 7

Increase: sympathetic (B2 adrenergic - relax VSM)
Decrease: Parasympathetic (muscarinic)

Question 8

Airflow profile – what are the 2 flow types? Which occurs at high/low velocity? Which ones have high/low resistance?

Answer 8

Laminar – At low flow rates/ low velocity
– Low resistance

Turbulent – At high flow rates/high velocity
– High resistance

Question 9

what number determines whether flow is turbulent or laminar? above what value will flow be turbulent?

Answer 9

Reynold’s number
flow is turbulent when Re>2000

Question 10

Features of turbulent flow:
_____ density gas
______ flow (v)
______ radius (r)
______ viscosity

Answer 10

High, Large, Large, Low

Question 11

What type of flow would we find in the following:
- Large airways
- Small airways

Answer 11

• Large airways —> Turbulent
• Small airways –> Laminar

Question 12

Which type of airways are a major site of resistance?

Answer 12

medium bronchi

Question 13

Relationship of elastic recoil and radial traction?

Answer 13

The greater the elastic recoil – the greater the radial traction

Question 14

Parenchyma?

Answer 14

The connective tissue surrounding the airways of the lung.

Question 15

Relationship between inspiration, expiration and resistance

Answer 15

Inspiration – Decrease in airway resistance as airways pulled open by radial traction

Expiration – increased airway resistance as inward recoil forces increase.

Question 16

At FRC ______ want to collapse and _____ wants to expand. The combined system however ______

Answer 16

Lungs
Chest wall
doesnt have a tendency to collapse or expand.

Question 17

Is inspiration/expiration more compliant?

Answer 17

Expiration

Question 18

During deflation, the lung volume at any given pressure is _________ than during inflation.

Answer 18

greater

Question 19

At higher volumes lung requires ______ pressure to expand

Answer 19

more. (compliance decreases at higher vol.)

Question 20

Compliance is measured on the ______
limb of the pressure-volume loop

Answer 20

expiration

Question 21

Which one is less compliant:
- air-liquid interface in the alveoli
- Saline- liquid interface in alveoli

Answer 21

Air-liquid interface
— saline-liquid interface is easier to fill and empty.

Question 22

Elasticity depends on?

Answer 22

1. elastin fibre content
2. surface tension

Question 23

Fluid Secretion in Lungs- Active transport of _____ accompanied by water flow from the ______ to the ______

Answer 23

Cl-
Interstitium
airspace

Question 24

Fluid Absorption in Lungs- Active transport of _____ accompanied by water flow _____ its _______ gradient

Answer 24

Na+
down
osmotic

Question 25

Is surface tension at the end of expiration in alveoli reduced or increased? Why?

Answer 25

Surface tension at end of expiration is reduced – as alveoli become smaller and thus the conc. of surfactant increases thus reducing surface tension.

Question 26

Compliance formula?

Answer 26

Compliance = change in V/change in P

Question 27

Work of breathing formula?

Answer 27

Work = pressure x volume