Pulmonary compliance and elasticity

Question 1

Compliance

Answer 1

-distension of lung relative to transpulmonary pressure
-in other words, how easy is it for the alveoli to stretch when filled with air

Question 2

Elasticity

Answer 2

-ability of the lung to resist distention/stretch
-in other words, how easy is it for the alveoli to recoil to its original shape

Question 3

Compliance equation

Answer 3

Change in volume divided by change in pressure

Question 4

What drives compliance?

Answer 4

-driven by pressure change

Question 5

What drives elasticity?

Answer 5

-surface tension
-elasticity of lung tissue

Question 6

Plastic bag vs balloon

Answer 6

Plastic bag is highly compliant, but not elastic
Balloon is both compliant and elastic

Question 7

Compliance high vs. low

Answer 7

When high, lung is readily distended (flexible)
When low, lung is not easily distended (stiff)

Question 8

Elastic components of lung tissue

Answer 8

• Possible due to connective tissue (collagen and elastin)
  o Collagen: provides strength and rigidity
  o Elastin: provides elastic properties
• Responsible for ~1/3rd of total lung elasticity

Question 9

Fibrosis (scar tissue) and how it related to elastic force

Answer 9

-fibrosis (scar tissue) increases collagen which causes the alveoli to become stiff. Results in increased elastic recoil and therefore low compliance

Question 10

Cohesive force

Answer 10

-molecules of same property exhibit strong intermolecular attractive forces toward each other

Question 11

Surface tension

Answer 11

-alveoli is lined with a fluid surface that creates an air-water interface and allows for the possibility of surface tension
-molecules at the surface have less surrounding neighbours, and the force is enhanced on their nearest neighbours at the surface (compared with cohesive force which is weaker and throughout the solution)

Question 12

Alveoli surface tension

Answer 12

-water that is lining the inner surface of the alveoli exerts attraction to each other and creates a net inward pull known as RECOIL EFFECT
-responsible for 2/3rds of lungs elastic property

Question 13

Surfactant

Answer 13

-complex lipoprotein produced by type II pneumocytes
-have hydrophilic head and hydrophobic tail which prevents it from entering the fluid and means that it stays on the surface

Question 14

Purpose of surfactant

Answer 14

-disrupts surface water attraction (surface tension force)= reduces surface tension of alveoli to prevent atelectasis
-decreases elasticity, improves compliance

Question 15

Atelectasis

Answer 15

-collapsed alveoli

Question 16

When is surfactant produced?

Answer 16

-produced during late gestation
-reason why premature birth often leads to respiratory difficulties (low compliance) in humans and animals

Question 17

Static compliance

Answer 17

-linear relationship
- occurs when there is no airflow

Question 18

Dynamic compliance

Answer 18

-airflow occurs and air resistance exists
-non-linear relationship

Question 19

Inspiration vs. expiration compliance

Answer 19

Differences in compliance because surface tension in alveoli contributes to elasticity and during inspiration greater pressure is needed during the initial phase to overcome the surface tension force
>Ex. initial blowing up of balloon compared to future breaths

In expiration, surface tension aids in shrinking the alveoli, requiring less pressure vs inspiration

Question 20

Hysteresis

Answer 20

-differences between required pressure change in inspiration vs expiration
*Non-recoverable work is required during inspiration to overcome the elastic properties

Question 21

Saline-filled lungs

Answer 21

Hysteresis is greatly reduced because of the absence of surface tension due to lack of air-fluid interface
*There will always be a small hysteresis present due to elastic properties of lung (elastin, collagen)

-When surface tension is eliminated, it greatly reduced pressure required to change volume
*steeper slope, increase in compliance

Question 22

What does Airway resistance effect?

Answer 22

-influences compliance/alveoli distension (how easy/difficult it is for the air to go through tip of nose/mouth)

Question 23

Airway resistance

Answer 23

• The air enters through the nasal/oral passage and encounters air resistance before getting to the alveoli which results in change in pressure generated in the alveoli caused by deviation between static and dynamic compliance.

**increase in air resistance results in decrease in dynamic compliance because less air

Question 24

Where does most airway resistance occur?

Answer 24

Most resistance occurs in conducting airways (from bronchi to the terminal bronchioles)
>fast turbulent airflow
>mucous secreting epithelial cells

Question 25

Laminar flow

Answer 25

-in respiratory zones
-flow reduces airway resistance

Question 26

Resistance in nasal (turbinate) vs. oral passage

Answer 26

-more resistant in nasal (turbinate) passage
-results in reflexive mouth breathing during exercise (naturally occurs because we want to reduce resistance to get more air in for oxygenating alveoli)

Question 27

Factors affecting airway diameter and therefore airway resistance

Answer 27

Can be external or internal

-Examples:
1.bronchoconstriction
2.abnormal tissure growth
3. mucous plug (inflammation)
4. pulmonary edema

Question 28

Steps of increased air resistance

Answer 28

1.increase air resistance by obstructing airflow in and out of alveoli
2. decrease compliance
3. interfere with gas exchange

Question 29

Pathological disease and compliance

Answer 29

different diseases have the ability to increase or decrease compliance and greatly effect animals ability to breath properly

Question 30

Low compliance vs. high compliance

Answer 30

Low: hard to inflate the alveoli=hypoxemia
High: hard to deflate the alveoli=hypercapnia

Question 31

Restrictive vs. obstructive

Answer 31

-restrictive- difficulty filling lungs with air
-obstructive- difficulty expelling air from lungs

Question 32

Pathological diseases resulting in low compliance

Answer 32

-pneumothorax- loss of pleural pressure
-fibrosis-increase elastic recoil
-abdominal/thoracic mass- diaphragm obstruction
-pulmonary edema- fluid in interstitial fluid that pressures the alveoli
-low surfactant- excess surface tension

Question 33

Pathological diseases resulting in high compliance

Answer 33

Chronic obstructive pulmonary disease (chronic inflammatory response from something like smoking)
>can lead to Emphysema or chronic bronchitis

Question 34

Emphysema

Answer 34

-structural destruction of alveoli wall. Alveolar macrophage produces elastase that degrades elastin fiber and results in loss of elasticity

Question 35

Chronic bronchitis

Answer 35

-excess mucous, results in obstructing airway
-obstruction makes it more difficult to get air out than in so air is trapped in lungs (hyperinflation of alveoli)