Session 2 - Vent And Lung Mechanics

Question 1

What generates automatic rhythmic impulses which guide involuntary breathing

Answer 1

Neurones in the resp center of the brain

Question 2

How is air drawn into the lungs

Answer 2

By expanding the thoracic cavity , not vice versa

Question 3

What is the tidal volume

Answer 3

Volume of air which enters and leaves the lungs

Question 4

What is the correct term for completely filling your lung with air to the max capacity

Answer 4

Inspiratory reserve volume

Question 5

What is the correct term for breathing out more than y ou would at rest

Answer 5

Expiration reserve volume

Question 6

What is a residual volume

Answer 6

We cannot empty ALL the air in our lungs even with expiratory reserve volume, so residual volume is the amount of air remaining

Question 7

Describe the concept of anatomical dead space

Answer 7

Only part of the tidal volume is used for gas exchange

Rest is in conducting part of bronchioles (ADS)

Question 8

Describe what alveolar dead space is

Answer 8

Air which not perfused or damaged that do not take part in gas exchange

Question 9

What is physiological dead space

Answer 9

Anatomical dead space + alveolar dead space

Question 10

Describe the forces acting on the chest region after “rest” (after quiet respiration)

Answer 10

Inward - lungs elasticity and surface tension (favours small lung volumes)

Out - muscles associated with ribs have elasticity 9outward movement of chest wall)

Net effect - at rest, these forces balance each other and create negative pressure within intrapleural space relative to atmospheric pressure

Question 11

What happens during inspiration

Answer 11

Contraction of diphragm and external intercostal muscles expands the thoracic cavity outwards from equal position

Pleural seal makes sure lungs expand along with thorax

As lung volume incr and pressure decr the atmospheric pressure flows from high to low and into the lung space

Question 12

After quiet respiration, what lets the thoracic cavity and lungs return back to this normal deflated protein

Answer 12

The natural recoil of the lungs which is stronger than the chest elasticity itself

Question 13

Describe the surface tension of the pleural cavity

Answer 13

The molecules within this cavity form a seal that holds the outer surface of the lungs to inner chest wall to ensure that the chest wall and lungs move together

Question 14

Describe how the pleural pressure differs when inspiration

Answer 14

At beginning pleural pressure is negative relative to atmospheric

At breath in, more negative (adding positive to neg) due to expansion of the thorax

Returns t resting neg pressure at end of quiet respiration

Question 15

What of the main muscles of expiration and inspiration

Answer 15

Inspire - diaphragm 70 % and external intercostal muscles 30 %

Exhale - none, passive process due to lungs elastic recoil

Question 16

What are the accessory muscles of respiration

Answer 16

Forced inspiration - SCM, scalene (neck) serrated anterior and pec major (chest wall)

Forced expiration - internal intercostal muscles and abdominal wall muscles

Question 17

When are accessory muscles of inspiration used

Answer 17

When ventilation increases

Exercise

Question 18

For what 2 things is energy used for when it comes to breathing

Answer 18

Inspiration (to stretch the lungs)and to (overcome airways resistance)

Question 19

What is compliance

Answer 19

Stretchiness of the lung

Question 20

Where do the elastic properties of lungs come from and why is this important to know

Answer 20

Elastic tissue

Surface tension forces of alveoli

To stretch lungs elastic recoil must be overcome

Question 21

Describe how surface tension in alveoli work

Answer 21

Want to “collapse” lung

As alveoli fill due to lung filling , opposing surface tension forces wants to minimalise surface area due to gas liquid interface and therefore brings it back down

Question 22

What is surfactant and its significance

What secretes it

Answer 22

Type 2 pneumocytes

Phospholipid structure made of proteins

Disrupt interaction between fluid molecules on surface therefore reducing surface tension

Question 23

Describe how surface tension differs between a large alveoli and small alveoli

Answer 23

As alveoli expands, surfactant molecules (in between water) are spread further apart increasing the amount of surface tension exerted making it harder for them to expand (as it expands, surface tension incr) (less efficient)

As it shrinks, the surfactant molecules are closer together meaning so is the surfactant reducing the surface tension making them easier to expand (more efficient) (surfactant reduces surface tension as area of alveolus decreases)

Question 24

What law determines the pressure within one alveoli bubble

Answer 24

Law of Laplace

Question 25

Describe how different sized alveoli are able to stay alive without collapsing

Answer 25

If ST was constant, small alveoli with high pressure would drain into big alveoli with low pressure and would collapse

This reduce SA for gas exchange since a few big alveoli (bullae) doesn’t = the same SA as many small alveoli

Surfactant prevents this from happening as it incr ST in big ones (less efficient) and decr in small ones (more efficient) which allow the pressure in different sized alveoli to remain constant and efficiently stabilise the lung

Question 26

What is respiratory distress syndrome and why is it a newborn condition

Answer 26

Cuz surfactant is not found in 25 weeks and younger babies

Due to lack of surfactant

Question 27

List 3 things surfactant does

Answer 27

Incr lung compliance by decr ST

Stabilise lungs by preventing small alveoli from collapsing into big ones

Prevents ST in alveoli creating suction force which can cause transudation fluid from pulmonary capillaries into alveoli

Question 28

What is poiseuille law

Answer 28

Resistance of an airway to flow is determined by this law (when flow is laminar)

Question 29

Where is resistance the most abundant in the resp tract

Answer 29

Upper rest tract cuz downstream is less resistant to laminar flow unless when small airways are compressed during forced expiration

Question 30

What compensates for small airways individual resistance (small diameter means higher resistance)

Answer 30

Numerous airways in parallel arrangement