3 - Ventilation & Pressure

Question 1

Ventilation:

Answer 1

-process of moving air in and out of lungs
-can be used to assess respiratory health

Question 2

How can ventilation be controlled?

Answer 2

-mechanical properties of lung and chest wall

Question 3

Types of lung volumes:

Answer 3

-tidal volume
-functional residual capacity (FRC)
-total lung capacity (TLC)
-vital capacity (VC)
-residual volume (RV)

Question 4

Tidal volume:

Answer 4

-air in/out with normal breath
-10mL/kg BW

Question 5

Functional residual capacity (FRC):

Answer 5

-amount of air in thorax after normal expiration
*reason why you have ~5mins after someone stops breathing to attempt CPR

Question 6

Total lung capacity (TLC):

Answer 6

-total volume of gas inside lungs after MAX INHALATION

Question 7

Vital capacity (VC):

Answer 7

-maximum amount of air that can be moved

Question 8

Residual volume (RV):

Answer 8

-amount of air in lung that CANNOT be exhaled
-~25%

Question 9

The lungs are always filled with:

Answer 9

-gas

Question 10

Air only moves when there is a:

Answer 10

-difference in gas pressure
>high to low
-Dalton’s law

Question 11

Dalton’s law:

Answer 11

-total pressure=sum of partial pressure of individual gases

Question 12

Moist tracheal total pressure:

Answer 12

-pressure of H20 displaces pressure of O2
>less than ambient air

Question 13

Alveolar gas total pressure:

Answer 13

-pressure of CO2 displaces pressure of O2
>even lower than before

Question 14

What is pleura?

Answer 14

-continuous serous membrane tissue

Question 15

Visceral pleura:

Answer 15

-covers the lungs
*elastic recoil pressure (tends to collapse) “pulls lung” away from chest wall

Question 16

Parietal pleura:

Answer 16

-cover chest cavity:
*elasticity of chest wall tends to spring out, push outwards

Question 17

What is the atmospheric pressure at rest?

Answer 17

-760mmHg

Question 18

What is the intrapleural pressure?

Answer 18

-756mmHg

Question 19

Ventilation mechanics at rest:

Answer 19

-opposing forces pull on the intrapleural space and creates a vacuum that generates negative ‘net’ pressure (-4mmHg or -5cm H20)
*prevents lungs from collapsing
>serous pleural fluid between

Question 20

Intrapleural space is really:

Answer 20

-‘theoretical
-pleura are continuous and held together in close contact

Question 21

What happens at rest or end of respiration?

Answer 21

-no airflow as alveolar pressure=atmospheric pressure

Question 22

What does ventilation require?

Answer 22

-muscular energy

Question 23

Ventilation mechanics for inspiration:

Answer 23

-contraction of external intercostal muscles moves ribs craniolaterally
-diaphragm moves ribs caudally
*expansion of lungs (volume increases)

Question 24

Boyle’s law:

Answer 24

P1V1=P2V2

Question 25

Expansion of lungs during inspiration: Boyle’s law

Answer 25

-causes an overall decrease in alveolar and intrapleural pressure
>’negative’ pressure with respect to atmospheric pressure
*pressure difference drives airflow into lungs

Question 26

When does inspiration stop?

Answer 26

-when alveolar pressure has equaled atmospheric pressure

Question 27

Ventilation mechanics for expiration:

Answer 27

-relaxation of external intercoastal and diaphragm=elastic compression of lung
*decrease in volume
*increase alveolar and intrapleural pressure

Question 28

What happens when alveolar pressure is greater than atmospheric pressure?

Answer 28

-gas including CO2 exits the respiratory system
*the net intrapleural pressure is less than atmospheric pressure=keeps the alveoli open

Question 29

Ventilation mechanics for forced expiration:

Answer 29

-contraction of abdominal muscles forces abdominal viscera against diaphragm and internal intercoastal muscle to depress the ribcage and reduce thoracic size
*significant reduction in lung volume=increase in pressure

Question 30

Significant reduction in lung volume and increase in pressure during forced expiration:

Answer 30

-drives forceful airflow
*utilized in exercise or coughing
-+20cm H20
>why you could collapse an alveoli if you cough too hard

Question 31

Are alveoli able to expand themselves?

Answer 31

-no, they are very compliant
-expand passively to DISTENDING pressure across the alveolar wall
*transmural pressure

Question 32

Transmural pressure:

Answer 32

-drives distension
-alveolar pressure – intrapleural pressure (0-(-4)=+4)
*must be positive for alveoli to stay open

Question 33

Higher transmural pressure=

Answer 33

-higher the distending force=more expanded and larger the alveoli
*affects gas exchange

Question 34

Effects of gravity on intrapleural pressure:

Answer 34

-higher near the bottom (smaller net pressure difference relative to atmospheric pressure)
>gravity causes a relative smaller volume between pleural space
*slinky model

Question 35

Transpulmonary pressure:

Answer 35

=alveolar pressure + intrapleural pressure
>alveolar pressure is always 0 at rest
>negative intrapleural pressure
*drives distension: greater the positive pressure=greater the pull=larger the alveoli

Question 36

How do you get a collapsed lung (pneumothorax)?

Answer 36

-puncture of intrapleural space
-loss of negative pressure caused by equalization with atmosphere pressure
*loss of positive transmural pressure required to hold lungs open

Question 37

Loss of positive transmural pressure required to hold lungs open leads to:

Answer 37

-lung collapse
>chest wall springs out
>prevents chest from expanding

Question 38

Gravity on alveolar size:

Answer 38

-cranial/dorsal half is larger than caudal/ventral half

Question 39

Inspiration overview:

Answer 39

-contraction of external intercostals and diaphragm=increase volume, decrease pressure
-intrapleural pressure decreases
-alveolar pressure peaks midway
-end of inspiration=when no net pressure exist

Question 40

Expiration overview:

Answer 40

-relaxation of external intercostals and diaphragm=decrease volume, increase pressure
-intrapleural pressure rises
-alveolar pressure peaks midway
-end of expiration=no net pressure