3 - ventilation

Question 1

What is chest-wall relationship?

Answer 1

If you split the two components of the chest:

• the ribcage naturally recoils outwards
• lung tissue naturally recoils inwards

at FRC (functional residual capacity), the lung-chest forces are in equilibrium
- they are attached through the pleural cavity, therefore are always under pressure

Question 2

What are the two components of the chest walls?

Answer 2

• bone + muscle + fibrous tissue

- lungs

Question 3

What is FRC?

Answer 3

Functional Residual Capacity
at the end of tidal respiration- the point at which the elastic recoil of the lungs and the the outward recoil of the ribcage are in equilibrium

Question 4

what are the skeletal muscles of them lungs?

Answer 4

peck major and minor
intercostal muscles
diaphragm

Question 5

for inspiration and expiration, give the equations that contain chest and lung recoil

Answer 5

inspiration: inspiratory muscle effort+ chest recoil> lung recoil
expiration: chest recoil< lung recoil + expiratory muscle effort
NOTE: when the two components are in this equilibrium, you need muscular effort to push equilibrium in one direction or another

Question 6

the pleural cavity has a _____ volume

Answer 6

fixed

Question 7

the pleural cavity is at _____ pressure

Answer 7

negative

Question 8

what is the parenchyma?

Answer 8

the functional tissue of the lungs that takes part in gas exchange

Question 9

if you puncture the chest wall or lungs (and it will eventually lead to a pneumothorax), what happens to the pleural cavity?

Answer 9

the fixed volume of the pleural cavity is compromised

NOTE: a haemothorax will occur much slower

Question 10

What is tidal breathing?

Answer 10

the amount of inspiration and expiration that meets the metabolic demand
(usually nasal)

Question 11

What does the end of a tidal breath mark?

Answer 11

Functional Residual Capacity (FRC)

Question 12

Why can the lungs not be emptied fully?

Answer 12

due to the surfactant in the alveoli (you don’t want the alveoli to stick together and not fully open)

Question 13

Define the 4 volumes of the lung

Answer 13

INSPIRATORY RESERVE VOLUME (IRV)
TIDAL VOLUME (TV) - the amount of air coming in to meet the demand of the body
EXPIRATORY RESERVE VOLUME (ERV)
RESERVE/RESIDUAL VOLUME (RV) - default amount of air that cannot physically be expelled

Question 14

Define a capacity

Answer 14

a combination of volumes

Question 15

Name the 4 capacities of the lung

Answer 15

TOTAL LUNG CAPACITY (TLC)
VITAL CAPACITY (VC)
FUNCTIONAL RESIDUAL CAPACITY (FRC)
INSPIRATORY CAPACITY (IC)

Question 16

What is total lung capacity?

Answer 16

all volumes combined
the maximal volume of the lung
not very clinically useful because it is very difficult to measure

Question 17

What is vital capacity?

Answer 17

How much air is within the confines of what we are able to inspire/expire
TLC-RV

Question 18

What is functional residual capaciity?

Answer 18

the volume of air in the lungs when the outwards recoil of the rib cage and the inward recoil of the lungs are in equilibrium (i.e. at the end of a tidal breath)
ERV+RV

Question 19

What is inspiratory capacity?

Answer 19

how much air can be inspired on top of the FRC

IRV+TV

Question 20

What factors affect lung volumes and capacities?

Answer 20

body size
sex
age
disease (pulmonary, neurological)
age (chronolgical and physical)
fitness

Question 21

what is the unit for lung volumes (for measuring in respiratory physiology)

Answer 21

cm H2O

Question 22

what are transmural pressures?

Answer 22

(general)
the pressure across a tissue or several tissues
compares 2 compartments

Question 23

how is transmural pressure calculated?

Answer 23

Pinside-Poutside

Question 24

what is transrespiratory pressure?

Answer 24

most important

will tell us if there will be airflow in/out of the lungs

Question 25

what is negative pressure breathing?

Answer 25

when the pressure in the lungs is lower than atmospheric pressure
normal breathing

Question 26

what is negative pressure breathing?

Answer 26

when the pressure in the lungs is lower than atmospheric pressure
normal breathing

Question 27

What is positive pressure breathing? Give some examples

Answer 27

involves increasing the pressure outside the lungs

this can be done using a ventilator or CPR

Question 28

What is dead space?

Answer 28

the part of the airways that does not participate in gas exchange
(normal DS= 150 mL)

Question 29

Which parts of the conducting zone and respiratory zone are dead space?

Answer 29

• all of the conducting zone is dead space- anatomical dead space
• alveoli that are not perfused or have collapsed are the alveolar dead space
  alveolar dead space= the parts of the lungs that could participate in gas exchange but do not

NOTE: in most healthy individuals, the alveolar dead space is zero so the physiological dead space is equal to the anatomical dead space

Question 30

what 2 processes can alter the dead space?

Answer 30

• tracheostomy - the upper airways are cut off so are not dead space
• ventilator - the extra tubing becomes dead space

Question 31

What specific properties allow the lung to be pulled with the chest wall as it expands?

Answer 31

the pleural cavity has a fixed volume and a negative pressure

Question 32

What is the chest wall pressure at FRC (functional residual capacity)?
What is the lung pressure?

Answer 32

-5 cm H2O

5 cm H2O

hence the FRC is 0 and in equilibrium