Ventilation ******

Question 1

What are the two components of the chest-wall?

Answer 1

Independent Lung

Independent rib cage and muscles ( bone, muscle and fibrous tissue)

Question 2

what would happen if we spilt up the components of the chest wall and how is this different to normal?

Answer 2

Rib cage would naturally recoil OUTWARDS.

The lungs have a tendency to recoil INWARDS.

Question 3

What is Functional Residual Capacity?

Answer 3

FRC = ERV + RV
ERV: additional air that can be forcibly exhaled after the expiration of a normal tidal volume.
RV: volume of air still remaining in the lungs after the expiratory reserve is exhaled
It is the volume of air remaining in the lungs at the end of a tidal breath. At FRC, the recoil inwards of the lungs and the recoil outwards of the chest wall are in equilibrium.

Question 4

Describe how the pleural cavity allows the chest wall and the lungs to move in unison.

Answer 4

The pleural cavity has a fixed volume and is at negative pressure.
This means that when the chest wall expands, the lung gets pulled with it..
The pleural cavity contains protein-rich pleural fluid.

Question 5

How may the fixed volume of the pleural cavity be compromised?

Answer 5

The pleural lining could get punctured in the case of a haemothorax (happens much more slowly) or pneumothorax.

Question 6

what is tidal volume?

Answer 6

Tidal breathing is usually nasal.
Tidal breathing= the amount of inspiration and expiration that meets metabolic demand.
-When exercising the tidal volume increases.

Question 7

what does the end of a tidal breath mark?

Answer 7

It marks the Functional Residual Capacity (FRC)

Question 8

why can’t we empty the lungs fully and what is this remaining volume called?

Answer 8

Due to surfactant in the the alveoli, you can’t empty the lungs fully because you don’t want the alveoli to stick together and not reopen.

Remaining volume is the RESIDUAL VOLUME

Question 9

Which volumes make up each of the following capacities:
Total Lung Capacity 
Vital Capacity
Functional Residual Capacity 
Inspiratory Capacity

Answer 9

Total Lung Capacity - all the volumes together. (When you inspire all the way in and fill your lungs up as much as possible, the volume of air in the lungs is the TLC)
Vital capacity + residual volume (RV)

Vital Capacity - expiratory reserve volume+ inspiratory reserve volume + tidal volume
IRV+TV+ERV
or
TLC- RV
How much air is within the confined of what we are able to inspire and expire.

Functional Residual Capacity - ERV + RV
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.

Inspiratory Capacity - TV + IRV
How much extra air you can take in on top of the FRC

Question 10

What unit is commonly used when describing lung pressures?

Answer 10

Unit: cm H2O

Question 11

What are the three main lung pressures involved in respiratory mechanics? Define them.

Answer 11

Transmural Pressure = pressure across a tissue or several tissues
Transpulmonary Pressure = difference between alveolar and intrapleural pressure
Transrespiratory Pressure = tells us the direction of airflow in the airways.

Question 12

How do you work out the orientation of the gradient?

Answer 12

You always do the pressure inside MINUS the pressure outside

Question 13

what is the normal reason we breathe?

Answer 13

Due to lower pressure inside the lung- this is NEGATIVE pressure breathing.

Question 14

Give two examples of positive pressure breathing.

Answer 14

CPR and Ventilators

Question 15

Define Dead Space.

Answer 15

Parts of the airways and lungs that do not participate in gas exchange.

Question 16

What is the difference in alveolar pressure between the end of a tidal expiration and the end of tidal inspiration? Explain your answer.

Answer 16

NO DIFFERENCE - during inspiration, the thoracic cavity expands and so the alveoli expand and the pressure decreases. Air is drawn in to the alveoli and the pressure becomes the same as it was at the end of expiration.

Question 17

what is the conducting zone

Answer 17

Is the Dead space.

Question 18

What are the two different types of dead space?

Answer 18

Anatomical Dead Space

Alveolar Dead Space= the parts of the lung that could participate in gas exchange but do not.

Question 19

What is the normal physiological dead space of a healthy individual?

Answer 19

150 mL - physiological dead space is usually equivalent to anatomical dead space because normal healthy people don’t have alveolar dead space

Question 20

State two reversible procedures that can change dead space.

Answer 20

Tracheostomy = cutting off the upper part of the airway so it is no longer dead space
ventilators= the extra tubing becomes dead space

Question 21

Explain the chest wall relationship diagram (volume against pressure).

Answer 21

Expanding the chest wall to 6 L takes relatively little pressure because its natural tendency is to expand. Expanding the lungs to 6 L takes a lot more effort and pressure because its natural tendency is to recoil inwards.

Question 22

what shape does the intact lung have?

Answer 22

It has a sigmoid shape in terms of its volume-pressure relationship.

Question 23

Define FVC, FEV1 and FET.

Answer 23

Forced Vital Capacity - volume of air that can be expelled from the lungs after a full inspiration
Forced Expiratory Volume 1 - maximum volume of air that can be expired within 1 second
Forced Expiratory Time - time taken to fully empty the lungs (except residual volume)

Question 24

How would these values change for a) someone with obstructive lung disease, b) someone with restrictive lung disease?

Answer 24

Obstructive lung disease: FVC = lower, FEV1 = lower, FET = higher

Restrictive lung disease: FVC = decrease, FEV1 = relatively high because their conducting airways are quite clear they can expel air relatively easily.

Question 25

State normal FEV1/FVC values for a normal person, someone with obstructive lung disease and someone with restrictive lung disease.

Answer 25

Normal = 73, 
Obstructive = 53, 
Restrictive = 87

Question 26

How else can you assess lung function?

Answer 26

Use the Wright Peak Flow meter. you blow through the mouthpiece and are interested in the first big expiration

Question 27

Describe the general arrangement of a flow-volume loop.

Answer 27

Inspiration= Downwards
Expiration= Upwards
Flow rate against volume - distance from the x axis indicates flow rate. Positive y direction indicates that the air is moving out (expiration) and a negative y direction suggests that the air is moving in (inspiration).

Question 28

How can residual volume be measured?

Answer 28

Residual volume can be measured in a closed circuit by inhaling and exhaling something with a known concentration of an inert gas in it (as it is inert, none of it leave the lungs and enter the circulation)- by measuring the concentration difference after we’ve kept breathing it in and out, we can determine the residual volume.

Question 29

Describe how the flow-volume loop changes for a) mild obstructive disease, b) severe obstructive disease and c) restrictive disease.

Answer 29

Mild Obstructive - the loop would move to the left because there is an increase in residual volume. The top right line will be indented. Because there is air trapped in the alveoli as the small airways linking the alveoli to the outside world have collapsed.

Severe Obstructive - same as mild obstructive but the top right line will be even more indented. Shorter curve

Restrictive - the loop will be narrower and it (may) move to the right.

Question 30

Describe how the flow-volume loop will change for a) variable extrathoracic obstruction, b) variable intrathoracic obstruction and c) fixed airway obstruction.

Answer 30

Variable Extrathoracic - inspiratory curve will be flattened because the flow rate is being limites by something in the way of it.
-the flow-volume loop is only affected during inspiration

Variable Intrathoracic - expiratory curve will be flattened but the inspiratory curve is the same.

Fixed Airway Obstruction - both the inspiratory and expiratory curves will be flattened

InTRAthoracic= EXpiration
Extrathoracic= INspiration

Question 31

what is the difference between the pulmonary and alveolar ventilation?

Answer 31

Pulmonary is air ventilating the entire airway, alveolar is air ventilating respiratory surfaces.

Question 32

distinguish between anatomical, alveolar and physiological dead space

Answer 32

Anatomical: conducting airways
Alveolar: Hypoperfused alveoli
Physiological: anatomical + alveolar

Question 33

Explain the mechanical relationship between the chest wall, pleura; membranes and the lung

Answer 33

• Healthy chest behaves as a single unit, pleural cavity is a partial vacuum
• Ventilation can be positive pressure ( ventilation/CPR) or negative pressure ( normal breathing)

Question 34

Distnguish the mechanical force involved in tidal and maximal ventilation?

Answer 34

• Tidal breathing is predominantly diaphragm- induced (syringe movement)
• Maximum ventilation involved full inspiratory muscle recruitment

Question 35

Explain the utility of COMMON LUNG FUNCTION TESTS

Answer 35

• peak flow: tests airway resistance ( how fast can air be expired)
• Time-volume curve- tests airway resistance and FVC
• Flow volume loop- tests airway resistance, flow rates, TV, IRV, ERV and FVC

Question 36

Explain the regional differences in ventilation and perfusion

Answer 36

Gravity favours ventilation and perfusion of the basal lung Vs the apical lung: perfusion more variable
-Basal lung has ‘wasted perfusion’ and apical lung has wasted ventilation