Resp 2 - Ventilation

Question 1

What is Functional Residual Capacity (FRC)?

Answer 1

When the elastic inward recoil of the lungs and the outward recoil of the rib cage are in equilibrium.

Occurs at the end of tidal expiration.

Question 2

What is the pleural cavity?

Answer 2

Space between parietal and visceral pleura. It is a fixed volume.

Contains protein rich pleural fluid.

It is at negative pressure

Question 3

How does the pleura play a role in ventilation?

Answer 3

It is the negative pressure of the pleura that allows the chest wall to pull the lungs with it.

If chest wall/lung punctured, fixed volume of pleura is compromised - elastic recoil takes over and lung will collapse

Question 4

What happens if the pleural cavity is breached?

Answer 4

Intrapleural bleeding may occur - haemothorax.

If there is a perforated chest wall - air enters pleural cavity = pneumothorax

Question 5

Define tidal breathing.

Answer 5

Amount of inspiration/expiration that meets metabolic demand

Question 6

What is residual volume?

Answer 6

Volume of air in the lungs that cannot (and should not) be expelled.

Question 7

Explain:

1. Total Lung Capacity (TLC)
2. Vital Capacity (VC)
3. Functional Residual Capacity (FRC)
4. Inspiratory Capacity (IC)

Answer 7

1. TLC = everything (including residual volume)
2. VC = air within our maximal inspiration/expiration confines
   (VC = TLC - RV)
3. Functional Residual Capacity (FRC) = Amount of air in the lungs at equilibrium
   (FRC = ERV + RV)
4. Inspiratory Capacity (IC) = how much air you can take on top of FRC.
   (IC = TV + IRV)

Question 8

Transmural pressures?

Answer 8

Pressure across a tissue or several tisses

Question 9

Transpulmonary pressure?

Answer 9

Difference between alveolar and intrapleural pressure

Question 10

Transrespiratory pressure (important one)?

Answer 10

Tells us if Airflow into or out of lung

Question 11

Negative pressure breathing vs positive pressure breathing?

Answer 11

Negative = normal breathing

Positive = ventilator / CPR

Question 12

What is dead space?

Answer 12

Part of the airways and lung that doesn’t participate in gas exchange.

Question 13

The conducting zone is dead space. What other dead space can there be?

Answer 13

Alveolar dead space = parts of the lung that can participate in gas exchange but do not.

Question 14

What is physiological dead space equal to?

Answer 14

Physiological dead space = Anatomical Dead space + alveolar dead space.

In healthy adults, physiological dead space should roughy equal anatomical dead space (usually around 150mL)

Question 15

In normal patients, FEV1/FVC ratio should be 75% ish.

Answer 15

T

Question 16

What is FET?

Answer 16

Forced Expiratory Time.

Time taken to expel all the air from the lungs

Question 17

What is the pattern of Forced values for obstructive lung disease?

Answer 17

1. FEV1 MUCH lower
2. FET higher
3. FVC lower

Question 18

What is the pattern of Forced values for restrictive lung disease? (e.g. sarcoidosis)

Answer 18

1. FVC lower

2. FEV1 relatively high

Question 19

Difference between restrictive and obstructive disease?

Answer 19

Obstructive = mechanical obstruction to airflow

Restrictive = inability of chest to expand

Question 20

What are flow-volume loop features of mild obstructive disease?

Answer 20

1. Displaced to the left

2. Coving

Question 21

What are flow volume loop features of a severe obstructive disease?

Answer 21

1. Shorter curve
2. Displaced to left
3. Greater extent of coving

Question 22

What are flow volume loop features of restrictive disease?

Answer 22

1. Displaced to the right

2. Narrower loop

Question 23

TLC may increase in people with obstructive disease. Why?

Answer 23

Air is trapped in the alveoli - because small airways linking alveoli to outside world have collapsed - causes increased residual volume.

Emphysema - degrades alveolar walls. Only a large alveolus instead of separate segments - increase in volume of the lungs.

Question 24

If airway obstructed, flow rate can be limited. Explain how extrathoracic and intrathoracic obstructions differ.

Answer 24

Extrathoracic obstruction = inspiratory curve flatten

Intrathoracic obstruction = expiratory curve flattened

Question 25

What does fixed airway obstruction do?

Answer 25

Both inspiratory and expiratory curves are blunted.