09. Respiratory Physiology

Question 1

Vital capacity can be measured by spirometry.

T/F

Answer 1

True

Question 2

Does closing volume increase or decrease with GA?

Answer 2

Decreases during anaesthesia.

Question 3

In what situations can you see an increase in closing volume?

Answer 3

Increases with age
Increases supine position
Increased in obesity

Question 4

FRC can be measured by which of the following:

1. Helium washout
2. Nitrogen wash out
3. Body plethysmography
4. Spirometry
   e. Intra-oesophageal balloon

Answer 4

Helium washout,
nitrogen washout
body plethysmography

…Spirometry will measure all lung volumes except FRC, residual volume and TLC…

Question 5

Surfactant is what type of protein?

Answer 5

Phospholipid

Question 6

Surfactant effect on compliance?

Answer 6

Increases compliance

Question 7

True or false:

Surfactant prevents transudation of fluid from the blood into the alveoli

Answer 7

True.

High surface tension would tend to draw fluid into the alveoli.

Question 8

Alveolar - arterial oxygen difference (A-a DO2) in exercise?

Answer 8

The A-a difference widens at high intensity levels of exercise.

Question 9

What can cause PaCO2-EtCO2 gradient increase.

Answer 9

The PaCO2-EtCO2 gradient increases with any cause of increased dead space.

Question 10

What are the major causes of Alveolar - arterial oxygen difference (A-a DO2)?

Answer 10

The major causes of and increased A-a difference are:

• Shunt - low V/Q ratio
• diffusion defects.

Question 11

When the V/Q ratio of a lung unit increases, what effect will this have on arterial PO2?

Answer 11

INCREASES - Contrary to intuition, this is true, although the cause of dead space in one lung unit may cause shunt in another with the net effect being hypoxia, such as seen after a PE.

Question 12

In an awake, healthy individual in the lateral position, the:

true or false for each of the following statements.

A. dependent lung has less ventilation
B. dependent lung has more perfusion
C. V/Q ratio is higher in the dependent lung
D. PAO2 is higher in the lower lung
E. PACO2 is lower in the lower lung

Answer 12

A. False. The dependent (lower) lung will have better ventilation

B. True.

C. False. The dependent lung will have a small degree of shunt (low V/Q ratio) whilst the non-dependent lung will have a degree of dead space (high V/Q)

D. False. The degree of shunt will lower PAO2 and raise PACO2

E. False.

Question 13

An area in the lung with increased V/Q ratio:

is responsible for a decrease in the PAO2 with no change in PACO2? T/F

Answer 13

False.

DEAD SPACE - PAO2 increases, whilst PACO2 decreases

Question 14

What is a pressure-volume curve used for?

Answer 14

Measurement of:

• work of breathing
• compliance

Question 15

A body plethysmograph can be used to measure what?

Answer 15

Compliance
Work of breathing
Airway resistance

Question 16

How do you estimate TV for a patient?

Answer 16

5-7 mls/kg

Question 17

How do you estimate dead space for a patient?

Answer 17

2 mls/kg

Question 18

T/F: Alveolar partial pressure of H2O exceeds that of CO2?

Answer 18

True.

Partial pressure of water vapour in the alveoli is around 6.3 kPa

Question 19

What equipment is needed to measure intrapleural pressure?

Answer 19

A body plethysmograph and an oesophageal balloon may be used to measure intrapleural pressure.

Measurements of pressure and volume may then be plotted against one another to give pressure: volume compliance loop.