Ventilation and Compliance

Question 1

Anatomical dead space

Answer 1

The volume of gas occupied by the conducting airways and this gas is not available for exchange.
Volume is 150ml.

Question 2

Tidal Volume (TV)

Answer 2

The volume of air breathed in and out of the lungs at each breath.

Question 3

Expiratory Reserve Volume (ERV)

Answer 3

The maximum volume of air which can be expelled from the lungs at the end of a normal expiration.

Question 4

Inspiratory Reserve Volume (IRV)

Answer 4

The maximum volume of air which can be drawn into the lungs at the end of a normal inspiration.

Question 5

Residual volume (RV)

Answer 5

The volume of gas in the lungs at the end of a maximal expiration.

Question 6

Vital Capacity (VC)

Answer 6

VC = tidal volume + inspiratory reserve volume + expiratory reserve volume

Question 7

Total Lung Capacity (TLC)

Answer 7

TLC = vital capacity + the residual volume.

Question 8

Inspiratory Capacity (IC)

Answer 8

IC = tidal volume + inspiratory reserve volume.

Question 9

Functional Residual Capacity (FRC)

Answer 9

FRC = expiratory reserve volume + residual volume.

Question 10

What is FEV1:FVC

Answer 10

Fraction of forced vital capacity expired in 1 second.

Question 11

Pulmonary ventilation

Answer 11

Total air movement into/out of lungs (relatively insignificant).

Question 12

Alveolar ventilation

Answer 12

Fresh air getting to alveoli and therefore available for gas exchange (much more significant).

Question 13

Partial Pressure

Answer 13

The pressure of a gas in a mixture of gases is equivalent to the percentage of that particular gas in the entire mixture multiplied by the pressure of the whole gaseous mixture

Pressure commonly expressed in mmHg or kPa units

Question 14

How does hyper-ventilation affect alveolar PO2 and PCO2?

Answer 14

PO2 rises to about 120 mm Hg and PCO2 falls to about 20 mmHg.

Question 15

How does hypo-ventilation affect alveolar PO2 and PCO2?

Answer 15

PO2 falls to 30 mmHg and PCO2 rises to 100 mmHg.

Question 16

What is Surfactant?

Answer 16

Detergent like fluid produced by Type II Alveolar cells

Question 17

What does Surfactant do?

Answer 17

Reduces surface tension on alveolar surface membrane thus reducing tendency for alveoli to collapse

Increases lung compliance (distensibilty)

Reduces lung’s tendency to recoil

Makes work of breathing easier

Is more effective in small alveoli than large alveoli because surfactant molecules come closer together and are therefore more concentrated.

Question 18

What is Lung Compliance?

Answer 18

Change in volume relative to change in pressure.

- The ease at which the lungs can expand under pressure.

Question 19

High Compliance

Answer 19

large increase in lung volume for small decrease in ip pressure

Question 20

Low Compliance

Answer 20

small increase in lung volume for large decrease in ip pressure

Question 21

Where is alveolar ventilation and compliance greatest?

Answer 21

Greatest at base of lung.

They decline with height from base to apex.

Question 22

Obstructive Lung Disorders

Answer 22

Increased airway resistance

E.g. Asthma, COPD

Question 23

Restrictive Lung Disorders

Answer 23

Loss of lung compliance

• lung stiffness
• Incomplete lung expansion

E.g. fibrosis, infant respiratory distress syndrome, oedema, pneumothorax.

Question 24

What is spirometry?

Answer 24

Technique commonly used to measure lung function

Measurements can be classed as static (where the only consideration made is the volume exhaled) or dynamic (where the time taken to exhale a certain volume is what is being measured).