Ventilation And Compliance

Question 1

Define the Anatomical dead space volume

Answer 1

• is 150mL
• volume of gas occupied by the conducting airways
• this gas is not available for exchange

Question 2

Define TV

Answer 2

• Tidal Volume

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

Question 3

Define ERV

Answer 3

• expiratory reserve volume

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

Question 4

Define IRV

Answer 4

• inspiratory reserve volume

- the maximum volume of air which can be drawn into the lungs at the end of normal inspiration

Question 5

Define RV

Answer 5

• residual volume

- the volume of gas in the lungs at the end of maximal expiration

Question 6

Define VC

Answer 6

• vital capacity

- tidal volume + inspiratory reserve volume + expiratory reserve volume

Question 7

Define TLC

Answer 7

• total lung capacity

- vital capacity + the residual volume

Question 8

Define IC

Answer 8

• inspiratory capacity

- tidal volume + inspiratory reserve volume

Question 9

Define FRC

Answer 9

• functional residual capacity

- expiratory reserve volume + residual volume

Question 10

Describe the significance of FEV1:FVC

Answer 10

Fraction of forced vital capacity expired in 1 second (forced exploratory volume in 1 second divided by forced vital capacity)

Question 11

Define pulmonary ventilation

Answer 11

The total air movement into/out of lungs.

Question 12

Define alveolar ventilation

Answer 12

The volume of fresh air getting to alveoli and therefore available for gas exchange.

Question 13

State how to calculate pulmonary ventilation

Answer 13

Multiply the tidal volume by respiration rate

Question 14

State how to calculate alveolar ventilation

Answer 14

Multiply the air to alveoli by respiration rate

Question 15

State the units used to measure pulmonary and alveolar ventilation

Answer 15

L/min

Question 16

Define partial pressure

Answer 16

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

Question 17

State the units used to measure partial pressure

Answer 17

mmHg or kPa

Question 18

What effect does increasing [gas]mixture have on partial pressure and why?

Answer 18

Partial pressure increases as all gas molecules exert same pressure

Question 19

Describe resting alveolar Po2 and Pco2 under normal conditions

Answer 19

Remains constant

Question 20

State the normal alveolar and arterial gas pressure for oxygen

Answer 20

13.3kPa (100mmHg)

Question 21

State the normal alveolar and arterial gas pressure for carbon dioxide

Answer 21

5.3kPa (40mmHg)

Question 22

Define hyper ventilation and describe what happens to Po2 and Pco2 during hyper-ventilation

Answer 22

• increased alveolar ventilation
• Po2 rises to ~120mmHg
• Pco2 falls to ~20mmHg

Question 23

Define Hypo-ventilation and describe what happens to Po2 and Pco2 during Hypo-ventilation

Answer 23

• decreased alveolar ventilation
• Po2 falls to ~30mmHg
• Pco2 rises to ~100mmHg

Question 24

Describe features of healthy lungs

Answer 24

• very elastic

- stretched slightly open even at the end of a relaxed expiration (tendency to recoil)

Question 25

Describe the 2 cell types that make up the alveolar walls

Answer 25

• Thin walled ‘Type I’ => permit gas exchange

- Specialised ‘Type II’ => secrete surfactant fluid

Question 26

What is surfactant?

Answer 26

Detergent like fluid produced by Type II alveolar cells

Question 27

Where does surface tension occur?

Answer 27

Where ever there is an air-water interface (air and water meet)

Refers to the attraction between water molecules

Question 28

State the functions of surfactant

Answer 28

• reduces surface tension on alveolar surface membrane => reduces tendency for alveoli to collapse
• increases lung compliance
• reduces lung’s tendency to recoil
• makes work of breathing easier

Question 29

Where is surfactant most effective?

Answer 29

In small alveoli (as opposed to large alveoli) because surfactant molecules come closer together => more concentrated

Question 30

Describe the development of surfactant production during gestation

Answer 30

• Starts ~25 weeks gestation
• Complete ~36 weeks
• stimulated by thyroid hormones and cortisol which increase towards end of pregnancy

Question 31

Describe why premature babies can suffer Infant Respiratory Distress Syndrome

Answer 31

Their lungs are developmentally deficient in surfactant, causing air-spaces to collapse and become difficult to expand.

Symptoms include fast breathing, chest wall retractions, blue discolouration of the skin during breathing efforts.

Question 32

Define compliance

Answer 32

• Change in volume relative to change in pressure
• Represents the stretchability of the lungs
• Changes in disease states/age

Question 33

Define high compliance

Answer 33

large increase in lung volume for small decrease in IP pressure

Question 34

Define low compliance

Answer 34

small increase in lung volume for large decrease in IP pressure