Ventilation & compliance 1

Question 1

State Dalton’s Law

Answer 1

The total pressure of a gas mixture is the sum total of the pressures of the individual gases.

Question 2

Effect of hyperventilation and hypoventilation on PCO2 and PO2

Answer 2

Hyperventilation: PO2 will rise and PCO2 will fall
Hypoventiation: PO2 decreases and PCO2 increases

Question 3

Functions of Type l & Type ll Pneumocytes

Answer 3

Type l: Thin walled cells allows gas exchange

Type ll: specialised cells that secretes surfactant liquid

Question 4

What is surfactant?

Answer 4

-phospholipid containing liquid produced by Type ll alveolar cells.

Question 5

What is surface tension?

Answer 5

tension caused by the attraction of water molecules

Question 6

Function of surfactant

Answer 6

• Reduces surface tension on alveolar surface membrane, hence preventing alveoli to collapse
• increases lung compliance
• more effective in small alveoli than large as surfactant molecules come closer together and become more concentrated

Question 7

Describe the stimulation of surfactant production

Answer 7

stimulated by thyroid horemeones and cortisol towards end of pregnancy

• 25 weeks gestation ; complete by 36 weeks
• saccular stage

Question 8

What do premature babies suffer from in terms of surfactant production? State the treatment

Answer 8

• Infant Respiratory distress syndrome ( IRDS)

- treat with aerosol can of surfactant and corticosteroids given to mother

Question 9

What is compliance?

Answer 9

Change in volume relative to change in pressure

-represents stretchability of lungs

Question 10

What does high/low compliance indicate?

Answer 10

High compliance: large increase in lung volume for decrease in pressire

Vice versa

Question 11

What is emphysema?

Answer 11

Loss of elastic tissue, hence expiration requires effort

Question 12

What does fibrosis mean?

Answer 12

• Accumulation of fibrous tissue,( due to fibrosis/scarring) hence inspiration requires effort
• leads to stiffness of lung

Question 13

Obstructive vs restrictive lung disease

Answer 13

Obstructive: obstruction of airflow on expiration. Causes increased airway resistance

Restrictive: restriction of lung expansion. Leads to loss of lung compliance + lung stiffness

Question 14

State examples of obstructive lung disorders

Answer 14

Asthma

COPD - Chronic bronchitis (inflammation of the bronchi ) & Emphysema ( destruction of alveoli, loss of elasticity)

Question 15

State examples of restrictive lung disorders

Answer 15

Fibrosis: (formation/development of excess fibrous connective tissue
Infant respiratory distress syndrome: (insufficient surfactant prod.)
Oedema:
Pneumothorax:

Question 16

What is spirometry?

Answer 16

A technique used to measure lung function. Measurements classed as static/dynamic

Question 17

Describe what is meant by static + dynamic lung volumes

Answer 17

Static:volume exhaled is measured
Dynamic: time taken to exhale a certain volume is measured

Question 18

State the effect of Obstructive lung disease on FVC, FRC+ FEV1

Answer 18

FEV1:decreases
FVC: can be normal
FRC:increases
FEV1.FVC: decreases

Question 19

State the effect of pulmonary fibrosis on absolute rate of airflow, total volume and the ratio

Answer 19

The absolute rate of airflow decreases + total volume is also reduced due to the limitations of lung expansions. The ratio is constant but can increase

Question 20

What is the tidal volume?

Answer 20

The volume of air breathed in/out of lungs at each breath

Question 21

What is the expiratory reserve volume (ERV) + IRV?

Answer 21

• The maximum volume of air expelled from the lungs in normal expiration
• The maximum volume of air drawn out from lungs in normal inspiration

Question 22

What is the residual volume?

Answer 22

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

Question 23

What is the vital capacity?

Answer 23

• Maximam volume of air that can be exhaled after maximal inspiration
• TV + ERV + IRV

Question 24

What is the Total lung capacity?

Answer 24

• All the air that can be inhaled in lungs

- vital capacity + residual volume?

Question 25

What is the inspiratory capacity?

Answer 25

• all the air that can be inspired

- Tidal volume + inspiratory reserve volume

Question 26

What is the functional residual capacity?

Answer 26

• volume of air left in lungs after normal expiration

- Expiratory reserve volume + residual volume

Question 27

What is the FEV1 + FEV1.FVC

Answer 27

FEV1: Forced expired volume in 1 second

FEV1.FVC: fraction of forced vital capacity expired in 1 second

Question 28

What is pulmonary(Minute) ventilation

Answer 28

Air movement into/out lungs

Question 29

What is alveolar ventilation

Answer 29

Fresh air getting into alveoli + available for gas exchange

Question 30

State PO2 and PCO2

Answer 30

PAO2 - 100mmHg
PACO2 - 40mmHg

P ṽ O2 - 40
P ṽ CO2 - 46
( remember Pa=PA unless pathology occurs preventing gas exchange at pulmonary capillaries)

Question 31

State the effect of Restrictive lung disease on FEV1, FVC, FEV1.FVC

Answer 31

FVC and FEV1 decreases

FEV1:FVC normal/increased

Question 32

What is the carbon monoxde transfer test?

Answer 32

• Test that measures lung function by testing diffusing capacity of the lungs for carbon monoxide
• Measures ability of lungs to transfer gas from inhaled air to RBC in pulmonary capillaries
• measured as mmol/min/kPA
• CO transfer = Tco/DLCo

Question 33

What may increase/decrease Tco ( CO transfer)

Answer 33

• increased with increased pulmonary blood flow/volume (shunts, pregnancy, haemorrhage occuring in alveoli)
• decreased in diseases ;COPD, anaemia, smoking (due to higher carboxyhaemoglobin and related disease)