Respiratory - Flow of air

Question 1

In emphysema, what happens to the lungs? How does this affect breathing?

Answer 1

Elastic fibres are lost fro the alveolar walls resulting in increased lung compliance. This means that the lungs becomes limp and soft so that the elastic recoil of the lungs is reduced making it harder to expire

Question 2

How does expiration in an emphysema patient and healthy patient differ?

Answer 2

Emphysema: the patient exhales using intercostal muscles to depress ribcage raising the intrapleural pressure which raises the alveolar air pressure pushing air out of the lungs (i.e. the chest presses down on the lungs to push air out)

Healthy patient: Elastic recoil of the lung tissue plus the rib cage inwards and the diaphragm upwards raisin alveolar air pressure but creating sub-atmosphereic pressure it the intrapleural space (i.e. lungs pulls chest inwards to push air out)

Question 3

What is this graph showing?

Answer 3

The intrapleural pressure

Question 4

What is this graph showing?

Answer 4

The alveolar pressure

Question 5

What is this graph showing?

Answer 5

The air flow

Question 6

What is this graph showing? What is the respiratory rate of this diagram

Answer 6

The tidal volume where the rate is 15 breaths min-1

Question 7

What is the pressure in the lungs relative to?

Answer 7

They are given relative to the atmospheric pressure (i.e. at the mouth/nose)

Question 8

What are the factors that affect the airflow?

Answer 8

Muscular efforts and lung characteristic

Question 9

What are the lung characteristics that affect air flow?

Answer 9

compliance, Resistance, dead-space and diffusion

Question 10

What is the muscular effort?

Answer 10

The force generated by the diaphragm and intercostal muscles

Question 11

What is compliance describing?

Answer 11

The elasticity of the lung tissue (change of V (volume) per change of P (pressure), i.e. the more change in V per change in P the more the compliance)

Question 12

What is the inverse of compliance?

Answer 12

Stiffness (i.e. lower compliance = greater stiffness)

Question 13

What is resistance?

Answer 13

Change of P (pressure) per change of F (flow) (i.e. the more that P needed per change in F, the more resistance)

Question 14

What is the inverse of resistance?

Answer 14

Conductance (i.e. the greater the resistance the lower the conductance)

Question 15

What is a greatly increased compliance characteristic of? What is happening to the lungs?

Answer 15

Emphysema due to a loss of elastic fibres

Question 16

What are the two different fluids filling the lungs in each graph? Why are they different?

Answer 16

When filled with air there is an air-water surface tension that has to be overcome which makes the lungs less compliant when filled with air while in water this air-water barrier is eliminated so it is

Question 17

In the Pressure-Volume of lungs being filled with air, why are the inflation and deflation loops different? What is this loop called

Answer 17

This is a hysterisis loop

At low volume the lungs are very compliant because most of the alveoli have collapsed so a large pressure is required to over come surface tension (hence the plateau at the start). The deflation curve is different because the

Question 18

What are the contributors to airway resistance?

Answer 18

Cross-sectional area and air flow rate

Question 19

How is air resistance proportional to the radius of the airway?

Answer 19

Resistance proportional to the radius^4

Question 20

What is the relative air resistance in the alveoli relative to the resistance in the mouth and nose? Why?

Answer 20

The air resistance is much lower in the alveoli because the smallest branches are arranged in parallel. This means that the total cross-sectional area of all the airways is the radius used to calculate air resistance and it is much larger than the mouth and nose area

Question 21

What is the characteristic that causes asthma? Why does it cause asthma

Answer 21

Sporadic broncho-constriction causes increased airway resistance

Question 22

What is anatomic dead-space?

Answer 22

The volume of the conduction airways (i.e. no gas exchange)

Question 23

What is the volume of the conduction airways?

Answer 23

150ml (FYI makes up only 3% of the lungs 5L volume)

Question 24

What is the consequence of the dead-space?

Answer 24

It means that for every breath taken, the air that was in the dead-space and is not fresh get re-inhaled and some of the fresh air that was inhaled is stuck in the dead space ‘diluting’ the fresh air

Question 25

How does the dead-space change as your breath size changes? Why?

Answer 25

It doesn’t, it is a constant 150ml as that is the volume of conduction airways and doesn’t change regardless of breath size

Question 26

What is the rate of gas exchange across a membrane proportional to?

Answer 26

(P_Agas [partial pressure of gas in the alveoli] - P_Cgas [partial pressure of gas in capillaries])

The surface area of gas exchange

Inversely proportional to the thickness of the membrane wall

The square root of the molecular weight of the gas

Question 27

What is law of the square root of the molecular weight of the gas?

Answer 27

Graham’s law

Question 28

What some conditions caused when the function of the lungs are compromised?

Answer 28

Respiratory Distress Syndrome

Emphysema

Asthma

Pulmonary oedema

Question 29

Who gets respiratory distress syndrome? What is not functioning properly?

Answer 29

Premature babies who haven’t developed their pulmonary surfactant yet

Question 30

Why does the absence of pulmonary surfactant affect breathing/chances of survival in premature babies?

Answer 30

Without the pulmonary sufactant there is a higher air-water surface tension which means that a greater interpleural pressure is required to inflate the lungs require greater muscular effort which they don’t have resulting in distress/fatigue

Question 31

What is the physiological cause of emphysema?

Answer 31

Destruction of inter-alveolar and inter alveolar tissue

Question 32

What do the inter-alveolar and inter alveolar tissue do?

Answer 32

Hold the smallest bronchioles open during expiration

Question 33

How does emphysema impact breathing?

Answer 33

Lung compliance decreases therefore less air can be expired per breath increasing the functional residual breath. This results in a lower tidal volume as if less air can get out, less air can get in

Question 34

What is pulmonary oedema?

Answer 34

Where there is water on the lungs

Question 35

How does pulmonary oedema affect breathing?

Answer 35

Water on the lung increases the distance which the oxygen has to travel across therefore decreasing gas exchange