Session 5 - part II

Question 1

What can cause diffusion impairment in the alveolar capillary membranes?

Answer 1

Fibrotic lung disease
Pulmonary oedema
Emphysema

Question 2

How does fibrotic lung disease effect diffusion?

Answer 2

Thickened alveolar membrane slows the gas exchange. O2 is effected more than CO2 as CO2 diffuses more easily

Question 3

How does Pulmonary oedema effect diffusion?

Answer 3

Fluid in the interstitial space increases diffusion disrance

Question 4

How does Emphysema effect diffusion?

Answer 4

Destruction of the alveoli reduces the surface area (by making less, bigger alveoli) for gas exchange

Question 5

What are the normal partial pressures of CO2 and O2 in the venous blood?

Answer 5

pO2 - 5.3

pCO2 - 6.1

Question 6

What are the normal partial pressures of CO2 and O2 in the alveolar air?

Answer 6

pO2 - 13.3

pCO2 - 5.3

Question 7

What is respiratory failure?

Answer 7

There is not enough O2 getting into the blood and/or not enough CO2 leaves the blood (They do not have to occur together)
2 types are Type 1 and Type 2

Question 8

What is Type 1 Respiratory failure?

Answer 8

Not enough O2 enters the blood
CO2 removal is not compromised
So pO2 of arterial blood low, pCO2 normal or low

Question 9

What is Type 2 Respiratory failure?

Answer 9

Not enough O2 enters the blood
Not enough CO2 leaves it
So pO2 of arterial blood is low, pCO2 high

Question 10

What are some of the signs/symptoms of Type 1 Respiratory failure?

Answer 10

Breathlessness
Exercise tolerance
Central cyanosis (So hypoxia of blood in major arteries)
Ventilation/Perfusion match poor
Poor uptake of O2 in some alveoli cannot be compensated for by increased uptake in others

Question 11

What can cause fibrosis of alveoli?

Answer 11

Fibrosing alveolitis (Long term inflammation)
Extrinsic allergic alveolitis
Pneumoconiosis (Coal dust irritates alveoli)
Asbestos (Irritates alveoli)

Question 12

What causes Type 2 Respiratory failure?

Answer 12

Issues with the chest wall eg. Scoliosis, Trauma, Pneumothorax.
Poor respiratory effort eg Narcotics, Opiodanalgesics Adverse Drug Reaction
Hard to ventilate lungs due to increased airway resistance eg COPD, Asthma

Question 13

How are the alveoli destroyed in Emphysema?

Answer 13

Trypsin is released from cells that are irritated eg by smoking and the lack of alpha1 antitrypsin (Due to genes) allows the cells to be destroyed

Question 14

What is the reaction to acute Hypoxia?

Answer 14

Peripheral chemoreceptors stimulated
Ventilation increases
If pCO2 drops, drive to breathe reduces due to central chemoreceptors

Question 15

What is the reaction to chronic Hypoxia?

Answer 15

Renal correction of acid/base balance

Increased ventilation

Question 16

What are the acute effects of Type 2 Respiratory failure?

Answer 16

Increased pCO2
Decrased O2
Breathlessness
Some compensation, but disease prevents full compensation for occurring

Question 17

What are the chronic effects of Type 2 Respiratory failure?

Answer 17

CO2 retention
Cerebrospinal fluid acidity corrected by the Choroid plexus
Central chemoreceptors ‘reset’ to allow a higher CO2 level
Persisting Hypoxia which drives breathing via peripheral chemoreceptors
Increased O2 transport capacity by having more Hb (Polycythaemia)

Question 18

What are the effects of chronic Type 2 Respiratory failure on the Pulomary circulation?

Answer 18

Pulmonary hypertension
Right heart failure
Cor Pulmonale (Heart disease due to lung issues)

Question 19

Why is giving O2 to a patient with chronic Type 2 Respiratory failure dangerous?

Answer 19

It removes the drive to breathe which is caused by the CO2 retention

Question 20

Why is it harder to breathe when some air is already trapped in the lungs?

Answer 20

The lungs start off more inflated so it harder to inflate them to the maximum point