Respiratory Failure

Question 1

What are the steps in the oxygen transport pathway from air to tissues?

Answer 1

Air

1. Airways
2. Alveolar gas
3. Alveolar membrane
4. Arterial blood
5. Regional arteries
6. Capillary blood

Tissues

Question 2

What are the disease processes that may affect the oxygen transport pathway?

Answer 2

• Low inspired oxygen
• Muscle and chest wall problems
• Obstructive airway disease
• Fibrosis
• Pulmonary oedema
• Ventilation-Perfusion matching
• Anaemia
• Shock
• Peripheral arterial disease

Question 3

What point in the oxygen transport pathway does low inspired oxygen affect?

Answer 3

The air

Question 4

What may cause low inspired oxygen?

Answer 4

High altitude

Question 5

What point in the oxygen transport pathway do muscle or chest wall problems affect?

Answer 5

The airways

Question 6

What are some potential muscle or chest wall problems?

Answer 6

• Scoliosis
• Kyphosis
• Pectus Excavatum
• Muscular dystrophy
• Myasthenia gravis
• Trauma

Question 7

What point in the oxygen transport pathway does obstructive airway disease affect?

Answer 7

Airways

Question 8

Give two obstructive airway diseases?

Answer 8

• Asthma
• COPD

Question 9

What point in the oxygen transport pathway does fibrosis affect?

Answer 9

Alveolar membrane

Question 10

What are some potential causes of fibrosis?

Answer 10

• Silicosis
• Alveolitis

Question 11

What point in the oxygen transport pathway does pulmonary oedema affect?

Answer 11

As oxygen leaves the alveolar membrane

Question 12

What are some potential causes of pulmonary oedema?

Answer 12

• Cardiogenic (left heart failure)
• Aspiration (e.g. vomit)
• Infection
• Trauma

Question 13

What point in the oxygen transport chain does ventilation-perfusion matching affect?

Answer 13

Just as the oxygen enters the arterial blood

Question 14

What are some potential causes of problems with ventilation-perfusion matching?

Answer 14

• Pulmomary emboli
• Pneumonia
• Consolidation
• Collapse of lobe
• Large airway destruction

Question 15

What point in the oxygen transport pathway does anaemia affect?

Answer 15

Arterial blood

Question 16

What are some potential causes of anaemia?

Answer 16

• Insufficient red blood cells produced in marrow
• Deficiency of B12/iron
• CO binding

Question 17

What point in the oxygen transport pathway does shock affect?

Answer 17

As oxygen is leaving arterial blood

Question 18

What is shock?

Answer 18

Global poor perfusion

Question 19

What point in the oxygen transport pathway does peripheral arterial disease affect?

Answer 19

Regional arteries

Question 20

What are some potential causes of peripheral arterial disease?

Answer 20

Local arterial insufficiency or damage to individual tissues, e.g. claudication or angina

Question 21

What are the types of respiratory failure?

Answer 21

• Type 1
• Type 2

Question 22

What are the features of type 1 respiratory failure?

Answer 22

• pO₂ of arterial blood low
• pCO₂ normal or low

Question 23

What are the features of type 2 respiratory failure?

Answer 23

• pO₂ of arterial blood low
• pCO₂ high

Question 24

What are the acute affects of respiratory failure?

Answer 24

Increase in CO₂ and a decrease in O₂

Question 25

What is the increase in CO₂ and a decrease in O₂ in acute respiratory failure detected by?

Answer 25

Central chemoreceptors

Question 26

What do the central chemoreceptors cause when they detect the increase in CO₂ and a decrease in O₂?

Answer 26

Breathlessness *(some compensation)*

Question 27

What are the chronic effects of respiratory failure?

Answer 27

* CO₂ retention * Right heart failure *(Cor pulmonare)* * Severely disabling

Question 28

What is the result of CO₂ retention in chronic respiratory failure?

Answer 28

* Cerebrospinal fluid acidity corrected by choroid plexus * Initial acidosis corrected by kidney * Reducation of respiratory drive * Persisting hypoxia

Question 29

What causes right heart failure in chronic respiatory failure?

Answer 29

It is the effect of hypoxia on pulmonary arteries resulting in pulmonary hypertension

Question 30

How is respiratory failure managed?

Answer 30

* Oxygen therapy * Removal of secretions * Assisted ventilation * Treat acute exacerbations