Respiratory Failure

Question 1

When does respiratory failure occur and what is it characterised by?

Answer 1

• Failure of gas exchange and/or ventilation
• Abnormalities in arterial oxygen and CO2 partial pressures (PaO2 and PaCO2)

Question 2

What are the two types of respiratory failure and what do they involve?

Answer 2

• TYPE 1 - Hypoxaemia (PaO2 < 8kPa or 60 mmHg) with normocapnia (PaCO2 < 6.0 kPa or 45 mmHg)
• TYPE 2 - Hypoxaemia with hypercapnia (PaCO2 >6.0 kPa / 45mmHg)

Question 3

What usually occurs with Type 1 respiratory failure?

Answer 3

V/Q mismatch
- PaO2 falls and PaCO2 rises
- Increase in alveolar ventilation corrects PaCO2 but not PaO2

Question 4

List some causes of Type 1 respiratory failure.

Answer 4

• Reduced ventilation and normal perfusion (e.g. pneumonia, pulmonary oedema, bronchoconstriction)
• Reduced perfusion with normal ventilation (e.g. pulmonary embolism)

Question 5

What usually occurs in Type 2 respiratory failure?

Answer 5

Alveolar hypoventilation
- Patients unable to oxygenate blood (so PaO2 falls) and eliminate CO2 (so PaCO2 rises)

Question 6

List some causes of Type 2 respiratory failure.

Answer 6

• Increased resistance due to airway obstruction (e.g. COPD)
• Reduced compliance of the lung tissue/chest wall (e.g. pneumonia, rib fractures, obesity)
• Reduced strength of the respiratory muscles (e.g. Guillain-Barré, motor neurone disease)
• Reduced respiratory drive (e.g. opioids and other sedatives)

Question 7

How can PaO2 and PaCO2 be determined?

Answer 7

Using ABGs

Question 8

How is Type 1 respiratory failure treated?

Answer 8

With oxygen therapy