Respiratory failure

Question 1

Define respiratory failure

Answer 1

It is defined as a low partial pressure of oxygen (PaO2) in the arterial blood. This is PaO2< 8kPa

Question 2

What are the two types of resp failure?

Answer 2

The two types are classified based on the partial pressure of CO2 in arterial blood.

Type 1 is defined as hypoxemia and a normal/low PaCO2
Type 2 is defined as hypoxaemia and hypercapnia (PaCO2>6kPa)

Question 3

What are the risk factors of resp failure?

Answer 3

• Smoking
• Young children/older adults
• Obesity
• All the causes baso

Question 4

What are the causes of type 1 resp failure?

Answer 4

Pneumonia
Pulmonary oedema e.g. due to HF
Pulmonary embolism
Pneumothorax
ARDS
Pulmonary fibrosis
COPD and Asthma also cause it

think ‘P’

Question 5

What are the aetiologies (development) of type 1 respiratory failure?

Answer 5

It is most commonly caused by V/Q mismatch, but also can be by other processes like shunts, diffusion limitation and alveolar hypoventilation.

Question 6

Explain the aetiology of V/Q mismatch in relation to type 1 resp failure

Answer 6

V/Q mismatch - ratio of alveolar ventilation to alveolar perfusion. Due to mismatch, these ratios can differ in parts of the lung due to disease which can lead to hypoxemia.
Low V/Q ratio - parts of the lung/some alveoli have poor ventilation but normal perfusion - low alveolar O2 so low in blood.

Question 7

What are the causes of type 2 resp failure?

Answer 7

COPD (most common)
severe asthma