Respiratory Failure

Question 1

What is the definition of respiratory failure?

Answer 1

Inadequate gas exchange resulting in hypoxia (PaO2 <8kPa.

Type depends on PaCO2 levels

Question 2

What is the definition of type 1 respiratory failure?

Answer 2

Hypoxia with normal or low PaCO2 levels

Question 3

What is the definition of type 2 respiratory failure?

Answer 3

Hypoxia with hypercapnia (PaCO2 > 6kPa)

Question 4

Name some of the causes of type respiratory failure.

Answer 4

V/Q mismatch (air flow doesn’t match blood flow)
Hypoventilation (pulmonary emobolism, pneumonia, asthma, oedema, fibrosis or ARDS)
Abnormal diffusion (oxygen can’t enter the blood due to parencyhmal disease e.g. ARDS and pneumonia)
Right to Left cardiac shunts (oxygenated blood mixes with non-oxygenated)

Question 5

Name some causes of type 2 respiratory failure.

Answer 5

Alveolar hypoventilation with or without V/Q mismtach
Pulmonary disease (asthma, COPD, obstructive sleep apnoea, pulmonary fibrosis)
Reduced respiratory drive (sedative, CNS tumour/trauma)
Neuromuscular disease (myaesthenia gravis, cervical cord lesion, Guillian-Barre syndrome)
Thoracic wall disease (kyphoscoliosis, flail chest)

Question 6

What are the clinical features of respiratory failure?

Answer 6

Those of the underlying disease
Hypoxia
- dyspnoea
- restless, agitated, confused
- central cyanosis
Hypercapnia 
- headache 
- peripheral vasodilation 
- increased heart rate, bounding pulse
- tremor, flap
- papilloedema 
- confused, drowsy, coma

Question 7

What investigations would you perform for respiratory failure?

Answer 7

Blood test
- FBC (anaemia can cause hypoxic tissue, polycythaemia can indicate underlying disease)
- U&Es (electrolyte disturbances can exacerbate respiratory failure)
- CRP (infective cause)
ABG
Chest X-Ray
Sputum and blood cultures if febrile
Spirometry

Question 8

What is the management for type 1 respiratory failure?

Answer 8

Treat the underlying cause
Oxygen 24-60% by facemask
Assisted ventilation if PaO2 <8kPa on 60% oxygen

Question 9

What is the management for type 2 respiratory failure?

Answer 9

Treat the underlying cause
Controlled by oxygen therapy (24% to start)
- hypoxic drive
ABG after 20 minutes
- if CO2 has dropped then oxygen can be increased to 28%
- if CO2 has risen, consider non-invasive ventilation
Tubing and ventilation is other methods fail