Respiratory failure - Causes and Complications

Question 1

What can cause hypoxaemia and tissue hypoxia?

Answer 1

Pathology can arise from dysfunction occurring at any part of ‘respiratory journey’.

1. Insufficient ventilation
   a) Obstruction of airways
   b) Failure to breath adequately
2. Insufficient gas exchange
   a) Exchange surface dysfunction
   b) VQ mismatch
3. Insufficient oxygen carrying capacity
4. Insufficient oxygen in atmosphere

Question 2

Type 1 Respiratory failure and its causes

Answer 2

↓ oxygenation

altitude, VQ mismatch, pneumonia

Question 3

Type 2 Respiratory failure and its causes

Answer 3

↓ ventilation

asthma, COPD, NMD, drug overdose, apnoea

Question 4

Type 1 respiratory failure readings

Answer 4

PAO2 Normal
PaO2 ↓
PaCO2 Normal
pH Normal

Question 5

Type 2 respiratory failure readings

Answer 5

PAO2 Normal ↓
PaO2 ↓
PaCO2 ↑
pH l ↓

Question 6

What is PAO2?

Answer 6

Alveolar oxygen pressure

Question 7

What is PaO2?

Answer 7

Arterial oxygen pressure

Question 8

How is PaO2 measured?

Answer 8

ABG

Question 9

How is PAO2 measured?

Answer 9

It is estimated using the alveolar gas equation

Question 10

What are the clinical signs/symptoms of respiratory distress

Answer 10

• Shortness of breath, tachypnoea, dyspnoea
• Tachycardia
• Laboured breathing, audible lung sounds
• Tiredness, drowsiness, loss of consciousness
• Fatigue (generally or upon exercise)
• Cyanosis

Question 11

What are the effects of acute hypoxaemia

Answer 11

Hypoxaemia
→ tissue hypoxia (e.g. cerebral hypoxia)
→organ failure
→death

Question 12

What are the effects of chronic hypoxaemia?

Answer 12

polycythaemia, hypoxic pulmonary vasoconstriction

→ pulmonary heart failure

Question 13

What are the effects of Hypercapnia?

Answer 13

Hypercapnia
→ acidosis
→ organ failure + cardiac arrhythmia
→ death