Respiratory Failure

Type I

hypoxia ($Pa{O}_2<8kPa$) with a normal or low $PaC{O}_2$. Its caused primarily by V/Q mismatch, hypoventilation, abnormal diffusion, right to left cardiac shunts. Eg of V/Q mismatch:

• pneumonia
• pulmonary oedema
• pulmonary embolism
• asthma
• emphysema
• pulmonary fibrosis
• ARDS

Type II

hypoxia with hypercapnia ($PaC{O}_2<6kPa$). Caused by alveolar hypoventilation with or without V/Q mismatch. Causes include:

• Pulmonary disease: asthma, COPD, pneumonia, pulmonary fibrosis, obstructive sleep apnoea
• Reduced respiratory drive: sedatives, CNS tumour/trauma
• Neuromuscular disease: Cervical chord lesion, diaphragmatic paralysis, poliomyelitis, myasthenia gravis, Guillain-Barre Syndrome
• Thoracic wall disease: fail chest, kyphoscoliosis

Clinical Features

Features are of underlying cause plus symptoms of hypoxia with or without hypercapnia

Hypoxia: dyspnoea, restlessness, agitation, confusion, central cyanosis - if chronic/long standing pulmonary Essential hypertension, polycythaemia, cor pulmonale

Hypercapnia: headache, peripheral vasodilation, tachycardia, bouncing pulse, confusion, drowsiness, coma

Diagnostic Tests

Find underlying cause

• Blood tests
• CXR
• Sputum culture
• Spirometry

Management

Treat underlying cause

• Oxygen
• assisted ventilation if necessary

Complications/red Flags