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Pathology
Term used to describe failure to maintain oxygenation
Type 1: hypoxia (PaO2 <8.0kPa) normal CO2. This a due to a ventilation/perfusion
(V/Q) mismatch (e.g. pulmonary embolus, pneumonia, fibrosis)
Type 2: hypoxia (PaO2 <8.0kPa) plus hypercapnia (PaCO2 >6.0KPa). Due to alveolar
hypoventilation (e.g. COPD, neuromuscular disease, sedation)
Aetiology
Pulmonary Disease: Asthma, COPD, pneumonia, pulmonary fibrosis, ARDS, obstructive sleep apnoea, tumour
Thoracic wall: flail chest, kyphoscoliosis
Reduced respiratory drive: sedatives, CNS disorder, brainstem stroke
Neuromuscular: Cervical cord lesions, diaphragm paralysis, poliomyelitis, Guillain-Barre, myasthenia gravis
Signs
Type 1: Tachycardia
Type 2: Bounding pulse, tremor, Papilloedema
Symptoms
Type 1: Agitation, dyspnoea, tachycardia and confusion
Type 2: Confusion, headache drowsiness
Investigations
ABG: Hypoxia +/- hypercapnia, respiratory acidosis
Treatment
BC with appropriate oxygen delivery (beware hypoxic drive in type 2 failure)
Treat underlying cause
Prognosis
30% 1 year survival rate for those requiring ventilation
Type 2 failure can cause cor pulmonale and pulmonary hypertension
Key Facts
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Key References
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