hypoxia – where is the underlying problem

1. respiratory centres – brainstem, cerebral lesions
2. phrenic nerve – diaphragm muscles
3. spinal nerve – intercostal muscles
4. ventilation
5. perfusion – PE, pneumonia (vasoconstriction in response to hypoxia)
6. diffusion – 1. surface area (emphysema); 2. nature of membrane (pulmonary oedema, fibrosis, atelectasis); 3. diffusion gradient
7. intrapleural – inflammatory, infective