Respiratory failure

Definition

P_aO₂<8kPa. There are two types which are defined based on the P_aCO₂.

Type I

P_aCO₂ is normal or low. Basically, hypoxia without hypercapnia (low oxygen, not high carbon dioxide). It doesn't matter if the CO₂ is low or normal - if it's not high and the patient is hypoxic, it's type I respiratory failure.

Anything which causes a ventilation/perfusion (V/Q) mismatch can cause type I respiratory failure. V/Q mismatch is where the amount of air coming into the lungs (ventilation) is just enough to oxygenate the amount of blood coming into the lungs (perfusion).