Respiratory failure is a meical term for inadequate gas exchange by the respiratory system. Respiratory failure can be indicated by observing a drop in blood oxygen level (hypoxemia) and/or a rise in arterial carbon dioxide (hypercapnia) which can be written as (PaO2 < 60 mmHg, PaCO2 > 45 mmHg). Classification into type I or type II relates to the absence or presence of hypercapnia respectively. (Values in kPA being PO2 below 8kPA and PCO2 above 6.7kPa