Table 1

Stages	Altitude	PaO₂(mm Hg)	% saturation of haemoglobin
Indifferent	0-10,000ft	100-60 mmHg	95-90%
Compensatory	10,000-15,000ft	60-56 mmHg	90-80%
Disturbance stage	15,000-20,000ft	45-35 mmHg	80-70%
Critical Stage	Above 20,000ft	Less than 35 mmHg	70-60%

Table 1: Stages of hypoxia in aviation depending on altitude.