When your body does not have enough oxygen, you'll get hypoxemia or hypoxia. These are dangerous conditions.
Without Oxygen, your brain, liver, and different organs will be damaged simply minutes once symptoms begin.
Hypoxemia (low oxygen in your blood) will cause drive (low O in your tissues) once your blood does not carry enough O to your tissues to satisfy your body's wants.
The word hypoxia is usually wont to describe each issues.