It is a condition when the oxygen level is a low or insufficient amount in tissues due to low blood supply or low oxygen content in the blood (hypoxemia)
Causes for hypoxia are impaired movement of oxygen from the lungs into the bloodstream, blood entering directly the left side of the heart without oxygenation, etc.
The first signs of hypoxia include coughing, confusion, restlessness, headache, shortness of breath, and bluish color in skin, fingernails, and lips.