Difference between hypoxaemia, hypoxia, anoxia and anoxia

By Cristiano Antonino On Jul 29, 2022

The term ‘hypoxia’ (in English ‘hypoxia’) refers to a pathological condition caused by a lack of oxygen in the tissues

Hypoxia, oxygen deficiency can be

generalised: oxygen deficiency in the entire body
tissue: oxygen deficiency in a specific region of the body.

Depending on the causes, various forms of hypoxia can be distinguished

The typical sign of tissue hypoxia is the paleness of the skin and mucous membranes in specific locations such as the palm of the hand, the pinna of the ear, the mucous membrane of the inside of the lips and the palpebral conjunctiva.

The first tissues to be affected by the lack or depletion of oxygen are the nerve tissues, in particular the brain, the visual and auditory apparatus: the lack of oxygen supply to the brain causes misperception of colours and scotoma, even syncope.

The term anoxia, on the other hand, refers to a marked decrease or complete lack of oxygen at the tissue and cellular level, i.e. a severe form of hypoxia

Anoxia can be histotoxic, i.e. due to tissue damage, or consequent to a severe decrease in blood supply to the affected tissues. In this case, one can speak of anoxia.

It is an emergency situation which, if not resolved quickly, leads in a short time to the death of tissues, especially those particularly sensitive to the lack of oxygen, such as nerve tissue.

The signs of anoxia are the same as for hypoxia, but more severe.

Hypoxemia refers to an abnormal decrease in oxygen content in the blood, resulting in cyanosis, Cheyne-Stokes respiration (impaired), apnoea, hypertension and even coma.

Particularly stressed is the heart, arrhythmias such as tachycardia (increased heart rate) occur at first, the flow increases and then suddenly decreases, leading to ventricular fibrillation or asystole.

Hypoxaemia characterises respiratory failure

Hypoxemia is therefore caused by insufficient oxygenation of the blood, which is different from the condition of hypoxia, which implies a decrease in the content and utilisation of O2 in the tissues.