Anoxia    - This refers to lack of oxygen in the cells / tissues. This could be anoxic anoxia, anaemic anoxia, stagnant anoxia, histotoxic anoxia.

Anoxic Anoxia - No oxygen in the lungs may be due to;

                            (a) Mechanical obstruction to respiration.  This is called Asphyxia.

                       e.g. strangulation, Hanging, choking, smothering etc.

                            (b) Lack of oxygen in the environment. This is called suffocation.

                      e.g.  trapped in a closed space, plastic bag over head etc.

Anaemic Anoxia - Oxygen present in the lungs but cannot reach the the blood as the haemoglobin is altered as in Carbon Monoxide poisoning.

Stagnant Anoxia - Oxygen present in the blood but cannot reach the tissues due to heart (pump) failure.

Histotoxic Anoxia - Oxygen present in the blood and reaches tissues but they cannot use the oxygen due to inactivation of tissue enzymes as in Cyanide poisoning.