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A condition  in which the body or a region of the body is deprived of adeuate oxygen at the tissue level.
Total deprivation : Anoxia
Hypoxia can be generalized or local

Causes of Hypoxia
High altitude - will lead to altitude sickness : high altitude pulmonary edema, high altitude cerebral edema
Diving underwater with closed circuit rebreather systems
Preterm birth

Types of Hypoxia
4 types
Hypoxemic type : spO2 in blood low - O2 going to tissues is low because the O2 in Hb is low
Anemic type : amount of functional Hb is  too  low
Stagnant type : flow of blood is low
Histotoxic type : tissue cell are poisoned and unable to make use of the O2 in circulation

Hypoxemic type :
A decrease in the amount of breathable oxygen (pilots, mountain climbers, people living at high altitudes due to decreased barometric pressure
Cardiopulmonary failure in  which the lungs are unable to efficiently transfer O2 from alveoli to blood

Anemic type : The total amount of Hb is too small to supply the needs, as in anemia, severe bleeding or is non functional as in CO poisoing, acquired methemoglobinemia

Stagnant type: blood flow through capillaries is insufficient : e.g. heart disease that impairs the circulation , impairment of venous return of blood or trauma that induces shock, Raynaud syndrome, Buerger disease, exposure to severe cold, tourniquets, overhelming systemic infection with shock

Histotoxic Type :  the cells of the  body are unable to use O2 - cyanide poisoning, narcotics, alcohol, formaldehyde, acetone - that it  the  cellular respiration  is impaired

Symptoms and Signs
Generalized hypoxia
Numbness, tingling of extremities
Confusion/disorientation/Hallucination/Behavioural changes
Severe headaches
Reduced level of consciousness
Pulmonary hypertension
Slow heart rate
Cor pulmonale
Low  blood pressure
Followed by death

Local Hypoxia
If local tissue is not  perfused well it becomes cold and pale - may become cyanotic - gangrene
Ischaemia - decreased blood supply to an area causing local hypoxia - in the brain may lead to stroke and in the heart lead to angina pectoris and later on myocardial infarction
Cause of local hypoxia may be due to atheromatous plaques in the arteries, arteriospasm, thrombi, emboli

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