Hypoxic Cell Injury
Hypoxia.
Hypoxia is the most common cause of cell injury.
Ischaemia.
Most common mechanism of hypoxic cell injury is by reduced supply of blood to cells due to interruption i.e. ischaemia.
Generally < 2% Oxygen.
hypoxia is referred to the relatively low (generally < 2%) oxygen content compared to normal status in a given organ, tissue, or cell type.
Hypoxia is a state of continuously lack of oxygen for a short (acute hypoxia, e.g., ischemia) or long (chronic hypoxia, e.g., chronic kidney disease, cancer) period of time.
Hypoxia is actually divided into four types:
– Hypoxic hypoxia,
– Hypemic hypoxia,
– Stagnant hypoxia,
– Histotoxic hypoxia.
Most common form of hypoxia encountered in flight.
occurs at the lung level
commonly called altitude hypoxia
Reduced partial pressure of oxygen.
The percentage of oxygen does not change as we ascend;
The partial pressure of oxygen in air decreases as we go to altitude.
Increasing altitude- the partial pressure of oxygen gets lower and the lungs cannot effectively transfer oxygen from the ambient air to the blood to be carried to all tissues in the body.
Hypemic Hypoxia – Reduced ability of the blood to carry oxygen
This type of hypoxia is caused by the reduced ability of the blood to carry oxygen.
Anemia, hemorrhage, hemoglobin abnormalities, sulfa drugs, nitrites, and carbon monoxide.
All of the above conditions interfere with the ability of the blood to carry oxygen, reducing the amount of oxygen the blood can carry to the cells.
Hypemic Hypoxia – Reduced ability of the blood to carry oxygen
Hemoglobin bonds with carbon monoxide 200 times more readily than it bonds with oxygen.
Stagnant Hypoxia
This type of hypoxia occurs at the circulatory level.
Ex – Heart Failure, Clod Temperature.
If the blood flow is compromised for any reason, then sufficient oxygen cannot get to the body tissues.
Histoxic Hypoxia.
This type of hypoxia happens at the cell level.
– There is an adequate supply of oxygen to breathe.
– Oxygen is being circulated by the blood.
– Cells are unable to accept or use the oxygen.
– Ex- Alcohol, narcotics, and cyanide
