The word hypoxia means "low oxygen". To put in other words, hypoxia is the reduced supply or availability of oxygen to the body tissues. Hypoxia can be generalized, affecting the whole body or it can be localized, confined to one part or region of the body. What makes hypoxia so dangerous is its ability to permanently damage body organs, like the brain. That’s because cells require an uninterrupted supply of oxygen to thrive. Once they lose that, they start to wither.
To understand hypoxia, you must know a little about how oxygen is supplied to different body parts. Our lungs are the main sites for gaseous exchange in the body. Each lung is composed of a huge number of tiny air pockets or sacs called "alveoli", which are covered with extremely small blood vessels called the capillaries. When air is inhaled into the lungs, the oxygen present in it moves through the walls of alveoli into the blood present in the capillaries and from there into the blood circulation. From here onwards, oxygen is transported to the tissues of body through the hemoglobin (a protein) in red blood cells. Once hemoglobin takes oxygen to the target tissues, oxygen detaches itself from hemoglobin and is utilized by body tissues.
Interference at any point in this oxygen transport pathway may result in hypoxia. So, the four important factors that lead to hypoxia include:
Decreased oxygen diffusion into the blood (at the level of lungs)
Decreased oxygen binding capacity of blood (at the level of blood cells)
Reduced blood supply to tissues (at the level of blood cells/body tissues)
Inability of tissue to utilize oxygen (at the level of body tissues)
Types of Hypoxia
With the basic understanding of hypoxia, it is easier to learn about the different types of hypoxia. Knowing different types of hypoxia is important because once you know the root of a problem, solving it becomes feasible. Here are the four basic types of hypoxia.
Hypoxic hypoxia occurs when there is a fall in the oxygen concentration in the blood. Low blood oxygen may be the result of low atmospheric oxygen, high altitude and in many cases, respiratory disorders like COPD, which progressively destroys the lungs and makes it hard to breathe.
In this case, the lungs are functional and oxygen moves into the blood at a normal rate but, either the quantity of hemoglobin in blood is not enough or the hemoglobin has an abnormal structure, making it impossible to bind to the oxygen properly. Iron and Vitamin B12 deficiencies usually result in this type of hypoxia.
Stagnant hypoxia is when the blood supply to tissues is reduced. Common causes are heart failure, blood loss and thrombosis (block of blood vessels due to a clot).
This type of hypoxia results when cells and tissue become unable to utilize oxygen. Common cause of this type of hypoxia is alcohol and narcotic abuse.