What is Hypoxia?

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:
    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.
  • Anemic hypoxia:
    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:
    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).
  • Histotoxic hypoxia:
    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.

How to Tell if You/Someone Has Hypoxia*?
Here are some warning signs to watch for when it comes to hypoxia.

  • Lightheadedness and dizziness
  • Fatigue and lethargy
  • Confusion
  • Breathlessness
  • Headache
  • Rapid heart rate
  • Increased respiratory rate
  • Tingling sensations in the body
  • Lack of coordination
  • Cyanosis or bluish discoloration of extremities (a sign of severe hypoxia)

*If you think you or someone you know is suffering from hypoxia of any sort please contact your physician immediately or call 911. This article is not to be used to diagnose, cure any illness.

How Oxygen Therapy Helps?
Oxygen therapy is the first line of defense in the fight against hypoxia. Once the oxygen level in body is maintained, the symptoms of hypoxia, like breathlessness, fade away automatically. Oxygen therapy can be administered using a nasal cannula attached to an oxygen concentrator. These concentrators take oxygen out of the surrounding air and purify it making it medical grade. Oxygen therapy is the best treatment for hypoxia, but its efficacy depends on the type of hypoxia. This therapy is 100% effective in hypoxic hypoxia (COPD) but, its efficacy reduces to 75% in anemic hypoxia and 50% in stagnant hypoxia. However, in histotoxic hypoxia, oxygen therapy is of no use because defect is with the cells ability to use oxygen, not with the oxygen availability.
This table sums up the efficacy of oxygen therapy.
Type of Hypoxia Efficacy of Oxygen Therapy (%)

  • Hypoxic hypoxia: 100%
  • Anemic hypoxia: 75%
  • Stagnant hypoxia: 50%
  • Histotoxic hypoxia: 0%

What Research Says?
If you or someone you love is suffering from a respiratory disease, you definitely know how painful the condition can be on yourself and those around you. Research has shown how beneficial oxygen therapy can be. For instance, a study at the University Hospital of Copenhagen, Denmark found that oxygen therapy can cause significant reduction in the symptoms of respiratory diseases (like COPD) including hypoxia. Moreover, the study also showed that oxygen therapy improved the quality of life of the patient.

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