Hypoxia

Hypoxia means the lack of Oxygen supply to the tissue.

Hypoxia is classified4 types on how it develops into a pathological condition:

• Hypoxic hypoxia: It is the condition where there is poor availability of Oxygen to the pulmonary tissues.
• Anemic Hypoxia: It is the condition of Hypoxia based on the Quantitative availability of Haemoglobin and the Quality of the Haemoglobin available.
• Stagnant Hypoxia: This condition is due to the decrease in the velocity of the blood which results in decrease in the amount of Oxygen supplied to the tissues.
• Histotoxic hypoxia: It is due to lack of ability of the peripheral tissues take up the Oxygen from the capillaries supplying to these tissues.

Now as we got a brief review on what hypoxia really is and how it is divided now let us  go deep into its description:

Hypoxia is a state of oxygen deficiency in the body which is sufficient to cause an impairment of function. Hypoxia is caused by the reduction in partial pressure of oxygen, inadequate oxygen transport, or the inability of the tissues to use oxygen.

Hypoxic hypoxia: is a reduction in the amount of oxygen passing into the blood. It is caused by a reduction in oxygen pressure in the lungs, by a reduced gas exchange area, exposure to high altitude, or by lung disease.

Causes:

• Low tension of Oxygen in the inspired air(this condition is seen in peolpe living in high altitudes)
• Pulmonary diseases

Under Hypoxic hypoxia we can see individual organ hypoxia and High altitude sickness.

In individual organ sickness it may be due to

• Spasm of the local artery leading to the necrosis of the tissue it supplies
• Venous Obstruction also causes local hypoxia.

In high altitude sickness.

We know that the normal Barometric pressure at sea level is 760mm Hg, in which Oxygen is 20% and nitrogen 80%, thus the partial pressure of oxygen comes to 152mm Hg which is at normal round level.

So when a normal Low lander gos to high altitudes(assume on Mt Everest) where the partial pressure of Oxygen becomes 40mm Hg and partial pressure of blood becomes 200mm Hg there is “Foaming of blood” This condition was known as “Boiling of blood” by older scientists.

Signs and Symptoms:

• Dizziness and light headedness.
• Loss of appetite nausea vomiting
• Fatigue or weakness
• Insomnia
• Pins and needles
• Shortness of breath upon exertion
• Persistent rapid pulse
• Drowsiness
• General malaise
• Peripheral edema (swelling of hands, feet, and face).

Tips that might help

• Avoiding alcohol ingestion
• Avoiding strenous activity
• Give time to yor body to Acclimatize
• Have sufficient supply of Oxygen
• Have Drugs which help in acclimatization.

Anemic Hypoxia:

Anemic Hypoxia or Hypemic Hypoxia is defined as a reduction in the oxygen carrying capacity of the blood. It is caused by a reduction in the amount of hemoglobin in the blood or a reduced number of red blood cells. A reduction in the oxygen transport capacity of the blood occurs through blood donation, hemorrhage, or anemia. A reduction in the oxygen carrying capacity of the blood occurs through drugs, chemicals, or carbon monoxide. [This hypoxia is usually experienced by smokers.]

It can be due to 2 main causes:

• Low concentrations of Hb in Blood
• Carbon monoxide poisoning where the concentration of Hb in blood is normal but it is not available for binding with Oxygen.

Stagnant Hypoxia:

Stagnant hypoxia is defined as a condition of oxygen deficiency due to poor circulation of the blood or poor blood flow and decrease in velocity of blood flow. Examples of this condition are high “G” forces, prolonged sitting in one position or hanging in a harness, cold temperatures. [This hypoxia usually experienced when sitting for hours in a boring class.]

Seen in Left ventricular failure, Cardiogenic shock, sometimes seen in snake bite where tight ligature is applied which causes decrease in the blood flow, this may lead to gangrene.

Histotoxic hypoxia:

Histotoxic Hypoxia is defined as the inability of the tissues to use oxygen. Examples are carbon monoxide and cyanide poisoning. Certain narcotics, chewing tobacco, and alcohol will prevent oxygen use by the tissues. [This hypoxia usually experienced after drinking too much.]

This is seen as the cytochrome oxidase system is inhibited which plays a key role in oxidation of tissues.

Here the inhibition of this system leads to stoppage of oxidation of tissues and then Oxygen from the capillaries is not extracted anymore and the partial pressure of venous blood remains high.