Hypoxia, simply means low oxygen conditions, and in the medical terminology it refers to a condition characterized by decreased oxygenation at one or all tissues of the body. This HealthHearty write-up provides a few details about the same.
Hypoxia refers to the condition where a particular tissue or all the tissues of the body experience oxygen deprivation, or do not get the amount of oxygen necessary for the different cellular processes. When all the tissues are affected, the condition is referred to as generalized hypoxia; whereas if a particular tissue is affected it is referred to as local hypoxia.
Given below is a brief account of the types of hypoxia and the respective causes, as well as the symptoms and treatment options for hypoxia.
Types of Hypoxia
Hypoxemia refers to the abnormal reduction of partial pressure of arterial oxygen, which ultimately causes lowered oxygen supply to all the body tissues. Hypoxia resulting due to such hypoxemia is termed hypoxemic hypoxia, and may arise due to:
- Exposure to high altitudes, and underwater diving.
- Pulmonary embolism
- Hypoventilation or respiratory distress which is accompanied with increase in carbon dioxide levels in blood.
- Respiratory disorders that affect lung function and/or involve pumonary shunting and aletered ventilation/perfusion ratio (V/Q ratio) which is a ratio of the air reaching the lungs to that reaching the blood. These disorders include pneumonia, bronchitis, asthma, etc.
Also known as stagnant hypoxia and circulatory hypoxia, this type refers to the hypoxia that arises when blood flow to a particular tissue is compromised. The condition of reduced blood supply to a particular region of the body is called ischemia. Ischemic hypoxia may occur in the event of:
- Extra-pulmonary shunt, wherein the venous blood bypasses the lungs, and gets mixed into the arterial blood in systemic circulation.
- Decreased cardiac output, heart attack and other cardiac problems.
- Arterial blockage due to embolism.
This type, as the name suggests, is the hypoxia that arises due to anemic conditions involving low hemoglobin content in blood. Low hemoglobin reduces the oxygen-carrying capacity of blood leading to hypoxia. The causes of anemic hypoxia include:
- Iron deficiency
- Reduced iron absorption from the intestines
- Heavy blood loss
- Methemoglobinemia
- Sickle cell disease
The hypoxia that arises due to the inability of cells to utilize the oxygen received through blood is termed histotoxic hypoxia. Here, although the tissue oxygenation levels are normal or above normal, the cells comprising the tissue are not able to process the oxygen through the cellular metabolic processes. Histotoxic anemia may be the result of:
- Cyanide poisoning
- Alcohol consumption
- Excessive use of narcotics
The ability of blood to carry and deliver oxygen, is the result of oxygen affinity of hemoglobin, and its dependence on factors like pH, carbon dioxide concentration, etc. Alterations in the oxygen affinity of hemoglobin may occur due to abnormalities in these factors, or the presence of molecules like carbon monoxide, to which hemoglobin shows higher affinity, as compared to oxygen.
A decrease in oxygen affinity affects oxygen pickup at the lungs, whereas an increase in oxygen affinity beyond normal affects oxygen delivery at the tissues, thus leading to hypoxia. Oxygen affinity of hemoglobin may get altered due to:
- Carbon monoxide poisoning
- Sulfur dioxide poisoning
- Massive blood transfusions
Symptoms of Hypoxia
Generalized hypoxia that affects oxygen availability to all the body cells and tissues may be manifested through the following symptoms.
- Nausea
- Fatigue
- Headache
- Confusion
- Drowsiness
- Blurred vision
- Shortness of breath
- Hot and cold flashes
- Altered coordination
In severe cases, the individual may lose consciousness, become comatose, or experience seizures. Moreover, suddenly ascending to, or being stranded at high altitudes, may give rise to severe conditions like High Altitude Cerebral Edema (HACE) or High Altitude Pulmonary Edema (HAPE) which are characterized by fluid accumulation in the brain and lungs respectively, and may prove to be fatal.
In case of local hypoxia that affects a particular tissue, cyanosis or blue discoloration of the skin is a typical sign of oxygen deprivation. In addition, the tissue may feel cold and appear pale. In severe cases, the cells of the respective tissue may die through necrosis, and may even cause gangrene.
Treatment of Hypoxia
The treatment for hypoxia depends on the precise etiology, as well as the type and severity of the condition.
» External breathing equipment may be used to deal with generalized hypoxemic hypoxia. These methods include employment of mechanical ventilation, oxygen therapy, and transfusion of packed RBCs. Transfusion of packed or concentrated RBCs helps to improve the oxygen carrying capacity of the cells. Transfusions are usually carried out to treat chronic cases of hypoxemia.
» Spontaneous breathing is encouraged through mechanical ventilation in the event of bronchial obstructions. This involves use of the CPAP (Continuous Positive Airway Pressure). It works by forcing air stream into the nasal passages, thus eliminating the obstruction of the airways.
» Intravenous fluids and medication may be administered for blood pressure regulation, or to deal with seizures and other symptoms.
» In certain cases like carbon monoxide poisoning or severe altitude sickness, hyperbaric oxygen therapy (HBOT) may be advised. This treatment involves the placing the individual in a room containing pure oxygen having a partial pressure about 2-3 times higher than normal air.
Disclaimer: This article is for informative purposes only, and should not be used as a substitute for professional medical advice.
