HYPOXIA

Hypoxia

Hypoxia

Introduction

Hypoxemia occurs when there is a low level of oxygen in the blood. Hypoxemia may be manifested by changes in mental status, shortness of breath, increase in blood pressure, changes in heart rate, dysrhythmias, cyanosis (late sign), diaphoresis, and cool extremities. Hypoxemia often leads to hypoxia, which is a reduce of oxygen to the tissues of the body.

The condition of hypoxemia refers to the low partial pressure of oxygen in the arterial blood. Hypoxemia is often confused with either anoxia, asphyxia, hypoxia or anemia. Although, these are in some way related to reduction in the levels of oxygen in the body, these are distinct medical conditions.

Anoxia is the absence of oxygen supply in the body. This implies extremely low levels of oxygen in the body.

Asphyxia is the absence of oxygen along with the accumulation of carbon dioxide.

Hypoxia is the deficiency of oxygen in some specific part of the body.

Anemia refers to a condition when oxygen content in the arterial blood is low and the partial pressures in the arterial blood are high.

Hypoxemia refers to refers to a condition when oxygen content in the arterial blood is low as also the partial pressures in the arterial blood.

A person is said suffer hypoxemia when the pulmonary alveoli are starved of oxygen. In this condition, a substantial decrease is observed in the levels of PaO2. In the case of patients suffering from severe hypoxemia, PaO2 levels in the blood fall below 80.Causes of Hypoxemia

Hypoxemia is usually triggered off by respiratory disorders. Additionally, hypoxemia may also be caused as a result of one or a combination of the following:

Hypoventilation:

This refers to a condition when the oxygen (PaO2) content is the blood decreases and a marked increase in the levels of carbon dioxide is observed. This lowered PaO2 content can cause hypoxemia.

Low Inspired Oxygen:

The FiO2 content in the blood is called as the fraction of inspired oxygen in the blood. A decrease in this fraction of inspired oxygen may cause hypoxemia.

Left to right shunt:

This is another cause of hypoxemia. A left-to-right shunt is a condition when there is a transfer of blood from the left side of the heart to its right side. This may occur as a result of a hole in the following walls: the arterial walls, the wall separating the two upper chambers (left and right atrium) or the wall separating the two lower chambers (left and right ventricles) of the heart.

Ventilation-Perfusion mismatch:

This is a condition in which an imbalance between the volume of gas expired by the alveoli (alveolar ventilation) and the pulmonary capillary blood flow is seen. This mismatch may cause hypoxemia.

Diffusion Impairment:

In this condition, a marked reduction is seen in the oxygen movement from the alveoli to capillaries. This restricted movement may trigger hypoxemia.Often, it is difficult to determine one single cause of hypoxemia in an acutely illnesses. It also becomes almost impossible to determine the extent of contribution of the causes of hypoxemia in such cases.

Symptoms

The symptoms of hypoxemia depend on the severity ...