Human life cannot exist without oxygen. This vital element is essential for each and every cell of the body for its survival. Decreased oxygen level in the body can therefore produce disastrous effect on health. Hypoxemia is a medical term which denotes decrease of oxygen in the blood flowing through the artery. For medical fraternity, it is decrease in partial pressure of oxygen in the arterial blood (PaO2). A blood test called arterial blood gas (ABG) helps to measure this pressure.
Oxygenation of blood is a physiological process, it occurs in the alveoli of the lungs.When there is low amount of oxygen due to many causes, saturation in arterial blood is hampered. Normally, the partial oxygen pressure should be between 95 to100 mmHg. When it is below 80mmHg, the condition is called as hypoxemia.
Causes Of Hypoxemia Or Low Blood Oxygen
Hypoxemia occurring from oxygen aberration mainly involves diseases of lungs where there is mismatch in ventilation perfusion, hypo-ventilation, shunting or diffusion impairment, low level of inspired oxygen etc.
- Mismatch in ventilation perfusion occurs when there is an imbalance in the amount of gas expired and oxygen that is saturated in the pulmonary capillaries.
- In hypo-ventilation, Oxygen level in the blood decreases with rise of carbon dioxide level in the blood. The lower PaO2 leads to hypoxemia.
- Shunting occurs in heart or between the major vessels. Right to left shunt occurs when there is congenital defect in heart valve. The blood between the atrium and ventricle gets mixed; as a result PaO2 decreases.
- In low inspired oxygen, oxygen is not available to its optimum due to various causes such as obstruction in airway passage.
Here are some respiratory diseases that trigger hypoxemia.
- Acute respiratory distress syndrome.
- Pulmonary embolism.
- Chronic obstructive pulmonary disease.
- Airway obstruction due to neoplasm, goiter, malignant tumors, infection of epiglottis, trauma.
- High altitude.
- Congenital heart ailments.
Signs And Symptoms Of Hypoxemia
The symptoms of hypoxemia vary greatly. It majorly depends on the amount of decreased partial pressure. Incase of mild hypoxemia, patient may become restless, anxious, confused, and sometimes it is associated with severe headache.
The symptoms of severe hypoxemia may include:
- Raised blood pressure.
- Cyanosis (blue discoloration of lips, tongue, nails, skin).
- Tachycardia (rapid heart rate).
- Markedly low blood pressure with an initial rise in cardiac output.
- Temporary cessation of breathing.
- Irregular rhythm of ventricles.
- Stoppage of heart beats or cardiac arrest.
- It can trigger a condition called polycythemia where there is abnormal rise in red blood cells and hemoglobin.
- Patient may become comatose.
Treatment Options For Hypoxemia
Depending on the severity, various treatment options are made available to the patient.
- Oxygen therapy: Oxygen administration is essential in all cases of hypoxemia. It can be provided through oxygen tanks or cylinders. An air entrainment mask (venturi mask) can be used to deliver precise dose of oxygen. If the mask is not available, oxygen can be delivered through nasal cannula.
- Therapy in patients suffering from asthma or COPD consists of oxygenation, adequate hydration and aggressive treatment of underlying factor with broncho-dilator and corticosteroids. Infection needs to be treated with appropriate antibiotics.
- Mechanical ventilation: Patients who have respiratory muscle fatigue may require mechanical ventilation to prevent respiratory arrest. In this procedure, a device mechanically aids in breathing process. The stream of air is passed though the nasal passage which can overcome any obstruction in the airway.
- Transfusion of packed red blood cells is another method of relieving hypoxemia. The blood gets highly saturated with oxygen in the process. Much care is needed to prevent infection while undergoing this therapy.