Oxygen is perhaps the single most vital element, without which the body may not be able to survive. Each and every body cell requires constant supply of oxygen for its healthy functioning as well as well being. Disruption in constant flow of oxygen to the body cells can cause low level of oxygen in the body. ‘Hypoxemia’ is a medical term used when there is reduction in the partial pressure of oxygen as well as low level of oxygen in the blood which flows through the artery.
Partial pressure of oxygen in the blood refers to the amount of oxygen dissolved in the blood at a given time. Hypoxemic state can cause damage to the body and its vital organs. Severe hypoxemic state can prove fatal.
The level of oxygen in the arterial blood is measured with the help of arterial blood gas test or more recently it is measured with a pulse oximeter. The normal reading of partial pressure of oxygen in the blood flowing through the artery is in the range of 95 to 100 mm Hg.
What Are The Causes Of Hypoxemia?
Hypoxemic state is generally present when the person is suffering from respiratory diseases or heart diseases. Such as emphysema and other chronic obstructive pulmonary diseases, obstructions in the air passage, pneumonia, acute respiratory distress syndrome, high altitudes, sleep apnea, congenital heart disease, low cardiac output, narcotic overdose or anesthetics are some of the conditions that can cause hypoxemia.
Following are some of the pathophysiological causes behind hypoxemia:
- Low inspiration of oxygen: there is reduced amount of oxygen in the alveoli (small sacs in the lungs where exchange of oxygen and carbon dioxide takes place) when the oxygen level in the inspired gas is low. This happens even if the lungs are functioning normally. For example in high altitudes there is low barometric pressure even when the person’s lungs are normal.
- Hypoventilation in the alveoli: It happens when the alveoli receive insufficient blood supply; due to causes associated other than the lungs and heart, for example depression in the respiratory center of the brain, obstruction of airways and weakness of muscles of breathing.
- Cardiac shunt: mixing of pure and impure blood in the chamber of heart can lead to hypoxemic state. This happens when there is a hole in the wall of the cardiac chamber.
- Diffusion problem in the lung: impairment in the diffusion of gases in the lungs due to blood gas membrane default can result in hypoxemia.
Symptoms Of Hypoxemia
The symptoms of hypoxemia may depend on the amount of reduction of partial pressure of oxygen in the arterial blood.
In mild to moderate condition the symptoms may be:
- Patient feels anxious.
- He becomes disorientated, fatigued and weak.
- Mild to severe headache.
- Nausea and vomiting.
Severe form of hypoxemic state:
- Patient is extremely breathless and coughs up foamy sputum.
- The face may become pale and the skin may turn cold and clammy.
- Cyanosis: the skin, fingernails, lips and tongues turns blue due to insufficiency of oxygen in the blood.
- Increased heart rate more than 100/minute.
- Low blood pressure: it is due to reduced cardiac output.
- There may be convulsions.
- Comprehension and mental performance decline rapidly and unconsciousness and coma supervenes.
Treatment And Prevention Of Hypoxemia
Hypoxemia is a serious condition and it needs a prompt medical attention. The patient requires hospitalization. In hospital set up, it is easier to do blood gas estimation test.
- Oxygen therapy: the most important and urgent procedure is to institute oxygen therapy once the cause and severity of hypoxemia have been assessed. The goal is to reduce hypoxemia and decrease the chances of raising carbon dioxide level in the blood.
- Care of airway: the airway must remain free from the secretions and must remain patent. Deep breathing, coughing and suctioning will help to mobilize and clean the secretions. Nebulizers are useful in removing the accumulated bronchial secretions.
- Ventilation support: endotracheal intubation and mechanical ventilation are considered if there is gradual rise of carbon dioxide level in the blood. Mechanical ventilation is indicated when hypoxemia may be extreme and which may lead to respiratory failure.
There are certain precautionary measures that can be taken to avoid worsening of hypoxemia which occurs in chronic diseases such as emphysema and chronic bronchitis. This includes complete cessation from smoking. Also avoid passive smoking too, it is considered as bad for the patient as smoking a cigarette.
Light exercises to strengthen and improve endurance of the respiratory muscles are valuable. They have to be performed as guided by the physiotherapist.