Abnormally low levels of oxygen in the blood, resulting from lung damage
- Age, gender, genetics, and lifestyle are not significant factors
Respiratory failure occurs if the amount of oxygen that enters the bloodstream from the lungs is greatly reduced, leading to severe shortness of breath and eventually to profound confusion or unconsciousness. Simultaneously, there may be an excess of carbon dioxide in the blood. Respiratory failure is a life-threatening condition that should be treated promptly to prevent damage to other organs, such as the heart, which need an adequate supply of oxygen to maintain their function.
What are the causes?
There are two broad groups of conditions that lead to respiratory failure. In the first group, there is no difficulty in moving air into and out of the lungs, but less oxygen than normal is transferred to the blood as a result of damage to the alveoli (air sacs) in the lungs. The most common causes of this type are long-term lung disorders such as fibrosing alveolitis. Less commonly, the alveoli may become filled with fluid, as occurs in acute respiratory distress syndrome. In this case, the levels of oxygen in the blood are low, but carbon dioxide levels are usually normal.
The second group of conditions consists of ventilation disorders, in which a person cannot move sufficient air into and out of the lungs. A ventilation disorder may develop suddenly after a stroke or an injury to the area of the brain that controls breathing. A drug overdose (see Drug overdose and accidental ingestion) or injury to the chest wall may also reduce breathing. In addition, breathing difficulties may result from disorders, such as chronic obstructive pulmonary disease, and myasthenia gravis, in which the muscles involved in breathing become progressively weakened. Ventilation problems usually lead to low levels of oxygen and high levels of carbon dioxide in the blood.
What are the symptoms?
Disorders that involve damage to the alveoli are usually long-term conditions, and symptoms develop gradually. In ventilation disorders, symptoms of respiratory failure may develop either suddenly or gradually over a period of time, depending on the cause.
The symptoms of respiratory failure are mainly due to low levels of oxygen in the blood and may include:
Shortness of breath.
A bluish tinge to the lips and tongue, a condition known as cyanosis.
In addition to the symptoms listed here, ventilation disorders may cause other symptoms, such as headache and drowsiness, due to the high concentration of carbon dioxide in the blood.
What might be done?
Respiratory failure can usually be diagnosed from the symptoms, and its severity can be assessed by measuring the levels of oxygen and carbon dioxide in blood (see Measuring blood gases). If the cause is not obvious, you may need further tests.
Respiratory failure due to permanent damage to the alveoli cannot be treated except with a lung transplant. However, symptoms may be relieved by long-term home oxygen therapy, which needs to be used continuously for at least 15 hours a day to prevent chronic heart failure.
If you develop respiratory failure caused by a ventilation disorder, you may need help from a ventilator to breathe. This is usually performed in hospital at first, but, if long-term ventilation is required, it may be possible to continue the treatment at home.
If respiratory failure occurs suddenly due to a ventilation disorder, recovery is possible if the underlying cause can be treated successfully. Cases of gradual respiratory failure are less likely to show significant improvement, but the symptoms can be controlled effectively with long-term oxygen therapy.
From the 2010 revision of the Complete Home Medical Guide © Dorling Kindersley Limited.
The subjects, conditions and treatments covered in this encyclopaedia are for information only and may not be covered by your insurance product should you make a claim.