Respiratory acidosis is excess acid in the blood caused by a build-up of carbon dioxide. Carbon dioxide is a normal by-product of metabolism, but it must be removed rapidly from the body through the lungs. When the lungs cannot eliminate it fast enough, it reacts with water in the blood to form carbonic acid. This increases the acidity of the blood and other body fluids. Respiratory acidosis can be caused by various diseases that interfere with breathing or respiratory gas exchange.
Respiratory acidosis can be chronic or acute. In the chronic state, acid builds up slowly. Acute respiratory acidosis occurs when the patient cannot increase his respiration enough to eliminate the carbon dioxide from the lungs and acid builds up quickly. Acute respiratory acidosis can be a life-threatening medical emergency.
Chronic respiratory acidosis can occur as a result of several severe long-term lung diseases, nervous system and muscular disorders and chest deformities that restrict or obstruct lung function. Acute respiratory acidosis can occur during sudden, rapid decreases in ventilation such as choking on food or other causes of airway obstruction. Breathing also can be hindered by paralysis, drug use or acute nervous and muscular events.
States of extremely high metabolism, such as in major burns, fevers or malignant hyperthermia, also can cause the production of too much carbon dioxide and lead to respiratory acidosis.
Confusion, fatigue, drowsiness, headache, anxiety, rapid heart rate and shortness of breath are some of the symptoms of respiratory acidosis. Long-term chronic cases may show daytime sleepiness, irritability, forgetfulness or inability to concentrate. More acute cases can cause extreme anxiety, a stupor or unconscious state.
Diagnosis and Treatment
Diagnostic tests include arterial blood sampling to measure carbon dioxide, acidity and bicarbonate levels. Tests will indicate acidic blood, elevated carbon dioxide and usually an increase in bicarbonate. However, if the acid has been fully buffered, the acidity reading may be near normal.
Treatment depends on the underlying cause of the respiratory insufficiency, but some assistance with ventilation is usually required. Oxygen may or may not be required, because it can be harmful if administered to patients with certain types of chronic lung disease.
Respiratory acidosis can become severe very quickly. Anyone with shortness of breath should receive immediate medical attention, and CPR should be administered any time a person stops breathing. However, oxygen should be administered only by a medical professional, because it can further decrease the breathing response in certain types of patients.