The body maintains blood acidity in a narrow range so it is neither too acidic nor too alkaline. The kidneys, respiratory system and buffering chemicals in the blood maintain acid-base balance. Even small deviations in pH, which is a measurement of acidity, can cause organ damage. The normal pH of the blood ranges between 7.35 and 7.4.
Acidosis
There are two disorders of acid-base balance--acidosis and alkalosis--and they are further categorized into metabolic and respiratory. Respiratory acidosis is primarily caused by lung dysfunction, resulting in a reduced breathing rate. The most common disorder that causes respiratory acidosis is chronic obstructive pulmonary disease (COPD). Metabolic acidosis occurs when the body produces too much acid or when the kidneys fail to remove acid from the blood. Conditions that cause metabolic acidosis include kidney disease, type 1 diabetes, genetic disorders of metabolism, certain drugs, sepsis and hemorrhage.
Carbon Dioxide
Carbon dioxide is a waste product of cellular metabolism. Cells release carbon dioxide into the blood, where it combines with water and forms bicarbonate and hydrogen ions, which increase the acidity of the blood. The blood transports bicarbonate to the lungs, where it is changed back into carbon dioxide gas and exhaled from the body. Therefore, the level of dissolved carbon dioxide in the blood is a determinant of blood pH, and respiration provides a mechanism to influence acid-base balance.
Respiration
Respiration includes the processes of gas exchange, gas transport and ventilation. The volume of air breathed in and out and the rate of breathing are regulated by control centers in the brain. These areas have cells that respond to changes in the amount of dissolved carbon dioxide in the blood. If blood acidity increases, these cells send a signal to muscles in the chest cavity to increase the volume of air breathed in and out and secondarily increase the rate of breathing. Thus, an increase in ventilation increases the amount of carbon dioxide that is exhaled and decreases blood acidity.
Acid-Base Compensation
Acid-base compensation is when the body modifies a particular process in order to restore acid-base balance. The respiratory system compensates for metabolic acidosis by increasing the volume of air exhaled in each breath and the rate of breathing. The respiration compensatory mechanism occurs within seconds and is maximal in 24 hours; however, it cannot fully compensate for chronic metabolic acidosis without starving cells for oxygen. In contrast, a study in the "Canadian Respiratory Journal" found that chronic respiratory acidosis occurring in patients with COPD is completely compensated for by an increase in kidney function.
Acidosis Symptoms
People with respiratory acidosis may exhibit headache, drowsiness, confusion and shallow breathing. People with metabolic acidosis may exhibit drowsiness, nausea, vomiting and deeper and slightly accelerated breathing. A severe episode of respiratory or metabolic acidosis may be treated with oxygen therapy and assisted ventilation. Additionally, intravenous fluids may be required to reduce blood acidity. In either respiratory or metabolic acidosis, treatment involves diagnosing and treating the underlying cause, such as diabetes or lung dysfunction.
