Causes and Symptoms of Respiratory Acidosis
What is this Condition?
An acid-base disturbance characterized by reduced alveolar ventilation, respiratory acidosis can be acute (caused by a sudden failure in ventilation) or chronic (as in long-term lung disease). The prognosis depends on the severity of the underlying disturbance as well as the person's general health.
What Causes it?
Decreased ventilation reduces the body's excretion of carbon dioxide produced through metabolism. The retained carbon dioxide then combines with water to form an excess of carbonic acid, decreasing the blood pH. As a result, the concentration of hydrogen ions in body fluids (which directly reflects acidity) increases. Some predisposing factors in respiratory acidosis are:
Drugs: Narcotics, anesthetics, hypnotics, and sedatives decrease the sensitivity of the respiratory center.
Central nervous system trauma: Spinal cord injury may impair ventilatory drive.
Chronic metabolic alkalosis: The body attempts to normalize pH by decreasing alveolar ventilation.
Neuromuscular disease (such as myasthenia gravis, Guillain-Barre syndrome, and poliomyelitis): Weakened muscles make breathing more difficult, reducing alveolar ventilation.
In addition, respiratory acidosis can be caused by airway obstruction or parenchymal lung disease, which interferes with alveolar ventilation; chronic obstructive pulmonary disease; asthma; severe adult respiratory distress syndrome; chronic bronchitis; large pneumothorax; extensive pneumonia; and pulmonary edema.
What are its Symptoms?
Acute respiratory acidosis produces central nervous system disturbances that reflect changes in the pH of cerebrospinal fluid rather than increased carbon dioxide levels in cerebral circulation. Symptoms range from restlessness, confusion, and anxiety to sleepiness, with a fine or flapping tremor, or coma. The person may complain of headaches and exhibit shortness of breath and rapid breathing with papilledema and depressed reflexes. Unless the person is receiving oxygen, hypoxemia (low level of oxygen in the tissues) accompanies respiratory acidosis. This disorder may also cause cardiovascular abnormalities, such as a rapid heartbeat, high blood pressure, irregular atrial and ventricular beats and, in severe acidosis, low blood pressure with vasodilation (bounding pulses and warm periphery).
How is it Diagnosed?
This condition is diagnosed by arterial blood gas analysis, which measures the levels of oxygen, carbon dioxide, and other gases in the blood.
How is it Treated?
Effective treatment of respiratory acidosis is designed to correct the underlying source of alveolar hypoventilation.
Significantly reduced alveolar ventilation may require mechanical ventilation until the underlying condition can be treated. In chronic obstructive pulmonary disease, this includes bronchodilators, oxygen, corticosteroids and, frequently, antibiotics; drug therapy for conditions such as myasthenia gravis; removal of foreign bodies from the airway; antibiotics for pneumonia; dialysis or charcoal to remove toxic drugs; and correction of metabolic alkalosis.
Dangerously low blood pH levels (less than 7.15) can produce profound central nervous system and cardiovascular deterioration and may require administration of intravenous sodium bicarbonate. In chronic lung disease, an elevated carbon dioxide level may persist despite optimal treatment.