Ventilatory failure

Alternative names
Chronic respiratory acidosis; Respiratory acidosis; Respiratory failure; Acidosis - respiratory

Definition

Respiratory acidosis occurs when the lungs cannot remove all of the carbon dioxide (a normal by-product of metabolism) produced by the body. Because of this disturbance of the acid-base balance, body fluids become excessively acidic.

Respiratory acidosis can be a consequence of any lung disease that prevents removal of carbon dioxide. Common lung diseases that lead to respiratory acidosis include: chronic obstructive pulmonary disease (COPD), severe asthma, or airway obstruction.

Other conditions that may lead to respiratory acidosis include: obesity hypoventilation syndrome, excessive fatigue of the diaphragm or muscles of the rib cage, or severe deformities of the spine and rib cage (for example, severe scoliosis).

In chronic respiratory acidosis, mild impairment of the lungs’ ability to remove carbon dioxide occurs over a long period of time, leading to a stable situation. This is because the kidneys increase their retention of bicarbonate to maintain an acid-base balance in the blood that is almost normal.

In severe cases, the carbon dioxide builds up very quickly, leading to severe disturbances in the acid-base balance of the blood.

Causes, incidence, and risk factors
Nearly any lung disease may lead to respiratory acidosis. Chronic obstructive pulmonary disease (COPD) is a major cause of respiratory acidosis. COPD is most often caused by cigarette smoking.

Symptoms

Symptoms of the diseases that cause respiratory acidosis are usually noticeable, and may include shortness of breath, easy fatigue, chronic cough, or wheezing.

When respiratory acidosis becomes severe, confusion, irritability, or lethargy may be apparent.

Signs and tests

     
  • A chest x-ray or CAT scan may be done to diagnose possible lung disease  
  • Pulmonary function tests may help diagnose lung disease  
  • Arterial blood gases help assess the severity of the respiratory acidosis, and may detect abnormal oxygen levels

Treatment

Treatment is aimed at the underlying lung disease.

     
  • Smoking cessation is extremely important  
  • Bronchodilator drugs may reverse some airway obstruction  
  • Oxygen may be necessary if the blood oxygen level is low  
  • Non-invasive positive-pressure ventilation or mechanical ventilation may be necessary if the respiratory acidosis is severe

Expectations (prognosis)
The prognosis depends on the underlying disease.

Complications

     
  • Respiratory acidosis may be a sign of respiratory failure, with dangerously low blood oxygen levels.  
  • Excessive respiratory acidosis may lead to confusion, lethargy, or poor organ function - in extreme cases, low blood pressure and shock may result.

Calling your health care provider

     
  • Call your health care provider if you have symptoms of lung disease.  
  • Call 911 or get to an emergency room if you suspect you have severe respiratory acidosis - this is a MEDICAL EMERGENCY.

Prevention

Not smoking - or quitting if you smoke - can prevent the development of many severe lung diseases that can lead to respiratory acidosis. Obese patients may prevent obesity hypoventilation syndrome by losing weight.

Johns Hopkins patient information

Last revised: December 3, 2012
by Martin A. Harms, M.D.

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