Respiratory acidosis (Hypercapnia)

ICD-9: 276.4


Respiratory acidosis is excessive acidity of body fluids attributable to inadequate removal of carbon dioxide (CO2) by the lungs. Whenever CO2 cannot be adequately ventilated, the CO2 dissolved in the blood rapidly increases. As the level of CO2—called the partial pressure of carbon dioxide (PaCO2)—rises, so does the amount of CO2 that combines with water to form carbonic acid. Consequently, the acidity or alkalinity (pH) of the blood decreases. The condition may be acute or chronic.


Acute respiratory acidosis occurs whenever there is a sudden impairment of ventilation resulting from airway obstruction. This may be due to such causes as a foreign object blocking the airway or to the effects of certain drugs, neuromuscular diseases, or cardiac arrest. Chronic respiratory acidosis is caused by pulmonary diseases that change the characteristics of lung tissue, impairing the ability to release CO2. Examples of such diseases include emphysema, bronchitis, and COPD. Chronic respiratory acidosis also may be a consequence of extreme obesity or obstructive sleep apnea.

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Signs and Symptoms

Signs and symptoms vary with the etiology, but typically they include weakness, shallow respirations, confusion and/or anxiety, muscle tremors, and tachycardia. Clients may complain of headaches and exhibit dyspnea.

Diagnostic Procedures

Diagnosis of respiratory acidosis is usually evident from the clinical situation. Arterial blood gas testing to confirm elevated PaCO2 levels is required to confirm the diagnosis. Chest x-ray, CT scan, MRI, and pulmonary function tests are likely, also.


The only useful treatment for respiratory acidosis involves measures to correct the underlying cause. Bronchodilators, increased ventilation, and oxygen therapy often are prescribed.

Complementary Therapy

No significant complementary therapy is indicated.

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Helping clients and family members understand the etiology is beneficial. In the case of hospitalization, staff will maintain airway, provide humidification, and alleviate the client’s anxiety as much as possible.


The prognosis for an individual with respiratory acidosis varies with the cause. Respiratory acidosis can cause shock or cardiac arrest.


There is no specific prevention other than treatment of the cause. Smoking cessation is an important aspect in the long-term treatment, especially when COPD is an issue. Weight loss is very helpful when clients are obese.