NCP Respiratory Acidosis (Primary Carbonic Acid Excess)


The body has the remarkable ability to maintain plasma pH within a narrow range of 7.35–7.45. It does so by means of chemical buffering mechanisms involving the lungs and kidneys. Although simple acid-base imbalances (e.g., respiratory acidosis) do occur, mixed acid-base imbalances are more common (e.g., the respiratory acidosis/metabolic acidosis that occurs with cardiac arrest).


Respiratory acidosis (elevated PaCO2 level) is caused by hypoventilation with resultant excess carbonic acid (H2CO3). Acidosis can be due to/associated with primary defects in lung function or changes in normal respiratory pattern. The disorder may be acute or chronic.

Compensatory mechanisms include (1) an increased respiratory rate; (2) hemoglobin (Hb) buffering, forming bicarbonate ions and deoxygenated Hb; and (3) increased renal ammonia acid excretions with reabsorption of bicarbonate.

Acute respiratory acidosis: Associated with acute pulmonary edema, aspiration of foreign body, overdose of sedatives/barbiturate poisoning, smoke inhalation, acute laryngospasm, hemothorax/pneumothorax, atelectasis, adult respiratory distress syndrome (ARDS), anesthesia/surgery, mechanical ventilators, excessive CO2 intake (e.g., use of rebreathing mask, cerebral vascular accident [CVA] therapy), Pickwickian syndrome.

Chronic respiratory acidosis: Associated with emphysema, asthma, bronchiectasis; neuromuscular disorders (such as Guillain-Barré syndrome and myasthenia gravis); botulism; spinal cord injuries.


This condition does not occur in isolation, but rather is a complication of a broader health problem/disease or condition for which the severely compromised patient requires admission to a medical-surgical or subacute unit.


Plans of care specific to predisposing factors/disease or medical condition, e.g.:

Cerebrovascular accident (CVA)/stroke

Chronic obstructive pulmonary disease (COPD) and asthma

Craniocerebral trauma (acute rehabilitative phase)

Eating disorders: obesity

Alcohol: acute withdrawal

Spinal cord injury (acute rehabilitative phase)

Surgical intervention

Ventilatory assistance (mechanical)


Fluid and electrolyte imbalances

Metabolic acidosis

Metabolic alkalosis

Patient Assessment Database

Dependent on underlying cause. Findings vary widely.


May report: Fatigue, mild to profound

May exhibit: Generalized weakness, ataxia/staggering, loss of coordination (chronic), to stupor


May exhibit: Low BP/hypotension with bounding pulses, pinkish color, warm skin (reflects vasodilation of severe acidosis)

Tachycardia, irregular pulse (other/various dysrhythmias)

Diaphoresis, pallor, and cyanosis (late stage)


May report: Nausea/vomiting


May report: Feeling of fullness in head (acute—associated with vasodilation)

Headache, dizziness, visual disturbances

May exhibit: Confusion, apprehension, agitation, restlessness, somnolence; coma (acute)

Tremors, decreased reflexes (severe)


May report: Shortness of breath; dyspnea with exertion

May exhibit: Respiratory rate dependent on underlying cause, i.e., decreased in respiratory center depression/ muscle paralysis; otherwise rate is rapid/shallow

Increased respiratory effort with nasal flaring/yawning, use of neck and upper body muscles

Decreased respiratory rate/hypoventilation (associated with decreased function of respiratory center as in head trauma, oversedation, general anesthesia, metabolic alkalosis)

Adventitious breath sounds (crackles, wheezes); stridor, crowing


Refer to specific plans of care reflecting individual predisposing/contributing factors.

Discharge plan

DRG projected mean length of inpatient stay: 4.9 days

May require assistance with changes in therapies for underlying disease process/condition

Refer to section at end of plan for postdischarge considerations.


ABGs: PaO2: Normal or may be low. Oxygen saturation (SaO2) decreased.

PaCO2: Increased, greater than 45 mm Hg (primary acidosis).

Bicarbonate (HCO3): Normal or increased, greater than 26 mEq/L (compensated/chronic stage).

Arterial pH: Decreased, less than 7.35.

Electrolytes: Serum potassium: Typically increased.

Serum chloride: Decreased.

Serum calcium: Increased.

Lactic acid: May be elevated.

Urinalysis: Urine pH decreased.

Other screening tests: As indicated by underlying illness/condition to determine underlying cause.


1. Achieve homeostasis.
2. Prevent/minimize complications.
3. Provide information about condition/prognosis and treatment needs as appropriate.


1. Physiological balance restored.
2. Free of complications.
3. Condition, prognosis, and treatment needs understood.
4. Plan in place to meet needs after discharge.