What is Respiratory Acidosis?
Respiratory acidosis is an acid-base imbalance marked by increased partial pressure of arterial carbon dioxide and decreased blood pH. Prognosis tracks the severity of the underlying disturbance and the patient's overall clinical condition.
The body compensates three ways: an increased respiratory rate, hemoglobin (Hb) buffering that forms bicarbonate ions and deoxygenated Hb, and increased renal ammonia acid excretion with reabsorption of bicarbonate.
Acute respiratory acidosis goes with acute pulmonary edema, aspiration of a foreign body, sedative overdose or barbiturate poisoning, smoke inhalation, acute laryngospasm, hemothorax or pneumothorax, atelectasis, adult respiratory distress syndrome (ARDS), anesthesia and surgery, mechanical ventilators, and excessive CO2 intake (rebreathing mask, cerebral vascular accident [CVA] therapy, Pickwickian syndrome). Chronic respiratory acidosis goes with emphysema, asthma, bronchiectasis, neuromuscular disorders (Guillain-Barré syndrome, myasthenia gravis), botulism, and spinal cord injuries.
Causes
Common causes include chronic obstructive respiratory disorders (emphysema, chronic bronchitis), chest wall trauma, pulmonary edema, atelectasis, pneumothorax, drug overdose, pneumonia, and Guillain-Barré syndrome.
Complications
The dangerous endpoints are shock and cardiac arrest.
Signs and Symptoms
Look for CNS disturbances ranging from restlessness, confusion, and apprehension to somnolence with a fine flapping tremor or coma. Patients also report headache, dyspnea, tachypnea, a rise in blood pressure, mental cloudiness with a feeling of fullness in the head, and weakness.
Assessment
Assessment cues depend on the underlying cause.
Activity and rest: fatigue that ranges from mild to profound, with generalized weakness, ataxia or staggering, and loss of coordination (chronic) progressing to stupor.
Circulation: low BP or hypotension with bounding pulses, pinkish color, and warm skin (vasodilation of severe acidosis); tachycardia and irregular pulse (various dysrhythmias); diaphoresis, pallor, and cyanosis in the late stage.
Food and fluid: nausea and vomiting.
Neurosensory: a feeling of fullness in the head (acute, from vasodilation), headache, dizziness, and visual disturbances; confusion, apprehension, agitation, restlessness, somnolence, and coma (acute); tremors and decreased reflexes (severe).
Respiration: shortness of breath and dyspnea on exertion. Respiratory rate depends on the cause, decreased with respiratory center depression or muscle paralysis, otherwise rapid and shallow. Watch for increased respiratory effort with nasal flaring and yawning, use of neck and upper body muscles, hypoventilation tied to decreased respiratory center function (head trauma, oversedation, general anesthesia, metabolic alkalosis), and adventitious breath sounds (crackles, wheezes, stridor, crowing).
Teaching and learning: refer to specific plans of care that reflect the individual predisposing and contributing factors.
Diagnostic Studies
Confirm the diagnosis with arterial blood gas (ABG) analysis showing PaCO2 higher than 45 mm Hg, pH below the normal range of 7.35 to 7.45, and a bicarbonate level that is normal (acute) or elevated as the kidneys retain bicarbonate to compensate (chronic) (StatPearls, Respiratory Acidosis). Chest X-ray and CT scan help determine the cause.
On ABGs, PaO2 is normal or low and oxygen saturation (SaO2) is decreased. PaCO2 is increased, greater than 45 mm Hg (primary acidosis). Bicarbonate (HCO3) is normal or increased, greater than 26 mEq/L (compensated or chronic stage). Arterial pH is decreased, less than 7.35. On electrolytes, serum potassium is typically increased, serum chloride is decreased, and serum calcium is increased. Lactic acid may be elevated. Urinalysis shows decreased urine pH. Other screening tests follow the underlying illness or condition.
Nursing Diagnosis
Possible nursing diagnoses include impaired gas exchange, ineffective breathing pattern, ineffective tissue perfusion, acute confusion, and risk for injury.
Nursing Priorities
Achieve homeostasis, prevent or minimize complications, and provide information about the condition, prognosis, and treatment needs as appropriate.
Discharge Goals
Restore physiologic balance, keep the patient free of complications, confirm the condition, prognosis, and treatment needs are understood, and put a plan in place to meet needs after discharge.
Care Setting
Respiratory acidosis does not occur in isolation. It is a complication of a broader disease or condition, and the severely compromised patient needs admission to a medical-surgical or subacute unit.
Nursing Interventions and Considerations
Stay alert for critical changes in respiratory, CNS, and cardiovascular function, and report those changes along with any variation in ABG values or electrolyte status immediately. Maintain adequate hydration. Maintain a patent airway and provide humidification if the acidosis requires mechanical ventilation, with frequent tracheal suctioning and vigorous chest physiotherapy if ordered. Institute safety measures and assist the patient with positioning. Continuously monitor arterial blood gases.
Frequently Asked Questions
What ABG values confirm respiratory acidosis? A PaCO2 above 45 mm Hg with a pH below 7.35 confirms respiratory acidosis (StatPearls, Arterial Blood Gas). Bicarbonate stays normal in the acute phase and rises in the chronic phase as the kidneys compensate.
What causes respiratory acidosis? It comes from anything that impairs ventilation and lets CO2 build up: COPD, chest wall trauma, pulmonary edema, atelectasis, pneumothorax, pneumonia, drug or sedative overdose, and neuromuscular disease such as Guillain-Barré syndrome.
How do you tell acute from chronic respiratory acidosis? Both show a high PaCO2 and low pH, but the chronic form shows an elevated bicarbonate because the kidneys have had days to retain it, which pulls the pH back toward normal (StatPearls, Respiratory Acidosis). The acute form has a near-normal bicarbonate and a more sharply dropped pH.
Why does respiratory acidosis raise serum potassium? As pH falls, hydrogen ions shift into cells in exchange for potassium moving out, so serum potassium tends to rise. Recheck potassium as the acidosis corrects, since it can swing back down.
What is the priority nursing intervention? Support the airway and ventilation so the patient can clear CO2: keep the airway patent, position to ease breathing, suction as needed, and prepare for mechanical ventilation if PaCO2 keeps climbing. Treat the underlying cause in parallel.
What are the dangerous endpoints if it is missed? Untreated respiratory acidosis can progress to shock and cardiac arrest, which is why early recognition and continuous ABG monitoring matter.