Urgent considerations

See Differentials for more details

Nearly all causes of acute respiratory acidosis can develop into life-threatening situations. The primary concern in these patients is impending respiratory failure, which may be indicated by clinical features such as signs of hypercapnia (e.g., altered sensorium and haemodynamic instability) and pulmonary-related manifestations (e.g., bradypnoea, use of accessory muscles, and paradoxical breathing).

Initial emergent treatment for respiratory acidosis, irrespective of the underlying cause, involves immediate assessment of the patient with basic stabilisation (airway, ventilatory, cardiovascular support) and rapid identification of potential aetiologies via a thorough secondary survey.

Initial assessment

Once respiratory acidosis is identified, the first objective is to determine the stability of the patient and provide airway, ventilatory, or cardiovascular support where necessary.

For patients with obtundation, haemodynamic instability, or evidence of respiratory muscle fatigue (accessory muscle use, dyspnoea, tachypnoea), consideration should be given to initiating mechanical ventilatory support and transfer to a monitored setting (e.g., intensive care unit [ICU]) prior to further investigative studies.[14]​​[15] Assessment for hypoxia should be completed, with supplemental oxygen provided as clinically indicated; however, oxygen must be used judiciously in patients with hypercapnic respiratory failure to avoid worsening hypercapnia and acidosis.[12]​[16]​​​ A generally accepted compromise between these conflicting goals is to adjust the flow rate of oxygen to achieve a target pulse oxygen saturation between 88% and 92%.[12]​[16]​​​ Further management of respiratory acidosis may require measures to improve ventilation that can be achieved by either mask ventilation (non-invasive ventilatory support) or invasive ventilation with endotracheal intubation in more seriously ill patients admitted to the ICU.​​

Further assessment

Once the patient is stabilised, evaluation for serious causes of respiratory acidosis should be initiated to allow prompt and specific treatment of the underlying cause.

Laboratory tests to consider should include the following:

  • Arterial blood gas analysis.

  • Full blood count to evaluate for polycythaemia or raised white blood cell count.

  • Electrolyte panel to check for severe electrolyte derangements.

  • Toxicology testing for possible drug ingestion.

  • Lumbar puncture to evaluate for central nervous system (CNS) infection.

Imaging would include the following depending on suspected causes:

  • Imaging of the chest (chest x-ray or computed tomography) to evaluate for serious parenchymal lung disease (pneumonia, cardiogenic pulmonary oedema, pneumothorax).

  • Urgent computed tomography scanning of the brain to screen for CNS causes, such as infarction, haemorrhage, or trauma.

Management of respiratory acidosis may include ventilatory support (invasive or non-invasive) and further specific medical therapies for the treatment of the causative pathophysiology.[11][15][17][18]

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