What are the indications for performing an ABG in a patient presenting with acute shortness of breath?

Indications for performing arterial blood gas (ABG) analysis in a patient presenting with acute shortness of breath include:

• Assessment of the severity of hypoxaemia and hypercapnia to guide urgent management decisions, especially when respiratory failure is suspected NICE NG115.
• Evaluation of acid-base status to identify metabolic or respiratory acidosis or alkalosis contributing to the clinical picture NICE NG115.
• When clinical signs suggest significant respiratory distress, altered mental status, or cyanosis, indicating possible severe gas exchange impairment NICE NG45.
• In patients with known chronic respiratory diseases such as COPD presenting with an acute exacerbation, to determine the need for ventilatory support or oxygen therapy adjustments NICE NG45,NICE NG115.
• When peripheral venous blood gas analysis is insufficient or inconclusive for diagnosing respiratory failure or metabolic disturbances, ABG remains the gold standard NICE NG115.

Explanation: ABG analysis is critical in acute shortness of breath to accurately measure arterial oxygenation, carbon dioxide levels, and acid-base balance, which cannot be reliably assessed by peripheral venous samples alone in all cases. UK guidelines emphasize ABG use in acute respiratory distress and exacerbations of chronic lung disease to guide treatment NICE NG45,NICE NG115. Recent literature supports that while peripheral venous blood gases can be useful for initial assessment, ABG is necessary when precise evaluation of respiratory failure or metabolic derangements is required Byrne et al. 2025.