Blood gases and pulmonary embolus

Pulmonary embolus (PE) results in a mismatch between alveolar perfusion and ventilation, with potential for development of hypoxemia (reduced pO₂) and hypocapnia (reduced pCO₂), so that arterial blood gases (ABG) are frequently ordered for patients either suffering or suspected of suffering PE. 

Is it possible to make or exclude a diagnosis of PE on the basis of ABG results? That was the question that a recent short-cut review of the literature was designed to answer. A Medline search using relevant key words produced 459 papers of which six were judged to provide the best evidence to answer the question. 

Analysis of the results of the research contained in these six papers allowed the conclusion that pO₂ and/or pCO₂ are not sufficiently sensitive/specific for PE. ABG cannot be used alone to make or exclude a diagnosis of PE.