Is the PO2 level on ABG analysis useful in diagnosing pulmonary embolism (PE)?

Updated: Jun 06, 2019
  • Author: Daniel R Ouellette, MD, FCCP; Chief Editor: Zab Mosenifar, MD, FACP, FCCP  more...
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Answer

The PO2 on arterial blood gases analysis (ABG) has a zero or even negative predictive value in a typical population of patients in whom pulmonary embolism is suspected clinically. This is contrary to what has been taught in many textbooks, and even though it seems counterintuitive, it is demonstrably true. This is because other etiologies that masquerade as pulmonary embolism are more likely to lower the PO2 than pulmonary embolism. In fact, because other diseases that may masquerade as pulmonary embolism (eg, chronic obstructive pulmonary disease [COPD], pneumonia, CHF) affect oxygen exchange more than does pulmonary embolism, the blood oxygen level often has an inverse predictive value for pulmonary embolism.


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