Acute respiratory distress syndrome laboratory tests

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Brian Shaller, M.D. [2] Abiodun Akanmode,M.D.[3]

Overview

Laboratory findings consistent with the diagnosis of ARDS include severe hypoxemia (low PaO2 with decreased P/F ratio) and hypercapnia (increased PaCO2) secondary to an increase in pulmonary dead space.

Laboratory Findings

Laboratory findings consistent with the diagnosis of ARDS include an arterial partial pressure of oxygen (PaO2) that is inappropriately low relative to the fraction of inspired oxygen (FIO2). This is referred to as the PaO2/FIO2 ratio (sometimes abbreviated as P/F ratio) and is calculated by dividing the PaO2 (in mmHg) by the FIO2 (as a decimal rather than a percentage). Below are three examples of P/F ratio calculations that correspond to the three different degrees of ARDS severity:

In addition to severe hypoxemia, hypercapnia (increased PaCO2) secondary to an increased pulmonary dead space may also be present.[1]

Additional Laboratory Tests

Other notable diagnostic findings are those that support an underlying diagnosis that may have led to the development of ARDS (e.g., positive blood cultures and an elevated white blood cell count in a septic patient or an elevated lipase in a patient with acute pancreatitis). Additional laboratory tests that may be helpful in diagnosing the underlying cause of ARDS include:

Further testing should be guided by clinical suspicion and the patient's medical history. These laboratory tests include:

References

  1. Kasper, Dennis (2015). Harrison's principles of internal medicine. New York: McGraw Hill Education. ISBN 978-0071802154.
  2. Matthay MA, Zemans RL, Zimmerman GA, Arabi YM, Beitler JR, Mercat A; et al. (2019). "Acute respiratory distress syndrome". Nat Rev Dis Primers. 5 (1): 18. doi:10.1038/s41572-019-0069-0. PMC 6709677 Check |pmc= value (help). PMID 30872586 PMID: 30872586 Check |pmid= value (help).