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Arterial blood gas analysis

Last updated: March 25, 2021

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Arterial blood gas (ABG) analysis is a test regularly performed to measure oxygen saturation, carbon dioxide, and bicarbonate blood levels. It provides quick assessment of gas exchange processes and acid-base balance.

  • Measured parameters
  • Reference ranges
    • PaCO2: 35–45 mm Hg
    • SaO2: ≥ 95%
    • pH: 7.35–7.45
    • HCO3-: 21 to 27 mEq/L
    • Base excess: -2 to +3 mmol/L
    • Resting PaO2 > 80 mm Hg is considered normal.
  • Procedure
    • A modified Allen test must be performed before the radial artery is punctured to assess collateral circulation in the hand.
      1. Manual pressure below the wrist is applied to both arteries, the hand is elevated, and the patient is asked to clench their fist for about 30 seconds to induce transient ischemia, leading to pallor of the hand.
      2. When the pressure is released from the ulnar artery, the patient's hand rapidly returns to normal color if collateral circulation is present.
      3. Interpretation: The test result is normal if the patient's hand rapidly returns to normal color. The test is negative and considered pathological if the patient's hand remains at least partially pale.
    • Arterial blood can be drawn from radial arteries or an indwelling arterial catheter.
  • Interpretation

  1. Chan ED, Chan MM, Chan MM. Pulse oximetry: Understanding its basic principles facilitates appreciation of its limitations. Respir Med. 2013; 107 : p.789-799. doi: 10.1016/j.rmed.2013.02.004 . | Open in Read by QxMD
  2. Jubran A. Pulse oximetry. Crit. Care. 2015; 19 (1): p.272. doi: 10.1186/s13054-015-0984-8 . | Open in Read by QxMD
  3. Mechem CC, Parsons PE, Finlay G. Pulse Oximetry in Adults. In: Post TW, ed. UpToDate. Waltham, MA: UpToDate. https://www.uptodate.com/contents/pulse-oximetry-in-adults.Last updated: April 6, 2016. Accessed: June 26, 2017.