- A measurement of oxygen, CO2, and the pH of the blood that provides a means of assessing the adequacy of ventilation (Paco2), oxygenation (PaO2).
- Allows assessment of the acid-base (pH) status of the body whether acidosis or alkalosis is present, whether acidosis or alkalosis is respiratory or metabolic in origin and to what degree (compensated or uncompensated).
- Allows evaluation of response to clinical interventions and diagnostic evaluation (oxygen therapy, exercise testing).
Nursing and Patient Care Considerations
- Blood can be obtained from any artery but is usually drawn from the radial, brachial, or femoral site. It can be drawn directly by arterial puncture or accessed by way of indwelling arterial catheter (see Procedure Guidelines 10-1, pages 204 to 206). Determine facility policy for qualifications for ABG sampling and site of arterial puncture.
- If the radial artery is used, an Allen test must be performed before the puncture to determine if collateral circulation is present.
- Arterial puncture should not be performed through a lesion, through or distal to a surgical shunt, or in area where peripheral vascular disease or infection is present.
- Coagulopathy or medium- to high-dose anticoagulation therapy may be a relative contraindication for arterial puncture.
- Interpret ABG values by looking at the following (normal values are listed):
- PaO2- partial pressure of arterial oxygen (80 to 100 mm Hg)
- Paco2- partial pressure of arterial carbon dioxide (35 to 45 mm Hg)
- Sao2- arterial oxygen saturation (> 95%)
- pH- hydrogen ion concentration, or degree of acid-base balance (7.35 to 7.45); bicarbonate (HCO3-) ion primarily a metabolic buffer 22 to 26 mEq/L.
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