Reading Blood Gases - Case Based Examples

Interpretation of blood gas analysis should be performed in a logical, consistent fashion. Blood gas analysis provides information regarding oxygenation, ventilation, and acid/ base status. Six steps can be used to interpret blood gases:

1. Step 1: Determine whether the blood samples if arterial or venous.

   1. If SO2 >88%, the sample is almost certainly arterial.

   2. If SO2 <88%, the sample could be venous, mixed, or could be an arterial sample from a patient with disease.
       

2. Step 2: Determine the acid/ base status.

   1. Determine whether the patient is academic (pH below reference range), alkalemic (pH above reference range), or normal pH.

   2. Determine whether pCO2 is normal or abnormal.

   3. Determine whether HCO3 is normal or abnormal.

   4. Using the information from 2a–2c, determine whether the primary problem is respiratory in origin or metabolic in origin.

   5. Determine whether compensation is occurring.

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