ABG Value

Which step?

 Rationale

  pH

 7.39

Step 1

 Normal pH
 PaCO2

 40

Step 2

Normal PaCO2
 Interpretation      Normal ABG (acid base is balanced; there are no pH changes, so if the respiratory acid is normal, the metabolic base cannot be causing changes either.)

ABG Value

Which step?

 Rationale

  pH

  7.2

Step 1

 Low pH indicates acidosis
 PaCO2

 50

 Step 2

 High PaCO2 indicates respiratory cause for acidosis
 Interpretation      respiratory acidosis

ABG Value

Which step?

 Rationale

  pH

 7.49

Step 1

 High pH indicates alkalosis
 PaCO2

 30

 Step 2

Low PaCO2 indicates respiratory cause for alkalosis (lo respiratory acid is causing higher pH)
 Interpretation      respiratory alkalosis

ABG Value

Which step?

 Rationale

  pH

 7.23

Step 1

 Low pH indicates acidosis
 PaCO2

 31

 Step 3

Low PaCO2 rules out respiratory cause for acidosis, therefore metabolic cause. Low respiratory acid is compensating for lower pH.
 Interpretation      metabolic acidosis

ABG Value

Which step?

 Rationale

  pH

  7.48

Step 1

 High pH indicates alkalosis
 PaCO2

  47

 Step 3

 High PaC02 and High pH indicates metabolic cause of alkalosis. Respiratory acid is compensating for high pH.
 Interpretation      Partially compensated metabolic alkalosis

ABG Value

Which step?

 Rationale

  pH

  7.43

Step 1

pH is normal but higher than 7.4, therefore compensated alkalosis.
 PaCO2

  33

 

 Step 3

  Low PaCO2 causes alkalosis
 Interpretation      Compensated respiratory alkalosis

Now return to Step 4 of "4 Steps to ABG Interpretation Page"


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