Walk Through Examples

Example 1

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.)

Example 2

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

Example 3

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

Example 4

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

Example 5

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

Example 6

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

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