Let’s Play….
Values:
pH (acid):
< 7.35
pH (normal): 7.35 – 7.45
pH (base):
> 7.45
ABG Tic-Tac-Toe
PaCO2 (acid):
PaCO2 (normal):
PaCO2 (base):
> 45
35 – 45
< 35
ABG values: pH______________ PaCO2__________________
Acid/Normal/Base: pH_________ PaCO2__________________
HCO3 (acid):
HCO3 (normal):
HCO3 (base):
< 22
22 – 26
> 26
HCO3_____________________
HCO3_____________________
Now plug in your values:
Acid
Normal
Base (Alkaline)
pH
PaCO2
HCO3
RESPIRATORY ACIDOSIS:
Respiratory acidosis uncompensated:
Respiratory acidosis partially compensated:
Respiratory acidosis totally compensated:
pH acid ()
pH acid ()
pH normal
PaCO2 acid ()
PaCO2 acid ()
PaCO2 acid ()
HCO3 normal
HCO3 base ()
HCO3 base ()
RESPIRATORY ALKALOSIS:
Respiratory alkalosis uncompensated:
Respiratory alkalosis partially compensated:
Respiratory alkalosis totally compensated:
pH base ()
pH base ()
pH normal
PaCO2 base ()
PaCO2 base ()
PaCO2 base ()
HCO3 normal
HCO3 acid ()
HCO3 acid ()
METABOLIC ACIDOSIS:
Metabolic acidosis uncompensated:
Metabolic acidosis partially compensated:
Metabolic acidosis totally compensated:
pH acid ()
pH acid ()
pH normal
PaCO2 normal
PaCO2 base ()
PaCO2 base ()
HCO3 acid ()
HCO3 acid ()
HCO3 acid ()
METABOLIC ALKALOSIS:
Metabolic alkalosis uncompensated:
Metabolic alkalosis partially compensated:
Metabolic alkalosis totally compensated:
pH base ()
pH base ()
pH normal
PaCO2 normal
PaCO2 acid ()
PaCO2 acid ()
HCO3 base ()
HCO3 base ()
HCO3 base ()
Interpretation:
Uncompensated: pH and one other value (either PaCO2 or HCO3) are abnormal. Abnormal pH determines whether acidosis or
alkalosis. Abnormal PaCO2 or HCO3 determines whether respiratory or metabolic.
PaCO2 abnormal = respiratory; HCO3 abnormal = metabolic.
Partial compensation: all values are abnormal. Two values “agree” (pH and either PaCO2 or HCO3 are BOTH acid or BOTH base),
and the remaining value (either PaCO2 or HCO3) is the OPPOSITE of the pH. The value (PaCO2 or HCO3) that “agrees” with the pH
is correct (determines whether respiratory or metabolic).
Compensation: pH is normal, both PaCO2 and HCO3 are abnormal. One will be acidotic, the other base. The value that most closely
matches the pH identifies the true (underlying) state. If the fully compensated pH is between 7.35-7.40, then the normal pH is closer to
the acid end and the acidotic value (either PaCO2 or HCO3) is correct. If the pH is between 7.40-7.45, then the normal pH is closer to
the alkalotic end and the base value (either PaCO2 or HCO3) is correct.
Acid-Base Interpretation
Table Values
Acid
Respiratory acidosis uncompensated
pH
PaCO2
HCO3
pH
PaCO2
HCO3
pH
PaCO2
HCO3
Respiratory alkalosis totally compensated
pH
PaCO2
HCO3
Metabolic acidosis uncompensated
pH
PaCO2
HCO3
Metabolic acidosis partially compensated
pH
PaCO2
HCO3
Metabolic acidosis totally compensated
pH
PaCO2
HCO3
Metabolic alkalosis uncompensated
X
Acid
pH
PaCO2
HCO3
X
Normal
Base
Normal
Base
X
X
Acid
Normal
Base
X
X
X
Acid
Normal
Base
X
X
X
Acid
Normal
Base
X
X
X
Acid
Normal
Base
X
X
Normal
X
Base
X
X
Acid
Metabolic alkalosis totally compensated
X
Base
X
Acid
pH
PaCO2
HCO3
Normal
X
X
pH
PaCO2
HCO3
Metabolic alkalosis partially compensated
X
Base
X
X
Acid
pH
PaCO2
HCO3
Normal
X
pH
PaCO2
HCO3
Respiratory alkalosis partially compensated
Base
X
Acid
Respiratory alkalosis uncompensated
X
Normal
X
X
Acid
Respiratory acidosis totally compensated
Base
X
X
Acid
Respiratory acidosis partially compensated
Normal
Normal
X
Base
X
X
X