ARTERIAL BLOOD GASES: NORMAL VALUES
pH
7.35 to 7.45
pO2*
80 to 100 mmHg
pCO2
35 to 45 mmHg
HCO3 21
to 25 mEq/L
O2 sat
95% to 99%
Base Excess -2
to +2
*In a patient >60 years of age, pO2 is equal to 80 mmHg - 1 mmHg for every year over 60. Expected pO2 can be determined
by multiplying the FIO2 by 5.
INTREPRETING ABGs
1. Check pH >7.45 = alkalosis <7.35
= acidosis
2. Check pCO2 elevated = CO2 retention (hypoventilation)
respiratory acidosis or compensation for metabolic
alkalosis.
decreased
= CO2 being blown off, (hyperventilation)
respiratory alkalosis or compensation for metabolic
acidosis.
nil = no respiratory component imbalance
3. Check HCO3 elevated = nonvolatile acid is lost, HCO3 gained
(metabolic alkalosis or compensation for respiratory
acidosis)
decreased = nonvolatile acid is added, HCO3 is lost
(metabolic acidosis or compensation for respiratory
alkalosis.
4. Determine Imbalance.
5. Determine if compensation exists.
IF
THEN
pH up and pCO2 down
or
RESPIRATORY DISORDER
pH down and pCO@ up
pH up and HCO3 up
or
METABOLIC DISORDER
pH down and HCO3 down
pCO2 up and HCO3 up
COMPENSATION OCCURING
or
pCO2 down and HCO3 down
pCO2 up and HCO3 down
or MIXED IMBALANCE
pCO@ down and HCO3 up
