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ABG ReviewDr Susan PrionSpring 2006Description Normal values

pH Negative log of[H+] Normal = 7.35-7.45

Acidosis = pH< 7.35

Alkalosis = pH>7.45PaCO2 The respiratory

parameter of ABG

interpretation

CO2 is a volatile acidthat is excretedprimarily as a gasthrough the lungs

PaCO2 > 45 meanshypoventilation and

respiratory ACIDOSIS

Pa CO2 < 35 meanshyperventilation andrespiratoryALKALOSIS

PaO2 Measure of the

oxygenation status ofthe central andperipheral tissues

Related to FiO2,amount of hgb, acid-base statusm SaO2and VA

Normal = 80 -100 torr

(decreases with age)

HCO3 Measures thebuffering ability of theblood and the amountof carbonic acid (themetabolic parameterof ABG interpretation)

Normal = 22-26 torr

HCO3 > 26 meansmetabolic alkalosis

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H+ + HCO3 H2CO3

CO2 + H2O

HCO3 < 22 meansmetabolic acidosis

SaO2 Saturation ofhemoglobin withoxygen

1 gram HgB can carry1.36 cc of O2

Normal = 90-100% (agedependent)

SaO2 > 100 =hyperoxia

SaO2 < 90 =hypoxiaBase excess Another way to

report amount ofbuffers

Zero point (BE = 0)corresponds to 24torr of HCO3

BE is reported as anegative or positive

value (e.g. +3 or -2)

Normal = -2 to +2 BE

A positive base excessmeans alkalosis

A negative baseexcess means acidosis