www.lecturio.com/nursing Watch Video
NOTES
ABG INTERPRETATION
Opposing
Systems
Lungs
control the CO2
CO2 level → blood pH HCO3 level → blood pH
Kidneys
control the HCO3
Normal ABG Values:
Compensatory mechanisms:
ABG interpretation in 5 steps:
Think through
this:
Remember:
Carbon dioxide makes
the blood more aCidic
1. pH → high = alkaline
2. CO2 → high = acidic
3. HCO3 → high = alkaline
Remember:
Bicarbonate makes the
blood more Basic
What would happen to
the “pH scale” if
there was more CO2
than HCO3?
pH < 7.35 pH > 7.45pH: 7.35-7.45
pH SCALE
Respiratory Metabolic
Alkaline pH CO2Lungs Respiratory Alkalosis
Match
Opposing system
in normal range?
System at fault
pH in normal
range?
Diagnosis
Diagnosis
Acidic pH CO2
Ye s
Lungs
No
Respiratory Acidosis
Uncompensated
Acidic pH HCO3
No
Kidneys
Ye s
Metabolic Acidosis
Fully compensated
Alkaline pH HCO3
No
Kidneys
No
Metabolic Alkalosis
Partially compensated
Acidic Basic (Alkaline)
CO2 HCO3
pH: 7.35 - 7.45
CO2: 35 - 45 mmHG
HCO3: 22 - 26 mEq/L
Step 4
Step 1 - 3 Interpretation: Partially compensated metabolic alkalosis
Interpret the
patient’s ABGs
Step 5
Match the pH label with HCO3 or CO2 and determine
system at fault
Check pH, CO2, HCO3 and label
Determine if the body is trying to compensate
(correct the imbalance)
pH 7.51
PaCO2 52
HCO3 31
EXAM HINT:
Kussmaul breathing (deep, rapid breathing) is the lung’s
way of responding to extreme acidosis by blowing off
CO2.
