Arterial Blood Gas (ABG) Interpretation
NURS 302 --- Pathophysiology
ARTERIAL BLOOD GAS INTERPRETATION
Normal ABG Acceptable Ranges
ABG
Acceptable Range
pH
7.35 – 7.45
PO2
95-100
PCO2
35 – 45
HCO3
22-26
Base excess
-2 to +2
O2 Sat
>95%
Definitions
Acidosis (acidemia) occurs when pH drops below 7.35
Alkalosis (alkalemia) occurs when the pH rises above 7.45
A primary respiratory problem is determined if the PaC02 is less than 35mmHg (alkalosis) or
greater than 45 mmHg (acidosis).
A primary metabolic problem is when the HC03 is less than 22mEq/L (acidosis) or greater
than 26mEq/L (alkalosis).
Abnormal ABGs
To determine type of ABG abnormality, label all values of your abnormal ABG as follows
(DO NOT USE ARROWS ( ↑ OR ↓) - Label all values as normal, acidotic or alkalotic)
pH < 7.35 = ACIDOSIS
pH > 7.45 = ALKALOSIS
pCO2 > 45 = acidotic value
pCO2 < 35 = alkalotic value
HCO3 < 22 = acidotic value
HCO3 > 26 = alkalotic value
ABNORMAL BLOOD GASES ??????
3
1. First - label all values as acidotic or alkalotic
a. Acid-base is determined by pH
b. Label pH first to determine acid base disturbance
2. Second - Label the respiratory component (pCO2) and the metabolic
component of your gas
3. Third – MATCH to tell you,
a. based on your pH, which kind of acidosis or alkalosis you have:
i. It’s a metabolic acidosis or alkalosis if that component matches
the pH (and therefore caused the shift in pH)
ii. It’s a respiratory acidosis or alkalosis if that component
matches your pH (and therefore caused the shift in pH)
Example 1
pH
7.25 acidosis
pCO2
55
acidotic value
HCO3
26
normal
Answer:
RESPIRATORY ACIDOSIS
pH
7.50
alkalosis
pCO2
25
alkalotic value
HCO3
24
normal
Answer:
RESPIRATORY ALKALOSIS
Example2
pH
7.20 acidosis
pH
pCO2
35
normal
pCO2
42 normal
acidotic
HCO3
30 alkalotic
HCO3
Answer:
15
METABOLIC ACIDOSIS
7.55 alkalosis
METABOLIC ALKALOSIS
ABG INTERPRETATION
1. pH
Acid
7.19
pCO2Norm 35
fpO2
60
HCO3 Acid 15
Acid 7.19
pCO2 Acid 65
fpO
60
2
HCO3Norm 22
Interpretation _________________________
Metabolic Acidosis
2. pH
Interpretation ________________________
Respiratory Acidosis
3. pH Alka 7.50
pCO
25
pO
90
HCO3Norm24
Alka
2
f2
Interpretation Respiratory
_________________________
Alkalosis
4. pH Alka 7.55
pCO2Norm40
pO
95
HCO3 Alka30
f2
Interpretation _________________________
Metabolic Alkalosis
5. pH Alka 7.50
pCO2 Alka25
fpO
75
2
HCO3
24
Interpretation ________________________
Respiratory Alkalosis
=
6. pH Acid 7.25
pO
90
pCO2 Acid 65
HCO3 Acid 18
f2
7. pH Alka 7.50
fpO
100
2
pCO2 Alka 25
Respiratory and
Metabolic Acidosis
Interpretation __________________________
Respiratory and
Interpretation _______
__________Alkalosis
___________
Metabolic
HCO3Alka 30
O sat 99%
f2