ABGs BB

ABG Analysis
Normal values:
pH – 7.35 – 7.45
PaO2 – 80 to 100 mm Hg
O2 Saturation – 95% - 100%
PaCO2 – 35 – 45 mm Hg
HCO3 – 22 – 26 mEq / L

1

ABG Analysis
pH – body must maintain a delicate balance of

acids and bases to maintain homeostasis
pH indicates the concentration of hydrogen ions in the blood
Respiratory and metabolic processes work to keep hydrogen ion (H+) levels stable
Normal pH of arterial blood is 7.35 – 7.45 (slightly alkaline or basic)
pH of less than 7.35 indicates acidosis (high H+)
pH of more than 7.45 indicates alkalosis (low H+)
2

ABG Analysis
pH is affected by carbon dioxide on respiratory

side
CO2 will combine with water in blood to form

carbonic acid (CO2 + H2O = H2CO3)
CO2 is considered an acid

pH is affected by bicarbonate on metabolic (renal)

side
HCO3 binds with free H+ to reduce its concentration

(HCO3 + H+ = H2CO3)
HCO3 is an alkaline substance or base
3

ABG Analysis
Respiratory alkalosis – blowing off CO2
pH up / CO2 down
Always caused by hyperventilation
Fear
 Anxiety
 Pain
 Fever
 Drugs
 High altitudes
 Pregnancy


4

ABG Analysis
Respiratory acidosis – retaining CO2
pH down / CO2 up
Always caused by hypoventilation
Neurological problems
 Respiratory disease states
 Pulmonary edema
 Airway obstruction
 Chest trauma
 Drugs (anesthesia, overdose)


5

ABG Analysis
Metabolic alkalosis – too much bicarbonate
pH up / HCO3 up
Loss of gastric acid (vomiting)
 Overuse of antacids
 Potassium wasting diuretics


6

ABG Analysis
Metabolic acidosis – too little bicarbonate
pH down / HCO3 down
Diarrhea
 Renal failure
 Shock
 ASA overdose
 Diabetic ketoacidosis
 Sepsis


7

ABG Analysis
Acid
pH

< 7.35

Normal
7.35 – 7.45

Alkaline
> 7.45

PaCO2

>45

35 – 45

<35

HCO3

< 22

22 - 26

>26

Acid

Normal

Alkaline

8

ABG Analysis
Compare patient’s ABG results to acid-base

parameters
Write “pH”, “PaCO2”, and “HCO3” under the appropriate column head
Column with pH tells you