Normal Arterial Blood Gas

Values

pH

PaC02

Pa02

HCO3

7.35-7.45

An ABC measures:

pH. The pH measures hydrogen ions (H+) in blood. The pH of blood isusually between 7.35 and 7.45. A pH of less than 7.0 is called acid and a pHgreater than 7.0 is called basic (alkaline). So blood is slightly basic.

Partial pressure of carbon dioxide (PaCO2). This measures how much3 & carbon dioxide is dissolved in the blood and how well carbon dioxide is able

to move out of the body.

Partial pressure of oxygen (PaO2). This measures the pressure of oxygen80-95 mm Hg dissolved in the blood and how well oxygen is able to move from the airspace

of the lungs into the blood.

Bicarbonate (HCO3). Bicarbonate is a chemical (buffer) that keeps the pH of22-26 mEq/L blood from becoming too acidic or too basic.

O2 Saturation 95-99%Oxygen content (O2CT) and oxygen saturation (O2Sat) values. O2 contentmeasures the amount of oxygen in the blood. Oxygen saturation measures howmuch of the hemoglobin in the red blood cells is carrying oxygen (O2).

Four-Step Guide to ABG Analysis

1. Is the pH normal, acidotic or alkalotic?2. Are the pCO2 or HCO3 abnormal? Which one appears to influence the pH?3. If both the pCO2 and HCO3 are abnormal, the one which deviates most from the norm is most likely

causing an abnormal pH.4. Check the pO2. Is the patient hypoxic?

Respiratory AcidosisAcutePartly CompensatedCompensated

Respiratory AlkalosisAcutePartly CompensatedCompensated

Metabolic AcidosisAcutePartly CompensatedCompensated

Metabolic AlkalosisAcutePartly CompensatedCompensated

<7.35<7.35

Normal

>7.45>7.45

Normal

<7.35<7.35

Normal

>7.45>7.45

Normal

>45>45>45

<35<35<35

Normal<35<35

Normal>45>45

Normal>26>26

Normal<22<22

<22<22<22

>26>26>26

Normal Ranges:pH - 7.35 to 7.45PaC02= 35 to 45HC03 = 22 to 26

1. Ask is PH in normal Limits? Use 7.4 as base line

Increasing number = Base (B) Decreasing number = Acid (A)

Example: pH is 7.43 = moving upward = B Base/alkaline

pH is 7.34 = moving downward = A Acidic

2. Is PaC02 high or low? Use 40 as base line Looking at it for Respiratory Disorder

Increasing number = Acid (A) Decreasing number = Base (B)

Example: PaC02 is 50 = moving upward = A Acidic

PaC02 is 30 = moving downward = B Base/alkaline

3. Is HC03 high or low? Use 24 as base line Looking at it for Metabolic Disorder

Increasing number = Base (B) Decreasing number = Acid (A)

Example: HC03 is 30 = moving upward = B Bas/alkaline

HC03 is 20 = moving downward = A Acidic

4. Which one is same as Ph (A or B) IfPaC02 then it is a Respiratory disorder

If HC03 then it is a Metabolic disorder

Example: pH 7.52 = moving upward = B Base/alkaline

PaC02 38 = moving downward = B Base/alkaline

HC03 21 = moving downward = A Acidic

Circle same letters and compare: pH tells you it is Alkalosis the PaC02 is same as Ph so it isRespiratory and the HC02 is out of normal range trying to compensate = Respiratory Alkalosiswith metabolic compensation working to bring the pH back into normal range.