Anarterial blood gas (ABG)is a blood test that measures the acidity (pH) and the levels of oxygen and carbon dioxide in the blood. Blood for an ABG test is taken from an artery whereas most other blood tests are done on a sample of blood taken from a vein. This test is done to monitor several conditions that can cause serious health complications especially to critically ill individuals.Every day, a lot of nursing and medical students assigned in acute areas encounter ABG results, which they may not necessarily be able to interpret with its knotty aspect. They struggle over the interpretation of its measurements, but they are not especially complicated nor difficult if you understand the basic physiology and have a step by step process to analyze and interpret them.Steps:1. Know the Normal ValuesKnow the normal and abnormal ABG values when you review the lab reports.

2. Check for Acidosis or AlkalosisThe first thing you need to determine when checking ABG results is the acidity of the blood which is determined by the value of the pH. The pH level in a healthy human should be between 7.35 to 7.45. Your body is constantly striving to keep pH in balance.pH level below 7.35 is AcidosispH level above 7.45 is Alkalosis3. Determine If the Acid Base is Respiratory or MetabolicNext thing you need to determine is whether the acid base is Respiratory or Metabolic.paCO2= RespiratoryHCO3= Metabolic4. Remember ROMEStill, it all boils down to mnemonics. The mnemonicRO-ME.RespiratoryOppositeWhen pH is up, PaCO2is down = AlkalosisWhen pH is down, PaCO2is up = AcidosisMetabolicEqualWhen pH is up, HCO3is up = AlkalosisWhen pH is down, HCO3is down = Acidosis5. Tic-Tac-ToeAnd yes, ABG problems work using the Tic-Tac-Toe method. All you have to do is make a blank chart a bit like a tic-tac-toe chart.

6. Mark the ChartUsing the lab result values, mark them on your Tic-Tac-Toe chart. Now begin with this given example.pH 7.26, PaCO232, HCO318pH is LOW = ACID so place pH under AcidPaCO2is LOW = BASE so place PaCO2under BaseHCO3is LOW = ACID so place HCO3under AcidYour chart should go like this:7. Match It upIn this step, look at which column matches up with the pH. In this case HCO3goes with pH. HCO3is considered Metabolic (shown in step 3), and both are under Acid, so this example implies Metabolic Acidosis.8. Determine CompensationThe last step is to determine if the ABG is Compensated, Partially Compensated, or Uncompensated.If pH is NORMAL, PaCO2and HCO3are both ABNORMAL = CompensatedIf pH is ABNORMAL, PaCO2andHCO3are both ABNORMAL = Partially CompensatedIf pH is ABNORMAL, PaCO2orHCO3is ABNORMAL = UncompensatedTherefore this ABG isMETABOLIC ACIDOSIS, PARTIALLY COMPENSATED .By applying the steps above, interpret the following ABGs.pH 7.44, PaCO2 30, HCO321pH is NORMAL = NORMAL so place pH under NormalPaCO2is LOW = BASE so place PaCO2under BaseHCO3is LOW = ACID so place HCO3under Acid*Since the acidity of the blood is determined by the value of the pH, determine whether the normal pH is SLIGHTLY ACIDIC or SLIGHTLY BASIC. In this example, pH is NORMAL but SLIGHTLY BASIC therefore it is ALKALOSIS.Your chart should go like this:

In this case PACO2 goes with pH. PACO2 is considered Respiratory (shown in step 3), and both are under Basic, so this example implies Respiratory Alkalosis. The HCO3is also abnormal. When pH is NORMAL and PaCO2and HCO3are both ABNORMAL, it indicates FULL COMPENSATION.Therefore this ABG isRESPIRATORY ALKALOSIS, FULLY COMPENSATED.pH 7.1, PACO2 40, HCO318pH is LOW = ACID so place pH under AcidPaCO2is NORMAL = NORMAL so place PaCO2under NormalHCO3is LOW = ACID so place HCO3under AcidYour chart should go like this:

In this case HCO3goes with pH. HCO3is considered Metabolic (shown in step 3), and both are under Acidic, so this example implies Metabolic Acidosis. The PaCO2is normal. When pH is ABNORMAL, PaCO2or HCO3is ABNORMAL, it indicates UNCOMPENSATION.Therefore this ABG isMETABOLIC ACIDOSIS, UNCOMPENSATED.