Question

what are the tricks to know ABG compensation, uncompensation, partially compensation?

what are the best ways to know ABG more easy to understand?

Answer 1

ABG (Arterial blood gas) is a laboratory test, which identity level of gases as well as the PH of the blood.

Important values in the ABG (Normal)

1. PH - 7.35 to 7.45

Below 7.35 is known as acidic and above 7.45 is alkaline

2. PCO2 (Partial pressure of Carbon-dioxide) 35 mm of hg to 45 mm of hg

It represents the respiratory part of the body. Increase PCO2 in blood cause acidosis and Decrease level cause alkalosis.

3. HCO3(Bicarbonate) 22meq/l to 28 meq/l

It represents the metabolic part of the body. Increase Hco3 causes alkalosis and decrease level causes acidosis.

4. Po2 (Partial pressure of oxygen)

80 mm of hg to 100 mm of hg

5. So2 (Saturation of Oxygen) should be above 90%.

The tricks to know ABG better

1. first look at the PH for acidosis and alkalosis

2. Then look for the causes

3. Look for compensation

Example 1. PH - 7.25

Pco2 - 56

Hco3 - 25

Look PH is acidic because it's lower than 7.35, the cause is Pco2 because it increases and hco3 is in the normal range.

PO2 is representing respiratory part of body So, it is Respiratory Acidosis(uncompensatory)

It is non-compensatory because the body is not doing anything to compensate for acidosis. If here Hco3 is increasing to 34 meq/l, It means to an alkaline state, then it will be a Partially compensatory Respiratory acidosis. Because now the body tries to manage acidosis by increasing level of Bicarbonate.

If here PH will increase to 7.35, Hco3 - 34 and Pco2 remain the same then it will be a compensatory Respiratory acidosis because now PH is in normal range and body is successful with his defense mechanism.

Remember one thing in compensation, partially compensation the cause of the disturbance(in the above example it is pco2 which was the reason for acidosis) and compensation value(here it was Hco3 - 34) will move in the same direction. (It means both are increasing)

Example 2. PH - 7.50

PCO2 - 40

Hco3 - 40

Here PH is in alkalosis state, and it is caused by HCo3 because It is increased than normal value. Hco3 represents metabolic part So, It is Metabolic acidosis(Uncompensatory).

If the body adopts defense mechanism and start co2 retention in the body then co2 will increase9(It is called Partially compensation, in this stage body tries but PH does not come to normal).

In fully compensation PH comes to normal.

Example 3. PH 7.45, Pco2 - 20, Hco3 - 15

It is a Fully compensatory respiratory alkalosis (HCO3 is compensating and Ph is in the normal range )

Example 4. PH - 7.24, PCo2 - 20 , Hco3 - 10

It is partially compensatory Metabolic acidosis(Because Pco2 is compensating but PH is still in the acidic state)