Investigation of the Disturbance of Acid Base Balance

There are three most frequently used parameter when investigating acid-base balance of the system, the parameter are;

1. Blood PH
2. Bicarbonate
3. And pressure of CO2(PCO2)

This parameter are frequently used for investigating acid-base balance.

Below are the mathematical interrelationship of the parameter;

                                            ( HCO3-)

1. pH = pK1 + log ——————————

                             (Dissolved CO2)

HCO3- and CO2 are express in mmol/L unit, and pK1, is constant.

Plasma have pK1 = 6.1. or

                                               ( HCO3-)

2. pH = pK1 + log ——————————

                             (0.0301 x PCO2)

PCO2 is express in mmHg unit.

0.0301 represent solubility constant of CO2.

This above calculation is drive by Henderson Hasselbalch, as such is known as Henderson Hasselbalch equation. The principle of the equation is that if any of this two parameter is known, then the third parameter can be calculated.

Nomogram

To determine any of this above parameter, nomogram can be used for the detection, if only two of the parameter is known. In a place where blood gas analyzer is not available, blood pH can be determine by potentiometric and bicarbonate via titration techniques. When PCO2 is determine with nomogram, the value obtain from the nomogram, can be join with nomogram scale with a ruler, and the line extended if the need arise to obtain the third value.