Determination Of Acid-Base Status

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Chapter: Anatomy, Physiology And Health Education : Acid-Base Balance

It is difficult to determine the acid-base status in the ECF by direct methods. So, an indirect method is followed by using Henderson-Hasselbalch equation. In this, to determine the pH of a fluid, the concentration of bicarbonate ions (HCO –) and the CO dissolved in the fluid are measured. The pH is calculated as follows:


Determination Of Acid-Base Status

 

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It is difficult to determine the acid-base status in the ECF by direct methods. So, an indirect method is followed by using Henderson-Hasselbalch equation. In this, to determine the pH of a fluid, the concentration of bicarbonate ions (HCO ) and the CO dissolved in the fluid are measured. The pH is calculated as follows:

 


 

Where, pK is constant with pH of 6.1 Thus,

 

 


In addition to this, the pH of plasma is also determined by using an instrument called pH meter.

 

Normal acid-base ratio is 1:20, i.e. the ratio of 1 partof CO  (derived from H CO ) and 20 parts of HCO

 

If this ratio is altered, the pH also is altered leading to either acidosis or alkalosis.

 

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Thus, the pH of arterial blood is an indirect measurement of H+ concentration and it reflects the balance of CO2 and HCO –.

 

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