Contribution by buffering systems

Contribution by buffer system

According to [WG21:p737-738]

• Respiratory acidosis and alkalosis
  * Almost all buffering is intracellular
  * ?? Include in RBCs by Hb
• Metabolic acidosis
  * 15-20% buffered by HCO3 in ECF
  * Rest is buffered in cells
• Metabolic alkalosis
  * 30-35% of OH- buffered in cells

Principle buffers in CSF and urine are bicarbonate and phosphate

According to KB's online acid-base text

Respiratory disorders predominately buffered in ICF
* 99% in respiratory acidosis buffered in ICF
* 97% in respiratory alkalosis

ECF is not not effective in buffering respiratory disorders because the main buffering system in ECF is bicarbonate

Metabolic acidosis

Contribution of buffering

• ECF = 43%
  * By bicarbonate & protein buffers (e.g. Hb)
• ICF = 57%
  * By protein phosphate and bicarbonate buffers
  Due to entry of H+ by:
  * Na-H exchange 36%
  * K-H exchange 15%
  * Other 6%

Metabolic alkalosis

ICF = 32%
* Na-H exchange is responsible for most of the transfer of H+

 

 

Other notes

Isohydric principle

All buffer systems which participate in defence of acid-base changes are in equilibrium with each other. There is after all only one value for [H+] at any moment.

This is known as the Isohydric Principle