There are several buffer systems involved in maintaining blood pH, but one is more important than the others for maintaining acid-base homeostasis in blood. To understand why an acid-base imbalance in the blood results from respiratory depression, you must first identify the major buffer system responsible for controlling blood pH. Which equilibrium reaction is the most important for maintaining acid-base homeostasis in the blood?

The Carbonic-Acid-Bicarbonate Buffer. In animals with lungs, the carbon / bicarbonate buffer system is especially effective. In these animals, the H2CO3 in the blood plasma is in equilibrium with the gaseous CO2 present in the airspace of the lungs, which represents a practically unlimited reserve of CO2 that can participate in the equilibrium.

Explanation:

In the Carbonic-Acid-Bicarbonate buffer system, 3 reversible equilibria take place between the CO2 gas in the lungs and the bicarbonate dissolved in the blood. The bicarbonate ion (HCO3-) can combine with a proton (H +) to form carbonic acid (H2CO3), thus absorbing protons from solution and raising blood pH. Carbonic acid, which can be formed from CO2 and water, can dissociate into H + and HCO3- to provide H + and lower blood pH. Carbonic acid, which can be formed from bicarbonate, is converted to CO2 and water by a very fast enzymatic reaction. CO2, being volatile, can be rapidly eliminated from the body in variable amounts through respiration.In the clinic, the system that is measured for the assessment of the acid-base status is the carbonic / bicarbonate system.

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