Role of respiratory system in Acid – base balance

ROLE OF RESPIRATORY SYSTEM

  • Blood PCO2 can be varied extensively because the partial pressure of CO2 in alveoli determines the amount of CO2 dissolved in blood.
  • The respiratory mechanism depends upon the sensitivity of respiratory control systems to change in blood PCO2 and pH.
  • A small increase in PCO2 or decrease in pH stimulates pulmonary ventilation, so that CO2 expiration increases.
  • If an acid is added to body fluids, chemical buffering results in formation of additional H2CO3 and leading to a depletion of HCO3

H+ + HCO3- ----->H2CO3 ----->CO2 + H2O

  • When the production of CO2 is increased or pulmonary hypoventilation occurs, it leads to the accumulation of CO2 in blood Therefore, the pH falls slightly.
  • However, the increase in CO2 and decrease in pH stimulate respiration, causing a rapid expiration of extra CO2. Then blood PCO2 decreases and pH returns to normal.
  • When an alkali is added to blood or pulmonary hyperventilation occurs, this causes a decrease in H2CO3 {CO2} level in blood. The respiratory system is inhibited and additional CO2 is retained in ECF. These increase PCO2 to balance the increased HCO3 resulted from added alkali.
Last modified: Saturday, 4 June 2011, 7:50 AM