VPB 121: Veterinary Physiology - II (2+1)

RESPIRATORY ALKALOSIS

• When alveolar hyperventilation occur the expiration of CO₂ may exceed the rate of its production within the body and respiratory alkalosis develops. There will be low plasma PCO₂ (Hypocapnia) and alkalemia.
• Hyperventilation is caused by abnormal stimulus to respiratory centres either directly as in NH₃ toxicity or through hypoxemia acting through peripheral chemoreceptors. Buffer reaction follows :

HHb + HCO₃ ---->Hb^- + H₂CO₃ ---->CO₂ + H₂O

• The HCO₃ falls. Renal compensation begins ; alkalemia depresses H⁺ ion secretion by renal tubules and excretion of filtered HCO₃ rises. This result in further fall of plasma HCO₃ and the ratio of HCO₃ to H₂CO₃ moves back to normal.