Question

A severe bout of vomiting eventually lowers blood plasma ​[H^+] (remember that the stomach contents are highly acidic because protons are pumped out of the stomach epithelium into the stomach lumen). After this occurs, what will happen to your alveolar ventilation rate?

A It will decrease.

B It will increase.

C It will stay the same.

Answer 1

The severe bouts of vomiting causes lowering the blood plasma levels and decrease in H⁺ ion concentration increases pH causing metabolic alkalosis. This would result in increase in HCO₃ concentrations. The decrease in H⁺ ion concentration is also a condition called hypovolemia and metabolic alkalosis. The compensation for metabolic alkalosis occurs mainly in the lungs. The lungs retain carbon dioxide through slower breathing, or hypoventilation. It is the mechanism of respiratory compensation. The CO₂ is used for the formation of the carbonic acid intermediate. This would decrease the pH. The decrease in H⁺ ion concentration suppresses the peripheral chemoreceptors sensitive to pH. The slow respiratory rate is responsible to increase in pCO₂ that counteracts the action of the central chemoreceptors. The central chemoreceptors are sensitive to the partial pressure of CO₂ in the cerebral spinal fluid. The counteraction of the central chemoreceptors result in increased respiration rate. Therefore, the alveolar ventilation rate will increase. The option B is correct.