Question

Explain how the acid base balance of the body is altered in a patient with emphysema ( reduced alveolar ventilation)

Answer 1

in emphysema , respiratory acidosis occurs in which decreased ventilation leads to increase in co2 concentration in the blood and decrease in pH of blood thus the name acidosis. if the body does not expel CO2 through alveolar ventilation excess amount of CO2 rapidly accumulates in the lungs. this condition is called alveolar hypoventilation which results in hypercapnea(high PaCO2) and decrease pH by decreasing ratio of HCO3- / PaCO2. normally metabolism of carbohydrates and fats leads to formation of CO2 which combines with water to generate H2CO3 . this H2CO3 gets volatalised by normal ventilation. alteration in ventilation process thus leads to acid base imbalance.

alveolar ventilation is under the control of respiratory center present in pons and medulla and ventilation is normally regulated by chemoreceptors for PACO2 , PAO2 present in the brain .

in emphysema alveolar walls disintegrate producing larger air spaces that filled with gas after expiration. this leads to reduction in surface area of lungs and co2 and 02 gas could not exchange, which further leads to trapping of co2 gas inside the alveoli.

kidneys compensate by retaining HCO3- and excreting H+