Renal response to mechanical ventilation in patients with chronic hypercapnia

Alkalosis in hypercapneic patients caused by abrupt respirator-induced reduction of the partial pressure of carbon dioxide leads to bicarbonate diuresis. Potassium is the predominant cation accompanying bicarbonate loss in the urine. The determining variable for induction of proportional changes in renal bicarbonate and potassium excretion is the partial pressure of carbon dioxide. The reduction of the partial pressure of carbon dioxide modifies bicarbonate regeneration directly by limiting the hydration reaction and facilitates potassium loss indirectly by reducing extracellular, and by inference intracellular, hydrogen ion activity.