Mobilizing Carbon Dioxide Stores. An Experimental Study.

Understanding the physiology of CO stores mobilization is a prerequisite for intermittent extracorporeal CO removal (ECCOR) in patients with chronic hypercapnia. To describe the dynamics of CO stores. Fifteen pigs (61.7 ± 4.3 kg) were randomized to 48 hours of hyperventilation (group "Hyper,"  = 4); 48 hours of hypoventilation (group "Hypo,"  = 4); 24 hours of hypoventilation plus 24 hours of normoventilation (group "Hypo-Baseline,"  = 4); or 24 hours of hypoventilation plus 24 hours of hypoventilation plus ECCOR (group "Hypo-ECCOR,"  = 3). Forty-eight hours after randomization, the current [Formula: see text]e was reduced by 50% in every pig. We evaluated [Formula: see text]co, [Formula: see text]o, and metabolic [Formula: see text]co ([Formula: see text]o times the metabolic respiratory quotient). Changes in the CO stores were calculated as [Formula: see text]co - metabolic V̇co. After 48 hours, the CO stores decreased by 0.77 ± 0.17 l kg in group Hyper and increased by 0.32 ± 0.27 l kg in group Hypo ( = 0.030). In group Hypo-Baseline, they increased by 0.08 ± 0.19 l kg, whereas in group Hypo-ECCOR, they decreased by 0.32 ± 0.24 l kg ( = 0.197). In the second 24-hour period, in groups Hypo-Baseline and Hypo-ECCOR, the CO2 stores decreased by 0.15 ± 0.09 l kg and 0.51 ± 0.06 l kg, respectively ( = 0.002). At the end of the experiment, the 50% reduction of [Formula: see text]e caused a Pa rise of 9.3 ± 1.1, 32.0 ± 5.0, 16.9 ± 1.2, and 11.7 ± 2.0 mm Hg h in groups Hyper, Hypo, Hypo-Baseline, and Hypo-ECCOR, respectively ( < 0.001). The Pa rise was inversely related to the previous CO stores mobilization ( < 0.001). CO from body stores can be mobilized over 48 hours without reaching a steady state. This provides a physiological rationale for intermittent ECCOR in patients with chronic hypercapnia.