IVOX WITH GRADUAL PERMISSIVE HYPERCAPNIA - A NEW MANAGEMENT TECHNIQUEFOR RESPIRATORY-FAILURE

IVOX (intravenous oxygenator and CO2 removal device) augments venous g as exchange in patients with severe respiratory failure. Controlled hy poventilation with permissive hypercapnia reduces airway pressures dur ing mechanical ventilation and augments CO2 exchange through the IVOX. To quantify the additive effects of gradual permissive hypercapnia an d IVOX on gas exchange and reduction of airway pressures, 13 adult she ep underwent tracheostomy and severe smoke inhalation injury. Seven we re mechanically ventilated alone (control), and six had mechanical ven tilation, systemic anticoagulation, and implantation of IVOX (size 7 w ith 0.21-m(2) surface area) (IVOX group). Both groups were anesthetize d and paralyzed for 24 hr. In the IVOX group, minute ventilation was d ecreased in a stepwise fashion to produce a gradual increase in PaCO2, from 30 to 95 mm Hg, over 12 hr, and then sustained for an additional 12 hr. Sodium bicarbonate was given intravenously as necessary to kee p arterial pH above 7.25. There were no significant differences in mea n arterial pressure, cardiac output, or pulmonary artery pressure betw een the two groups. In the IVOX/permissive hypercapnia group, IVOX CO2 removal increased as a linear function of PaCO2 (gamma = 0.81x + 8.99 , R(2) = 0.80). IVOX CO2 removal was only 40 ml/min at normocapnia (40 mm Bg) but increased to 91 ml/min when PaCO2 was 95 mm Hg. Both peak inspiratory pressure and minute ventilation of the IVOX/ permissive hy percapnia group were significantly lower than the control group, 30 +/ - 4 mm Hg vs 51 +/- 3 mm Hg and 3.9 +/- 0.3 liters vs 8.4 +/- 0.5 lite rs (P < 0.05) respectively. CO2 removal by IVOX can be substantially a ugmented under conditions of permissive hypercapnia, reducing the vent ilatory requirements in an ovine model of acute smoke inhalation injur y. (C) 1994 Academic Press, Inc.