Hypercapnia: is there a cause for concern?

Concern that barotrauma may lead to further deterioration in pulmonary function in patients with ARDS has stimulated interest in developing methods of reducing it. These new modalities have had limited acceptance. The reasons for this include technical difficulties, associated complications, and the hypercapnia produced by the reduction in minute ventilation associated with diminished peak inspiratory pressure (PIP). Recent reports have shown that hypercapnia does not produce many of the adverse effects previously attributed to it. We studied the effects of moderate levels of hypercapnia produced by inverse ratio ventilation with low tidal volumes in patients with severe pulmonary dysfunction (Lung Injury Score > or = 2.5). The mean peak PaCO2 and PIP of the group were 63.3 +/- 15.7 mm Hg and 44.0 +/- 12.4 cm H2O, respectively. We found no adverse effects on cardiac function, oxygen utilization, or long-term neurologic function in patients after hypercapnia. We conclude that moderate levels of hypercapnia are safe, and may be permitted in the care of patients with severe pulmonary dysfunction.