Gastric mucosal pH and blood flow during weaning from mechanical ventilation in patients with chronic obstructive pulmonary disease

To determine if gastric intramucosal pH changes during weaning from mechani cal ventilation are related to gastric mucosal blood flow modifications, we studied 16 ventilator-supported patients with chronic obstructive pulmonar y disease (COPD) who tolerated a 2-h trial of spontaneous breathing with pr essure support ventilation and were successfully extubated and 11 patients with COPD who failed such a trial. Gastric mucosal perfusion was assessed u sing gastric intramucosal pH (pH) by tonometry and laser-Doppler flowmetry. During the weaning attempt, the failure weaning group developed a rapid, s hallow breathing pattern with acute respiratory acidosis. The pH(i) was low er and gastric intramucosal Pco(2), (Pco(2)im) was higher in the failure we aning group than in the successful weaning group (p < 0.05). No change in g astric intramucosal-arterial Pco(2) difference was observed and a linear co rrelation was found between arterial Pco(2) and Pco(2)im (r(2) = 0.70; p < 0.001). Cardiac index increased in the failure group (p < 0.05) and remaine d stable in the success group whereas gastric mucosal blood flow decreased in the failure group (H-120 min-22 +/- 11% from baseline; p < 0.05) and inc reased in the success group (H-120 min: 85 +/- 27% from baseline; p < 0.05) . We conclude that gastric intramucosal pH changes during a 2-h weaning tri al are mainly due to arterial Pco(2), variations. Nevertheless, gastric muc osal blood flow changes do occur and differ according to the weaning succes s or failure.