GASTRIC INTRAMUCOSAL PH - AN INDICATOR OF WEANING OUTCOME FROM MECHANICAL VENTILATION IN COPD PATIENTS

The aim of this study was to determine whether gastric intramucosal pH (pHim) and/or gastric intramucosal carbon dioxide tension (PCO2,im) m easured by tonometry can be used to predict the success of weaning in chronic obstructive pulmonary disease (COPD) patients, Twenty six cons ecutive COPD patients, undergoing mechanical ventilation for acute res piratory failure and satisfying the criteria of weaning from mechanica l ventilation with nasogastric tonometer in place, were studied. Arter ial blood gas values and PCO2,im were measured 24 h before (H-24), jus t before (H0), and after 20 min of a weaning trial on T-piece (H20min) , Weaning failure was defined as the development of respiratory distre ss and/or arterial blood gas impairments during the first 2 h of spont aneous breathing on T-piece, or reintubation within 24 h after extubat ion. Between the weaning failure (n=6) and weaning success (n=20) grou ps, there were no differences in blood pas analysis readings at H-24 a nd H0 before the weaning period, age, Simplified Acute Physiology Scor e (SAPS) on admission, SAPS an the day of weaning trial, and duration of ventilation. Clinical status, tonometric and arterial gasometric da ta were similar at H-24 and H0 in all patients, During mechanical vent ilation, pHim was less than or equal to 7.30 in patients who failed we aning and >7.30 in patients who were successfully weaned (p<0.001; 100 % sensitivity and specificity), The threshold value for PCO2,im of 8.0 kPa (60 mmHg) represents a clear demarcation with respect to outcome before the weaning trial, PCO2,im values during mechanical ventilation are significantly different (p<0.001) between patients who were succe ssfully weaned and those who were not (6.9+/-0.9 vs 9.9+/-1.1 kPa (51. 9+/-6.7 vs 74.3+/-8.0 mmHg, respectively)), At H20min, pHim and PCO2,i m were still statistically different between the weaning failure and t he weaning success group. We conclude that measurement of gastric intr amucosal pH (or gastric intramucosal carbon dioxide tension) represent s a simple and accurate index to predict weaning outcome in chronic ob structive pulmonary disease patients before attempting weaning.