Early prediction of successful weaning during pressure support ventilation in chronic obstructive pulmonary disease patients

G Conti, R De Blasi, P Pelaia, S Benito, M Rocco, M Antonelli, M Bufi, C Mattia, A Gasparetto
Critical Care Medicine 1992, 20 (3): 366-71

OBJECTIVE: The aim of this study was to examine variables for early prediction of successful weaning in chronic obstructive pulmonary disease (COPD) patients during pressure support ventilation weaning.

DESIGN: Thirteen COPD patients were prospectively studied to compare the respiratory pattern (inspiratory time, expiratory time, total breath cycle duration, tidal volume, respiratory rate, minute ventilation), the respiratory drive (airway occlusion pressure at 0.1 sec, tidal volume/inspiratory time), and blood gases after 30 mins of pressure support weaning.

SETTING: The study was performed in the 20-bed General Critical Care Unit of the Rome "La Sapienza" University Hospital.

PATIENTS: We evaluated 13 consecutive COPD patients fulfilling the standard weaning criteria (including clinical status, blood gases, forced vital capacity, maximum inspiratory pressure, and spontaneous respiratory rate after a 30-min T-piece trial) in which we compared respiratory pattern, respiratory drive, and blood gases after 30 mins of pressure support weaning.

MEASUREMENTS AND MAIN RESULTS: After 30 mins of pressure support ventilation weaning (pressure support level 20 cm H2O), we measured respiratory pattern (airway pressure and airflow tracing), airway occlusion pressure at 0.1 sec (occluding the inspiratory line during expiration with a rubber balloon), tidal volume/inspiratory time, maximal inspiratory pressure, and blood gases. According to the result of the weaning trial, the patients were divided into two groups (not weaned and weaned), and the statistical difference between the evaluated variables was analyzed in weaned and not weaned groups. We did not observe a significant difference in breathing pattern data and arterial blood gases between weaned and not weaned patients. By contrast, airway occlusion pressure at 0.1 sec and maximum inspiratory pressure measured after 30 mins of weaning trial appeared significantly (p less than .001) different in patients in whom the weaning trial succeeded or failed. Considering maximum inspiratory pressure, we could not separate weaned from not weaned patients, while all patients showing values of airway occlusion pressure at 0.1 sec less than 4.5 cm H2O were easily weaned.

CONCLUSIONS: This study confirms that conventional weaning criteria are often inadequate in predicting successful weaning of COPD patients, while airway occlusion pressure at 0.1 sec during the first phase of pressure support ventilation weaning can represent a good weaning predictor.

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