[Clinical study of weaning predictors in COPD patients with prolonged mechanical ventilation].

OBJECTIVE: To evaluate the combined pulmonary function test at bedside as a predicting parameter of weaning in prolonged mechanically ventilated (MV) patients with chronic obstructive pulmonary disease (COPD).

METHODS: 58 patients [mean duration of MV (18.4 +/- 9.2) d] who were divided into two groups were enrolled in this study. Group I included 43 patients [male 30, female 13, mean age (65 +/- 12) y] were successful in weaning, group II included 15 patients [male 10, female 5, mean age (64 +/- 10) y] were failed. ABGs, APACHEII, pulmonary function test and respiratory mechanics were measured in both groups after 30 minutes stable spontaneous breathing.

RESULTS: There were no significant difference in ABGs, APACHEII, oxygenation index (OI), dynamic compliance (Cdyn) and airway resistance (Raw) between two groups (all P values > 0.05). There were significant differences in the following parameters between two groups: vital capacity/tidal volume (VC/VT, 2.10 +/- 0.20 vs. 1.30 +/- 0.20), maximal inspiratory pressure (Pimax), (-21 +/- 4) vs. (-13 +/- 3) cm H2O, rapid shallow breath index (RSBI), f/VT, (74 +/- 30) vs. (115 +/- 20) times.min-1.L-1, all P values < 0.05. By the use of VC/VT(> 1.8), Pimax(< -18 cm H2O) and f/VT(< 105 times.min-1.L-1) as the criteria of weaning, the specificity (90%) was significantly higher than each of the above three parameters.

CONCLUSION: The bedside combined pulmonary function test (VC/VT, Pimax and f/VT) was a valuable weaning predictor in prolonged mechanically ventilated COPD patients.