Spontaneous minute ventilation (V_E), peak inspiratory airway pressure (Plmax), rapid shallow breathing index (f/v_T), relative inspiratory effect (RIE), and the P(A-a)O₂, blood urea nitrogen and gender score (A + B + G) are used in predicting weaning success. Some patients are transferred from intensive care to subacute care facilities when prolonged mechanical ventilation (MV) is anticipated. This prospective. observational study compares the role of weaning indices versus APACHE II score in identifying patients requiring prolonged MV.

The study included 84 patients referred for weaning assessment, when their underlying acute conditions had stabilized but immediate successful extubation was not expected. Plmax, V_E and respiratory rate were measured. APACHE II score. f/V_T, RIE, and A + B + G were calculated. Prolonged and successful weaning were defined as dependance on MV for ≥ 7 and < 7 days respectively from the day of weaning assessment. Weaning outcome was categorized into three: death, prolonged weaning, and successful weaning. Student's t-test was used to compare differences in means. P value < 0.05 was considered significant.

Patients' mean age was 55.9 ± 13.8 years: 42 were male; 42 were black, 41 white and 1 Hispanic. The main causes of the respiratory failure were pneumonia (25) and COPD (17). The patients had been on MV for a median of 9 days before weaning assessment. Eleven (13%) patients died: 22 (26%) had prolonged weaning: 51 (61%) were successfully weaned. The mean APACHE II score and weaning indices are listed in the table.