Weaning and extubation in the intensive care unit - Clinical or index-driven approach?

Objective: To assess the outcome of a clinical judgement-based approach to weaning and extubation and to adduce the predictive accuracy of various mechanical respiratory indices measured in parallel. Design: Prospective study. Setting: Multidisciplinary intensive care unit at a university teaching hospital. Patients: 163 consecutive mechanically ventilated patients, excluding tracheotomy, for weaning trial and extubation. Interventions: Using bedside clinical assessment aided by arterial gas analysis, patients were weaned from mechanical ventilation to spontaneous ventilation via the continuous positive airway pressure (CPAP) circuit with pressure support) of a microprocessor-controlled ventilator. Extubation occurred from the CPAP circuit at 7 cmH(2)O pressure support, fractional inspired oxygen (FIO2) less than or equal to 0.5 and CPAP level of less than or equal to 5 cmH(2)O, such that the partial pressure of oxygen in arterial blood (PaO2) was greater than or equal to 65 mmHg. Before extubation, observation for a 1-h (T-0 and T-60) trial period allowed measurement of vital capacity (VC), expired minute volume (VE), respiratory rate/tidal volume (f/V-T) and maximal inspiratory pressure (MIP) using a one-way valve technique over 25 s. Measurements and main results: Over 7 months, 163 patients (62 females and 101 males; mean(SD) age 64(15) years) were considered. There were 91 surgical (18 with chronic obstructive pulmonary disease; COPD) and 72 medical (28 with COPD) patients. Ventilation was for greater than or equal to 1 day (median 5 days, range 1-31) in 115 [group I; APACHE II score 23(8)] and less than or equal to 1 day in 48 [Group II; APACHE II score 17(6)]. Three patients (all Group I: 2 surgical, 1 medical) were reintubated within 24 h, an overall extubation failure rate of 1.8%. In group I, at T-0, PaO2/FIO2 was 238(65), f/VT 50(26), MIP 44(21) cmH(2)O, VE 10.6(3.7) l/min, VC 13(5) ml/kg. Cardiorespiratory variables did not change significantly in either group, T-0 to T-60. For prediction of reintubation (n = 163), only VE (threshold >10 l/min) and f/V-T (threshold >100) demonstrated moderate sensitivity and specificity at T-60: 67 and 52% and 33 and 94%, respectively. Conclusions: Bedside clinical judgement of weaning and extubation produces satisfactory outcomes. As a routine, mechanical predictive indices have limited utility.