Post-intubation pulmonary function test in Guillain-Barré syndrome

The value of daily postintubation respiratory function tests in predicting duration of ventilation in 37 mechanically ventilated patients with Guillain-Barré syndrome (GBS) was studied. Patients ventilated for less than 3 weeks were compared with those ventilated more than 3 weeks. Daily vital capacity and maximal inspiratory and expiratory pressures were summed to an integrated pulmonary function (PF) score. We calculated the PF ratio, which represents the PF score at day 12 after intubation divided by the PF score on the day of intubation. The PF ratio was greater than 1 in all 10 patients ventilated less than 3 weeks and was less than 1 in 19 of 27 patients ventilated for longer (P = 0.0001, Fisher exact test). The sensitivity of a PF ratio less than 1 for predicting duration of ventilation greater than 3 weeks was 70%; the specificity and positive predictive value were 100%. This study thus suggests that serial postintubation respiratory tests can provide a measure of respiratory status in patients with GBS. These parameters may help predict duration of ventilation and need for tracheostomy. If, at day 12, the PF ratio is less than 1, it is highly unlikely that patients will be weaned within 3 weeks, and tracheostomy should be performed. If the ratio is greater than 1, tracheostomy should be deferred, because a substantial proportion of these patients may be successfully weaned from the ventilator within 3 weeks.