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Excerpt
Introduction: Mechanical ventilation is required in 20-30% of patients with Guillain-Barre syndrome (GBS). The value of daily respiratory function tests in predicting duration of ventilation in GBS is not known. If this is expected to be less than 21 days tracheostomy may be avoided. In most instances the decision for tracheostomy can be deferred until about day 12 after intubation, to allow assessment of the clinical response to plasma exchange.
Methods: Retrospective review of 32 mechanically ventilated patients with GBS in whom detailed serial respiratory function parameters were available. Patients ventilated for < 22 days were compared to those ventilated > 22 days. Daily vital capacity (ml/kg) and maximal inspiratory and expiratory pressures (mm H20) were summed to an integrated pulmonary function (PF) score to provide a global bedside assessment of neuromuscular respiratory status. The PF score at intubation (day 1) was compared to the score on day 12 (PF index is PF score day 12 after intubation divided by PF score day 1).
Results: Twenty-two patients (69%) were ventilated for > 3 weeks and 10 patients (31%) were ventilated < 3 weeks. Age and frequency of pulmonary disease were greater in the prolonged ventilation group but the antecedent illness, time to peak disability and electrophysiologic data were similar in both groups. In patients ventilated < 3 weeks, the PF score showed an increase at day 12, whereas patients ventilated for greater than 3 weeks generally showed a PF score reduction. The PF index was greater than 1 in all 10 patients ventilated < 3 weeks and less than 1 in 15 of 22 patients ventilated > 3 weeks (p=0.0003, Fisher exact test). The sensitivity of the PF index of < 1 for predicting duration of ventilation > 3 weeks was 68%, the specificity and positive predictive value were 100%.
Conclusions: The PF index in GBS can help predict duration of ventilation and need for tracheostomy. If the PF index is less than 1 it is highly unlikely patients will be weaned before three weeks and tracheostomy should be performed. If the PF index is greater than 1 then continued observation and postponement of tracheostomy is warranted.
