Clinical and electrophysiological predictors of respiratory failure in Guillain-Barré syndrome: a prospective study.

Background: Respiratory failure is the most serious short-term complication of Guillain-Barré syndrome and can require invasive mechanical ventilation in 20-30% of patients. We sought to identify clinical and electrophysiological predictors of respiratory failure in the disease.

Methods: We prospectively assessed electrophysiological data and clinical factors, including identified predictors of delay between disease onset and admission, inability to lift head, and vital capacity, in patients admitted with Guillain-Barré syndrome. We related these factors to subsequent need for ventilatory support. Neurophysiological findings were classified as demyelinating, axonal, equivocal, unexcitable, or normal. Predictive values of clinical and electrophysiological data were tested using classification trees to build up a predictive model. This model was initially built up in a two-third (fitting set) then validated in a one-third (validation set) of the total sample. The fitting and validation sets were randomly selected. We also assessed the predictive value of this model for disability at 6 months.

Findings: From 1998, to 2006, 154 patients with Guillain-Barré syndrome were included in the study and 34 (22%) were subsequently ventilated. Demyelinating Guillain-Barré syndrome was more common in patients who went on to be ventilated than in those who were not (85%vs 51%, p=0.0003). Vital capacity and the proximal/distal compound muscular amplitude potential (p/dCMAP) ratio of the common peroneal nerve were retained in the tree model, with a probability of needing ventilation of less than 2.5% in patients with a ratio of greater than 55.6% and a vital capacity more than 81% of predicted. A p/dCMAP ratio of the peroneal nerve less than 55.6% and age older than 40 years were retained as independent predictors of disability at 6 months.

Interpretation: Neurophysiological testing is helpful for assessing risk of respiratory failure, which is highest in patients with evidence of demyelination and very low in those without both 55.6% conduction block of the common peroneal nerve and a 20% reduction in vital capacity.