Which pulmonary pattern supports a diagnosis of GBS?

• A. Decreasing tidal volume, vital capacity, and maximal inspiratory pressure
• B. Increased peak expiratory flow
• C. Hyperinflation with low rib cage expansion
• D. Normal tidal volumes

Answer: (A)

Guillain-Barré syndrome often leads to weakness of the respiratory muscles, particularly the diaphragm and intercostals. That weakness produces a restrictive ventilatory pattern, with reductions in tidal volume and vital capacity and a lower maximal inspiratory pressure, reflecting weakened inspiratory effort. As these muscles weaken, the patient can’t generate adequate tidal volumes, leading to hypoventilation and the risk of hypoxemia and hypercapnia. The other patterns don’t fit neuromuscular weakness: increased peak expiratory flow isn’t typical of this condition, hyperinflation with low rib cage expansion suggests obstructive disease and air-trapping, and normal tidal volumes would not indicate developing respiratory failure in GBS.