To evaluate diaphragmatic ultrasound parameters may predict the need for mechanical ventilation (IMV) in Guillain-Barré syndrome (GBS) patients and their association with established prognostic scales.

We conducted a single-center prospective cohort study in adults with GBS admitted to Guadalajara Civil Hospital (2023–2025). Clinical, laboratory, and electrodiagnostic data were collected at baseline. Diaphragmatic excursion, thickening fraction (TFdi), and sniff test were assessed by ultrasound according to EXODUS consensus guidelines. Outcomes included IMV, tracheostomy, and in-hospital mortality. Associations were analyzed using Mann–Whitney U, Fisher’s exact test, ROC analysis, Spearman correlation, Firth-penalized logistic regression, and Cox proportional hazards models.

A total of 49 patients were included (median age 45 years; 65.3% male). Nine (18.4%) required IMV. These patients had greater disease severity: higher GBS disability score (5 vs 3, p=0.001), mEGOS (7 vs 4, p=0.029), EGRIS (5 vs 3, p=0.009), and lower MRC scores (28 vs 42, p=0.013). Excursion <2.0 cm predicted IMV with high sensitivity (100%) and VPN (100%) but low specificity (25%). ROC analysis showed moderate discrimination (excursion AUC 0.76; TFdi AUC 0.50; sniff AUC 0.64). Logistic regression identified bulbar weakness (OR 6.79, p=0.023) as the strongest independent predictor. In Cox models, an increase in diaphragmatic excursion is considered a protective factor for IMV (per 1-cm increase, aHR 0.10, p=0.030). Higher EGRIS (aHR 3.43, p=0.010) and bulbar weakness (aHR 29.6, p=0.011) were associated with earlier IMV.

In this cohort, diaphragmatic excursion greater than 2 cm upon hospital admission is an excellent predictor of non-IMV. This provides a tool with utility for monitoring patients with GBS in settings with limited resources.