Utility of Diaphragmatic Ultrasound and Diaphragmatic Electromyogram in Amyotrophic Lateral Sclerosis

<bold>Introduction:</bold> Amyotrophic Lateral Sclerosis(ALS) is conditioned by respiratory involvement, and non-invasive mechanical ventilation(NIV) is the best support therapy when it is affected. Indication for NIV is typically assessed through respiratory functional tests(PFRs), although not all patients, particularly those with bulbar ALS, are capable of performing them. Diaphragmatic ultrasound(DUS), and the diaphragmatic thickening fraction(TFDI) variable, have potential usefulness for respiratory muscle assessment. Our aim is to study the correlation between diaphragmatic ultrasound measurements, respiratory function data, and diaphragmatic Electromyogram(EMG). <bold>Methods:</bold> cross-sectional study, between 2020 and 2023,involved consecutively recruiting ALS patients without an indication for NIV in a multidisciplinary consultation setting. Data included descriptive variables, symptoms, gasometry,PFRs, nocturnal oximetry, diaphragmatic ultrasound (including TFDI),and diaphragm surface EMG. Baseline parameters and correlations between tests were analyzed. <bold>Results:</bold> 76 patients were recruited. Sociodemographic variables are presented in Table 1. No correlation was found between diaphragmatic ultrasound measurements and blood gas variables or nocturnal oximetry. Statistically significant correlation was observed between forced vital capacity(FVC%) and TFDI(r=0.46), though not with PIM or SNIP. Diaphragmatic EMG showed no significant relationship with any of the monitoring parameters. <bold>Conclusion:</bold> Among the parameters evaluated, only diaphragmatic ultrasound measurements showed a significant correlation with FVC%,offering a more accessible and non-invasive alternative for assesing respiratory muscle strength.