Agreement between Diaphragm Ultrasound and Pulmonary Function Testing in the Evaluation of Diaphragm Function in Patients with ALS

Background: In ALS patients, diaphragmatic dysfunction is usually assessed by pulmonary function testing (PFTs) that requires patient cooperation. Evidence suggest that diaphragm ultrasound (DU) can be utilized, as an alternative to PFTs, to detect reduced diaphragmatic motility in ALS patients. This study aimed to verify the agreement between the results obtained by DU with those obtained by PFTs in both standing-up and supine positions.Methods: Twenty nine spinal ALS and thirteen healthy controls were studied in standing up and lying 30° supine position. All subjects performed PFTs and DU, to assess of diaphragmatic excursion, delta-thickness between end inspiration and end expiration (ΔT), and the thickening fraction (TF). Results: The standing position, ΔT correlates with VC (r=0.58p=0.001) and FVC (r=0.61 p<0.001); in lying 30° supine position, ΔT correlates with VC(r=0.59 p=0.001) and FVC (r=0.62 p<0.001). In standing up position, TF correlates with VC (r=0.55 p=0.003) and FVC (r=0.53 p=0.005); in lying 30° supine position, TF correlates with VC (r=0.55 p=0.003) and FVC (r=0.51 p=0.007). The following correlations were also observed: the standing position, diaphragmatic excursion correlated with VC(r=0.55 p=0.007) and FVC (r =0.65 p<0.001). In lying 30° supine position, diaphragmatic excursion correlated with VC(r=0.59 p=0.003); and FVC(r=0.63 p=0.001).Conclusion: DU adequately assesses the diaphragmatic impairment in ALS patients. Thickening and excursion appear as complementary indices in the evaluation of diaphragm motility.