The utility of diaphragm ultrasound thickening indices for assessing respiratory decompensation in amyotrophic lateral sclerosis

Muscle Nerve. 2023 Nov;68(6):850-856. doi: 10.1002/mus.27980. Epub 2023 Oct 10.


Introduction/aims: Amyotrophic lateral sclerosis (ALS) leads to diaphragmatic weakness at some point during its course, which is a major cause of respiratory insufficiency. The aim of this study was to evaluate ultrasound-based measures for assessing the diaphragmatic competency and the need for ventilatory support.

Methods: Twenty-six subjects with ALS and 12 healthy controls were enrolled. All participants underwent B-mode diaphragm ultrasound (DUS). Diaphragm thickness and thickening indices were recorded. In the subjects with ALS, further assessments included functional scales and spirometry. We investigated the diagnostic accuracy of DUS thickening indices in predicting diaphragmatic dysfunction and the correlation between clinical, spirometric, and DUS data.

Results: Significant relationships were found between forced vital capacity and all diaphragmatic thickening indices. Similarly, all diaphragmatic thickening indices correlated with both Milano Torino staging and disease progression rate. Only thickening fraction (TFdi) correlated with score on the revised ALS Functional Rating Scale (r = 0.459, P = .024). TFdi had better accuracy in predicting diaphragmatic dysfunction (area under the curve [AUC] = 0.839, 95% confidence interval [CI] 0.643 to 0.953) and the need for initiation of noninvasive ventilation (NIV) (AUC = 0.989, 95% CI 0.847 to 1.000) compared with the other indices. A TFdi cut-off point of 0.50 was a sensitive threshold to consider NIV.

Discussion: DUS successfully identifies diaphragmatic dysfunction in ALS, being a valuable accessory modality for investigating respiratory symptoms. TFdi was found to be the most useful DUS index, which encourages further investigation.

Keywords: ALS; diaphragm thickening fraction; diaphragm ultrasound; diaphragmatic weakness; respiratory failure.

MeSH terms

  • Amyotrophic Lateral Sclerosis* / complications
  • Amyotrophic Lateral Sclerosis* / diagnostic imaging
  • Diaphragm / diagnostic imaging
  • Humans
  • Noninvasive Ventilation*
  • Respiratory Insufficiency* / diagnostic imaging
  • Respiratory Insufficiency* / etiology
  • Ultrasonography