Serial Ultrasound Assessment of Diaphragmatic Function and Clinical Outcome in Patients with Amyotrophic Lateral Sclerosis.

Background: Ultrasound (US) evaluation of the diaphragm may be a non-volitional useful tool in the clinical management of patients with ALS. Aim of the present study was then to evaluate the impact of serial assessment of ΔTmax index on clinical outcomes during the follow-up in these patients and to correlate non-volitional US indices and other volitional measures with these outcomes. Methods: A cohort of 39 consecutive patients with ALS was followed up to 24 months. At baseline and every 3-month spirometry (forced vital capacity-FVC), sniff inspiratory nasal pressure (SNIP), and US of the diaphragm (ΔTdi and ΔTmax) were recorded. These parameters were correlated with clinical outcomes (hypercapnia, nocturnal hypoventilation, NIV start in the following 6 month, and death within 1 year). Results: The occurrence of ΔTmax >0.75 during follow-up increased the risk for NIV (HR=5.6, p=0.001) and death (HR=3.7, p=0.0001) compared with patients with stable lower values. The evidence of diaphragmatic dysfunction, i.e. ΔTmax >0.75, occurs 3.2 month earlier than the onset of NIV. Moreover, ΔTmax >0.75 correlated with onset of nocturnal hypoventilation, NIV initiation within 6 months, and death within 12 months, similarly to FVC <50% predicted and better than other functional indices. Conclusions: Serial monitoring of diaphragmatic ΔTmax by US may be useful to predict initiation of NIV and death in patients with ALS. The occurrence of an abnormal ΔTmax value in the follow-up precedes the decision for starting NIV.