ALS patients and age- and sex-matched healthy volunteers were recruited. For each participant, EIT was obtained during PFT measurements and at rest and repeated 2-6 months later. The primary analyses assessed the relationship between an aggregate EIT z-metric obtained simultaneously with the SVC measurement and with tidal breathing and change over time.

64 individuals (44 men, 20 women, half with ALS, overall age±SD of 63.1±11.5 years), were enrolled. There was a strong positive correlation between the EIT z-metric and SVC with r² =0.63, p< 0.001 in ALS patients. The at-rest, tidal breathing EIT z-metric data also correlated strongly with upright SVC (r² =0.56, p< 0.001). Immediate reproducibility was high with an intraclass correlation coefficient of 0.96. Reduction in EIT values on follow-up were observed in ALS patients, consistent with PFT decline.

These data support the potential for EIT, using either forced maneuvers or tidal breathing, as a valuable approach for assessing pulmonary function in ALS patients. Improvements and simplification of the technique to be assessed in a multicenter study with a larger group of ALS patients is now being planned.