Improving Measurement of Lung Function in ALS: The Results of the Pulmonary Function via Impedance Tomography (PuFIT) Study
Seward Rutkove1, Courtney McIlduff1, Elijah Stommel2, Ethan Murphy3, Sarah Verga1, Soleil Samaan1, Allaire Doussan3, Kathy Phipps2, Christy Smith1, Sean Levy1, Ajitesh Nanda1, Teresa Capella1, Ryan Halter3
1Beth Israel Deaconess Medical Center, 2Dartmouth Hitchock Medical Center, 3Thayer School of Engineering at Dartmouth
Objective:
To determine the value of thoracic electrical impedance tomography (EIT) in assessing pulmonary function in ALS patients.
Background:
Pulmonary function testing (PFT) is used in ALS for monitoring clinical status, planning interventions, and in clinical trials. However, PFTs are limited by effort and orofacial weakness. A more easily applied objective measure of lung function could find wide value. Thoracic EIT is a painless, noninvasive procedure which uses a series of electrodes placed around the chest to produce real-time images of the lungs during respiration. The aggregate data used to create this image can serve as a quantitative measure of lung aeration. Here we present the results of the recently completed two-center Pulmonary Function via Impedance Tomography (PuFIT) study.
Design/Methods:
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.
Results:
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.
Conclusions:
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.