Thoracic electrical impedance tomography for assessing progression of pulmonary dysfunction in ALS

Area of Science:

• Pulmonary Medicine
• Biomedical Engineering
• Neurology

Background:

• Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disease affecting motor neurons.
• Pulmonary function decline is a critical factor in ALS progression and patient outcomes.
• Current methods for monitoring pulmonary function may have limitations in longitudinal assessment.

Purpose of the Study:

• To compare thoracic electrical impedance tomography (EIT) with slow vital capacity (SVC) for monitoring pulmonary function in ALS patients longitudinally.
• To assess the feasibility of using EIT-derived impedance-SVC (zSVC) to track pulmonary changes over time in ALS.
• To evaluate the sensitivity of EIT to detect changes in pulmonary function compared to SVC in a longitudinal study.

Main Methods:

• A cohort of 22 ALS patients and 20 healthy controls (HCs) underwent thoracic EIT and SVC measurements in upright and supine positions at baseline and follow-up (~3.9 months).
• EIT data were summarized as impedance-SVC (zSVC), representing averaged impedance change across both lungs.
• Longitudinal changes in SVC and zSVC were analyzed for both groups.

Main Results:

• Upright SVC significantly declined by 5% in the ALS group over time, while no significant change was observed in HCs.
• Supine SVC showed no significant change in either group.
• Although zSVC trajectories mirrored SVC trajectories, changes in zSVC in ALS patients did not reach statistical significance due to higher variability in repeated EIT measures.

Conclusions:

• Thoracic EIT demonstrated strong cross-sectional correlations with SVC but failed to detect significant longitudinal decline in pulmonary function in ALS patients over approximately four months.
• Increased variability in EIT measurements is a key limitation hindering its sensitivity for longitudinal pulmonary function assessment in ALS.
• Technological advancements and meticulous electrode placement are crucial for optimizing EIT's utility in longitudinal monitoring of pulmonary function in ALS.