A77-10 Inspiratory Neuroplasticity During Maximal Voluntary Efforts Following Acute Intermittent Hypoxia in Amyotrophic Lateral Sclerosis

Background Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disease characterized by motoneuron death that leads to respiratory muscle weakness, hypoventilation, and shortened lifespan. Acute intermittent hypoxia (AIH) is a nonpharmacologic therapy comprised of repeatedly alternating the levels of inspired oxygen. In ALS rat models, AIH elicits phrenic neuroplasticity, and proof-of-concept work in human ALS suggests it can also improve breathing. However, the effects of AIH on inspiratory muscle recruitment of patients remain unclear. This ancillary analysis from an ongoing clinical trial assessed inspiratory muscle activity during maximal voluntary efforts, in response to a single AIH session. Methods Ten participants with ALS (8 males; mean age 63.9 years [range 39-75]), underwent a single AIH session (15 cycles, 1min 10% O2, 2min 21% O2). Maximal inspiratory pressure (MIP) was tested before and 1 hour following AIH. Surface EMG of the bilateral diaphragm (DIA), 2nd parasternal (PS), and scalene (SCA) was recorded at 4kHz, amplified, and bandpass filtered (5-500 Hz). Differences in median frequency (MF) and total power (TP) for each muscle were analyzed with Wilcoxon signed-rank tests and reported as mean ± SEM. Results Participants had varying levels of underlying respiratory impairment (forced vital capacity: 96.83±-17.73% predicted), and resting fasciculations were observed in three. One hour after AIH exposures, median frequency significantly increased in the left PS (pre: pre: 61.8±5.0 Hz, post: 61.8±5.0 Hz, p = 0.0059) and trended higher in the left DIA (pre: 47.9±5.1 Hz, post: 53.1±3.2 Hz, p = 0.1602). Additionally, total power of the right DIA significantly increased following AIH (pre: 0.3625±0.1441 mV2, post: 0.7811±0.2596 mV2, p = 0.0195. Frequency characteristics of the scalenes remained unchanged. Conclusions Despite considerable variability in the respiratory involvement of participants, single AIH exposures were associated with increased median frequency and total power of the diaphragm and parasternal sEMG during MIP. These changes suggest improved motor unit activation and/or higher firing rates during maximal inspiratory efforts following AIH. This abstract is funded by: ALS Association