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Respiratory Muscle Activity during Maximal Efforts in ALS Patients and Healthy Controls
Author(s) -
Sajjadi Elaheh,
Ehrbar Jessica G.,
Seven Yasin B.,
Dickinson Patrick G.,
Mitchell Gordon S.,
Smith Barbara K.
Publication year - 2020
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.2020.34.s1.06199
Subject(s) - parasternal line , medicine , amyotrophic lateral sclerosis , cardiology , diaphragm (acoustics) , respiratory system , motor neuron , electromyography , lower motor neuron , ventilation (architecture) , physical medicine and rehabilitation , disease , mechanical engineering , physics , acoustics , loudspeaker , engineering
Amyotrophic lateral sclerosis (ALS) is a type of neurodegenerative disease involving upper and lower motor neuron loss. ALS patients usually die of respiratory failure due to breathing muscle weakness from motor neuron death. It is important to better understand how breathing changes in ALS to design effective treatments to target breathing insufficiency. Breathing capacity is preserved until late stages of disease in the SOD1G93A rodent model of ALS. Possible mechanisms preserving breathing in ALS rats include: 1) spinal synaptic plasticity; 2) neuromuscular junction plasticity; and 3) transition in balance from more affected muscles (eg. diaphragm) to less affected accessory respiratory muscles. If these mechanisms also exist in humans with ALS, we predict that characteristic patterns of altered respiratory muscle activity would precede ventilatory failure, assessed via traditional pulmonary function tests. Thus, using surface EMGs (sEMG) in ALS patients, we tested the hypothesis that ALS patients exhibit differential recruitment patterns of inspiratory muscle activity during a maximal inspiratory pressure (MIP) test versus healthy age‐ and sex‐ matched controls . EMG electrodes (Bagnoli surface electrode, Delsys, Massachusetts, USA) were bilaterally placed on the diaphragm, 2 nd parasternal, scalene and sternocleidomastoid muscles. Subjects (8 patients and 8 controls) were instructed to perform the MIP test. The test was repeated until 3 measurements were obtained within 10% variability. RMS EMG amplitude of MIP testing was calculated using a 100ms sliding window with MATLAB v.9.2., and relationships between MIP and EMG activity were evaluated using a linear regression. A moderate relationship (r=0.65) was seen between parasternal muscle activity and MIP in ALS patients, while the controls showed moderate correlations between neck muscle activity (sternocleidomastoid and scalene) and MIP (r SCM = 0.56 and r scalene =0.69). Moreover, MIP‐generated parasternal (r=0.76) and diaphragm (r=0.7) activity corresponded strongly with disease severity of patients, as measured by the ALS‐FRS scale. Interestingly, we did not see a clear relationship between diaphragm surface EMG activity and MIP in either patients or controls. Several factors could account for this, including the use of surface electrodes and the mass‐effort nature of the MIP test. Further analyses are underway to assess respiratory muscle activity during other inspiratory challenges and compare the amount of sEMG output distribution between controls and ALS patients. These preliminary results support the idea that ALS patients use a different pattern of muscle activity during maximal breathing effort from controls. Support or Funding Information Supported by: UF Clinical and Translational Science Institute (supported by NIH UL1TR001427), UF “Moonshot” grant initiative, and UF McKnight Brain Institute