Acute Intermittent Hypoxia and Breathing in Neuromuscular Disease (AIH in ALS)

This project seeks to investigate the effects of a single acute intermittent hypoxia (AIH) session on respiratory and non-respiratory motor function and EMG (electromyography) activity on patients with ALS (amyotrophic lateral sclerosis) and healthy controls.

Most ALS patients survive less than 5 years after diagnosis, and the main cause of death is respiratory failure. The investigators are interested in the therapeutic potential of acute intermittent hypoxia (AIH) for individuals with neuromuscular diseases, such as ALS. More than two decades of research indicates AIH elicits meaningful respiratory and non-respiratory motor recovery. Acute intermittent hypoxia (AIH) consists of alternating periods of breathing mildly hypoxic (lowered oxygen concentration) and normoxic (normal oxygen concentration) air. The investigators propose to study mechanisms of respiratory plasticity associated with a single presentation of mild AIH. The fundamental hypothesis guiding this proposal is that even a single AIH trial improves respiratory (and non-respiratory) motor function in ALS patients procedure. Participants will then be asked to breathe air with reduced oxygen for short periods of time, for a duration of 45 minutes. The activity of your muscles and your heart function will be monitored throughout the procedure.

acute intermittent hypoxia (AIH), respiratory motor function, hypoxia, normoxia, EMG (electromyography)

Participants will complete both the AIH and the sham AIH visits. The order of these visits will be randomized, but all subjects will complete both visits in the course of the study.

Participants will be blind to the order of the AIH/sham AIH visits, but this information will be provided to the participant after completion of last visit.

Participants will complete a single 45 minute session of acute intermittent hypoxia (AIH), as well as, the 45 minute sham AIH session, consisting of breathing air with normal oxygen levels. Breathing, muscle activity and heart activity will be monitored before, during and after both procedures.

Participants will complete a single 45 minute session of acute intermittent hypoxia (AIH), as well as, the 45 minute sham AIH session, consisting of breathing air with normal oxygen levels. Breathing, muscle activity and heart activity will be monitored before, during and after both procedures.

AIH entails continuous breathing as the level of oxygen in the air is decreased, then returned to normal. Participants will alternate between breathing normal air and breathing hypoxic air (air that has less oxygen). Participants will complete a single 45 minute session of acute intermittent hypoxia (AIH). Breathing, muscle activity and heart activity will be monitored before, during and after the procedure. The intervals will last 1 minute each.

Participants will complete the sham acute intermittent hypoxia, consisting of a single 45 minute session of breathing air with normal oxygen levels. All aspects of this procedure will otherwise be the same as for the AIH procedure. Breathing, muscle activity and heart activity will be monitored before, during and after the procedure.

Maximal voluntary static contractions of the inspiratory or expiratory muscles against a closed valve, measured at the mouth. Sniff nasal inspiratory pressure measures inspiratory force generation at the nose.The test will be repeated until 3 measurements are obtained within 10% variability; a minimum 20-second rest will be provided between hypoxic episodes.

Maximal static voluntary handgrip contractions will be evaluated in a seated position with the arm at the side and elbow flexed to 90 degrees. The test will be repeated until 3 measurements are obtained with <10% variability, and a minimum 15-second rest between measurements.

A pneumotachograph and pressure transducer connected to the face mask will record breath-by-breath flow, volume, mouth pressure, and breathing rate. After achieving a stable tidal volume, 5 minutes of tidal breathing will be recorded.

Respiratory drive will be estimated with pressure generation against a transiently occluded airway in the first 0.1 sec of inspiration. Five measurements will be conducted, with 5-15 un-occluded breaths between each P0.1 measurement. This validated test is resistant to learning or sensory bias and reflects unaltered neuromuscular effort.

Surface EMGs of the respiratory muscles (up to six muscles, bilaterally: scalene, sternocleidomastoid, 2nd parasternal, 5th external intercostal, 8th external intercostal, and diaphragm) will be recorded during the test session. The root mean square (RMS) of each muscle will be averaged.

Inclusion Criteria: a healthy adult clinical diagnosis of ALS baseline FVC >60% predicted for age, sex and height. Exclusion Criteria: pregnant diagnosed cardiovascular disease a BMI >35 kg/m2 currently take selective serotonin reuptake inhibitors (SSRI) history of seizures history of hospitalization for sepsis respiratory infection or took antibiotic medications within the past 4 weeks use external respiratory support during any waking hours participate in a pharmaceutical trial to treat ALS have any other medical condition the PI or medical director identify would make it unsuitable to participate.